The Uterine corpus Flexion Angle: A Novel and Objective Sonographic Marker for Endometriosis Severity and the Quantification of the Question Mark Sign 

The Uterine corpus Flexion Angle: A Novel and Objective Sonographic Marker for Endometriosis Severity and the Quantification of the Question Mark Sign | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The Uterine corpus Flexion Angle: A Novel and Objective Sonographic Marker for Endometriosis Severity and the Quantification of the Question Mark Sign Jing Chen, ShuLin Zhong, JiaLe Liang, Fang Liu, LiJuan Li, ShuYi Guo, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8831280/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 14 You are reading this latest preprint version Abstract Background The current study investigated the correlation between the uterine corpus flexion angle (UCFA) and the severity of endometriosis, evaluated its clinical utility as a novel objective sonographic parameter, and provided an angular definition for the question mark sign. Methods This observational case-control study enrolled 621 women. The participants were then classified into the endometriosis, benign control, and normal groups (n = 207 per group). All participants underwent standardized transvaginal ultrasonography. The UCFA and uterine flexion angle (UFA) were measured in the midsagittal plane. The subjective question mark sign was assessed by sonographers. In the endometriosis group, pelvic adhesions were graded intraoperatively. The correlation of the UCFA with the severity of endometriosis and the question mark sign was evaluated via Spearman’s correlation, multivariate regression, and receiver operating characteristic curve analyses. Results The UCFA progressively increased with a higher revised American Society for Reproductive Medicine stage (P < 0.001) and a greater pelvic adhesion severity (P < 0.001). Based on the multivariate analysis, the UCFA was primarily determined by adhesion score (β = 0.441). Meanwhile, the UFA was predominantly influenced by baseline uterine position (β = 0.508). The optimal cutoff for the sonographic question mark sign was UCFA ≥ 220° (area under the curve = 0.958). The UCFA had relative stability in the absence of endometriosis, with a median of 179.0° in the benign control group and 178.0° in the normal group. Conclusions The UCFA is an objective sonographic marker of endometriosis severity. The proposed criterion of UCFA ≥ 220° provides a validated, quantitative definition for the question mark sign, offering a practical tool for standardized ultrasonography assessment and preoperative evaluation. endometriosis pelvic adhesions ultrasonography uterine corpus flexion angle uterine flexion angle question mark sign Figures Figure 1 Background Endometriosis is a systemic inflammatory condition associated with the presence of displaced endometrium-like tissues outside the uterus [ 1 ] . As a common benign gynecological disease, it is often overlooked [ 2 ] . Its diagnosis is often delayed, which has an average time of 5–12 years after symptom onset, with most women consulting 3 or more clinicians prior to diagnosis [ 3 ] . The main clinical manifestations include menstrual pain, dyspareunia, lower abdominal pain, and subfertility or infertility [ 4 , 5 ] . A retroflexed uterus is defined as a condition in which the cervix is pointing downward and forward and the uterine corpus axis is directed backward toward the sacral hollow [ 6 ] . The retroflexed uterus is a normal physiologic variant observed in 20% of women. However, it can also be associated with chronic retracting posterior deep infiltrating endometriosis and adhesions [ 7 ] . Fixed uterine retroflexion, particularly the question mark sign, is one of the indirect findings of endometriosis [ 8 ] . This indicates significant adhesions pulling the uterine fundus or corpus backward to the bowel or the posterior pelvic wall [ 9 ] . This prompted the hypothesis that the uterine corpus flexion angle (UCFA), rather than the uterine flexion angle (UFA), is pathologically correlated with endometriosis. To test the hypothesis, this study aimed to systematically evaluate the correlation of both UBFA and UFA with the presence and severity of endometriosis and to establish a new objective and precise ultrasonographic parameter for clinical assessment. Methods Study design and participants The prospective observational case-control study was performed at The Tenth Affiliated Hospital of Southern Medical University from March 2023 to June 2025. The study was approved by the Ethics Committee of the Hospital (registration number: KYKT2023-039).We prospectively collected data from 207 endometriosis patients and retrospectively collected 207 cases each in the benign and normal control groups during the same period. Written informed consent was obtained from all endometriosis patients, and consent was waived for the two control groups due to retrospective and anonymized data analysis. The endometriosis group comprised patients who underwent laparoscopic surgery for clinically suspected endometriosis with the diagnosis subsequently confirmed via postoperative histopathological examination. All the patients underwent transvaginal ultrasonography (TVUS) performed by two expert sonographers using an endovaginal probe(6–12 MHz,Resona R9;,Mindray, Shenzhen, China) no more than one month prior to the surgery. The benign control group included patients who underwent laparoscopic surgery for sonographically identified benign ovarian cystic lesions, such as mature teratomas and serous/mucinous cystadenomas. Intraoperative and final pathological examinations confirmed the benign nature of these lesions and ruled out the presence of endometriosis. The normal control group consisted of participants who underwent routine physical examination, with no abnormal findings on gynecological examination and TVUS. The exclusion criteria were as follows: patients with suspected malignancy, those aged < 18 years, menopausal women, pregnant women, those who presented with uterine leiomyomas with a maximum diameter exceeding 3 cm, those with congenital uterine anomalies, and those using an intrauterine device. Patients with imaging findings indicative of adenomyosis on TVUS or MRI were excluded from the benign and normal control groups. Testing methods We collected data on demographic characteristics, symptoms (dysmenorrhea, dyspareunia, dyschezia, pelvic pain, and dysuria), and previous history of uterine body surgeries in all participants. All TVUS scans were performed by a single gynecologist with 10 years of experience in gynecologic US, using an endovaginal probe with a frequency range of 4–9 MHz (VolusonE6; GE Healthcare, Zipf, Austria) or 6–12 MHz (Resona R9; Mindray, Shenzhen, China). All participants were instructed to empty their bladder before the examination and were placed in the lithotomy position. The probe was inserted to the vagina gently to prevent applying external force that might alter the natural uterine position. The uterine position was determined in the standard midsagittal plane, which clearly visualized the whole length of the cervix and uterine corpus. The uterus was classified as anteverted if the uterine corpus was oriented toward the anterior abdominal wall or retroverted if oriented toward the posterior pelvic wall. A clear image of the uterine midsagittal plane was acquired and stored for subsequent analysis. The endometriosis group underwent TVUS that was performed in four steps according to the International Duration Evaluation of Adjuvant group recommendations and nomenclature for describing the location and extent of endometriosis using the pelvis approach within 1 month prior to surgery. The benign control and normal groups underwent a routine TVUS examination. Angle measurement protocol: Angle measurements were performed independently by two sonographers who were blinded to the clinical data. Measurements were conducted using the angle measurement tool within our institution’s Picture Archiving and Communication System on the stored midsagittal uterine images (Fig. 1 ). Definition of angles: The UFA was evaluated as the anterior angle between the longitudinal axis of the cervix and the longitudinal axis of the uterine corpus [ 10 ] . The UCFA was examined as the anterior angle at the midpoint of the uterine corpus curvature, formed between the axis of the upper uterine segment and the axis of the lower uterine segment. This angle quantifies the curvature of the uterine corpus. Assessment of the question mark sign: The presence of the question mark sign was jointly assessed by two sonographers. In cases of disagreement, a third sonographer provided an independent assessment, and the majority opinion was adopted as the final determination. Both the endometriosis and benign control groups underwent laparoscopy or laparotomy. Endometriosis group: The surgeons assessed and staged the condition based on intraoperative observations, strictly following the revised modified American Society for Reproductive Medicine adhesion scoring scale. Then, it was categorized as mild (1–15 points), moderate (16–40 points), or severe (> 40 points). Pelvic adhesions were investigated using a modified scoring system based on the modified American Society for Reproductive Medicine scoring system. Adhesions were classified as mild (1–2 points), moderate (3–4 points), or severe (5–6 points). Severe adhesions were defined as dense adhesive tissues involving > 25% of the operative field. The presence of dense uterine fixation to the rectum and complete obliteration of the pouch of Douglas were specifically documented. Benign control group: The operating surgeon retrospectively scored pelvic adhesions based on the operative records. Statistical analysis The participants were stratified according to uterine position (anteverted/retroverted) for the subgroup analyses. The analysis of qualitative variables involved calculating the absolute and percentage frequencies of all possible values that these variables could assume. Continuous data with non-normal distributions were presented as median (interquartile range, IQR). The 95% confidence intervals for the median were estimated using the bootstrap method with 1,000 replications to provide robust estimates. The correlations between quantitative variables were analyzed using the Spearman’s correlation coefficient. The comparison of quantitative variables between two groups was conducted using the Mann–Whitney U test. To compare quantitative variables across three or more groups, the Kruskal–Wallis test was utilized, followed by the Dunn’s post-hoc test in the presence of statistically significant differences among the groups. Categorical data were expressed as numbers (percentages), and group comparisons were conducted using the chi-square (χ²) test. A two-sided P-value of < 0.05 indicated statistically significant differences. In the endometriosis group, variables associated with the flexion angles at P < 0.10 in the univariate analyses were considered candidates for the multivariate model. The diagnostic performance of the UCFA was evaluated via receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) and optimal cutoff values were calculated. The statistical analyses were performed using the Statistical Package for the Social Sciences software (version 26.0; IBM Corp., Armonk, NY, the USA). Results Clinical characteristics of the participants In total, 621 women were included in the final analysis. The gravidity, parity, uterine corpus surgical history, and uterine position in the three patient groups were similar. The maximum diameter of ovarian cystic lesions in the endometriosis and benign control groups were also comparable. The endometriosis group had a significantly lower body mass index (BMI) than the benign control and normal groups. The normal group was significantly younger than the benign control and endometriosis groups (Table 1 ). Table 1 Clinical characteristics of the three patient groups Variables Endometriosis (n = 207) Benign (n = 207) Normal (n = 207) P Value Age, median (IQR) 33.0 (28.0, 42.0) 37.0 (32.0, 42.0) 34.0 (29.0, 39.0) < 0.001 BMI, median (IQR) 21.6 (20.0, 23.4) 22.7 (20.2, 24.7) 22.1 (19.8, 24.1) 0.028 Gravidity [n (%)] 0.395 0 48 (23.2) 57 (27.5) 53(25.6) 1 50 (42.0) 41 (19.8) 35 (16.9) ≥ 2 109(52.7) 109(52.7) 119(57.5) Parity [n (%)] 0.948 0 64(30.9) 67 (32.4) 61(29.5) 1 61 (29.5) 63 (30.4) 61 (29.5) ≥ 2 82(39.6) 77(37.2) 85(41.1) History of uterine corpus surgery (cesarean section, myomectomy) 0.451 0 151(72.9) 157(75.8) 162(78.3) 1 56(27.1) 50(24.2) 45(21.7) Uterine position [n (%)] 0.514 Anteflexed 139 (68.6) 145(70.0) 134 (64.7) Retroflexed 86 (31.4) 62 (30.0) 73 (35.3) Maximum diameter, median (IQR) 58.0 (45.0, 76.5) 61.0 (46.5, 74.5) —— 0.470 Two angle measurements across the uterine position subgroups among the three patient groups Both the UFA and UCFA did not significantly differ between the benign and normal groups, irrespective of uterine position. The median UCFA was remarkably similar between the benign control and normal groups (179.0° vs 178.0°), with fully overlapping 95% confidence intervals for the median (177.0º–180.0° for both groups) as estimated using 1,000 replications bootstrap resampling. The distributions in both groups exhibited comparable dispersion (interquartile range: 16° vs. 15°). Based on these results, the presence of ovarian cysts did not significantly affect the UFA or UCFA. In the absence of substantial uterine corpus or cavity occupying lesions and severe pelvic adhesions, the uterine retroversion angle remained relatively stable. The stratified analysis based on the uterine position (Table 2 ) showed that in both anteflexed and retroflexed uteri, the UCFA was significantly greater in the endometriosis group than in the benign control and normal groups. In contrast, the UFA showed a statistically significant difference only within the anteflexed uterine subgroup, without significant difference observed in the retroflexed subgroup. Further, there were no significant differences in either the UFA or UCFA between the benign control and normal groups. Therefore, compared with the UFA, the UCFA is more suitable for assessing endometriosis and pelvic adhesions. Table 2 Comparison of the two angle measurements across the uterine position subgroups among the three patient groups Clinical features Category UCFA (°), median (IQR) [n] P-value (overall) P-value (anteverted) P-value (retroverted) All patients (n = 207) Patients with anteverted uterus (n = 139) Patients with retroverted uterus (n = 68) rASRM Stage Mild 184.0 (179.0–188.8)[16] 182.0 (179.0–188.0)[11] 188.0 (181.5–220.5)[5] < 0.001 0.003 < 0.001 Moderate 183.0 (177.0–194.0)[71] 179.0 (175.0–190.8)[52] 191.0 (181.0–211.0)[19] Severe 216.0 (186.5–232.8)[120] 202.0 (176.0–229.0)[76] 228.0 (212.3–241.0)[44] Pelvic Adhesion Score Mild 179.0 (173.5–186.0)[53] 178.0 (171.0–184.0)[39] 185.5 (182.0–194.8)[14] < 0.001 < 0.001 < 0.001 Moderate 196.0 (179.0–219.3)[78] 188.0 (176.8–206.3)[54] 213.5 (192.8–228.0)[24] Severe 223.0 (199.5–239.0)[76] 207.5 (180.5–232.8)[46] 231.5 (218.0–247.8)[30] DIE Absent 188.0 (177.0–222.0)[121] 182.0 (174.0–200.5)[84] 216.0 (189.5–232.0)[37] 0.011 0.024 0.346 Present 207.0 (180.8–229.0)[86] 201.0 (177.0–223.0)[55] 221.0 (199.0–234.0)[31] Adenomyosis Absent 188.5 (177.0–222.3)[166] 183.0 (175.0–206.5) [117] 210.0 (186.0–228.0) [49] < 0.001 0.004 0.025 Present 219.0 (196.5–238.0)[41] 206.5 (184.0–223.0) [22] 228.0 (217.0–243.5) [19] Correlation between the UCFA and the clinical pathological features of endometriosis The UCFA progressively increased with disease severity regardless of uterine position (Table 3). Both the anteverted and retroverted uterine had significant positive correlations between pelvic adhesion severity and the angle (all P < 0.001). Deep infiltrating endometriosis was correlated with a higher overall UCFA (207° vs. 188°, P = 0.011), primarily attributed to anteverted uteri. No significant difference was found in the retroverted uterine (P = 0.346). Adenomyosis was significantly associated with increased uterine retroversion (219° vs. 188.5°, P < 0.001). Analysis of the multiple linear regression models for the UFA and UCFA Based on the univariate correlation and multivariate linear regression analyses, maximum cyst diameter (r = 0.061, P = 0.193) and history of uterine surgery (r = 0.040, P = 0.286) were not significantly associated with the UCFA. Thus, the final model retained uterine position, ASRM stage, pelvic adhesion score, and adenomyosis (Table 4 ). Table 4 Univariate analysis of the UFA and UCFA in the endometriosis group Variables n = 139(A) n = 68(R) ρ/Z p Value ρ/Z p Value UFA ASRM 0.021 0.809 0.215 0.078 Adhesion 0.245 0.004 0.149 0.227 Adenomyosis 0.239 0.005 -0.032 0.456 UCFA ASRM 0.276 0.001 0.557 <0.001 Adhesion 0.445 <0.001 0.569 <0.001 Adenomyosis 0.244 0.004 0.337 0.005 According to the multivariate linear regression analysis, both the UFA and UCFA were statistically significant in their respective models. The UCFA model exhibited a stronger explanatory power (adjusted R² = 0.341) compared with the UFA model (adjusted R² = 0.293). The pelvic adhesion score was a significantly stronger independent predictor of UCFA (standardized β = 0.441, P < 0.001) rather than of UFA (standardized β = 0.132, P = 0.030). In contrast, the overall uterine position was the dominant factor influencing UFA (β = 0.508, P < 0.001), exerting a comparatively weaker effect on UCFA (β = 0.249, P < 0.001). Further, the presence of adenomyosis was independently associated with UCFA (P = 0.008) but not with UFA (P = 0.406)(Table 5 ). Table 5 Comparative multivariate linear regression analysis of the determinants for the two uterine flexion angles Predictor Variable UCFA UFA Model Characteristics Adjusted R² 0.341 0.293 Model P value < 0.001 < 0.001 Regression Coefficients B (95% CI) Beta (P value) B (95% CI) Beta (P value) Constant 153.86 (143.19, 164.53) - (< 0.001) 114.33 (98.53, 130.12) - (< 0.001) Adhesion Score 12.90 (9.54, 16.26) 0.441 (< 0.001) 5.53 (0.55, 10.51) 0.132 (0.030) Retroverted vs. Anteflexed 14.19 (7.74, 20.64) 0.249 (< 0.001) 41.39 (31.84, 50.94) 0.508 (< 0.001) Adenomyosis(Yes vs. No) 10.59 (2.84, 18.35) 0.158 (0.008) 4.86 (-6.63, 16.34) 0.051 (0.406) Abbreviations: B, unstandardized regression coefficient; CI, confidence interval; beta, standardized regression coefficient. Notes: Both parsimonious models included the three predictors listed. All variance inflation factors (VIFs) were < 1.1, indicating no multicollinearity. Question mark sign In the endometriosis group, 50 women were diagnosed with the question mark sign on US. It had a high specificity (87.0%) but limited sensitivity (43.4%) for severe pelvic adhesions. The ROC analysis showed that the UCFA effectively discriminated the question mark sign, with an AUC of 0.958 (95% CI: 0.934–0.982, P < 0 .001). The maximum Youden index was 0.801, yielding an optimal cutoff of UCFA ≥ 220°, corresponding to a sensitivity of 91.3% and a specificity of 88.8%. These results provide a reliable and reproducible quantitative criterion for this classic yet subjective US sign. Discussion This study showed that UCFA was a novel, objective sonographic marker that quantified the anatomical distortion associated with endometriosis. Our findings confirmed that UCFA is a quantifiable parameter strongly correlated with the pathological features of endometriosis, particularly pelvic adhesions. Further, the UFA is primarily influenced by uterine version. The multivariate linear regression analysis validated our hypothesis that the dominant influence of pelvic adhesion scores on UCFA (β = 0.441) supported the model of posterior compartment disease that exerts direct traction on the uterine corpus. The UFA was primarily determined by uterine position (β = 0.508), with only a modest additional effect from adhesions (β = 0.132). In 2015, Di Donato et al. initially described the question mark sign as a sonographic feature indicative of adenomyosis. If the uterine corpus was flexed backward, the uterine fundus was facing the posterior pelvic compartment, and the cervix was directed anteriorly toward the urinary bladder [ 11 ] . Further, it is recognized as an indirect sonographic indicator of endometriosis and a marker of pelvic adhesions [ 12 , 13 ] . Adenomyosis emerged as the third independent determinant of UCFA (β = 0.158). However, it had no significant independent effect on UFA. A significantly high UCFA warrants consideration of both pelvic adhesions and coexistent adenomyosis. These two factors may act synergistically to exacerbate uterine retroflexion, jointly contributing to the pathological basis of the question mark sign. In both the normal and benign control groups, the UCFA remained relatively stable, which can be attributed to the synergistic combination of the inherent structural resilience of the uterus as a muscular organ and its physiological contractile tone. Via the ROC curve analysis, the optimal cutoff value for the question mark sign was determined to be 220°. Compared with the subjective assessment of the question mark sign, this provides a clear, measurable diagnostic threshold for sonographers. It can improve interobserver consistency. In routine gynecologic US examinations, UCFA can be a practical tool for the rapid screening of endometriosis-associated severe adhesions. The presence of the question mark sign or a significantly elevated UCFA indicates dense posterior pelvic adhesions, which may require the involvement of colorectal or urologic surgeons and is associated with a longer surgical duration and higher complication risks. The endometriosis group had a lower BMI than the benign pathology and normal groups, which is similar with previous literature reports [ 14 ] . Chronic pain associated with endometriosis may suppress appetite. Meanwhile, the gastrointestinal side effects of non-steroidal anti-inflammatory drugs, which is a common therapy, could reduce food tolerance and contribute to weight loss [ 15 ] . Growing evidence indicates that body composition, particularly both low BMI and obesity, influences disease progression by regulating chronic inflammation, hormonal balance, and immune responses [ 16 ] . This study has limitations. Its single center design might have affected the generalizability of the results. Although UCFA was linked to surgical adhesion scores, it was not associated with pelvic pain or fertility metrics. Nevertheless, future prospective, multicenter studies should be performed to validate the prognostic value of the UCFA ≥ 220° criterion for predicting surgical complexity. Conclusions The UCFA is a robust and objective ultrasonographic parameter that is closely correlated with the severity of endometriosis-associated pelvic adhesions. We propose UCFA ≥ 220° as a validated, quantitative criterion for the question mark sign, effectively translating a subjective sonographic finding into a reliable diagnostic measurement. This advancement provides clinicians with a practical tool that can improve the standardized US assessment of endometriosis, thereby contributing to a more precise diagnosis and preoperative evaluation. Abbreviations UFA Uterine flexion angle UCFA Uterine corpus flexion angle DIE Deep infiltrating endometriosis BMI body mass index TVUS transvaginal ultrasonography Declarations Ethics approval and consent to participate The study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Medical Ethics Committee of Dongguan People's Hospital, which is affiliated to The Tenth Affiliated Hospital, Southern Medical University (Dongguan People's Hospital), before the study began. The endometriosis patients’ right to be informed about the study was ensured, and all patients provided written consent to participate. For the two control groups, consent to participate was waived by this same ethics committee due to retrospective data collection and anonymized analysis. Consent for publication Not applicable. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Competing interests The authors declare no competing interests. Funding Dongguan Science and Technology of Social Development Program;NO：20231800904322 Authors' contributions Conceptualization,Jing Chen; Data curation,Jing Chen , JiaLe Liang ,ShuLin Zhong; Statistical analysis,Jing Chen and Fang Liu;Angle easurement,LiJuan Li,ShuYi Guo; Writing and editing,Jing Chen and XiaoLing Leng;All authors read and approved the final manuscript. Acknowledgements Not applicable. Authors' information Jing Chen,JiaLe Liang,Fang Liu, LiJuan Li,ShuYi Guo,XiaoLeng Ling Department of Ultrasonography,The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）, Dongguan,Guangdong 523000, China ShuLin Zhong Department of gynecology,The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）, Dongguan,Guangdong 523000, China References Guerriero S, Condous G, Rolla M, Pedrassani M, Leonardi M, Hudelist G, Ferrero S, Alcazar JL, Ajossa S, Bafort C, Van Schoubroeck D, Bourne T, Van den Bosch T, Singh SS, Abrao MS, Di Giovanni A, Tomassetti C, Timmerman D. Addendum to consensus opinion from the International Deep Endometriosis Analysis (IDEA) group: sonographic evaluation of superficial endometriosis. Ultrasound Obstet Gynecol. 2025 Oct;66(4):541–547. Zhang J, Pang M, Li L, Guo C. 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Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 13 May, 2026 Reviews received at journal 11 May, 2026 Reviews received at journal 09 May, 2026 Reviewers agreed at journal 07 May, 2026 Reviewers agreed at journal 04 May, 2026 Reviews received at journal 04 May, 2026 Reviewers agreed at journal 04 May, 2026 Reviewers agreed at journal 03 May, 2026 Reviewers agreed at journal 02 May, 2026 Reviewers invited by journal 22 Apr, 2026 Editor assigned by journal 24 Feb, 2026 Editor invited by journal 24 Feb, 2026 Submission checks completed at journal 21 Feb, 2026 First submitted to journal 21 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8831280","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":627981901,"identity":"21b476de-e718-435b-80e0-2dd160cb1a20","order_by":0,"name":"Jing Chen","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"Jing","middleName":"","lastName":"Chen","suffix":""},{"id":627981902,"identity":"06742002-26b3-43be-ad5b-f9c4aeeb65b7","order_by":1,"name":"ShuLin Zhong","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"ShuLin","middleName":"","lastName":"Zhong","suffix":""},{"id":627981903,"identity":"aa7aab91-a218-49e6-9967-d7d8601b836f","order_by":2,"name":"JiaLe Liang","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"JiaLe","middleName":"","lastName":"Liang","suffix":""},{"id":627981904,"identity":"1c65aa04-52c6-4732-ae66-f7d2d571974e","order_by":3,"name":"Fang Liu","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"Fang","middleName":"","lastName":"Liu","suffix":""},{"id":627981905,"identity":"18faf315-3fca-4e43-98df-23ebbdfb6752","order_by":4,"name":"LiJuan Li","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"LiJuan","middleName":"","lastName":"Li","suffix":""},{"id":627981906,"identity":"c08e3490-8a24-421e-8867-2907d834d339","order_by":5,"name":"ShuYi Guo","email":"","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":false,"prefix":"","firstName":"ShuYi","middleName":"","lastName":"Guo","suffix":""},{"id":627981907,"identity":"511c3984-3322-4055-bdbf-89a87b90a074","order_by":6,"name":"XiaoLing Leng","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCklEQVRIie2SsUoEMRCGdwlkm7ndNjarjzAQCAqLL2Izi5DqFMFG8OAODs5KbO8xBF/gYECbRV8hdoIWK1aCiHPHWXiwe61FviL5i/nITJIkiUT+IflqRQlKdrowZaEUhz5F/yp6qYSmsjtX2uN2ZR3S55mv8Qn2TK+SXfMrnB2WOhvwC2kmyyCnjqqjTgUe/cEcj61Wud8n4FPHg0VI7v3JpEsxQ4ctqnqmwCEZPnecE6YT7lZ236QSx2sFub6bAppexYANrVSKYgORr2/VNgWGLp3jg8wCLqFFZQ3LJVPPLEXW2A/4uiyLorHvn9/ylDfMoR1Vncqqt80g36C7fIlqN0MkEolE/vADU1lRKVPeoaIAAAAASUVORK5CYII=","orcid":"","institution":"The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）","correspondingAuthor":true,"prefix":"","firstName":"XiaoLing","middleName":"","lastName":"Leng","suffix":""}],"badges":[],"createdAt":"2026-02-09 13:55:06","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8831280/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8831280/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":108405874,"identity":"d48d488b-e84b-40a2-8abe-51b2b5bf8f60","added_by":"auto","created_at":"2026-05-04 09:40:47","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1385401,"visible":true,"origin":"","legend":"\u003cp\u003eUltrasonographic representation of the angle of uterine flexion measurement. (A) The uterine flexion angle. (B) The uterine corpus flexion angle.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8831280/v1/38fdcd5f98d68208f21b25fa.png"},{"id":108493506,"identity":"aa831764-882b-48e8-8b3a-961fd77eb663","added_by":"auto","created_at":"2026-05-05 10:00:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1651176,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8831280/v1/0679c03d-6372-4936-809b-b362f08b24d9.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Uterine corpus Flexion Angle: A Novel and Objective Sonographic Marker for Endometriosis Severity and the Quantification of the Question Mark Sign ","fulltext":[{"header":"Background","content":"\u003cp\u003eEndometriosis is a systemic inflammatory condition associated with the presence of displaced endometrium-like tissues outside the uterus \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e1\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. As a common benign gynecological disease, it is often overlooked \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e2\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Its diagnosis is often delayed, which has an average time of 5\u0026ndash;12 years after symptom onset, with most women consulting 3 or more clinicians prior to diagnosis \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e3\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. The main clinical manifestations include menstrual pain, dyspareunia, lower abdominal pain, and subfertility or infertility \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e4\u003c/sup\u003e,\u003csup\u003e5\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eA retroflexed uterus is defined as a condition in which the cervix is pointing downward and forward and the uterine corpus axis is directed backward toward the sacral hollow \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e6\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. The retroflexed uterus is a normal physiologic variant observed in 20% of women. However, it can also be associated with chronic retracting posterior deep infiltrating endometriosis and adhesions \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e7\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Fixed uterine retroflexion, particularly the question mark sign, is one of the indirect findings of endometriosis \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e8\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. This indicates significant adhesions pulling the uterine fundus or corpus backward to the bowel or the posterior pelvic wall \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e9\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis prompted the hypothesis that the uterine corpus flexion angle (UCFA), rather than the uterine flexion angle (UFA), is pathologically correlated with endometriosis. To test the hypothesis, this study aimed to systematically evaluate the correlation of both UBFA and UFA with the presence and severity of endometriosis and to establish a new objective and precise ultrasonographic parameter for clinical assessment.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy design and participants\u003c/h2\u003e \u003cp\u003eThe prospective observational case-control study was performed at The Tenth Affiliated Hospital of Southern Medical University from March 2023 to June 2025. The study was approved by the Ethics Committee of the Hospital (registration number: KYKT2023-039).We prospectively collected data from 207 endometriosis patients and retrospectively collected 207 cases each in the benign and normal control groups during the same period. Written informed consent was obtained from all endometriosis patients, and consent was waived for the two control groups due to retrospective and anonymized data analysis.\u003c/p\u003e \u003cp\u003eThe endometriosis group comprised patients who underwent laparoscopic surgery for clinically suspected endometriosis with the diagnosis subsequently confirmed via postoperative histopathological examination. All the patients underwent transvaginal ultrasonography (TVUS) performed by two expert sonographers using an endovaginal probe(6\u0026ndash;12 MHz,Resona R9;,Mindray, Shenzhen, China) no more than one month prior to the surgery.\u003c/p\u003e \u003cp\u003eThe benign control group included patients who underwent laparoscopic surgery for sonographically identified benign ovarian cystic lesions, such as mature teratomas and serous/mucinous cystadenomas. Intraoperative and final pathological examinations confirmed the benign nature of these lesions and ruled out the presence of endometriosis.\u003c/p\u003e \u003cp\u003eThe normal control group consisted of participants who underwent routine physical examination, with no abnormal findings on gynecological examination and TVUS.\u003c/p\u003e \u003cp\u003eThe exclusion criteria were as follows: patients with suspected malignancy, those aged\u0026thinsp;\u0026lt;\u0026thinsp;18 years, menopausal women, pregnant women, those who presented with uterine leiomyomas with a maximum diameter exceeding 3 cm, those with congenital uterine anomalies, and those using an intrauterine device. Patients with imaging findings indicative of adenomyosis on TVUS or MRI were excluded from the benign and normal control groups.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eTesting methods\u003c/h3\u003e\n\u003cp\u003eWe collected data on demographic characteristics, symptoms (dysmenorrhea, dyspareunia, dyschezia, pelvic pain, and dysuria), and previous history of uterine body surgeries in all participants. All TVUS scans were performed by a single gynecologist with 10 years of experience in gynecologic US, using an endovaginal probe with a frequency range of 4\u0026ndash;9 MHz (VolusonE6; GE Healthcare, Zipf, Austria) or 6\u0026ndash;12 MHz (Resona R9; Mindray, Shenzhen, China).\u003c/p\u003e \u003cp\u003e All participants were instructed to empty their bladder before the examination and were placed in the lithotomy position. The probe was inserted to the vagina gently to prevent applying external force that might alter the natural uterine position. The uterine position was determined in the standard midsagittal plane, which clearly visualized the whole length of the cervix and uterine corpus.\u003c/p\u003e \u003cp\u003eThe uterus was classified as anteverted if the uterine corpus was oriented toward the anterior abdominal wall or retroverted if oriented toward the posterior pelvic wall. A clear image of the uterine midsagittal plane was acquired and stored for subsequent analysis.\u003c/p\u003e \u003cp\u003eThe endometriosis group underwent TVUS that was performed in four steps according to the International Duration Evaluation of Adjuvant group recommendations and nomenclature for describing the location and extent of endometriosis using the pelvis approach within 1 month prior to surgery. The benign control and normal groups underwent a routine TVUS examination.\u003c/p\u003e \u003cp\u003eAngle measurement protocol: Angle measurements were performed independently by two sonographers who were blinded to the clinical data. Measurements were conducted using the angle measurement tool within our institution\u0026rsquo;s Picture Archiving and Communication System on the stored midsagittal uterine images (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDefinition of angles: The UFA was evaluated as the anterior angle between the longitudinal axis of the cervix and the longitudinal axis of the uterine corpus \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e10\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. The UCFA was examined as the anterior angle at the midpoint of the uterine corpus curvature, formed between the axis of the upper uterine segment and the axis of the lower uterine segment. This angle quantifies the curvature of the uterine corpus.\u003c/p\u003e \u003cp\u003eAssessment of the question mark sign: The presence of the question mark sign was jointly assessed by two sonographers. In cases of disagreement, a third sonographer provided an independent assessment, and the majority opinion was adopted as the final determination.\u003c/p\u003e \u003cp\u003eBoth the endometriosis and benign control groups underwent laparoscopy or laparotomy.\u003c/p\u003e \u003cp\u003eEndometriosis group: The surgeons assessed and staged the condition based on intraoperative observations, strictly following the revised modified American Society for Reproductive Medicine adhesion scoring scale. Then, it was categorized as mild (1\u0026ndash;15 points), moderate (16\u0026ndash;40 points), or severe (\u0026gt;\u0026thinsp;40 points). Pelvic adhesions were investigated using a modified scoring system based on the modified American Society for Reproductive Medicine scoring system. Adhesions were classified as mild (1\u0026ndash;2 points), moderate (3\u0026ndash;4 points), or severe (5\u0026ndash;6 points). Severe adhesions were defined as dense adhesive tissues involving\u0026thinsp;\u0026gt;\u0026thinsp;25% of the operative field. The presence of dense uterine fixation to the rectum and complete obliteration of the pouch of Douglas were specifically documented.\u003c/p\u003e \u003cp\u003eBenign control group: The operating surgeon retrospectively scored pelvic adhesions based on the operative records.\u003c/p\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eThe participants were stratified according to uterine position (anteverted/retroverted) for the subgroup analyses. The analysis of qualitative variables involved calculating the absolute and percentage frequencies of all possible values that these variables could assume. Continuous data with non-normal distributions were presented as median (interquartile range, IQR). The 95% confidence intervals for the median were estimated using the bootstrap method with 1,000 replications to provide robust estimates. The correlations between quantitative variables were analyzed using the Spearman\u0026rsquo;s correlation coefficient. The comparison of quantitative variables between two groups was conducted using the Mann\u0026ndash;Whitney U test. To compare quantitative variables across three or more groups, the Kruskal\u0026ndash;Wallis test was utilized, followed by the Dunn\u0026rsquo;s post-hoc test in the presence of statistically significant differences among the groups. Categorical data were expressed as numbers (percentages), and group comparisons were conducted using the chi-square (χ\u0026sup2;) test.\u003c/p\u003e \u003cp\u003eA two-sided P-value of \u0026lt;\u0026thinsp;0.05 indicated statistically significant differences. In the endometriosis group, variables associated with the flexion angles at P\u0026thinsp;\u0026lt;\u0026thinsp;0.10 in the univariate analyses were considered candidates for the multivariate model.\u003c/p\u003e \u003cp\u003eThe diagnostic performance of the UCFA was evaluated via receiver operating characteristic (ROC) curve analysis. The area under the curve (AUC) and optimal cutoff values were calculated.\u003c/p\u003e \u003cp\u003eThe statistical analyses were performed using the Statistical Package for the Social Sciences software (version 26.0; IBM Corp., Armonk, NY, the USA).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eClinical characteristics of the participants\u003c/h2\u003e \u003cp\u003eIn total, 621 women were included in the final analysis. The gravidity, parity, uterine corpus surgical history, and uterine position in the three patient groups were similar. The maximum diameter of ovarian cystic lesions in the endometriosis and benign control groups were also comparable. The endometriosis group had a significantly lower body mass index (BMI) than the benign control and normal groups. The normal group was significantly younger than the benign control and endometriosis groups (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical characteristics of the three patient groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEndometriosis\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;207)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBenign\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;207)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNormal\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;207)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e33.0 (28.0, 42.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e37.0 (32.0, 42.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e34.0 (29.0, 39.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBMI, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.6 (20.0, 23.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.7 (20.2, 24.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22.1 (19.8, 24.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.028\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGravidity [n (%)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.395\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e48 (23.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e57 (27.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e53(25.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e50 (42.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e41 (19.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e35 (16.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e109(52.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e109(52.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e119(57.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParity [n (%)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.948\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e64(30.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e67 (32.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e61(29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e61 (29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e63 (30.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e61 (29.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u0026ge;\u0026thinsp;2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e82(39.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e77(37.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e85(41.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHistory of uterine corpus surgery (cesarean section, myomectomy)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.451\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e151(72.9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e157(75.8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e162(78.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e56(27.1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50(24.2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e45(21.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUterine position [n (%)]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.514\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAnteflexed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e139 (68.6)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e145(70.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e134 (64.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRetroflexed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e86 (31.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e62 (30.0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e73 (35.3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMaximum diameter, median (IQR)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e58.0 (45.0, 76.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e61.0 (46.5, 74.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026mdash;\u0026mdash;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.470\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eTwo angle measurements across the uterine position subgroups among the three patient groups\u003c/h2\u003e \u003cp\u003eBoth the UFA and UCFA did not significantly differ between the benign and normal groups, irrespective of uterine position. The median UCFA was remarkably similar between the benign control and normal groups (179.0\u0026deg; vs 178.0\u0026deg;), with fully overlapping 95% confidence intervals for the median (177.0\u0026ordm;\u0026ndash;180.0\u0026deg; for both groups) as estimated using 1,000 replications bootstrap resampling. The distributions in both groups exhibited comparable dispersion (interquartile range: 16\u0026deg; vs. 15\u0026deg;). Based on these results, the presence of ovarian cysts did not significantly affect the UFA or UCFA. In the absence of substantial uterine corpus or cavity occupying lesions and severe pelvic adhesions, the uterine retroversion angle remained relatively stable.\u003c/p\u003e \u003cp\u003eThe stratified analysis based on the uterine position (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) showed that in both anteflexed and retroflexed uteri, the UCFA was significantly greater in the endometriosis group than in the benign control and normal groups. In contrast, the UFA showed a statistically significant difference only within the anteflexed uterine subgroup, without significant difference observed in the retroflexed subgroup. Further, there were no significant differences in either the UFA or UCFA between the benign control and normal groups. Therefore, compared with the UFA, the UCFA is more suitable for assessing endometriosis and pelvic adhesions.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of the two angle measurements across the uterine position subgroups among the three patient groups\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eClinical features\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCategory\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eUCFA (\u0026deg;), median (IQR) [n]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003cp\u003e(overall)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003cp\u003e(anteverted)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003cp\u003e(retroverted)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAll patients\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;207)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003ePatients with anteverted uterus\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;139)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003ePatients with retroverted uterus\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;68)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003erASRM Stage\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMild\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e184.0 (179.0\u0026ndash;188.8)[16]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e182.0 (179.0\u0026ndash;188.0)[11]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e188.0 (181.5\u0026ndash;220.5)[5]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e183.0 (177.0\u0026ndash;194.0)[71]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e179.0 (175.0\u0026ndash;190.8)[52]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e191.0 (181.0\u0026ndash;211.0)[19]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e216.0 (186.5\u0026ndash;232.8)[120]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e202.0 (176.0\u0026ndash;229.0)[76]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e228.0 (212.3\u0026ndash;241.0)[44]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePelvic Adhesion Score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMild\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e179.0 (173.5\u0026ndash;186.0)[53]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e178.0 (171.0\u0026ndash;184.0)[39]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e185.5 (182.0\u0026ndash;194.8)[14]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eModerate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e196.0 (179.0\u0026ndash;219.3)[78]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e188.0 (176.8\u0026ndash;206.3)[54]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e213.5 (192.8\u0026ndash;228.0)[24]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSevere\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e223.0 (199.5\u0026ndash;239.0)[76]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e207.5 (180.5\u0026ndash;232.8)[46]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e231.5 (218.0\u0026ndash;247.8)[30]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDIE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e188.0 (177.0\u0026ndash;222.0)[121]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e182.0 (174.0\u0026ndash;200.5)[84]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e216.0 (189.5\u0026ndash;232.0)[37]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.011\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.024\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.346\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e207.0 (180.8\u0026ndash;229.0)[86]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e201.0 (177.0\u0026ndash;223.0)[55]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e221.0 (199.0\u0026ndash;234.0)[31]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdenomyosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAbsent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e188.5 (177.0\u0026ndash;222.3)[166]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e183.0 (175.0\u0026ndash;206.5) [117]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e210.0 (186.0\u0026ndash;228.0) [49]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.025\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePresent\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e219.0 (196.5\u0026ndash;238.0)[41]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e206.5 (184.0\u0026ndash;223.0) [22]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e228.0 (217.0\u0026ndash;243.5) [19]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCorrelation between the UCFA and the clinical pathological features of endometriosis\u003c/h3\u003e\n\u003cp\u003eThe UCFA progressively increased with disease severity regardless of uterine position (Table\u0026nbsp;3). Both the anteverted and retroverted uterine had significant positive correlations between pelvic adhesion severity and the angle (all P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Deep infiltrating endometriosis was correlated with a higher overall UCFA (207\u0026deg; vs. 188\u0026deg;, P\u0026thinsp;=\u0026thinsp;0.011), primarily attributed to anteverted uteri. No significant difference was found in the retroverted uterine (P\u0026thinsp;=\u0026thinsp;0.346). Adenomyosis was significantly associated with increased uterine retroversion (219\u0026deg; vs. 188.5\u0026deg;, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\n\u003ch3\u003eAnalysis of the multiple linear regression models for the UFA and UCFA\u003c/h3\u003e\n\u003cp\u003eBased on the univariate correlation and multivariate linear regression analyses, maximum cyst diameter (r\u0026thinsp;=\u0026thinsp;0.061, P\u0026thinsp;=\u0026thinsp;0.193) and history of uterine surgery (r\u0026thinsp;=\u0026thinsp;0.040, P\u0026thinsp;=\u0026thinsp;0.286) were not significantly associated with the UCFA. Thus, the final model retained uterine position, ASRM stage, pelvic adhesion score, and adenomyosis (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eUnivariate analysis of the UFA and UCFA in the endometriosis group\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eVariables\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;139(A)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003en\u0026thinsp;=\u0026thinsp;68(R)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eρ/Z\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003ep Value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eρ/Z\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep Value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUFA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eASRM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.809\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.215\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.078\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdhesion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.245\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.149\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.227\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdenomyosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.239\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e-0.032\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.456\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUCFA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eASRM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.557\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdhesion\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.445\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.569\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e\u0026lt;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAdenomyosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.244\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.337\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.005\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAccording to the multivariate linear regression analysis, both the UFA and UCFA were statistically significant in their respective models. The UCFA model exhibited a stronger explanatory power (adjusted R\u0026sup2; = 0.341) compared with the UFA model (adjusted R\u0026sup2; = 0.293). The pelvic adhesion score was a significantly stronger independent predictor of UCFA (standardized β\u0026thinsp;=\u0026thinsp;0.441, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) rather than of UFA (standardized β\u0026thinsp;=\u0026thinsp;0.132, P\u0026thinsp;=\u0026thinsp;0.030). In contrast, the overall uterine position was the dominant factor influencing UFA (β\u0026thinsp;=\u0026thinsp;0.508, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001), exerting a comparatively weaker effect on UCFA (β\u0026thinsp;=\u0026thinsp;0.249, P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Further, the presence of adenomyosis was independently associated with UCFA (P\u0026thinsp;=\u0026thinsp;0.008) but not with UFA (P\u0026thinsp;=\u0026thinsp;0.406)(Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparative multivariate linear regression analysis of the determinants for the two uterine flexion angles\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePredictor Variable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eUCFA\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003eUFA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel Characteristics\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"4\" nameend=\"c5\" namest=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdjusted R\u0026sup2;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e0.341\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e0.293\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel P value\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c5\" namest=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegression Coefficients\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eB (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBeta (P value)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eB (95% CI)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eBeta (P value)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eConstant\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e153.86 (143.19, 164.53)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e- (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e114.33 (98.53, 130.12)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e- (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdhesion Score\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.90 (9.54, 16.26)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.441 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.53 (0.55, 10.51)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.132 (0.030)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRetroverted vs. Anteflexed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.19 (7.74, 20.64)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.249 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e41.39 (31.84, 50.94)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.508 (\u0026lt;\u0026thinsp;0.001)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdenomyosis(Yes vs. No)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.59 (2.84, 18.35)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.158 (0.008)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.86 (-6.63, 16.34)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.051 (0.406)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eAbbreviations: B, unstandardized regression coefficient; CI, confidence interval; beta, standardized regression coefficient.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003eNotes: Both parsimonious models included the three predictors listed. All variance inflation factors (VIFs) were \u0026lt;\u0026thinsp;1.1, indicating no multicollinearity.\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eQuestion mark sign\u003c/h2\u003e \u003cp\u003eIn the endometriosis group, 50 women were diagnosed with the question mark sign on US. It had a high specificity (87.0%) but limited sensitivity (43.4%) for severe pelvic adhesions. The ROC analysis showed that the UCFA effectively discriminated the question mark sign, with an AUC of 0.958 (95% CI: 0.934\u0026ndash;0.982, P\u0026thinsp;\u0026lt;\u0026thinsp;0 .001). The maximum Youden index was 0.801, yielding an optimal cutoff of UCFA\u0026thinsp;\u0026ge;\u0026thinsp;220\u0026deg;, corresponding to a sensitivity of 91.3% and a specificity of 88.8%. These results provide a reliable and reproducible quantitative criterion for this classic yet subjective US sign.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study showed that UCFA was a novel, objective sonographic marker that quantified the anatomical distortion associated with endometriosis. Our findings confirmed that UCFA is a quantifiable parameter strongly correlated with the pathological features of endometriosis, particularly pelvic adhesions. Further, the UFA is primarily influenced by uterine version.\u003c/p\u003e \u003cp\u003eThe multivariate linear regression analysis validated our hypothesis that the dominant influence of pelvic adhesion scores on UCFA (β\u0026thinsp;=\u0026thinsp;0.441) supported the model of posterior compartment disease that exerts direct traction on the uterine corpus. The UFA was primarily determined by uterine position (β\u0026thinsp;=\u0026thinsp;0.508), with only a modest additional effect from adhesions (β\u0026thinsp;=\u0026thinsp;0.132).\u003c/p\u003e \u003cp\u003eIn 2015, Di Donato et al. initially described the question mark sign as a sonographic feature indicative of adenomyosis. If the uterine corpus was flexed backward, the uterine fundus was facing the posterior pelvic compartment, and the cervix was directed anteriorly toward the urinary bladder \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e11\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Further, it is recognized as an indirect sonographic indicator of endometriosis and a marker of pelvic adhesions \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e12\u003c/sup\u003e, \u003csup\u003e13\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Adenomyosis emerged as the third independent determinant of UCFA (β\u0026thinsp;=\u0026thinsp;0.158). However, it had no significant independent effect on UFA. A significantly high UCFA warrants consideration of both pelvic adhesions and coexistent adenomyosis. These two factors may act synergistically to exacerbate uterine retroflexion, jointly contributing to the pathological basis of the question mark sign.\u003c/p\u003e \u003cp\u003eIn both the normal and benign control groups, the UCFA remained relatively stable, which can be attributed to the synergistic combination of the inherent structural resilience of the uterus as a muscular organ and its physiological contractile tone.\u003c/p\u003e \u003cp\u003eVia the ROC curve analysis, the optimal cutoff value for the question mark sign was determined to be 220\u0026deg;. Compared with the subjective assessment of the question mark sign, this provides a clear, measurable diagnostic threshold for sonographers. It can improve interobserver consistency. In routine gynecologic US examinations, UCFA can be a practical tool for the rapid screening of endometriosis-associated severe adhesions. The presence of the question mark sign or a significantly elevated UCFA indicates dense posterior pelvic adhesions, which may require the involvement of colorectal or urologic surgeons and is associated with a longer surgical duration and higher complication risks.\u003c/p\u003e \u003cp\u003eThe endometriosis group had a lower BMI than the benign pathology and normal groups, which is similar with previous literature reports \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e14\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Chronic pain associated with endometriosis may suppress appetite. Meanwhile, the gastrointestinal side effects of non-steroidal anti-inflammatory drugs, which is a common therapy, could reduce food tolerance and contribute to weight loss \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e15\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e. Growing evidence indicates that body composition, particularly both low BMI and obesity, influences disease progression by regulating chronic inflammation, hormonal balance, and immune responses \u003csup\u003e[\u003c/sup\u003e\u003csup\u003e16\u003c/sup\u003e\u003csup\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThis study has limitations. Its single center design might have affected the generalizability of the results. Although UCFA was linked to surgical adhesion scores, it was not associated with pelvic pain or fertility metrics. Nevertheless, future prospective, multicenter studies should be performed to validate the prognostic value of the UCFA\u0026thinsp;\u0026ge;\u0026thinsp;220\u0026deg; criterion for predicting surgical complexity.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe UCFA is a robust and objective ultrasonographic parameter that is closely correlated with the severity of endometriosis-associated pelvic adhesions. We propose UCFA\u0026thinsp;\u0026ge;\u0026thinsp;220\u0026deg; as a validated, quantitative criterion for the question mark sign, effectively translating a subjective sonographic finding into a reliable diagnostic measurement. This advancement provides clinicians with a practical tool that can improve the standardized US assessment of endometriosis, thereby contributing to a more precise diagnosis and preoperative evaluation.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUFA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUterine flexion angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUCFA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUterine corpus flexion angle\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eDIE\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eDeep infiltrating endometriosis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBMI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ebody mass index\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eTVUS\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003etransvaginal ultrasonography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Medical Ethics Committee of Dongguan People's Hospital, which is affiliated to The Tenth Affiliated Hospital, Southern Medical University (Dongguan People's Hospital), before the study began. The endometriosis patients\u0026rsquo; right to be informed about the study was ensured, and all patients provided written consent to participate. For the two control groups, consent to participate was waived by this same ethics committee due to retrospective data collection and anonymized analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDongguan Science and Technology of Social Development Program;NO：20231800904322\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization,Jing Chen; Data curation,Jing Chen , JiaLe Liang ,ShuLin Zhong; Statistical analysis,Jing Chen and Fang Liu;Angle easurement,LiJuan Li,ShuYi Guo; Writing and editing,Jing Chen and XiaoLing Leng;All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJing Chen,JiaLe Liang,Fang Liu, LiJuan Li,ShuYi Guo,XiaoLeng Ling\u003c/p\u003e\n\u003cp\u003eDepartment of Ultrasonography,The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）, Dongguan,Guangdong 523000, China\u003c/p\u003e\n\u003cp\u003eShuLin Zhong\u003c/p\u003e\n\u003cp\u003eDepartment of gynecology,The Tenth Affiliated Hospital，Southern Medical University（Dong guan People's Hospital）, Dongguan,Guangdong 523000, China\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eGuerriero S, Condous G, Rolla M, Pedrassani M, Leonardi M, Hudelist G, Ferrero S, Alcazar JL, Ajossa S, Bafort C, Van Schoubroeck D, Bourne T, Van den Bosch T, Singh SS, Abrao MS, Di Giovanni A, Tomassetti C, Timmerman D. Addendum to consensus opinion from the International Deep Endometriosis Analysis (IDEA) group: sonographic evaluation of superficial endometriosis. Ultrasound Obstet Gynecol. 2025 Oct;66(4):541\u0026ndash;547.\u003c/li\u003e\n\u003cli\u003eZhang J, Pang M, Li L, Guo C. Global, regional, and national burden of endometriosis among women of reproductive age, 1990\u0026ndash;2021: Insights from the global burden of disease study 2021. PLoS One. 2025 Nov 26;20(11):e0337074.\u003c/li\u003e\n\u003cli\u003eAs-Sanie S, Mackenzie SC, Morrison L, Schrepf A, Zondervan KT, Horne AW, Missmer SA. Endometriosis: A Review. JAMA. 2025 Jul 1;334(1):64\u0026ndash;78.\u003c/li\u003e\n\u003cli\u003eSmolarz B, Szyłło K, Romanowicz H. Endometriosis: Epidemiology, Classification, Pathogenesis, Treatment and Genetics (Review of Literature). IntJ Mol Sci. 2021;22(19):10554.\u003c/li\u003e\n\u003cli\u003eAllaire C, Bedaiwy MA, Yong PJ. Diagnosis and management of endometriosis. CMAJ. 2023 Mar 14;195(10):E363-E371.\u003c/li\u003e\n\u003cli\u003eHaylen BT, Vu D. The Retroverted Uterus and Pelvic Floor Dysfunction: 400 BC to 2025 AD. Int Urogynecol J. 2025 Oct;36(10):1951\u0026ndash;1957.\u003c/li\u003e\n\u003cli\u003eSeracchioli R, Raimondo D, Del Forno S, Leonardi D, De Meis L, Martelli V, Arena A, Paradisi R, Mabrouk M. Transvaginal and transperineal ultrasound follow-up after laparoscopic correction of uterine retrodisplacement in women with posterior deep infiltrating endometriosis. Aust N Z J Obstet Gynaecol. 2019 Apr;59(2):288\u0026ndash;293.\u003c/li\u003e\n\u003cli\u003eYoung SW, Jha P, Chami\u0026eacute; L, Rodgers S, Kho RM, Horrow MM, Glanc P, Feldman M, Groszmann Y, Khan Z, Young SL, Poder L, Burnett TL, Hu EM, Egan S, VanBuren W. Society of Radiologists in Ultrasound Consensus on Routine Pelvic US for Endometriosis. Radiology. 2024 Apr;311(1):e232191.\u003c/li\u003e\n\u003cli\u003eMetzler JM, Finger L, Burkhardt T, Hodel ME, Manegold-Brauer G, Imboden S, Pape J, Imesch P, Witzel I, Bajka M. Systematic, noninvasive endometriosis diagnosis in transvaginal sonography by the Swiss Society of Ultrasound in Medicine. Ultraschall Med. 2024 Aug;45(4):367\u0026ndash;388.\u003c/li\u003e\n\u003cli\u003eXholli A, Scovazzi U, Londero AP, Evangelisti G, Cavalli E, Schiaffino MG, Vacca I, Oppedisano F, Ferraro MF, Sirito G, Molinari F, Cagnacci A. Angle of Uterine Flexion and Adenomyosis. J Clin Med. 2022 Jun 4;11(11):3214.\u003c/li\u003e\n\u003cli\u003eDi Donato N, Bertoldo V, Montanari G, Zannoni L, Caprara G, Seracchioli R. Question mark form of uterus: a simple sonographic sign associated with the presence of adenomyosis. Ultrasound Obstet Gynecol. 2015 Jul;46(1):126-7.\u003c/li\u003e\n\u003cli\u003eYoung SW, Jha P, Chami\u0026eacute; L, Rodgers S, Kho RM, Horrow MM, Glanc P, Feldman M, Groszmann Y, Khan Z, Young SL, Poder L, Burnett TL, Hu EM, Egan S, VanBuren W. Society of Radiologists in Ultrasound Consensus on Routine Pelvic US for Endometriosis. Radiology. 2024 Apr;311(1):e232191.\u003c/li\u003e\n\u003cli\u003eMetzler JM, Finger L, Burkhardt T, Hodel ME, Manegold-Brauer G, Imboden S, Pape J, Imesch P, Witzel I, Bajka M. Systematic, noninvasive endometriosis diagnosis in transvaginal sonography by the Swiss Society of Ultrasound in Medicine. Ultraschall Med. 2024 Aug;45(4):367\u0026ndash;388.\u003c/li\u003e\n\u003cli\u003eLiu Y, Zhang W. Association between body mass index and endometriosis risk: a meta-analysis. Oncotarget. 2017 Jul 18;8(29):46928\u0026ndash;46936.\u003c/li\u003e\n\u003cli\u003ePantelis A, Machairiotis N, Lapatsanis DP. The Formidable yet Unresolved Interplay between Endometriosis and Obesity. ScientificWorldJournal. 2021 Apr 20;2021:6653677.\u003c/li\u003e\n\u003cli\u003eRahman MS, Park Y, Hosseinirad H, Shin JH, Jeong JW. The interplay between endometriosis and obesity. Trends Endocrinol Metab. 2025 Dec;36(12):1140\u0026ndash;1153.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-womens-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmwh","sideBox":"Learn more about [BMC Women's Health](http://bmcwomenshealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmwh/default.aspx","title":"BMC Women's Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"endometriosis, pelvic adhesions, ultrasonography, uterine corpus flexion angle, uterine flexion angle, question mark sign","lastPublishedDoi":"10.21203/rs.3.rs-8831280/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8831280/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe current study investigated the correlation between the uterine corpus flexion angle (UCFA) and the severity of endometriosis, evaluated its clinical utility as a novel objective sonographic parameter, and provided an angular definition for the question mark sign.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eThis observational case-control study enrolled 621 women. The participants were then classified into the endometriosis, benign control, and normal groups (n\u0026thinsp;=\u0026thinsp;207 per group). All participants underwent standardized transvaginal ultrasonography. The UCFA and uterine flexion angle (UFA) were measured in the midsagittal plane. The subjective question mark sign was assessed by sonographers. In the endometriosis group, pelvic adhesions were graded intraoperatively. The correlation of the UCFA with the severity of endometriosis and the question mark sign was evaluated via Spearman\u0026rsquo;s correlation, multivariate regression, and receiver operating characteristic curve analyses.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe UCFA progressively increased with a higher revised American Society for Reproductive Medicine stage (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and a greater pelvic adhesion severity (P\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Based on the multivariate analysis, the UCFA was primarily determined by adhesion score (β\u0026thinsp;=\u0026thinsp;0.441). Meanwhile, the UFA was predominantly influenced by baseline uterine position (β\u0026thinsp;=\u0026thinsp;0.508). The optimal cutoff for the sonographic question mark sign was UCFA\u0026thinsp;\u0026ge;\u0026thinsp;220\u0026deg; (area under the curve\u0026thinsp;=\u0026thinsp;0.958). The UCFA had relative stability in the absence of endometriosis, with a median of 179.0\u0026deg; in the benign control group and 178.0\u0026deg; in the normal group.\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eThe UCFA is an objective sonographic marker of endometriosis severity. The proposed criterion of UCFA\u0026thinsp;\u0026ge;\u0026thinsp;220\u0026deg; provides a validated, quantitative definition for the question mark sign, offering a practical tool for standardized ultrasonography assessment and preoperative evaluation.\u003c/p\u003e","manuscriptTitle":"The Uterine corpus Flexion Angle: A Novel and Objective Sonographic Marker for Endometriosis Severity and the Quantification of the Question Mark Sign ","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-04 09:39:39","doi":"10.21203/rs.3.rs-8831280/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-13T07:34:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T17:43:22+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-09T05:46:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"80782830647046458786761624278885099410","date":"2026-05-07T10:46:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"107706146550165706926886537093051952347","date":"2026-05-04T12:49:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T10:35:27+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171030497465934395963758472951812526371","date":"2026-05-04T10:14:13+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"205077193367865041116264021417875978729","date":"2026-05-03T15:06:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"217377913418216004873921797461217304413","date":"2026-05-02T11:45:07+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-22T09:08:37+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-24T12:33:38+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-24T12:28:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-21T07:16:39+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Women's Health","date":"2026-02-21T06:28:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-womens-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"bmwh","sideBox":"Learn more about [BMC Women's Health](http://bmcwomenshealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/bmwh/default.aspx","title":"BMC Women's Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f36a7dd7-31d2-4fd1-8722-70e9c4472361","owner":[],"postedDate":"May 4th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-13T07:34:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-11T17:43:22+00:00","index":59,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-09T05:46:00+00:00","index":58,"fulltext":""},{"type":"reviewerAgreed","content":"80782830647046458786761624278885099410","date":"2026-05-07T10:46:59+00:00","index":57,"fulltext":""},{"type":"reviewerAgreed","content":"107706146550165706926886537093051952347","date":"2026-05-04T12:49:00+00:00","index":56,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-04T10:35:27+00:00","index":55,"fulltext":""},{"type":"reviewerAgreed","content":"171030497465934395963758472951812526371","date":"2026-05-04T10:14:13+00:00","index":54,"fulltext":""},{"type":"reviewerAgreed","content":"205077193367865041116264021417875978729","date":"2026-05-03T15:06:49+00:00","index":51,"fulltext":""},{"type":"reviewerAgreed","content":"217377913418216004873921797461217304413","date":"2026-05-02T11:45:07+00:00","index":50,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2026-05-13T07:42:22+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-04 09:39:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8831280","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8831280","identity":"rs-8831280","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}