Colo-ovarian fistula masquerading as tubo-ovarian abscess: a case report

Abstract

Background: Colo-ovarian fistulas are exceptionally rare complications of diverticulitis, with very few cases documented. Their nonspecific presentation often mimics gynecologic pathology, frequently leading to misdiagnosis and delayed treatment. Currently, there are no standardized guidelines for diagnosis or management of colo-ovarian fistulas. This unique case describes a patient who initially presented with findings suggestive of a tubo-ovarian abscess (TOA), but contrast-enhanced computed tomography (CT) with oral and rectal contrast revealed a colo-ovarian fistula, illustrating a potential diagnostic pathway for this rare condition. Case Description: A 36-year-old woman with no significant medical history presented with left lower quadrant abdominal pain. Initial evaluation at an outside facility suggested a TOA and empiric antibiotics were initiated. Upon transfer, contrast-enhanced CT with oral and rectal contrast revealed a 6.8 cm left adnexal fluid collection containing air, with a fistulous tract connecting the sigmoid colon to the left ovary. Percutaneous drainage was deemed unsafe due to the posterior location of the lesion and surrounding bowel. She underwent robotic-assisted sigmoid colectomy with primary anastomosis and left salpingo-oophorectomy. Intraoperative findings confirmed dense adhesions and purulent material within the ovary. Pathology revealed diverticulitis with colonic perforation and an ovarian abscess containing digested food, confirming colo-ovarian fistula. Postoperatively, she recovered uneventfully, was discharged on postoperative day three, and remained asymptomatic at follow-up, with plans for interval colonoscopy. Conclusions: Colo-ovarian fistulas are rare, diagnostically challenging, and often misidentified as gynecologic pathology. Early recognition with contrast-enhanced CT-including selective use of rectal contrast-may improve diagnostic accuracy and facilitate timely management. Definitive treatment generally requires surgical resection, and multidisciplinary coordination is critical to optimizing outcomes. This case adds to the limited literature by emphasizing both the diagnostic value of rectal contrast and the importance of timely surgical intervention, providing clinicians with an example of a systematic approach to complex pelvic infections.