Teaching Case

Caroli's disease. US and MRCP findings. we describe a case of pure form Caroli' s disease involving both hepatic lobes, in which both US (detection of fibrovascular bundles inside the cystic lesions) and MRCP (demonstration of the communication of the multiple cyst with biliary tree) allowed a noninvasive diagnosis.

Past history was not significant. Physical examination revealead slight tenderness in the rigth upper quadrant of the abdomen. No evidence of epato-spenomegaly. No fever. Laboratory test showed midly elevated serum alkaline phosphatase (320 IU/L) and gamma-glutamylpeptidase (127 IU/L). Serum total bilirubin and creatine were normal. Clinical diagnostic hypothesis was cholelithiasis.

Caroli' s disease is a rare congenital disorder characterized by nonobstructive saccular or fusiform dilatation of intrahepatic bile ducts (communicating cavernous ectasia of the biliary tree). The disease is presumably of autosomal recessive hereditary character, and is consequence of insufficient resorption of bile duct plates surrounding the portal vein during embrional development, with dilatation of primitive bile duct segments. Two types of disease have been described: the rare, so-called pure form (Type 1), described by Jacques Caroli, characterized by segmental, saccular, communicating intrahepatic bile duct ectasia involving a single segment or lobe or the whole liver, and the more common form associated with congenital hepatic fibrosis (Type 2), in which bile duct dilatation is less prominent. The disease is most often diagnosed in children or young adults. Symptoms are often non specific and related to the type of disease: if the predominant lesion is intrahepatic duct dilatation (type 1), there are episodic abdominal pain, fever, jaundice secondary to biliary stone disease, ascending cholangitis and liver abscesses. In type 2, symptoms and signs of portal hypertension due to hepatic fibrosis such as splenomegaly, esophageal varices, and hemorrhage in gastrointestinal tract commonly prevail over biliary problems. Associated conditions include polycystic kidney disease, medullary sponge kidney or choledhocal cyst. An increased risk for cholangiocarcinoma (up to 7%) has been described. Demonstration of the cystic lesions communicating with the biliary tree is the essential diagnostic feature of this condition. The differential diagnosis includes congenital hepatic cystic disease, multiple abscesses and other more unusual malformations of the bile ducts (i.e. multiple bile duct amartomas or Von Meyenburg complex). Endoscopic retrograde cholangiopancreatogrphy (ERCP) and percutaneous transhepatic cholangiography (PTC), are the accepted method for an accurate anatomic evaluation of the biliary tree, but are invasive and may cause serious traumatic or infectious complication [1]. In Caroli's disease, ultrasonography has the capability to identify the dilated intrahepatic ducts as cystic lesions containing a parietal nodule with a central hypoechoic spot which, on Color Doppler, can be recognized as a vascular structure by presence of flow signals [2]. These images are due to fibrovascular bundles containinig a portal vein radicle and a small branch of the hepatic artery surrounded by the dilated intrahepatic bile ducts and can be considered as pathognomonic for Caroli's disease [3]. Their demonstration makes the diagnosis possible also when anatomic continuity of the cysts with the biliary ducts cannot be identified. They have been described also on contrast enhanced CT studies of these patients. The use of CT after injection of a cholangiographic contrast medium has been suggested as an additional means to achieve a firm diagnosis of Caroli' s disease [4]. Magnetic resonance cholangiopancreatography (MRCP) is a noninvasive technique alternative to ERCP and PTC for evaluating the bile ducts. In Caroli' s disease, heavily T2-weighted images, on single slices and axial plane, show multiple, hyperintense cystic lesion in the hepatic parenchyma, interesting segment or both lobes [Fig 2A]. The possibility of maximum intensity projection (MIP) reconstruction allows rotation of the images in the coronal plane with demonstration of continuity beetwen cystic lesion and the biliary tree [5], identification and evaluation of the morphology and size of the main bile duct [Fig 2B], which is generally normal (type V in Todani' s classification of choledhochal cyst) [Fig 3]. In conclusion, we describe a case of pure form Caroli' s disease involving both hepatic lobes, in which both US (detection of fibrovascular bundles inside the cystic lesions) and MRCP (demonstration of the communication of the multiple cyst with biliary tree) allowed a noninvasive diagnosis.