Tumefactive Sludge Mimicking Gallbladder Neoplasm: A Case Report and Review of the Literature.

Biliary sludge (or very thick bile) is mainly comprised of calcium bilirubinate granules and lesser amounts of cholesterol crystals, and it can produce a layer of low amplitude of echoes in the most dependent part of the gallbladder (GB). In tumefactive biliary sludge, low-amplitude echoes do not form a fluid-fluid level but instead tend to give the appearance of a polypoid mass that is bounded by a smooth margin, round, and lobulated. Differential diagnoses for an echogenic mass in the GB lumen include GB carcinoma, tumefactive sludge, and gangrenous cholecystitis.