A 72-year-old woman presents with 3 days of colicky central abdominal pain, distension, and bilious vomiting. She has no previous surgeries. Plain abdominal X-ray shows dilated small bowel loops, a calcified opacity in the right iliac fossa, and branching gas lucencies projected over the liver. The most likely diagnosis is:

• A Adhesive small bowel obstruction
• B Gallstone ileus due to cholecystoduodenal fistula ✓
• C Caecal carcinoma with obstruction
• D Emphysematous cholecystitis with paralytic ileus

Explanation

This is Rigler's triad: pneumobilia, small bowel dilation, and an ectopic radio-opaque gallstone, diagnostic of gallstone ileus. A large stone erodes through an inflamed gallbladder into the duodenum, forms a cholecystoduodenal fistula, and impacts typically at the narrow terminal ileum. Adhesive obstruction cannot occur without prior surgery, caecal carcinoma gives large bowel dilation rather than pneumobilia, and emphysematous cholecystitis produces gas in the gallbladder wall, not branching intrahepatic duct gas.

Reference: Sabiston Textbook of Surgery, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.