The stilette sign: the appearance of dilated bile ducts in the fatty liver.

The appearances of hepatic steatosis and of dilated intrahepatic bile ducts occurring independently are well described. When both conditions occur simultaneously a major sign of biliary obstruction, a double lumen with echogenic walls (the double-barrelled shotgun sign), is modified by the abnormally echogenic liver. The combined appearance is of a tubular structure with no echogenic interface with the liver, containing an echogenic structure at its centre representing echoes from the adjacent bile duct and portal vein walls. We have named this appearance the 'stilette' sign because of its resemblance to a fine needle within a tube. Its importance lies in the fact that it makes dilated intrahepatic bile ducts difficult to recognise by ultrasound.