EP426 - Rare Presentation of Urachal Abscess and Urachal-Sigmoid Fistula in an Adult with Diverticular Disease

Purpose/Background: The urachus is an embryologic remnant connecting the allantois to the fetal bladder, which involutes after birth to form the median umbilical ligament. In adults, urachal disease may present atypically, often limited to nonspecific abdominal pain; therefore, it should remain a consideration in the differential diagnosis. We present a case of a urachal abscess with a fistulous connection to the sigmoid colon in an adult male with diverticular disease.

Methods/Interventions: A 58-year-old male with a past medical history of gastroesophageal reflux disease, coronary artery disease, status post percutaneous coronary intervention to the right coronary artery in 2017, and a prior episode of diverticulitis requiring hospitalization presented to the emergency department with severe mid-abdominal and epigastric pain. The pain was unrelated to food intake and not associated with nausea, vomiting, fever, pneumaturia, fecaluria, or urinary tract infections. The initial work up including right upper quadrant ultrasound and HIDA scan did not reveal a suspected gallbladder pathology and subsequently CT Abdomen/Pelvis revealed a 4.5 × 5.7 cm urachal abscess with a fistulous connection to the sigmoid colon. A CT-guided abscess drainage was performed, with purulent output demonstrating Escherichia coli and Bacteroides fragilis on final cultures. The patient’s symptoms improved following drainage and intravenous antibiotic therapy with a plan for elective sigmoid resection and takedown of the urachal-sigmoid fistula. Patient underwent an uncomplicated robotic sigmoid resection and takedown of urachal remnant under enhanced recovery after surgery pathway with an uncomplicated course and was discharged on post-operative day 3. The pathology demonstrated chronic diverticulitis with microperforation and urachal remnant.

Results/Outcomes: Incomplete obliteration of urachus during childhood may lead to one of four recognized urachal anomalies: patent urachus, urachal cyst, urachal sinus, or urachal diverticulum. Urachal fistulae involving the colon are uncommon, with only few urachal-sigmoid fistula cases described in the literature. In the present case, chronic inflammation and localized infection from diverticulitis contributed to fistulization into a preexisting urachal remnant, resulting in abscess formation and fistulous communication with the sigmoid colon. Management aligned with the standard approach for complicated diverticulitis is based on intravenous antibiotics, interventional radiology–guided drainage, and planned elective surgical resection. Complete excision of the urachal remnant is recommended and supported by urological society guidelines to prevent recurrence and mitigate the risk of malignant transformation, which has been reported in chronically inflamed urachal remnants.

Conclusion/Discussion: This case highlights the rare occurrence, characteristic imaging findings, and multidisciplinary management of a urachal-sigmoid fistula associated with diverticulitis in an adult. Given the minimal number of reported cases, continued documentation of similar presentations is crucial to enhance recognition, inform diagnostic evaluation, and optimize management of this rare condition.

Urachal Abscess in Diverticular Disease


Saggital view of urachal abscess in diverticular disease