An unusual cause of a vesical mass: Small bowel diverticulum presenting with a bladder fistula: A case report and review of the literature

RATIONALE: Small intestinal diverticulum is rare (<5% incidence) and often asymptomatic. Its presentation as a bladder mass mimicking tumor, leading to vesico-enteric fistula, is exceptionally uncommon. This case highlights the diagnostic challenge and potential for misdiagnosis. PATIENT CONCERNS: A 35-year-old woman presented with a complex clinical course spanning 4 surgical interventions over 20 months. Initial symptoms included urinary frequency, urgency, dysuria, and persistent right lower quadrant abdominal pain. Recurrent "bladder tumors" were noted on serial cystoscopies, and the patient experienced expulsion of flocculent, particulate matter during micturition postoperatively. DIAGNOSIS: Dynamic cystoscopy revealed a mass protruding through a bladder wall defect when the bladder was empty and retracting when filled. Laparoscopic exploration confirmed a 3 × 3 cm small bowel diverticulum located 20 cm proximal to the ileocecal valve, adherent to the bladder with a 1 × 1 cm fistula. Histopathology showed chronic inflammation of the diverticulum and reactive nephrogenic adenoma-like hyperplasia in the bladder mucosa, with no evidence of malignancy. INTERVENTIONS: The patient underwent combined laparoscopic diverticulectomy and two-layer bladder fistula repair with omental flap interposition. Intraoperative frozen section of the bladder edge confirmed chronic inflammation with glandular metaplasia, negative for malignancy. OUTCOMES: Postoperative recovery was uneventful. At 3-month follow-up, cystoscopy showed a healed fistula site with no recurrence, and computed tomography enterography revealed no residual diverticulum or fistula. The patient's symptoms completely resolved. LESSONS: Small bowel diverticulum can masquerade as recurrent bladder tumor over multiple surgeries. Key diagnostic clues include the dynamic protrusion/retraction phenomenon with bladder filling status and flocculent material in urine. Persistent "recurrent" bladder masses with atypical features warrant consideration of enteric sources. Multidisciplinary collaboration between urology and general surgery was essential for definitive diagnosis and management.