Teaching Case

A 69-year-old lady presented with a two-day history of severe upper abdominal pain and vomiting. She had no significant past medical history.

A CT scan of the abdomen and pelvis was performed with 100 ml of intravenous iodinated contrast medium and images acquired in the portal venous phase.
Pneumobilia was noted (Fig. 1). Further the CT scan demonstrated gas within the gallbladder and significant inflammatory changes around the first and second part of duodenum. In addition a soft tissue density track extending from the gallbladder to the duodenum, in keeping with a cholecysto-duodenal fistula and the gallstone which had eroded into the duodenum were also identified (Fig. 2). Based on these findings a diagnosis of Bouveret’s syndrome was made. Subsequently the patient underwent endoscopy, during which a duodenogram confirmed the presence of the gallstone within the duodenal cap (Fig. 3). The stone was crushed and removed at endoscopy. The patient is currently awaiting surgery.

Bouveret’s syndrome is a rare condition with a significant morbidity and mortality [1, 2]. In 1896, Leon Bouveret reported 2 cases presenting with gastric outlet obstruction due to large gallstones [3]. This condition occurs as a complication of gallstone disease, wherein a gallstone fistulates from the gallbladder into the duodenum forming a cholecysto-duodenal fistula [4]. In the majority of patients with biliary-enteric fistula, the gallstones pass without causing bowel obstruction. But occasionally they get impacted in the duodenum or the pylorus, which leads to gastric outlet obstruction presenting with sudden onset of abdominal pain with or without jaundice and vomiting.
On plain abdominal radiograph, the Rigler triad of bowel obstruction, pneumobilia, and ectopic gallstones is specific for gallstone ileus but is seen in only 30–35% of patients [5] because the majority of gallstones is not calcified and therefore not visible. This triad of findings, however, is more often apparent on CT, which is an effective imaging technique in this clinical setting.
Several studies have suggested that the best imaging modality is CT [6, 7, 8]. However there are a few drawbacks of CT as 15–25% of gallstones are iso-attenuating relative to bile or fluid. MRCP may be useful in such cases because it clearly delineates fluid from calculi, which appear as signal voids against the high-signal fluid. MRCP can also directly depict the cholecysto-duodenal fistula if sufficient fluid is present [7]. A subgroup of these patients is not picked up on CT often because of underestimation of stone size. A higher accuracy can be achieved by paying attention to pick up subtle signs on CT to assess stone size correctly [9]. Fluoroscopic contrast examination can confirm diagnosis in suspected cases by directly revealing a large filling defect in the duodenal bulb [7].