Rigler triad — small bowel obstruction, pneumobilia and an ectopic gallstone — seen together on CT; the fistula (usually cholecystoduodenal) and a second stone determine the operation.
Orient first
- Elderly patients with chronic cholecystitis; the stone erodes through a cholecystoenteric fistula and impacts in the distal ileum.
- Only a minority of stones are calcified enough to see on radiographs; CT sees most.
- Another stone upstream causes recurrence if missed.
Acquire the study
- Portal venous phase CT with coronal reformats; lung window for biliary gas.
The manoeuvre
- Follow the dilated loops to the transition point; the stone sits there (rim-calcified or laminated).
- Lung window: gas in the gallbladder and bile ducts.
- Gallbladder: collapsed, thick-walled, adherent to the duodenum — the fistula.
- Search the upstream small bowel and stomach for a second stone.
What confirms it
- Small bowel obstruction with an ectopic gallstone at the transition point, with pneumobilia or a cholecystoenteric fistula.
What licenses you to exclude it
- An obstruction with no intraluminal stone at the transition point and no pneumobilia excludes gallstone ileus.
The classic misread
- An isodense stone at the transition read as a faecal pellet.