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Figure 1. Two large gallstones obstructing the sigmoid colon.

Figure 2. Two large gallstones following transanal extraction.

Gallstone ileus is caused by the erosion of a gallstone (usually >2.5 cm in diameter) into the intestinal lumen via a cholecystenteric fistula (Figure 2). Most commonly, it erodes into the duodenum, but occasionally can erode into the stomach or colon.¹

As the gallstone passes down the length of the intestinal tract, it intermittently obstructs the lumen, producing characteristic waxing and waning of symptoms, consistent with small-bowel obstruction. The stone frequently becomes lodged at the ileocecal valve, resulting in complete small-bowel obstruction.^1- 2

Gallstone ileus represents a true mechanical obstruction rather than a defect in motility. The median age at onset is greater than 70 years, and most patients are women (M:F, 1.0:3.5). Gallstone ileus is the cause of intestinal obstruction in fewer than 1% of patients younger than 70 years but it accounts for nearly 25% of cases of intestinal obstruction in patients older than 70 years.^1- 2

The diagnosis of gallstone ileus remains challenging, as it is correctly diagnosed in only 43% of patients prior to operation.¹ Although symptoms are typical of mechanical intestinal obstruction, including abdominal cramps, vomiting, and abdominal distention, these signs and symptoms are present in only 50% to 70% of patients. Only a few patients have symptoms suggestive of acute cholecystitis, and about 50% have a history of gallstones. Liver function tests are abnormal in 40% of these patients but overt jaundice is rare. Abdominal radiographs demonstrate an intestinal gas pattern compatible with intestinal obstruction, and pneumobilia is present in approximately half of all affected patients.^1- 2 The aberrant gallstone will be visible in few plain film radiographs. Ultrasonography is useful in demonstrating air in the biliary tract and may identify the presence of a fistula.²

Treatment is primarily surgical. Propulsion of the stone into the large intestine or enterotomy and stone extraction should be performed. The fistula should not be addressed at the time of initial surgery, as morbidity and mortality are significantly higher when repair is undertaken in the setting of acute bowel obstruction.^1- 3

In unusual cases where the gallstone obstructs the colon, stricture or cancer must be excluded because most gallstones will pass without difficulty.¹ In our patient, the obstruction was at the level of the sigmoid colon, and transanal extraction was performed.

Corresponding author: Alberto Madrid, MD, Department of Surgery, Lyndon B. Johnson Hospital, 5656 Kelley St, Suite 30S62008, Houston, TX 77026.