Caroli disease and Caroli syndrome are congenital disorders comprising of multifocal cystic dilatation of segmental intrahepatic bile ducts. However, some series show that extrahepatic duct involvement may exist. They are also classified as a type V choledochal cyst, according to the Todani classification.
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Terminology
Two types of Caroli disease have been described 11:
type I or simple Caroli disease: cystic dilatation of larger intrahepatic bile ducts
type II Caroli disease also known as Caroli syndrome: combination of small bile duct dilatation and congenital hepatic fibrosis or cirrhosis +/- portal hypertension
Epidemiology
Caroli disease and Caroli syndrome are rare autosomal recessive disorders with an incidence of 1 per 1,000,000 people 9,11. Presentation is in childhood or early to mid-adulthood with equal sex distribution 9. Patients are often asymptomatic for the first 20-40 years of life and may never become symptomatic 9,11.
Associations
autosomal dominant polycystic kidney disease (very rarely)
Clinical presentation
Caroli disease can present with right upper quadrant pain, recurrent cholelithiasis, and cholangitis with fever and jaundice 10.
Caroli syndrome presents with the previous symptoms along with signs of portal hypertension, including hematemesis and melena secondary to bleeding varices.
Pathology
Pathologically, Caroli disease and Caroli syndrome belong to the spectrum of fibropolycystic liver disease which results from in utero malformation of the ductal plate 4. There is a high association with fibrocystic anomalies of the kidneys which share the same genetic defect (PKHD1 gene, chromosome region 6p21) 5.
The ductal plate is a layer of hepatic precursor cells that surround the portal venous branches and is the anlage of the intrahepatic bile ducts. The manifestation of ductal plate malformation depends on the level of the biliary tree that is affected 3-5.
Caroli disease (the simple type) results from the abnormal development of the large bile ducts.
In contrast, in Caroli syndrome (the periportal type of Caroli disease), both the central intrahepatic bile ducts and the ductal plates of the smaller peripheral bile ducts are affected, with the latter leading to the development of fibrosis.
At the other end of the fibropolycystic disease spectrum are von Meyenburg complexes (biliary hamartomas), which result from discrete foci of ductal plate malformation affecting the smallest bile ducts 5.
Radiographic features
The disease may be diffuse, lobar or segmental. Dilatation is most frequently saccular rather than fusiform, a feature that might help in the differential diagnosis.
Ultrasound
may show dilated intrahepatic bile ducts
intraductal bridging: echogenic septa traversing the dilated bile duct lumen
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small portal venous branches partially or completely surrounded by dilated bile ducts 1,3
intraluminal portal vein sign: dilated ducts surrounding the portal vein
intraductal calculi
CT
multiple hypodense rounded areas which are inseparable from the dilated intrahepatic bile ducts
“central dot” sign: enhancing dots within the dilated intrahepatic bile ducts, representing portal radicles 1
MRI
T1: hypointense dilatation of IHBD
T2: hyperintense
T1 C+ (Gd): enhancement of the central portal radicles within the dilated IHBD 1
MRCP: demonstrates continuity with the biliary tree
Nuclear medicine
Intrahepatic bile ducts can have a beaded appearance on HIDA scans 8.
Treatment and prognosis
The prognosis is generally poor. If the disease is localized, segmentectomy or lobectomy may be offered. In diffuse disease management is generally with conservative measures; liver transplantation may be an option 1.
Complications
-
simple type
intrahepatic stone formation
recurrent cholangitis that may lead to bacteremia and sepsis
-
periportal fibrosis type
up to 100x increased risk of cholangiocarcinoma, which develops in ~10% (range 2.5–17.5%) of patients 1,11
History and etymology
This disease is named after Jacques Caroli (1902-1979), a French gastroenterologist, who described it in 1958 7.
Differential diagnosis
-
no associated biliary duct dilatation
rarely communicate with the biliary ducts
-
may be cystic
generally do not communicate with the biliary tree
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primary sclerosing cholangitis
dilatation typically more fusiform and isolated, with a "beaded" appearance
associated inflammatory bowel disease in 70% of White patients
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recurrent pyogenic cholangitis
both present with sepsis and biliary dilatation
saccular (vs fusiform) dilatation favors Caroli disease 2
For a further CT differential, consider also focal hypodense hepatic lesions on a non-contrast CT scan.
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