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E1153. Wandering Gallstones: Imaging of Uncommon Complications of Cholelithiasis
Authors
  1. Temilola Akinola; Lahey Clinic
  2. Jeremy Wortman; Lahey Clinic
  3. Francis Scholz; Lahey Clinic
Background
1) Cholelithiasis is stone formation at any point along the biliary tree. Though asymptomatic in 25% of cases, the most common complication of cholelithiasis are biliary colic and inflammation of the gallbladder (cholecystitis). 2) There are many uncommon complications of cholelithiasis resulting in ectopic gallstones, including fistulous communication with the remainder of the gastrointestinal tract, “dropped” gallstones, Mirizzi syndrome, and fistulous communication with the skin, among others. 3) Gallstones may travel to other parts of the gastrointestinal tract by forming fistulous tracts, usually as a result of recurrent inflammation. Examples of this include gallstone ileus, Bouveret syndrome, and Gallbladder-to-colon fistulae. 4) Gallstones can also be “dropped” following cholecystectomy, which can result in pain and superinfection.

Educational Goals / Teaching Points
1) Epidemiology and pathophysiology of the more common “wandering gallstone” pathologies 2) Review of appropriate imaging work-up of patients with possible ectopic gallstones 3) Case-based review of the imaging findings in gallstone ileus, Bouveret syndrome, Mirizzi syndrome, dropped gallstones and gallbladder cutaneous fistula, with a focus on findings that will change patient management 4) Summary of diagnostic pitfalls and how they can be avoided

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Gallstone ileus is bowel obstruction due to fistula formation and migration of ectopic gallstones into the distal small bowel. Classic findings are Rigler’s KUB triad of gas in the biliary tree, small bowel obstruction, and distal small bowel obstructing gallstone. A fourth sign on computerized tomography (CT), is obliteration of gallbladder fat planes with adjacent structures. Multiple stones may remain in the gallbladder and can drop over months to years after the initial episode. Bouveret syndrome is gastric outlet obstruction from ectopic gallstone in the duodenal bulb or gastric antrum. Findings include pneumobilia, gastric distention, obstructing stone in gastric antrum/duodenal bulb. The fistulous tract may be visible on fluoroscopy or CT. Mirizzi syndrome is obstruction of the common hepatic duct by an impacted stone in the cystic duct or gallbladder infundibulum. On fluoroscopy, this appears as a smooth right-sided impression on the common hepatic duct. On Magnetic Resonance Imaging (MRI/MRCP), stones are seen as T2 hypointense filling defects; MRCP also delineates the narrowed common hepatic duct. Imaging findings of unexplained fluid collections, bowel obstruction in a patient with persistent symptoms after cholecystectomy may be pointers of “dropped” gallstones. In cirrhotic patients who incidentally have cholelithiasis, cholecystitis and ‘silent’ gallbladder perforation can occur, with peritoneal signs masked by underlying ascites. This results in stones being “dropped” into the pelvis which can be confirmed to be mobile on prone imaging.

Conclusion
Imaging plays a crucial role in diagnosing ectopic gallstones, however imaging findings can be confusing. Radiologists must be aware of the typical and atypical imaging appearance of these entities to avoid misdiagnosis.