Intrahepatic lithiasis in Western populations: an underrecognized diagnosis and its mimickers

Intrahepatic lithiasis (IHL), defined as the presence of calculi within the intrahepatic bile ducts proximal to the hepatic confluence, has traditionally been considered rare in Western populations. However, increasing evidence suggests that Low-Phospholipid-Associated-Cholelithiasis (LPAC) syndrome, which is a genetic cholangiopathy caused by ABCB4 variants affecting biliary phospholipid secretion, represents a frequently underrecognized cause of IHL.The imaging spectrum of IHL varies according to stone composition and underlying etiology. In Eastern populations, pigment stones associated with recurrent pyogenic cholangitis prevail, whereas in Western patients, cholesterol microlithiasis characteristic of LPAC syndrome is more common. Targeted hepatobiliary ultrasound remains the cornerstone diagnostic modality, capable of detecting findings that are frequently missed on routine examination. Computed tomography (CT) and magnetic resonancecholangiopancreatography (MRCP) provide complementary information regarding stone characterization, biliary anatomy, and complications.Accurate diagnosis requires familiarity with the major mimickers of IHL, including primary sclerosing cholangitis (PSC), Caroli disease, iatrogenicbiliary strictures, and recurrent pyogenic cholangitis, as well as recognition of imaging pitfalls such as pneumobilia and biliary hamartomas.Greater awareness of LPAC syndrome and careful analysis of biliary imaging patterns may enable radiologists to reframe intrahepatic lithiasisfrom an overlooked finding into a diagnosable and treatable condition.