Diagnostic Value of Imaging Findings Compared with Pathology in the Diagnosis of Endometriosis

& Objective: Laparoscopic and histological evaluation is the most reliable method for confirming the presence of endometriosis; nevertheless, imaging

may provide useful information. In this study, the diagnostic value of imaging findings for the diagnosis of endometriosis was compared with that of pathology.

& Methods: This cross-sectional study was conducted in Khorramabad, Lorestan, Iran. The imaging results of 118 patients with symptoms of endometriosis who had undergone ultrasound, Computed Tomography (CT) scan, and Magnetic Resonance Imaging (MRI), and who had a positive result suggestive of endometriosis in at least one of the three modalities, were compared with their pathology reports. Additionally, information such as the history of cesarean section, delivery, laparoscopic procedures, marital status, and type of lesion was collected and analyzed.

In this study, the sensitivity of ultrasound for the diagnosis of endometriosis was 93.2%. The sensitivity of MRI for the diagnosis of endometriosis was 98.3%. CT scan had the lowest sensitivity among these three modalities, at 65.8%.

Based on the results of this study, ultrasound and MRI have a remarkable ability to diagnose endometriosis with the least number of false negatives due to their high sensitivity. Given their limited sensitivity and high radiation exposure, the use of CT scans for diagnosing endometriosis in the abdominal and pelvic cavities is not practical.

CT scan, Endometriosis, Imaging, MRI, Ultrasound Received: 2024/04/06 Accepted: 2024/09/15 Published Online: 28 Jun. 2026 Corresponding Information: Mohammad Heidarian, Department of Internal Medicine, School of Medicine, Shahid Rahimi Hospital, Lorestan University of Medical Sciences, Khorramabad, Iran Email: [email protected] Copyright © 2025, This is an original open -access article distributed under the terms of the Creative Commons Attribution-noncommercial 4.0 International License which permits copy and redistribution of the material just in noncommercial usages with proper citation . 1. Introduction Endometriosis arises when endometrial glands and stroma are present outside the uterus (1). Although lesions are typically limited to the pelvis, they can also appear in the bladder, diaphragm, and pleural cavity (2). Although endometriosis is a benign condition, the presence of ectopic endometrial tissue and the inflammation it causes can impair menstruation and

in persistent pelvic discomfort and infertility. The severity of the symptoms may range from minor to severe (3). The precise prevalence of endometriosis in the overall population has not been determined and varies depending on the study population as well as the type of diagnostic approach (clinical or surgical) (4). Nevertheless, endometriosis is estimated to affect 10% of women of reproductive age. The prevalence of endometriosis remains debatable because some patients are asymptomatic or present with vague symptoms, and a definitive diagnosis requires a surgical biopsy (3). Diagnostic laparoscopy and histological confirmation of suspected lesions are the only valid diagnostic methods for endometriosis. However, histological evaluation of endometriosis is not always Arian Karimi Rouzbahani, et al. 714 Volume 11, May 2026 Journal of Obstetrics, Gynecology and Cancer Research reliable (5), because it may be inconclusive for macroscopic or microscopic peritoneal lesions (6). Because surgery is expensive and potentially harmful, non -invasive diagnostic approaches such as imaging and biomarkers are widely used as alternative tools for clinical evaluation (7). A reliable noninvasive test can avoid the need for surgery or limit its use to patients who are most likely to have endometriosis (6). Earlier diagnosis of endometriosis may improve patients’ quality of life by reducing diagnostic delay and allowing timely treatment. Noninvasive imaging modalities such as transvaginal ultrasound and MRI play an important role in the early detection of endometriosis due to their accessibility, safety, and cost-effectiveness (8). Given the importance of imaging modalities in diagnosing endometriosis, we compared the sensitivity of imaging findings, including Computed Tomography (CT) scans, ultrasound, and Magnetic Resonance Imaging (MRI), with the pathology and histological findings of patients with endometriosis. 2. Materials and Methods Study Population The study population consisted of 118 women who were referred between 2018 and 2021 with clinical signs of endometriosis (chronic pelvic pain, dysmenorrhea, painful and palpable abdominal mass, or infertility) and who had undergone different imaging modalities and biopsy for definitive diagnosis. All patient information was kept confidential, and no personal information was included in the study. The ethics code was obtained from the Ethics Committee of Lorestan University of Medical Sciences (IR.LUMS.REC.1400.230). Inclusion and Exclusion Criteria Inclusion criteria included women who were referred to medical centers with clinical signs suggestive of endometriosis, for whom ultrasound, CT scan, and MRI results were available, who had positive imaging findings (in at least one imaging modality), and who had positive pathology results. Subjects without an available pathology report and those who had not undergone imaging with all three modalities were not included. Finally, based on the exclusion criteria, most patients were excluded from the study, and 118 patients were selected. Data Acquisition This study was conducted in Khorramabad, Lorestan Province, Iran. First, a list was prepared of patients with suspected clinical signs of endometriosis who had been referred to the radiology centers of hospitals in Khorramabad for imaging and were diagnose d with endometriosis. To maintain confidentiality, an identification code was assigned to each patient. The patients' demographic information, past medical history, and clinical data were recorded. Imaging information and pathology results were documented separately. Then, the findings of each imaging modality were compared with those of the other modalities as well as with the pathology report of the same patient. Statistical Analysis The data was entered into SPSS statistical software version 22. The sensitivity and specificity of different imaging modalities for the diagnosis of endometriosis were compared with pathological findings. Mann – Whitney and Chi-square tests were used to analyze the data. A P-value of <0.05 was considered statistically significant. 3. Results Patients were analyzed (Figure 1). Descriptive Analysis Results In this study, among 118 patients, the maximum age was 49 years, the minimum age was 15 years, and the mean age of patients with endometriosis was 31.14 years. The number of married patients was 92 (78%). Most of the patients (68.6%) had a history of cesar ean section. A total of 81 patients (68.6%) had a history of diagnostic laparoscopy (Table 1). Imaging Findings All patients had undergone an ultrasound. In 90 patients (76.3%), a transvaginal ultrasound had been performed, and in 28 patients (23.7%), a transabdominal ultrasound had been performed. The most frequently reported disorder on ultrasound was cystic lesions (n=87, 73.7%). In the CT scans of patients, hypodense lesions were reported in 60 cases (50.8%). Based on MRI reports, 92 cases (78%) showed hypersignal lesions in both phases, and 24 cases (20.3%) were hypersignal in T1 and hyposignal in T2. No cases were reported as hyposignal in both phases (Table 2). Pathology Findings In this study, all 118 patients had pathology results confirming endometriosis. The pathology findings demonstrated that 90 patients (71.3%) had ovarian involvement, 38 patients (32.2%) had uterosacral ligament involvement, and 48 patients (40.7%) had cul- de-sac involvement. The results also showed that 13 patients (11%) had cesarean section scar endometriosis. Further information is shown in Table 3. Clinical Findings The clinical findings demonstrated that chronic pelvic pain was the most common symptom, observed in 81 715 Imaging vs Pathology Findings in Endometriosis Volume 11, May 2026 Journal of Obstetrics, Gynecology and Cancer Research patients (68.6%). In all cases, the patients’ pathology

confirmed endometriosis (Table 3). Specificity and Sensitivity Calculation In this study, the sensitivity of ultrasound for the diagnosis of endometriosis was 93.2%. The sensitivity of MRI for the diagnosis of endometriosis was 98.3%. CT scan had the lowest sensitivity among these three modalities, at 65.8%. As the pathology results of all patients were positive for endometriosis and patients with negative results were excluded, the specificity and P-value for the other variables could not be calculated. Table 1. Demographic and clinical characteristics of the patients Characteristic Frequency Percentage Age ≤30 >30 63 55 53.4% 46.6% Marital status Married Single 92 26 78.0% 22.0% Type of birth Cesarean Natural birth 81 37 68.6% 31.4% History of diagnostic laparoscopy No Yes 37 81 31.4% 68.6% Table 2. Imaging findings in the studied patients Imaging modalities Frequency Percentage Ultrasound Transvaginal Transabdominal Cystic lesion Solid lesion Adhesion Normal 90 28 87 16 8 7 76.3% 23.7% 73.7% 13.6% 6.8% 5.9% CT scan Hypodense lesion Hyperdense lesion Normal 60 18 40 50.8% 15.3% 33.9% MRI Hypersignal in T1 and T2 Hypersignal in T1 and hyposignal in T2 Hyposignal in T1 and T2 Normal 92 24 0 2 78% 20.3% 0% 1.7% Arian Karimi Rouzbahani, et al. 716 Volume 11, May 2026 Journal of Obstetrics, Gynecology and Cancer Research Table 3. Pathology and clinical findings of endometriosis patients Pathology and clinical findings Frequency Percentage Ovarian lesion No Yes 28 90 23.7% 76.3% Uterosacal ligament involvement No Yes 80 38 67.8% 32.2% Coldosac's involvement No Yes 70 48 59.3% 40.7% Cesarean’s scar No Yes 105 13% 89% 11% Umbilical involvement No Yes 115 3 97.5% 2.5% Bladder involvement No Yes 117 1 99.2% 0.8% Pelvic wall involvement No Yes 117 1 99.2% 0.8% Palpable mass No Yes 110 8 93.3% 6.6% Chronic pelvic pain No Yes 37 81 31.4% 68.6% 4. Discussion Endometriosis is a relatively common disease that presents a wide range of symptoms (9). The gold standard for its diagnosis is diagnostic laparoscopy, a costly and invasive procedure (10). Another diagnostic approach, imaging, has been proposed as a low -cost, noninvasive alternative that can greatly reduce the need for diagnostic laparoscopy. So far, the findings of several studies that have evaluated the sensitivity and specificity of ima ging have been satisfactory. In this study, we compared the diagnostic outcomes of several imaging modalities with their pathological results in an effort to assess the utility of imaging. In the present study, which was performed on 118 patients, all participants were of reproductive age. Due to the positive pathology results in all patients, it was not possible to determine the specificity in comparison with the imaging methods. On ultraso und, endometriosis usually appears as a multilocular or unilocular cyst with diffuse low-level echoes and a wall with hyperechoic centers (11,12). In this study, 73.7% of patients had cystic lesions. In addition, 13.6% of patients had a solid lesion on ult rasound. Transvaginal ultrasound is typically the first choice for examining patients with signs of endometriosis, persistent pelvic discomfort, or infertility, and its results are comparable to those of MRI (13,14). In this study, transvaginal ultrasound had been performed in 90 patients (76.3%). Ultrasound can also help diagnose abdominal wall endometriosis. Although imaging findings alone cannot confirm endometriosis, combining these findings with the patient’s symptoms, proximity to the surgical scar site, and the association of symptoms with the patient’s menstruation can make the diagnosis of endometriosis more likely (15). In the CT scan reports of patients, 60 cases (50.8%) had hypodense lesions, and 18 cases (15.3%) had 717 Imaging vs Pathology Findings in Endometriosis Volume 11, May 2026 Journal of Obstetrics, Gynecology and Cancer Research hyperdense lesions. Also, in 40 cases (33.9%), a normal CT scan result was reported. According to the findings, the sensitivity of CT scan in the diagnosis of endometriosis was 65.8%. Due to the positive pathology results in all patients, it was impossible to determine the specificity. Considering that all endometriosis lesions were found in the abdominal cavity, the results indicate that the use of CT scan in diagnosing endometriosis in the abdominal cavity is limited. In terms of MRI reports, 92 cases (78%) had hypersignal lesions in both phases, and 24 cases (20.3%) had T1 hypersignal and T2 hyposignal lesions. No cases were reported as hyposignal in both phases. Also, 2 cases (1.7%) did not have any findings on MRI. This study demonstrated that MRI has a sensitivity of 98.3% in the diagnosis of endometriosis. The specificity of this modality could not be calculated due to the positive pathology results in all patients. In other studies, MRI has also shown high sensitiv ity and specificity in diagnosing endometriosis (16). Because the foci of endometriosis have functional properties, they are affected by hormonal changes during menstruation. Endometriosis foci can show different signal intensities on T1- and T2-weighted images, and these differences are related to the duration of bleeding within the lesions. Subacute hemorrhage can appear as very high signal intensity on T1 -weighted images, which is more pronounced on fat -suppressed images. These lesions may appear as low signal intensity on T2- weighted images. In women with chronic endometriosis, reactive fibrosis increases with recurrent bleeding. Fibrotic endometriosis lesions appear as irregular lesions with low signal intensity on both T1- and T2-weighted images. Caref ul evaluation for small foci of high signal intensity on T2 -weighted images, and often on T1 -weighted images, which are related to dilatation of endometrial glands within fibrotic tissue, can be diagnostic because the low signal intensity on T2 -weighted im ages of these lesions is very similar to that of the abdominal wall (17,18). Collectively, our findings suggest that ultrasound and MRI are sensitive modalities for diagnosing endometriosis. These findings, along with the high radiation dose and low sensitivity of CT scans, indicate that the use of CT scans in the diagnostic appr oach to endometriosis of the abdominal and pelvic cavities should be limited. Among the 118 patients, 81 cases (68.6%) had a history of diagnostic laparoscopy, while the others did not. In some patients, more than one site of involvement was present; therefore, the total number of lesions based on the site of involvement is greater than 118. The most common sites of endometriosis are the ovary, the uterosacral ligaments, the ovarian fossa, the pouch of Douglas, and the bladder (19). In our study population of 118 patients, 90 patients (71.3%) had ovarian involvement with endometriosis, while 28 patients (23.7%) had no ovarian involvement. Thirty - eight patients (32.2%) had uterosacral ligament involvement, whereas 80 patients (67.8%) had no involvement of the uterosacral ligaments. Forty -eight patients (40.7%) had cul-de-sac involvement, while 70 patients (59.3%) had no cul -de-sac involvement. In addition, 105 patients (89%) had no endometriosis at the site of the cesarean section, whereas 13 patients (11%) had endometriosis at the cesarean section site. Only three patients (2.5%) had umbilical involvement, while 115 patients (97.5%) had no umbilical involvement. Bladder involvement was observed in only one patient (0.8%). Similarly, only one patient (0.8%) had pelvic wall involvement. In a prospective study of 1101 patients with laparoscopically confirmed endometriosis, the most common sites of endometriosis were the ovary (67%), uterosacral ligament (46%), and ovarian fossa (32%). Deep infiltration has also been reported in 14% of patients with endometriosis (19). In some cases, endometriosis in the anterior wall of the abdomen, especially at the site of a previous surgical incision, has been reported (20). Rarely, endometriosis has also been reported in the breast, pancreas, liver, gallbladder, urethra, vertebrae, etc. Most patients have involvem ent at several sites (3,21). In this study, the ovary, with 71.3% involvement, was the most common site of involvement, while the bladder and pelvic wall, each with about 0.8% involvement, had the lowest frequency. No cases of thoracic endometriosis, diaphragmatic, intestinal, or ureteral involvement were reported in this study. The prevalence of bladder endometriosis was also very low. As described in the literature, bladder involvement in endometriosis has been reported to be very rare (<1%) (22). Transvaginal sonography is recommended as the initial diagnostic method for individuals with signs of deep pelvic endometriosis. Endometriotic cysts can be identified more accurately using transvaginal ultrasound; however, MRI is superior for diagnosing lesions of the torus uterinus, uterosacral ligaments, intestine, and bladder. MRI is also the imaging modality of choice for diagnosing intestinal or rectal nodules, as well as nodules of the rectovaginal septum (23). Moreover, the findings of a meta -analysis indicated that transvaginal ultrasound and MRI have comparable diagnostic value for deep infiltrating endometriosis. This evidence supports the use of transvaginal ultrasound as the first -line modality for detecting endometriosis (16).

The limitation of the present study is the use of data from a single center. Therefore, it is recommended that similar multi-center studies with larger populations be conducted to allow for greater generalizability of the results. 5. Conclusion Arian Karimi Rouzbahani, et al. 718 Volume 11, May 2026 Journal of Obstetrics, Gynecology and Cancer Research Based on the results of this study, ultrasound and MRI have a remarkable ability to diagnose endometriosis with the fewest false negatives due to their high sensitivity. In addition, because of the low sensitivity of CT scans and their high radiation dose, their use in diagnosing endometriosis of the abdominal and pelvic cavities is not recommended. It is recommended that this study be conducted on a larger scale with a greater statistical population so that the

have stronger statistical value. This is because not all types of endometriosis may be observed in a small study population, and there may also be homogeneity in the distribution of pathology results. For a more detailed evaluation of the sensitivity of ultrasound, the results of transvaginal ultrasound should be compared separately with those of transabdominal ultrasound. Finally, it would be beneficial to evaluate MRI results with and without gadolinium in a separate study. 6. Declarations Acknowledgments Not applicable Ethical Considerations This study was approved by the Ethics Committee of Lorestan University of Medical Sciences (IR.LUMS.REC.1400.230). Written informed consent was obtained from all participants before inclusion in the study. All procedures were conducted in accordance with t he ethical standards of the Declaration of Helsinki. Authors' Contributions AKR contributed to data collection; GM and MAKT contributed to drafting the manuscript; SNC contributed to data collection; MB and MKS critically revised the manuscript; and MH conceptualized the study and finalized the manuscript. All authors read and approved the final version of the manuscript. Conflict of Interest The authors attest that they have no conflict of interest to declare. Fund or Financial Support This research received no specific grant from any funding agency in the public, commercial, or not -for- profit sectors. 1. Mohebbi A, Hojati V, Zolbin MM, Aflatoonian R. Histopathologic evaluation of the inflammatory factors and stromal cells in endometriosis lesions: a case‑control study. Int J Reprod Biomed. 2022;20 (10):819‑30. [doi:10.18502/ijrm.v20i10.12266] 2. Salari S, Coyne K, Flyckt R. Deep Infiltrating Endometriosis: Diagnosis and Fertility -Sparing Management in the ART Patient. In: Lindheim, S.R., Petrozza, J.C. (eds) Reproductive Surgery. Springer, Cham ; 2022. p.251‑67. [doi:10.1007/978-3-031-05240-8_20] 3. Schenken RS. Endometriosis: pathogenesis, clinical features, and diagnosis. Waltham (MA): Wolters Kluwer Health; 2016. 4. Laufer MR, Barbieri RL, Blake D. Endometriosis in adolescents: diagnosis and treatment. UpToDate. Waltham (MA): UpToDate Inc.; 2016. 5. Martire FG, Russo C, Selntigia A, Nocita E, Soreca G, Lazzeri L, et al. Early non‑invasive diagnosis of endometriosis: dysmenorrhea and specific ultrasound findings are important indicators in young women. Fertil Steril. 2023;119(3):455-64. [doi:10.1016/j.fertnstert.2022.12.004] 6. Kiesel L, Sourouni M. Diagnosis of endometriosis in the 21st century. Climacteric. 2019;22(3):296‑302. [doi:10.1080/13697137.2019.1578743] 7. Chacko N & Ankri, R. Non-invasive early-stage cancer detection: current methods and future perspectives. Clin Exp Med . 2025;25(1):17. [doi:10.1007/s10238-024-01513-x] 8. Very JC, Knox S, Deslandes A, Leonardi M, Lo G, Wang H, et al. Imagendo Study Group. Noninvasive diagnostic imaging for endometriosis part 2: a systematic review of recent developments in magnetic resonance imaging, nuclear medicine and computed tomography. Fertil Steril. 2024;121(2):189-211. [doi:10.1016/j.fertnstert.2023.12.017] 9. Nouri B, Arab M, Nasiri M. Endometriosis: clinical, magnetic resonance imaging and pathologic findings. J Obstet Gynecol Cancer

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