Not just a gallstone

A 78-year-old male patient presented at the emergency department with diffuse pain in the abdomen and vomiting for 2 weeks. No history of fever, loss of weight or any other complaints. No previous relevant medical history. Laboratory investigations were within normal limits.

Contrast-enhanced CT of the abdomen at presentation revealed a 3 cm stone impacted in the gall bladder (GB) neck with mild acute cholecystitis (Fig. 1). Compared to prior CT done 4 years before, the stone had enlarged with interval appearance of a circumferential soft tissue rim (Fig. 2).  This episode was conservatively managed.

A year later, he presented with severe epigastric pain and deranged liver function tests. The CT then showed the same stone impacting the duodenal diverticulum with pneumobilia. A diagnosis of Bouveret’s syndrome variant (Fig. 3) secondary to development of cholecystodiverticular fistula with partial duodenal obstruction was made. Both magnetic resonance cholangiopancreatography (MRCP) (Fig. 4) and endoscopic retrograde cholangiopancreatography (ERCP) performed subsequently confirmed the CT findings with a large filling defect in the diverticular neck.  In the following days after ERCP, the patient developed worsening pain in the abdomen and a repeat CT illustrated small bowel obstruction with migration of the diverticular stone into the distal ileum (Fig.5).

Bowel obstruction is an uncommon but known complication of cholelithiasis and has been described in the literature with an incidence of less than 1% [1]. The name gallstone ileus is a misnomer as it denotes mechanical obstruction rather than ileus and comprises a group of conditions depending on level of obstruction. These vary from the most common-ileal/ ileocaecal valve obstruction (60%) to the least common, colonic obstruction (2.8%) [2]. The clinical symptomatology is often nonspecific with patients presenting with features of bowel obstruction and biliary colic. The condition is associated with high morbidity and mortality due to its occurrence in a debilitated elderly population where often the associated comorbidities limit the surgical options [3].  

CT is the diagnostic modality to look for gallstone-associated complications, especially gallstone ileus, and should include close scrutiny of size and morphology of previously documented gallstones, if any [3]. Ectopic obstructive gallstones are usually more than

2.5 cm in size. While measuring size, one should be aware of soft tissue rim/density surrounding calcified component (also called as soft tissue rim sign) and compressed foci of air in the dependent part of the bowel at the level of the gallstone (air crescent sign) [4]. Irrespective of the level of obstruction, three features to look for in gallstone ileus are: Ectopic gallstone, pneumobilia and small bowel obstruction (Rigler’s triad) [4, 5]. All three are seldom seen in a single patient and are rather uncommon in proximal (stomach/duodenal) obstruction, also called Bouveret’s syndrome. MRCP in addition can provide more accurate assessment of the size of the gallstone but its role in gallstone ileus is not fully established. Few features to look for in MR are focal GB wall thinning, blurring of cholecystoduodenal fat planes and a large calculus predisposing to fistula [1].

Our case presents the spectrum of complications arising from gallstone disease, varying from commonly observed mild acute cholecystitis to rare intestinal ones.  Important and uncommonly seen is the impaction of gallstone in the duodenal diverticulum secondary to the development of cholecystodiverticular fistula (considered a variant of Bouveret’s syndrome, which typically represents duodenal obstruction secondary to cholecystoduodenal fistula). Subsequently, the same calculus migrated to the distal ileum causing small bowel obstruction. The patient was operated with per operative findings in agreement with CT diagnosis of gallstone ileus.

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