Ultrasound of Biliary Cast Syndrome and Its Mimics

Biliary cast syndrome (BCS) consists of mass-like hardened collections of inspissated bile and sloughed biliary mucosa filling the intrahepatic and/or extrahepatic bile ducts, which show an alternating pattern of dilatation and stricture. It is a rare but serious complication of liver transplantation frequently necessitating repeated percutaneous, endoscopic or surgical stent placements, and cast retrieval. Although not typically considered as the modality of choice for BCS compared with magnetic resonance cholangiopancreatography and endoscopic retrograde cholangiopancreatography, ultrasound can be quite useful for this diagnosis. This article reviews the sonographic appearance of BCS in postliver transplant patients and correlates with other imaging modalities including computed tomography, MRCP, and endoscopic retrograde cholangiopancreatography. Also reviewed are other intrahepatic pathologies that mimic the appearance of BCS on ultrasound.