Figure 14a. Gallstone ileus from cholecystoduodenal fistula. (a) Supine radiograph in a 76-year-old woman shows bowel gas pattern suggestive of small-bowel obstruction, two ectopic calcified gallstones (arrowheads), and air in the biliary tree (arrows). These findings constitute the Rigler triad. (b) Transverse CT scans obtained without intravenous contrast agent in an 85-year-old woman show pneumobilia (arrowheads) and high-grade small-bowel obstruction from an ectopic gallstone (short arrow). Note also orthotopic gallstones (long arrow) with a similar appearance.