Malformations des voies biliaires, rôle de l'imagerie

Malformations of the biliary tract are rare, but US and MRI play a major role for diagnosis. Biliary atresia is the first cause of neonatal cholestasis. In case of persistent discoloured stools, the diagnosis can be suggested in about half of the cases on US findings including the absence of bile duct (BD) dilatation, a macro- or microcyst in the hepatic pedicle, a triangular cord sign, an atretic or irregular gallbladder, elements of the polysplenia syndrome. If the diagnosis remains doubtful, BD opacification or direct surgery are recommended. Kasai procedure allows 18% of patients to keep native liver at 20 years of age. Liver transplantation is indicated in case of failure or complications. Choledochal cyst is secondary to anomalous pancreatico-biliary junction and may present with pancreatitis, cholangitis, choleperitonitis. MRI is diagnostic. Hepaticojejunostomy is mandatory to avoid degeneration. In Alagille syndrome there is paucity of intrahepatic BD, secondary to mutation of genes also implicated in angiogenesis. Imaging shows butterfly vertebrae, renal anomalies, stenoses of pulmonary, cerebral and visceral arteries. The most frequent hepatorenal fibrocystic disease is congenital hepatic fibrosis with recessive poycystic kidney disease. The severity of liver and kidney disease is variable and independant. US and MRI are usually diagnostic.