The Rigler triad in gallstone ileus

An 82-year-old, previously healthy lady presented at the emergency department with acute-onset abdominal pain. She complained of vomiting, cessation of flatus, high-pitched bowel sounds and rebound tenderness. Laboratory results revealed elevated gamma-GT levels.

A Computed Tomography (CT) scan was performed as soon as possible given the rapidly worsening condition of the patient. The scout view already showed multiple distended bowel loops and revealed a round density projecting over the pelvis. The axial slices through the abdomen confirmed the presence of the dilated small bowel loops and also showed an impacted ectopic gallstone in the pelvis and associated aerobilia. These three findings are pathognomonic of gallstone ileus.

Background:
Gallstone ileus is a rare cause of mechanical small bowel obstruction due to intestinal impaction of a biliary stone. [1] It follows the creation of a cholecysto-enteric fistula by erosive penetration of the gallbladder stone through the wall layers, usually facilitated by chronic inflammation of the gall bladder wall due to recurrent episodes of cholecystitis. The calculus migrates to the small intestine via the cholecysto-enteric fistula and, if large enough, impacts at the terminal ileum (narrowest portion of the bowel) or the ileocaecal valve, where it causes mechanical obstruction. [2]

Clinical perspective:
Erosion of a cholecystolithiasis through the gallbladder wall only seldomly results in intestinal obstruction, usually when the stone has a large enough calibre (> 2.5 cm). [1] Nevertheless, gallstone ileus is responsible for 25% of small bowel obstructions in patients over 65 years of age, and should thus be ruled out especially in patients with a history of cholecystolithiasis or recurrent cholecystitis. [1, 2]

Imaging perspective:
The radiological sign of gallstone ileus is the so called "Rigler triad", first described in 1941. The triad is characterized by distended small bowel loops (due to the mechanical intestinal obstruction), aerobilia (due to the cholecysto-enteric fistula) and an ectopic, radiopaque (calcified) gallstone. [2] Ultrasonography offers good visualisation of the gallstones. Plain radiography and especially multi-slice CT can provide more information. CT imaging allows a better visualization of the fistula and a more detailed localization of the level of bowel obstruction. On CT the complete Rigler’s triad is observed in around 78% of patients. [1]

Outcome:
A delay in diagnosis and treatment can lead to electrolyte imbalance and ischaemic lesions with ulceration or perforation of the bowel wall, followed by abscess formation. [1] The patient discussed in this case report was surgically treated with enterolithotomy and cholecysto-enteric fistula repair. She was able to leave the hospital after a couple of days.

Take home messages:
The Rigler triad is characterised by distended small bowel loops, aerobilia and an ectopic, calcified gallstone. [2] Gallstone ileus is responsible for 25% of small bowel obstruction in patients over 65 years of age and should therefore be ruled out as a cause of abdominal pain in the geriatric population. [1]