Imaging Findings in Symptomatic Appendiceal Endometriosis: A Systematic Review of Case Reports

Context: Imaging is crucial in evaluating women with suspected appendiceal endometriosis (AE), as the condition often mimics acute or chronic appendicitis and presents a diagnostic challenge. While modalities like ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) can help identify abnormalities, their findings are frequently nonspecific. Therefore, awareness of imaging features is essential for accurate diagnosis and management, though definitive confirmation still relies on histopathological examination after surgical excision. O bjectives: The present study aimed to review and investigate imaging findings in symptomatic AE.

This systematic review was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. PubMed, Scopus, Web of Science, CINAHL Plus, and the Cochrane Library were searched using keywords including appendix, endometriosis, MRI, transvaginal sonography (TVS), and transrectal high intensity focused US. Studies were included if they reported imaging findings in symptomatic AE. Exclusion criteria were randomized controlled trials, controlled case studies, review articles, cohort studies, systematic reviews, conference abstracts, articles without full text, and non- English language articles. Study selection and data extraction were performed independently by two reviewers. The quality of included case reports was independently assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist for case reports.

Twenty-six out of the total number of patients who underwent CT (30) had positive findings (86.6%), while 7 out of the total number of patients who underwent MRI (11) and 11 out of the total number of patients who underwent sonography (13) also had positive findings (63.6% and 84.6%, respectively). The mean age of the patients was 37.2 ± 7.07 years. Out of the total sample, 8 patients were pregnant. The overall imaging findings were: Normal (6 cases, 15%), wall thickening (9 cases, 22.5%), mass (15 cases, 37.5%), cystic mass (1 case, 2.5%), solid lesion in the left ovary (1 case, 2.5%), mucocele (3 cases, 7.5%), intussusception (4 cases, 10%), obstruction (5 cases, 12.5%), suspected obstruction (1 case, 2.5%), appendicitis (4 cases, 10%), fluid (11 cases, 27.5%), and abscess (3 cases, 7.5%).

Right lower quadrant (RLQ) mass and bowel wall thickening are the most commonly reported findings in patients with AE. Further studies are required to retrospectively evaluate the imaging findings of the appendix in pathologically confirmed AE after pelvic surgery. Keywords:Appendiceal Endometriosis,Bowel Endometriosis,Deep Endometriosis,Transvaginal Sonography,Computed Tomography,Magnetic Resonance Imaging,MR Enterography 1. Context Endometriosis is a chronic inflammatory condition characterized by the growth of endometrium-like epithelium and/or stroma outside the uterus. It affects approximately 2 - 10% of women in the general population and could be seen in up to 50% of women with fertility problems (1). The most common symptoms of endometriosis include dysmenorrhea, dyspareunia, menorrhagia, and infertility (2). Deep infiltrating endometriosis (DIE) is endometrium-like tissue lesions in the abdomen, extending on or under the peritoneal Shakki Katouli F et al. Brieflands 2 I J Radiol. 2025; 22(2): e142342 surface, usually in nodular form, with the ability to invade adjacent structures, and in association with fibrosis and disruption of normal anatomy (3). This is the most severe type of endometriosis, which can involve the intestines and urinary tract, leading to severe symptoms in patients. Appendiceal endometriosis (AE) is a rare site of DIE. In the literature, AE prevalence is highly variable (from 0.2% to 39%) based on the study population. Among patients undergoing appendectomy for suspected acute appendicitis, the prevalence of AE has been reported as 2.67%. The type and severity of endometriosis may influence AE prevalence; rates of 11.6% in women with superficial endometriosis and 39.0% in those with DIE have been reported (4, 5). The symptoms of AE can mimic those of acute or chronic appendicitis. Preoperative imaging diagnosis is challenging, and AE is often diagnosed after appendectomy on histopathological examination. Bowel obstruction, bowel intussusception, bowel habit disturbance, cyclic acute abdominal symptoms, and positive occult blood test/colonoscopy are other reported symptoms of AE. Timely, accurate imaging assessment is essential as endometriosis has a heterogeneous presentation and a substantial impact on quality of life (6-11). Noninvasive imaging methods such as transvaginal sonography (TVS) and magnetic resonance imaging (MRI) can help determine the exact location and spread of endometriosis. In addition, magnetic resonance enterography (MRE) can assist particularly in the detection of bowel DIE and surgical planning in cases with multiple lesions. Laparoscopic surgery is the preferred approach for surgical planning and treatment of endometriosis, and appendectomy may be performed when appendiceal involvement is suspected (5, 12-20). Accurate preoperative imaging assessment of symptomatic AE is essential for selecting the most appropriate treatment through precise disease mapping. In this review, we focus on the imaging findings of AE in symptomatic patients to highlight the utility of imaging modalities in timely and accurate preoperative diagnosis. 2. O bjectives The present systematic review aimed to review and collect the imaging abnormalities associated with symptomatic AE confirmed by histopathology, and to describe detection patterns by modality to aid in preoperative planning. 3. Methods 3.1. Study Design This systematic review adhered to the preferred reporting items for systematic reviews and meta- analyses (PRISMA) guidelines. Given the rarity of symptomatic AE, we included case reports to capture detailed imaging findings. Additionally, we aimed to include case series and observational studies to enhance data richness, though no suitable comparative studies were identified during screening. 3.2. Search Strategy We conducted a comprehensive literature search across five databases: PubMed, Scopus, Web of Science, CINAHL Plus, and the Cochrane Library. The search included combinations of the following terms: "appendix", "endometriosis", "magnetic resonance imaging", "transvaginal sonography", and "transrectal high-intensity focused ultrasound". Boolean operators were used to refine search queries. Filters were applied to include only English-language articles with full text available, published up to 2024. The proposed search strategy is as follows: PubMed (Title/Abstract): (“appendix” AND “endometriosis”) AND (MRI OR “magnetic resonance imaging”) OR (“transvaginal sonography”) OR (“transrectal high-intensity focused ultrasound”)). 3.3. Eligibility Criteria We included studies that reported imaging findings in symptomatic patients diagnosed with AE and provided histopathological confirmation of diagnosis. We excluded randomized controlled trials, review articles, cohort studies, and systematic reviews, conference abstracts, non-English articles, and studies without full-text availability. 3.4. Study Selection and Data Extraction Two reviewers independently screened titles/abstracts using Covidence software. Discrepancies were resolved through discussion. Full-text articles of potentially relevant studies were reviewed to determine Shakki Katouli F et al. Brieflands I J Radiol. 2025; 22(2): e142342 3 eligibility. Out of 494 initial records, 128 duplicates were removed. After title and abstract screening, 323 records were excluded. Following full-text review, 39 studies (comprising 40 cases) were included. Data extracted included study characteristics, patient demographics, imaging modalities used, imaging findings, and treatment outcomes. Extracted data were managed using Excel. 3.5. Risk of Bias and Quality Assessm ent The quality of included case reports was assessed using the Joanna Briggs Institute (JBI) critical appraisal checklist for case reports. Each case was evaluated for completeness in patient history, diagnostic methods, and outcome reporting. Risk of bias was considered based on clarity of imaging interpretation, potential confounding conditions, and consistency with histopathological findings. 3.6. Data Analysis Given the nature of case reports, data were analyzed descriptively. Frequencies and percentages were calculated for imaging modalities and findings. No statistical tests were conducted due to the absence of comparative or quantitative data. 3.7. Protocol Registration This review was registered with PROSPERO (Registration No.: CRD42022335388) and approved by the ethics committee (IR.TUMS.IKHC.REC.1401.094). These steps ensure transparency, credibility, and adherence to ethical standards in the research process, aligning with best practices in systematic reviews and academic research as highlighted in the provided sources. 4. Results From 39 studies, we identified 40 cases of symptomatic AE with reported imaging findings. The mean patient age was 37.2 years (SD ± 7.07). Of the 40 patients, 8 (20%) were pregnant. An overview of the included studies and patient characteristics is summarized in Table 1. 4.1. Clinical Presentation The most frequent symptom was abdominal pain, particularly in the RLQ, reported in 77.5% of cases. Other common symptoms included vomiting (42.5%), nausea (30%), abdominal tenderness (55%), and bowel obstruction (20%). Less frequent symptoms included bowel habit disturbance (10%), dysmenorrhea (15%), and fever (5%). The clinical symptoms observed among patients are detailed in Table 2. Table 2. Summary of Main Clinical Symptoms Clinical sym ptom s No. (%) Bowel obstruction 8 (20) Bowel intussusception 2 (5) Bowel habit disturbance 4 (10) Cyclic sym ptom s 1 (2.5) Abdom inal pain 31 (77.5) Pelvic pain 1 (2.5) Abdom inal tenderness 22 (55) Abdom inal distension 10 (25) Guarding 7 (17.5) Fluid accum ulation 5 (12.5) Diarrhea 6 (15) Constipation 3 (7.5) Nausea 12 (30) Vom iting 17 (42.5) Anorexia 4 (10) Fever 2 (5) Leukocytosis 11 (27.5) Dysm enorrhea 6 (15) Irregular bleeding 4 (10) 4.2. Im aging M odalities 1. Computed tomography (n = 30): Positive findings were seen in 26 patients (86.6%). Common findings included RLQ mass, appendiceal wall thickening, and ascites or free fluid. 2. Magnetic resonance imaging (n = 11): Positive findings were seen in 7 patients (63.6%). Key features included RLQ mass with signal heterogeneity, wall thickening, and nodular lesions with T2 hypointensity. 3. Ultrasound (n = 13): Positive findings were seen in 11 patients (84.6%), identifying features like wall thickening, mass, and signs of intussusception. Of the 40 patients included in this review, 14 underwent more than one imaging modality, which enabled cross-modality comparison of findings in a subset of cases. 4.3. Com parative Im aging Trends Among imaging findings: Shakki Katouli F et al. Brieflands 4 I J Radiol. 2025; 22(2): e142342 - Right lower quadrant mass was most commonly detected by MRI (54.54%) and CT (33.33%). - Appendiceal wall thickening was seen across all modalities but most frequently in CT (26.67%). - Magnetic resonance imaging identified unique soft tissue characteristics, useful for differentiating endometriosis from other pathologies. - Sonography remained useful in initial assessment, especially in pregnant patients. A comparative analysis of imaging findings across modalities is shown in Table 3. Table 3. Detailed Comparison of Imaging Findings by Sonography, Computed Tomography, and Magnetic Resonance Imaging a Im aging findings Sonography (n = 13) CT (n = 30) MRI (n = 11) Wall thickening 3 (23.07) 8 (26.67) 1 (9.09) Mass 2 (15.38) 10 (33.33) 6 (54.54) Cystic m ass 0 (0.00) 0 (0.00) 0 (0.00) Solid lesion in the left ovary 0 (0.00) 1 (3.33) 0 (0.00) Mucocele 1 (7.69) 2 (6.66) 1 (9.09) Intussusception 2 (15.38) 3 (10.00 2 (18.18) O bstruction 0 (0.00) 4 (13.33) 1 (9.09) Suspected bowel obstruction 0 (0.00) 1 (3.33) 0 (0.00) Appendicitis 1 (7.69) 2 (6.66) 0 (0.00) Fluid 2 (15.38) 7 (23.33) 0 (0.00) Abscess 0 (0.00) 2 (6.66) 1 (9.09) Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging. a Values are expressed as No. (%). 4.4. Interpretation Across imaging techniques, RLQ mass and wall thickening emerged as the most consistent findings suggestive of AE. The MRI, due to its soft tissue resolution, added value in identifying concurrent pelvic endometriosis lesions. These trends support MRI as the modality of choice in complex or inconclusive cases, while CT remains the workhorse in acute settings. Sonography complements both but is limited in specificity. This synthesis improves our understanding of imaging findings in a rare condition and provides guidance for diagnosis and surgical planning. 5. Discussion Despite advances in medical and surgical treatment, women with DIE experience significant impairment in quality of life (60). Endometriosis of the appendix presenting with acute appendicitis is rare and accounts for less than 1% of all appendiceal pathologies that can resemble the clinical picture of acute appendicitis (61). Patients with cyclic bowel symptoms, chronic RLQ pain, and severe endometriosis are at a higher risk for developing AE. However, in our study, only 55% of patients were known cases of endometriosis who presented with abdominal tenderness (62). Despite none of the patients having definitive imaging findings of endometriosis before surgery, retrospective evaluation of MRI in patients suggested findings in favor of AE, including: Concomitant hypo- intense T1 and T2 nodularity along the terminal ileum serosal surface, hypo-intense T1 and T2 mass in the cecal base and appendix orifice, and skipped DIE lesions in the rectum and rectosigmoid. In 2023, Medeiros et al. conducted a systematic review on the accuracy of MRI for DIE and reported that MRI has a high sensitivity and specificity for the detection of intestinal endometriosis [pooled sensitivity of 0.84 (95% CI 0.78 - 0.88) and specificity of 0.97 (95% CI 0.94 - 0.98)] (63). These findings suggest that careful evaluation of pelvic MRI in women of reproductive age with RLQ symptoms could help suggest the preoperative imaging findings of AE and provide patients with benefits from non-surgical treatments. It should be noted that in some conditions, differentiation of AE in nodular form is impossible from a carcinoid tumor, and definitive diagnosis often relies on surgical and histopathological findings. In 2020, Aas-Eng et al. in Norway reviewed the literature on endometriosis imaging, focusing on TVS and MRI for DIE and adenomyosis. The study suggested that TVS and MRI are reliable methods for diagnosing endometriosis, adenomyosis, and especially DIE. The information obtained from these imaging methods can assist physicians in planning surgery and estimating its risks. Therefore, the use of TVS and MRI should be the first step in the imaging findings and treatment of endometriosis patients (16). In 2020, Indrielle-Kelly et al. conducted a prospective observational study to investigate the accuracy of TVS and MRI in identifying pelvic DIE. The study included 49 out of 111 patients who underwent imaging with these two methods to plan surgical treatment. Both methods had similar sensitivity and specificity in identifying lesions of the upper rectum and rectosigmoid. The TVS had lower sensitivity and more specificity than MRI in evaluating the bladder, uterosacral ligament, vagina, Shakki Katouli F et al. Brieflands I J Radiol. 2025; 22(2): e142342 5 rectovaginal septum, and pelvis in general. MRI was significantly superior to TVS in identifying lesions in the uterosacral ligament. The study concluded that the use of both methods is useful in identifying pelvic DIE (62). Bazot et al. conducted a study in 2020 to review the use of MRI in diagnosing DIE involving the small intestine, including its protocols, indications, technical requirements, patient preparation, and criteria. According to the study, MRI should be used as the second-line tool after TVS for evaluating endometriosis in the rectosigmoid colon. It is also recommended to use MRI before surgery to determine the stage of the disease. In addition, MR-enterography should be performed to check for ileocecal and appendicular lesions (63). The RLQ mass and appendiceal wall thickening were the most common imaging findings in our review. In addition, RLQ mass was the most frequent MRI finding. Although the exact prevalence and accuracy of imaging findings in AE are not defined in the literature, the reported imaging findings include: An enlarged appendix involved by hypodense soft tissue masses, luminal dilation or focal nodules within the appendiceal body in CT, and discrete serosal hyperintense foci on pre-contrast fat-saturated T1 images to nodular lesions that appear hypointense on T2 images, occupying the tip or body of the appendix, luminal obstruction resembling an appendiceal mucocele on MRI (64). The imaging findings of AE causing acute appendicitis can be challenging, as it is often mistaken for other diseases. In cases of acute appendicitis, the exact cause is not always clear but is often attributed to infection or obstruction. Although endometriosis is a relatively common disease in women of reproductive age, isolated involvement of the appendix is rare. The

of our study suggest that CT and MRI are the preferred modalities for detecting RLQ pathologies in patients with underlying endometriosis, particularly MRI because of the higher soft tissue resolution and ability to detect concomitant endometriotic lesions in both pelvic and extrapelvic locations (65). The RLQ mass, bowel intussusception, mucocele, and bowel wall thickening were the most prevalent reported findings in MRI (66). The bowel wall thickening, obstruction, appendicitis, and free fluid were the most prevalent reported findings in CT. A major limitation of our review is the absence of eligible observational studies or case series, primarily due to the rarity of symptomatic AE, which reduces the generalizability and strength of the synthesized findings. Our systematic search did not identify any analytical studies containing sufficient cases for inclusion. Even hypothetically, if such studies existed, their descriptive findings would likely focus broadly on clinical outcomes rather than detailed imaging-specific data, potentially introducing heterogeneity and interpretational bias. In conclusion, RLQ mass and bowel wall thickening are the most commonly reported findings in patients with AE. The MRI appears to be a useful modality in patients suspected of appendicitis and has the added benefit of detecting other foci of pelvic or abdominal endometriosis. We recommend the use of MRI in clinical settings where endometriosis complications are suspected. Further studies are required to retrospectively evaluate the imaging findings of the appendix in pathologically confirmed AE, particularly in patients undergoing pelvic surgery. Footnotes Authors' Contribution: F. S. K. conceived and designed the assessments and drafted the manuscript. S. T. participated in designing the assessments and contributed to the statistical analysis and drafting of the manuscript. A. A. and R. Y. re-evaluated the clinical data, revised the manuscript, performed statistical analysis, and revised the manuscript. P. R. F., F. A., L. B., and H. Q. collected and interpreted the clinical data. J. Z. and F. S. K. re-analyzed the clinical and statistical data and revised the manuscript. All authors read and approved the final manuscript. Conflict of Interests Statem ent: The authors declare no conflict of interests. Data Availability: The protocol registration number for the study is CRD42022335388 on PROSPERO, a key platform for registering systematic reviews. Ethical Approval: The present study received approval from the ethics committee with the reference number of IR.TUMS.IKHC.REC.1401.094 . Shakki Katouli F et al. Brieflands 6 I J Radiol. 2025; 22(2): e142342 Funding/Support: The present study received no funding/support.

1. Andres MP, Arcoverde FVL, Souza CCC, Fernandes LFC, Abrao MS, Kho RM. Extrapelvic Endometriosis: A Systematic Review. J M inim Invasive Gynecol. 2020;27(2):373-89. [PubMed ID: 31618674]. https://doi.org/10.1016/j.jmig.2019.10.004. 2. Tomassetti C, Johnson NP, Petrozza J, Abrao MS, International Working Group of Aagl EE; Esge Eshre Wes. An International Terminology for Endometriosis, 2021. Facts Views Vis Obgyn. 2021;13(4):295-304. [PubMed ID: 34672510]. [PubMed Central ID: PMC9148705]. https://doi.org/10.52054/FVVO.13.4.036. 3. Yovich JL, Rowlands PK, Lingham S, Sillender M, Srinivasan S. Pathogenesis of endometriosis: Look no further than John Sampson. Reprod Biom ed Online. 2020;40(1):7-11. [PubMed ID: 31836436]. https://doi.org/10.1016/j.rbmo.2019.10.007. 4. Mabrouk M, Raimondo D, Mastronardi M, Raimondo I, Del Forno S, Arena A, et al. Endometriosis of the Appendix: When to Predict and How to Manage-A Multivariate Analysis of 1935 Endometriosis Cases. J M inim Invasive Gynecol. 2020;27(1):100-6. [PubMed ID: 30849476]. https://doi.org/10.1016/j.jmig.2019.02.015. 5. Allahqoli L, Mazidimoradi A, Momenimovahed Z, Gunther V, Ackermann J, Salehiniya H, et al. Appendiceal Endometriosis: A Comprehensive Review of the Literature. Diagnostics (Basel). 2023;13(11). [PubMed ID: 37296678]. [PubMed Central ID: PMC10253163]. https://doi.org/10.3390/diagnostics13111827. 6. Berlanda N, Somigliana E, Frattaruolo MP, Buggio L, Dridi D, Vercellini P. Surgery versus hormonal therapy for deep endometriosis: is it a choice of the physician? Eur J Obstet Gynecol Reprod Biol. 2017;209:67-71. [PubMed ID: 27544308]. https://doi.org/10.1016/j.ejogrb.2016.07.513. 7. Rolla E. Endometriosis: advances and controversies in classification, pathogenesis, diagnosis, and treatment. F1000Res. 2019;8. [PubMed ID: 31069056]. [PubMed Central ID: PMC6480968]. https://doi.org/10.12688/f1000research.14817.1. 8. Okeke TC, Ikeako LC, Ezenyeaku CC. Endometriosis. Niger J M ed. 2011;20(2):191-9. 9. Moulder JK, Siedhoff MT, Melvin KL, Jarvis EG, Hobbs KA, Garrett J. Risk of appendiceal endometriosis among women with deep- infiltrating endometriosis. Int J Gynaecol Obstet. 2017;139(2):149-54. [PubMed ID: 28755505]. https://doi.org/10.1002/ijgo.12286. 10. Taylor HS. Endometriosis: a complex systemic disease with multiple manifestations. Fertil Steril. 2019;112(2):235-6. [PubMed ID: 31280952]. https://doi.org/10.1016/j.fertnstert.2019.06.006. 11. Chen RJ, Kerdemelidis P, Wijeratne S. Appendiceal endometriosis: a challenging diagnosis. ANZ J Surg. 2020;90(9):1810-2. [PubMed ID: 31943679]. https://doi.org/10.1111/ans.15699. 12. Jeong DH, Jeon H, Adkins K. Appendiceal endometriosis: a greater mimicker of appendicitis. Hong Kong M ed J. 2019;25(6):492-3. [PubMed ID: 32127505]. https://doi.org/10.12809/hkmj187654. 13. Feldhaus DJ, Harris RK, Dayal SD. Appendiceal Endometriosis Presenting as Possible Cecal Mass. Am Surg. 2020;86(11):1528-30. [PubMed ID: 32683922]. https://doi.org/10.1177/0003134820933606. 14. Shen AY, Stanes A. Isolated Appendiceal Endometriosis. J Obstet Gynaecol Can. 2016;38(10):979-81. [PubMed ID: 27720099]. https://doi.org/10.1016/j.jogc.2016.06.006. 15. Parra RS, Feitosa MR, Biagi GBB, Brandao DF, Moraes M, Silvestre L, et al. Neuroendocrine appendiceal tumor and endometriosis of the appendix: a case report. J M ed Case Rep. 2020;14(1):152. [PubMed ID: 32921300]. [PubMed Central ID: PMC7489048]. https://doi.org/10.1186/s13256-020-02490-x. 16. Aas-Eng MK, Montanari E, Lieng M, Keckstein J, Hudelist G. Transvaginal Sonographic Imaging and Associated Techniques for Diagnosis of Ovarian, Deep Endometriosis, and Adenomyosis: A Comprehensive Review. Sem in Reprod M ed. 2020;38(2-03):216-26. [PubMed ID: 33232986]. https://doi.org/10.1055/s-0040-1718740. 17. Mittal KR, Thornton CT, Tamirisa NP. Endometriosis of the appendix: comprehensive review of literature. J Surg Educ. 2006;63:395-9. 18. Logman I, Westergaard JG, Graversen HP. Endometriosis foci in the muscle, serosa, and subserosa of the subserous area. Fertil Steril. 1988;49:654-7. 19. Yela DA, Quagliato IP, Benetti-Pinto CL. Quality of Life in Women with Deep Endometriosis: A Cross-Sectional Study. Rev Bras Ginecol Obstet. 2020;42(2):90-5. [PubMed ID: 32227324]. [PubMed Central ID: PMC10316839]. https://doi.org/10.1055/s-0040-1708091. 20. Emre A, Akbulut S, Yilmaz M, Bozdag Z. An unusual cause of acute appendicitis: Appendiceal endometriosis. Int J Surg Case Rep. 2013;4(1):54-7. [PubMed ID: 23124069]. [PubMed Central ID: PMC3537945]. https://doi.org/10.1016/j.ijscr.2012.07.018. 21. Akagi T, Yamamoto S, Kobayashi Y, Fujita S, Akasu T, Moriya Y, et al. A case of endometriosis of the appendix with adhesion to right ovarian cyst presenting as intussusception of a mucocele of the appendix. Surg Laparosc Endosc Percutan Tech. 2008;18(6):622-5. [PubMed ID: 19098675]. https://doi.org/10.1097/SLE.0b013e318180f67f. 22. Teiga E, Radosevic A, Sánchez J, Busto M, Aguilar G, Maiques J, et al. A rare case of right lower quadrant pain. BJR Case Rep. 2019;5(2). https://doi.org/10.1259/bjrcr.20170024. 23. Drumond JPN, de Melo ALA, Germini DE, Morrell AC. Acute Appendicitis Secondary to Appendiceal Endometriosis. Case Rep Surg. 2020;2020:8813184. [PubMed ID: 33101752]. [PubMed Central ID: PMC7569452]. https://doi.org/10.1155/2020/8813184. 24. Slesser AA, Sultan S, Kubba F, Sellu DP. Acute small bowel obstruction secondary to intestinal endometriosis, an elusive condition: a case report. W orld J Em erg Surg. 2010;5:27. [PubMed ID: 20846366]. [PubMed Central ID: PMC2949747]. https://doi.org/10.1186/1749-7922-5- 27. 25. Al-Talib A. Appendiceal Endometriosis. Saudi Journal of M edicine and M edical Sciences. 2013;1(2). https://doi.org/10.4103/1658-631x.123645. 26. Lebastchi AH, Prieto PA, Chen C, Lui FY. Appendiceal endometriosis in a pregnant woman presenting with acute perforated appendicitis. J Surg Case Rep. 2013;2013(12). [PubMed ID: 24968435]. [PubMed Central ID: PMC3888003]. https://doi.org/10.1093/jscr/rjt104. 27. Lainas P, Dammaro C, Rodda GA, Morcelet M, Prevot S, Dagher I. Appendiceal endometriosis invading the sigmoid colon: a rare entity. Int J Colorectal Dis. 2019;34(6):1147-50. [PubMed ID: 30666405]. https://doi.org/10.1007/s00384-019-03242-0. 28. Lopez MPJ, Chan V, Melendres MF, Lutanco R. Appendiceal intussusception from endometriosis. BM J Case Rep. 2021;14(6). [PubMed ID: 34158326]. [PubMed Central ID: PMC8220524]. https://doi.org/10.1136/bcr-2021-241592. Shakki Katouli F et al. Brieflands I J Radiol. 2025; 22(2): e142342 7 29. Marin MR, Parra Banos PA, Gonzalez Valverde FM, Moncada JR, Arenas MFC, Martinez MM, et al. Appendiceal Intussusception Resulting from Endometriosis Presenting as Acute Appendicitis. Am Surg. 2010;76(8):906-8. [PubMed ID: 28958241]. 30. Trefois C, Coche E. Appendiceal Intussusception Secondary to Endometriosis: A Rare Etiology of Right Lower Quadrant Abdominal Pain. J Belg Soc Radiol. 2022;106(1):34. [PubMed ID: 35600761]. [PubMed Central ID: PMC9075099]. https://doi.org/10.5334/jbsr.2739. 31. Gupta AK, Mann A, Belizon A. Appendicitis Caused by Endometriosis Within the Bowel Wall. Cureus. 2020. https://doi.org/10.7759/cureus.9614. 32. Bekki T, Fukuda T, Moriuchi T, Namba Y, Okimoto S, Mukai S, et al. Appendicitis with submucosal fecalith mimicking a submucosal tumor: a case report. Surg Case Rep. 2021;7(1):105. [PubMed ID: 33905033]. [PubMed Central ID: PMC8079595]. https://doi.org/10.1186/s40792-021-01169-9. 33. Basso MP, Christiano AB, Oliveira ALCD, Cunrath GS, Netinho JG. Appendicular endometriosis as a cause of chronic abdominal pain alone in the right iliac fossa: case report and literature review. J Coloproctol (Rio de Janeiro). 2012;32(1):79-82. https://doi.org/10.1590/s2237-93632012000100012. 34. Gupta R, Singh AK, Farhat W, Ammar H, Azzaza M, Mizouni A, et al. Appendicular endometriosis: A case report and review of literature. Int J Surg Case Rep. 2019;64:94-6. [PubMed ID: 31622934]. [PubMed Central ID: PMC6796600]. https://doi.org/10.1016/j.ijscr.2019.07.046. 35. Alizadeh Otaghvar H, Hosseini M, Shabestanipour G, Tizmaghz A, Sedehi Esfahani G. Cecal endometriosis presenting as acute appendicitis. Case Rep Surg. 2014;2014:519631. [PubMed ID: 25126441]. [PubMed Central ID: PMC4120490]. https://doi.org/10.1155/2014/519631. 36. Hakoda K, Yoshimitsu M, Miguchi M, Kohashi T, Egi H, Ohdan H, et al. Characteristic findings of appendicular endometriosis treated with single incision laparoscopic ileocolectomy: Case report. Int J Surg Case Rep. 2020;67:9-12. [PubMed ID: 31991379]. [PubMed Central ID: PMC7076268]. https://doi.org/10.1016/j.ijscr.2019.12.039. 37. Nojkov B, Duffy MC, Amin M, Cappell MS. Colonic endometriosis presenting as a sigmoid stricture requiring laparoscopic colonic surgery for diagnosis and treatment. Dig Dis Sci. 2013;58(11):3368-73. [PubMed ID: 23907335]. https://doi.org/10.1007/s10620-013-2771-1. 38. Millochau JC, Abo C, Darwish B, Huet E, Dietrich G, Roman H. Continuous Amenorrhea May Be Insufficient to Stop the Progression of Colorectal Endometriosis. J M inim Invasive Gynecol. 2016;23(5):839- 42. [PubMed ID: 27130533]. https://doi.org/10.1016/j.jmig.2016.04.008. 39. Tsunemitsu A, Tsutsumi T, Ikura Y. Deciduosis of the Appendix During Pregnancy. Intern M ed. 2021;60(10):1641-4. [PubMed ID: 33361675]. [PubMed Central ID: PMC8188025]. https://doi.org/10.2169/internalmedicine.5960-20. 40. Curbelo-Pena Y, Guedes-De la Puente X, Saladich-Cubero M, Molinas- Bruguera J, Molineros J, De Caralt-Mestres E. Endometriosis causing acute appendicitis complicated with hemoperitoneum. J Surg Case Rep. 2015;2015(8). [PubMed ID: 26253154]. [PubMed Central ID: PMC4528180]. https://doi.org/10.1093/jscr/rjv097. 41. Choi JDW, Yunaev M. Endometriosis of the appendix causing small bowel obstruction in a virgin abdomen. BM J Case Rep. 2019;12(7). [PubMed ID: 31337629]. [PubMed Central ID: PMC6663186]. https://doi.org/10.1136/bcr-2019-230496. 42. Khairy GA. Endometriosis of the appendix: a trap for the unwary. Saudi J Gastroenterol. 2005;11(1):45-7. [PubMed ID: 19861847]. https://doi.org/10.4103/1319-3767.33337. 43. Zhu MY, Fei FM, Chen J, Zhou ZC, Wu B, Shen YY. Endometriosis of the duplex appendix: A case report and review of the literature. W orld J Clin Cases. 2019;7(15):2094-102. [PubMed ID: 31423443]. [PubMed Central ID: PMC6695541]. https://doi.org/10.12998/wjcc.v7.i15.2094. 44. Karaman K, Pala EE, Bayol U, Akman O, Olmez M, Unluoglu S, et al. Endometriosis of the terminal ileum: a diagnostic dilemma. Case Rep Pathol. 2012;2012:742035. [PubMed ID: 22997597]. [PubMed Central ID: PMC3446655]. https://doi.org/10.1155/2012/742035. 45. Terada T. Endometriosis of the Vermiform Appendix Presenting as a Tumor. Gastroenterol Res. 2009;2(6):353. https://doi.org/10.4021/gr2009.12.1330. 46. Alatise OI, Sabageh D, Ogunniyi SO, Olaofe OO. Ileal endometriosis presenting as acute small intestinal obstruction: a case report. W est Afr J M ed. 2010;29(5):352-5. [PubMed ID: 21089025]. 47. Yaghi M, Nassar H, Zadeh C, Faraj W. Incidental appendiceal mass as the only manifestation of endometriosis. BM J Case Rep. 2021;14(2). [PubMed ID: 33619136]. [PubMed Central ID: PMC7903092]. https://doi.org/10.1136/bcr-2020-239090. 48. Zenger S, Bilgic C, Bugra D. Laparoscopic partial cecum resection in appendiceal intussusception. Turk J Surg. 2019;35(1):74-7. [PubMed ID: 32550307]. [PubMed Central ID: PMC6791683]. https://doi.org/10.5578/turkjsurg.3633. 49. Lee WY, Noh JH. Leiomyomatosis peritonealis disseminata associated with appendiceal endometriosis: a case report. J M ed Case Rep. 2015;9:167. [PubMed ID: 26215629]. [PubMed Central ID: PMC4532259]. https://doi.org/10.1186/s13256-015-0637-1. 50. Tsuda M, Yamashita Y, Azuma S, Akamatsu T, Seta T, Urai S, et al. Mucocele of the appendix due to endometriosis: a rare case report. W orld J Gastroenterol. 2013;19(30):5021-4. [PubMed ID: 23946611]. [PubMed Central ID: PMC3740436]. https://doi.org/10.3748/wjg.v19.i30.5021. 51. Porter J, Eisdorfer J, Yi C, Nguyen C. Multifocal abdominal endometriosis, a case report. J Surg Case Rep. 2020;2020(6):rjaa120. [PubMed ID: 32595921]. [PubMed Central ID: PMC7303103]. https://doi.org/10.1093/jscr/rjaa120. 52. Morotti M, Camerini G, Biscaldi E, Remorgida V, Ferrero S. Pre- Operative Evaluation of an Appendiceal Mucocele in a Woman with Endometriosis. J Endom etriosis Pelvic Pain Disorders. 2013;5(3):120-2. https://doi.org/10.5301/je.5000160. 53. Shichiri K, Nishida K, Lefor AK, Kubota T. Preoperative hormonal therapy for a patient with appendiceal endometriosis. BM J Case Rep. 2021;14(11). [PubMed ID: 34764095]. [PubMed Central ID: PMC8587620]. https://doi.org/10.1136/bcr-2021-245667. 54. How R, Wikiel KJ, Hamad GG. Right lower quadrant pain during pregnancy. JAM A Surg. 2014;149(5):489-90. [PubMed ID: 24671308]. https://doi.org/10.1001/jamasurg.2013.1686. 55. Miyakura Y, Kumano H, Horie H, Lefor AT, Yasuda Y, Yamaguchi T, et al. Rupture of appendiceal mucocele due to endometriosis: report of a case. Clin J Gastroenterol. 2012;5(3):220-4. [PubMed ID: 26182324]. https://doi.org/10.1007/s12328-012-0302-9. 56. Kobayashi K, Yamadera M, Takeo H, Murayama M. Small bowel obstruction caused by appendiceal and ileal endometriosis: a case report. J Surg Case Rep. 2022;2022(6):rjac282. [PubMed ID: 35721264]. Shakki Katouli F et al. Brieflands 8 I J Radiol. 2025; 22(2): e142342 [PubMed Central ID: PMC9200432]. https://doi.org/10.1093/jscr/rjac282. 57. Koyama R, Aiyama T, Yokoyama R, Nakano S. Small Bowel Obstruction Caused by Ileal Endometriosis with Appendiceal and Lymph Node Involvement Treated with Single-Incision Laparoscopic Surgery: A Case Report and Review of the Literature. Am J Case Rep. 2021;22. e930141. [PubMed ID: 33755660]. [PubMed Central ID: PMC8006474]. https://doi.org/10.12659/AJCR.930141. 58. Sali PA, Yadav KS, Desai GS, Bhole BP, George A, Parikh SS, et al. Small bowel obstruction due to an endometriotic ileal stricture with associated appendiceal endometriosis: A case report and systematic review of the literature. Int J Surg Case Rep. 2016;23:163-8. [PubMed ID: 27153232]. [PubMed Central ID: PMC5022069]. https://doi.org/10.1016/j.ijscr.2016.04.025. 59. Iwamuro M, Tanaka T, Sugihara Y, Harada K, Hiraoka S, Kondo Y, et al. Two Cases of Endometriosis in the Cecum Detected by Contrast- enhanced Computed Tomography with Air/Carbon Dioxide Insufflation. Intern M ed. 2021;60(11):1697-701. [PubMed ID: 33390498]. [PubMed Central ID: PMC8222140]. https://doi.org/10.2169/internalmedicine.6418-20. 60. Chamie LP, Ribeiro D, Tiferes DA, Macedo Neto AC, Serafini PC. Atypical Sites of Deeply Infiltrative Endometriosis: Clinical Characteristics and Imaging Findings. Radiographics. 2018;38(1):309- 28. [PubMed ID: 29320327]. https://doi.org/10.1148/rg.2018170093. 61. Medeiros LR, Rosa MI, Silva BR, Reis ME, Simon CS, Dondossola ER, et al. Accuracy of magnetic resonance in deeply infiltrating endometriosis: a systematic review and meta-analysis. Arch Gynecol Obstet. 2015;291(3):611-21. [PubMed ID: 25288268]. https://doi.org/10.1007/s00404-014-3470-7. 62. Indrielle-Kelly T, Fruhauf F, Fanta M, Burgetova A, Lavu D, Dundr P, et al. Diagnostic Accuracy of Ultrasound and MRI in the Mapping of Deep Pelvic Endometriosis Using the International Deep Endometriosis Analysis (IDEA) Consensus. Biom ed Res Int. 2020;2020:3583989. [PubMed ID: 32083128]. [PubMed Central ID: PMC7011347]. https://doi.org/10.1155/2020/3583989. 63. Bazot M, Kermarrec E, Bendifallah S, Darai E. MRI of intestinal endometriosis. Best Pract Res Clin Obstet Gynaecol. 2021;71:51-63. [PubMed ID: 32653334]. https://doi.org/10.1016/j.bpobgyn.2020.05.013. 64. Guerriero S, Saba L, Pascual MA, Ajossa S, Rodriguez I, Mais V, et al. Transvaginal ultrasound vs magnetic resonance imaging for diagnosing deep infiltrating endometriosis: systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2018;51(5):586-95. [PubMed ID: 29154402]. https://doi.org/10.1002/uog.18961. 65. Chaar CI, Wexelman B, Zuckerman K, Longo W. Intussusception of the appendix: comprehensive review of the literature. Am J Surg. 2009;198(1):122-8. [PubMed ID: 19249733]. https://doi.org/10.1016/j.amjsurg.2008.08.023. 66. de Bree E, Schoretsanitis G, Melissas J, Christodoulakis M, Tsiftsis D. Acute intestinal obstruction caused by endometriosis mimicking sigmoid carcinoma. Acta Gastroenterol Belg. 1998;61(3):376-8. [PubMed ID: 9795475]. Shakki Katouli F et al. Brieflands I J Radiol. 2025; 22(2): e142342 9 Table 1. Characteristics of Included Case Reports of Appendiceal Endometriosis a No Article title Country First author Patient age Clinical characteristics Reasons for inclusion in this review (case features) Pregnancy status 1 A Case of Endometriosis of the Appendix with Adhesion to Right Ovarian Cyst Presenting as Intussusception of a Mucocele of the Appendix Japan Akagi (21) 35 Intussusception, ovarian cyst adhesion Symptomatic AE, intussusception No 2 A Rare Case of Lower Quadrant Pain Portugal Eduardo (22) 40 RLQ pain Symptomatic AE, RLQ pain No 3 Acute Appendicitis Secondary to Appendiceal Endometriosis Brazil Drumond (23) 32 Acute appendicitis Symptomatic AE, acute appendicitis No 4 Acute Small Bowel Obstruction Secondary to Intestinal Endometriosis, an Elusive Condition: A Case Report United Kingdom Slesser (24) 33 Small bowel obstruction Symptomatic AE, small bowel obstruction No 5 Appendiceal Endometriosis Saudi ArabiaA. Al-Talib (25) 31 Endometriosis of the appendix Symptomatic AE, abdominal pain No 6 Appendiceal Endometriosis in a Pregnant Woman Presenting with Acute Perforated Appendicitis United States Lebastchi (26) 33 Acute perforated appendicitis Symptomatic AE, acute perforated appendicitis Yes 7 Appendiceal Endometriosis Invading the Sigmoid Colon: A Rare Entity France Lainas (27) 41 Endometriosis invading sigmoid colon Symptomatic AE, sigmoid colon involvement No 8 Appendiceal Intussusception from Endometriosis PhilippinesLopez (28) 39 Intussusception due to endometriosis Symptomatic AE, intussusception No 9 Appendiceal Intussusception Resulting from Endometriosis Presenting as Acute Appendicitis Spain Marin (29) 29 Acute appendicitis due to intussusception Symptomatic AE, acute appendicitis No 10 Appendiceal Intussusception Secondary to Endometriosis: A Rare Etiology of Right Lower Quadrant Abdominal Pain Belgium Trefois (30) 30 RLQ pain Symptomatic AE, RLQ pain No 11 Appendicitis Caused by Endometriosis Within the Bowel Wall United States Gupta (31) 36 Appendicitis due to bowel wall endometriosis Symptomatic AE, appendicitis No 12 Appendicitis with Submucosal Fecalith Mimicking a Submucosal Tumor: A Case Report Japan Bekki (32) 40 Submucosal fecalith Symptomatic AE, appendicitis No 13 Appendicular Endometriosis as a Cause of Chronic Abdominal Pain Alone in the Right Iliac Fossa: Case Report and Literature Review Brazil Basso (33) 44 Chronic abdominal pain Symptomatic AE, chronic abdominal pain No 14 Appendicular Endometriosis: A Case Report and Review of Literature India Gupta (34) 35 Endometriosis of the appendix Symptomatic AE, abdominal pain No 15 Cecal Endometriosis Presenting as Acute Appendicitis Iran Alizadeh Otaghvar (35) 43 Acute appendicitis Symptomatic AE, acute appendicitis No 16 Characteristic Findings of Appendicular Endometriosis Treated with Single Incision Laparoscopic Ileocolectomy: Case Report Japan Hakoda (36) 51 Laparoscopic treatment of appendicular endometriosis Symptomatic AE, laparoscopic findings No 17 Colonic Endometriosis Presenting as a Sigmoid Stricture Requiring Laparoscopic Colonic Surgery for Diagnosis and Treatment United States Nojkov (37) 29 Sigmoid stricture due to endometriosis Symptomatic AE, sigmoid stricture No 18 Continuous Amenorrhea May Be Insufficient to Stop the Progression of Colorectal Endometriosis France Millochau (38) 26 Amenorrhea related to endometriosis Symptomatic AE, amenorrhea No 19 Deciduosis of the Appendix During Pregnancy Japan Tsunemitsu (39) 35 Deciduosis during pregnancy Symptomatic AE, pregnancy-related symptoms Yes 20 Endometriosis Causing Acute Appendicitis Complicated with Hemoperitoneum Spain Curbelo (40) 39 Acute appendicitis with hemoperitoneum Symptomatic AE, acute appendicitis No 21 Endometriosis of the Appendix Causing Small Bowel Obstruction in a Virgin Abdomen Australia Choi (41) 29 Small bowel obstruction Symptomatic AE, bowel obstruction No 22 Endometriosis of the Appendix: A Trap for the Unwary Saudi ArabiaKhairy (42) 33 Endometriosis of the appendix Symptomatic AE, abdominal pain No 23 Endometriosis of the Duplex Appendix: A Case Report and Review of the Literature China Zhu (43) 44 Duplex appendix with endometriosis Symptomatic AE, duplex appendix No 24 Endometriosis of the Terminal Ileum: A Diagnostic Dilemma Turkey Karaman (44) 27 Diagnostic challenges in terminal ileum Symptomatic AE, ileal symptoms No 25 Endometriosis of the Vermiform Appendix Presenting as a Tumor Japan Terada (45) 41 Tumor-like presentation of AE Symptomatic AE, tumor- like symptoms No 26 Ileal Endometriosis Presenting as Acute Small Intestinal Obstruction: A Case Report Nigeria Alatise (46) 34 Small intestinal obstructionSymptomatic AE, intestinal obstruction No 27 Incidental Appendiceal Mass as the Only Manifestation of Endometriosis Lebanon Yaghi (47). 34 Incidental finding of appendiceal mass Symptomatic AE, incidental findings No 28 Laparoscopic Partial Cecum Resection in Appendiceal Intussusception Turkey Zenger (48) 35 Laparoscopic treatment of intussusception Symptomatic AE, intussusception No 29 Leiomyomatosis Peritonealis Disseminata Associated Shakki Katouli F et al. Brieflands 10 I J Radiol. 2025; 22(2): e142342 No Article title Country First author Patient age Clinical characteristics Reasons for inclusion in this review (case features) Pregnancy status with Appendiceal Endometriosis: A Case Report South Korea Lee (49) 31 Endometriosis with leiomyomatosis Symptomatic AE, leiomyomatosis No 30 Mucocele of the Appendix due to Endometriosis: A Rare Case Report Japan Tsuda (50) 43 Appendiceal mucocele Symptomatic AE, mucocele No 31 Multifocal Abdominal Endometriosis: A Case Report United States Porter (51) 52 Multifocal presentation of endometriosis Symptomatic AE, multifocal symptoms No 32 Preoperative Evaluation of an Appendiceal Mucocele in a Woman with Endometriosis Italy Morotti (52) 35 Preoperative assessment of mucocele Symptomatic AE, mucocele assessment No 33 Preoperative Hormonal Therapy for a Patient With Appendiceal Endometriosis Japan Shichiri (53) 40 Hormonal therapy prior to surgery Symptomatic AE, hormonal therapy No 34 Lower Quadrant Pain During Pregnancy United States How (54) 26 RLQ pain during pregnancy Symptomatic AE, pregnancy-related pain Yes 35 Rupture of Appendiceal Mucocele due to Endometriosis: Report of a Case Japan Miyakura (55) 56 Ruptured appendiceal mucocele Symptomatic AE, ruptured mucocele No 36 Small Bowel Obstruction Caused by Appendiceal and Ileal Endometriosis: A Case Report Japan Kobayashi (56) 37 Small bowel obstruction due to endometriosis Symptomatic AE, bowel obstruction No 37 Small Bowel Obstruction Caused by Ileal Endometriosis with Appendiceal and Lymph Node Involvement Treated with Single-Incision Laparoscopic Surgery: A Case Report and Review of the Literature Japan Koyama (57) 40 Small bowel obstruction with lymph node involvement Symptomatic AE, lymph node involvement No 38 Small Bowel Obstruction due to an Endometriotic Ileal Stricture with Associated Appendiceal Endometriosis: A Case Report and Systematic Review of the Literature India Sali (58) 44 Endometriotic ileal stricture Symptomatic AE, ileal stricture No 39 Two Cases of Endometriosis in the Cecum Detected by Contrast-Enhanced Computed Tomography with Air/Carbon Dioxide Insufflation Japan Iwamuro (59) 40 and 40 Endometriosis in the cecum Symptomatic AE, cecal symptoms No Abbreviations: AE, appendiceal endometriosis; RLQ, right lower quadrant. a Because all included items are case reports, study-level inclusion criteria do not apply. This table lists review-level eligibility (symptomatic AE, histopathologic confirmation, and sufficient clinical/imaging/surgical detail). No exclusion criteria were prespecified; all case reports meeting these features were included.