Caroli’s disease, also known as communicating cavernous ectasia of the intrahepatic ducts, is a rare congenital disorder characterized by non-obstructive multiple cystic dilatation of the intrahepatic bile ducts. In about 50% of the patients, there may be dilatation of the extrahepatic bile ducts as well. This disease was first described in 1958 by Jacques Caroli.
The cause of Caroli’s disease is unknown, but genetic inheritance [autosomal recessive] has been implicated. Marchal, et al supported the hypothesis that arrest of the normal embryogenesis of the intrahepatic bile ducts plays a role in the pathogenesis of the disease, resulting in varying degrees of destructive inflammation, segmental dilatation and periductal fibrosis.
Classification - Two forms of Caroli’s disease have been described:
1.The so called ‘pure form’ or isolated type [Caroli’s disease] –
•This can be focal or diffuse
• Involvement of the larger intrahepatic bile ducts
• Dilatation is segmental and saccular
• There is a marked predisposition to cholangitis and liver abscesses.
2.The form associated with congenital hepatic fibrosis [Caroli’s syndrome] –
• Presents in childhood
• The bile duct dilatation is less prominent and there is involvement of the small interlobular ducts which results in fibrosis
• A predilection to the development of portal hypertension and eventual liver failure
• This form may be seen in association with autosomal recessive polycystic kidney disease.
Clinical presentation and Complications - Patients may have abdominal pain due to recurrent episodes of cholangitis. Associated complications that may develop include –
• Intrahepatic calculi,[ According to Nakanuma, et al, biliary malformation is a lithogenic factor in hepatolithiasis as it causes bile stasis as well as bacterial infection that most likely promote stone formation and their growth].
• Biliary obstruction
• Hepatic abscess
• Cirrhosis and
• Malignancy [cholangiocarcinoma] in 7% of the cases.
Associations of the disease process – may be associated with autosomal recessive polycystic kidney disease [ARPKD], congenital hepatic fibrosis, choledochal cysts. Recently its association with neurofibromatosis-type 1 has also been suggested.
Imaging findings -According to Taylor, et al the diagnosis rests on demonstrating cystic spaces in the liver communicating with the biliary tree. Ultrasound and CT scan are diagnostic and usually no further imaging is required. MR with MRCP is also very specific in diagnosing the disease and its complications.
• Cystic spaces in the liver, which communicate with bile ducts.
• Isolated dilated intrahepatic ducts in majority of the cases, which may be saccular or fusiform and segmental or diffuse.
• Associated extrahepatic ductal dilatation in 50% of the cases. [Recognition of this feature is important, as Caroli’s disease should be considered in patients with both intra and extrahepatic dilatation.]
• Intraluminal bulbar protrusions of the wall resulting in irregular bile duct walls.
• Portal venous radicles partially or completely surrounded by dilated bile ducts.
• Central dot sign- this is seen on color Doppler with the centrally placed color filled portal vein radicles in close proximity to the/ within the dilated intrahepatic biliary channels. [This sign is not specific for Caroli’s disease and can be seen in other entities such as peribiliary cysts].
• With color Doppler, multiple small arterial color Doppler signals [with its characteristic wave-pattern] can be observed in the vascular radicles within the dilated bile ducts or in the center of the lumen apart from the portal radicles, in the protrusions of the dilated ducts.
• If associated malignancy, a focal hepatic or intraductal mass may be seen.
CT scan findings:
• Intrahepatic ducts with saccular dilatation.
• Tiny, enhancing foci within or along the margin of the dilated intrahepatic bile ducts; these correspond to the intraluminal or marginal fibrovascular bundle [central dot sign].
Differential diagnosis – the following differentials may be considered:
1. Primary sclerosing cholangitis –ductal dilatation is more isolated and fusiform and not saccular; 70% patients have associated inflammatory bowel disease.
2. Recurrent pyogenic cholangitis – may be difficult to differentiate, but saccular dilatation favors Caroli’s disease.
3. Polycystic liver disease – the cysts in the liver do not communicate with the biliary tree.
Management- For the isolated form of Caroli’s disease limited to a lobe, hepatectomy is the curative option. In the diffuse form treatment options include conservative or endoscopic therapy, internal biliary bypass procedures and liver transplantation in carefully selected cases.