Clinical Importance and Natural History of Biliary Sludge in Outpatients.

Objectives: Gallbladder sludge is a common diagnosis on routine abdominal sonography, yet its clinical importance is uncertain, especially in outpatients. To determine its natural history and potential future complications in this setting, we reviewed the imaging and clinical histories of nonhospitalized patients with a diagnosis of sludge on sonography.

Methods: We conducted a retrospective search of our institutional radiology information system for all sonographic reports using the key words "biliary sludge without gallstones" over a 3-year period. For each of the 104 patients with isolated biliary sludge on initial sonography, we reviewed the electronic medical records and all imaging for the development of pancreaticobiliary complications.

Results: We found an overall prevalence of biliary sludge in outpatients of 1.8%. Of the 104 patients reviewed with a mean follow up of 630 days (21 months), 25 developed a pancreaticobiliary complication, including cholelithiasis, cholecystitis, choledocholithiasis, and pancreatitis. The most frequent complication was cholecystitis, with a total of 14 diagnoses (12 chronic acalculous and 2 acute with gallstones). An additional 6 patients developed gallstones without cholecystitis features; 4 patients developed pancreatitis; and 1 developed choledocholithiasis. Biliary sludge remained quiescent or resolved in 76% of patients.

Conclusions: Biliary sludge always represents a pathologic process, but its clinical implications among outpatients have not been previously investigated. Our ambulatory population developed pancreaticobiliary complications at similar rates as prior mixed-patient setting studies. Regardless of the patient setting, biliary sludge is likely of more clinical importance than previously regarded.