Objective: Gallstones are a rare cause of duodenal or gastric outlet obstruction and therefore are not commonly suspected. Rigler's radiographic triad of pneumobilia, bowel obstruction, and an ectopic gallstone is seen in few of these patients. The symptoms are insidious and nonspecific, and the diagnosis is usually made radiologically. Although CT scans are far more sensitive, 25% of cases are still missed, often because the size of the offending gallstone is underestimated.
Conclusion: Better assessment of stone size, and therefore higher accuracy of diagnosis, could be achieved if attention is paid to more subtle but nonetheless important signs. These include compressed air in dependent areas of the duodenal lumen, an area of soft-tissue rather than fluid density surrounding the calcified rim of the stone, and a faint radiolucency in or beyond this soft-tissue area that could represent laminations of fat or air in the stone.