Biliary ascites due to spontaneous biliary duct perforation is a rare case presentation usually seen in the paediatric age group of 6-36 months. We are presenting the case of a 14-month-old baby with abdominal distention associated with abdominal pain, vomiting, fever, and a history of no passage of stools. Upon examination, the abdomen was tense and tender. On radiological investigations, gross free fluid was present in the abdominal cavity along with bowel obstruction and partial situs inversus of the spleen and stomach. The bowel obstruction was relieved by rectal stimulation, after which oral feeds were well tolerated. Bilious fluid was found on diagnostic paracentesis, confirming the diagnosis. The patient was managed further by broad-spectrum antibiotics and drainage of the free fluid. The management ranges from conservative treatment to Roux-en-Y anastomosis. A non-surgical diagnosis is uncommonly seen and helps improve the patient\'s prognosis if detected early. This case report highlights the importance of early diagnosis and non-surgical treatment modality in critical patients.

BACKGROUND: Situs inversus viscerum, a congenital condition in which the visceral organs are a mirror image of their normal physiological positions, could be total or partial. Persistent descending mesocolon (PDM) is a congenital anomaly that is asymptomatic because of its short length. PDM causing intestinal obstruction is a known clinical complication.
METHODS: A 74-year-old woman presented with pneumaturia and enteruria for two months, and recurrent cystitis for a month. An enhanced computed tomography (CT) showed air in the bladder along with sigmoid colonic diverticula adherent to it, suspecting a fistula. The CT also showed partial situs inversus with the common hepatic artery, and left colic artery arising abnormally from the superior mesenteric artery (SMA). Minimally invasive endoscopic closure using the over-the-scope clipping system was difficult because of thickening and scar tissue due to chronic inflammation from diverticulitis. Thus, a sigmoidectomy was performed to close the fistula. Intraoperatively, we noted an abnormally fixed descending mesocolon. An emergency reoperation was performed on the sixth postoperative day owing to an anastomotic leak. Suture failure was attributed to these congenital abnormalities due to insufficient blood flow from an absent marginal vessel and a high endocolonic pressure by adhesions. Sigmoid colon re-resection and maturation of an ileostomy was performed. The patient had no specific postoperative complications, and the ileostomy was closed after three months.
CONCLUSIONS: We report an extremely rare case of colovesical fistula due to a PDM in a patient having partial situs inversus with abnormal branches originating from the SMA.