Intra-Operative Discovery of a 150mm Anterior Vaginal Wall Endometrioma during Repair of a Stage 4 Cystocele

Introduction: The involvement of the anterior vaginal wall by endometriosis is exceedingly rare and may present as an anterior compartment mass simulating a cystocele or urethral diverticulum. Due to its atypical location and broad clinical spectrum, the diagnosis may be difficult and is usually incidentally established during surgery. Case Presentation: A 36-year-old woman, with one previous vaginal delivery, with no significant medical or surgical history, presented for repair of a stage IV cystocele. Intra-operatively, a large cystic lesion of about 150 mm in size was noted between the bladder and the anterior vaginal wall. The mass was completely excised. Leakage of chocolate colored liquid confirmed the presence of endometriosis. The postoperative course was uneventful, and the patient remained asymptomatic at follow-up. Discussion: Literature review showed only a few cases of anterior vaginal wall endometrioma, the majority of which were diagnosed preoperatively on magnetic resonance imaging. Our case is remarkable for its extraordinary size and incidental intraoperative finding. This underscores that a wide differential diagnosis must be maintained when assessing anterior vaginal wall protrusions. Conclusion: Anterior vaginal wall endometrioma is an infrequent presentation of endometriosis that may present as pelvic organ prolapse. Preoperative imaging in atypical or unusually large anterior-compartment lesions may help in avoiding unexpected intraoperative findings.