A 70-year-old woman presents with colicky abdominal pain, distension, and bilious vomiting. Plain abdominal X-ray shows dilated small bowel loops, and CT demonstrates air within the biliary tree and a calcified structure in the distal ileum. What is the most likely underlying mechanism?

• A Gallstone erosion through a cholecystoduodenal fistula with impaction in the terminal ileum ✓
• B Migration of an ingested foreign body through the ileocaecal valve
• C Intussusception of a benign polyp at the duodenojejunal flexure
• D Ischaemic stricture of the jejunum following previous vascular surgery

Explanation

This is gallstone ileus. A large stone erodes through the gallbladder wall into the duodenum, forms a cholecystoduodenal fistula, and impacts typically at the narrow terminal ileum or ileocaecal valve. The classic imaging combination of pneumobilia, small bowel obstruction, and an ectopic calcified stone constitutes Rigler's triad. Foreign body migration and jejunal strictures do not explain pneumobilia, and intussusception would show a target sign rather than intraluminal gas.

Reference: Bailey and Love's Short Practice of Surgery, 28th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.