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Figure 1. Computed tomographic scan of the abdomen demonstrates the obstructing stone in the sigmoid colon.

Figure 2. Intraoperative sigmoid colon enterotomy and gallstone extraction.

Gallstone ileus accounts for only 1% to 3% of cases of intestinal obstruction, but the rate rises to 25% in patients older than 65 years.¹ Meanwhile, intestinal obstruction is a complication in only 0.3% to 0.5% of all cases of cholelithiasis.² Gallstone ileus with colonic obstruction is very rare, accounting for 2% to 8% of all cases of gallstone ileus since Courvoisiers' original article in 1890.³

Gallstone ileus is most commonly seen in conjunction with a cholecystoduodenal fistula but may be associated (in decreasing incidence) with cholecystogastric, cholecystocolic, and cholecystoduodenocolic fistulas.¹ Elderly women in their sixth or seventh decade of life are most commonly affected. The incidence of concomitant disease with gallstone ileus is high, with many series reporting diabetes, cardiovascular disease, and morbid obesity in 50% to 60% of patients.²

Most patients with cholecystocolic fistulae exhibit vomiting, watery diarrhea, and abdominal pain. Bilious vomiting is characteristic of high obstruction, whereas feculent vomiting and abdominal distension are more prominent in ileal obstruction. Most cases of intestinal obstruction occur in the terminal ileum. In patients with incomplete bowel obstruction, the symptoms are intermittent, as the stone lodges at various levels, characterized as "tumbling obstruction."² Physical examination may indicate abdominal distension, muscle guarding, dehydration, and the presence of concurrent disease. Jaundice is uncommon.² Laboratory studies are usually nonspecific but reflect dehydration and electrolyte imbalance due to intestinal obstruction.²

A fistula forms when the gallbladder ruptures into one of the surrounding adherent viscera or when a large gallstone causes pressure necrosis of the gallbladder wall, leading to perforation. Under these circumstances, gallstones that exceed 2.5 cm may cause large-bowel obstruction most commonly at the sigmoid colon, where there is often underlying diverticular disease.³

The signs of gallstone ileus on plain abdominal radiography are (1) pneumobilia or air in the bilary tree (75% of cases); (2) evidence of partial or complete intestinal obstruction; and (3) with the aid of contrast media, direct or indirect evidence of an obstructing stone in the intestine.² Contrast imaging is essential for delineating the fistulous connections and locating the level of obstruction. Computed tomographic imaging may show pneumobilia and gallstone impaction at the point of obstruction (Figure 1).

Gallstone ileus requires emergency enterolithotomy (Figure 2) to relieve the obstruction. However, concomitant surgery to the cholecystocolic fistula is discouraged on the basis that subsequent symptoms of weight loss, malabsorption, and cholangitis are rare. Furthermore, a minimalist approach is recommended in these patients, who are often elderly and debilitated.²

Recurrent obstruction occurs in 3% to 5% of cases, prompting consideration of single-stage cholelithotomy, cholecystectomy, and exteriorization of the fistula as a diverting colostomy.⁴ However, relief of obstruction should be the primary goal, leaving definitive fistula surgery for the elective setting, where the morbidity of the disease must be weighed against the hazards of surgical repair.³

Corresponding author: Gerrard O'Donoghue, AFRCSI, Department of Surgical Research, Education and Research Centre, Beaumont Hospital, Dublin 9, Ireland (e-mail: gerry8941@eircom.net).