Caroli’s disease (CD),
also known as communicating cavernous ectasia or congenital saccular dilatation of the intrahepatic bile ducts,
is a rare congenital disorder first specifically described in 1958.
Although they are diagnosed in patients of all ages,
biliary tree cysts are primarily seen in children,
particularly in Asian populations.
It is characterized by multifocal segmental dilatation of the intrahepatic bile ducts,
involving the entire liver,
a lobe or a single segment,
while these ducts remain connected with the main duct system.
The disease is also characterized by the formation of intraductal calculi and susceptibility to infection.
Two types of CD were later recognized.
Type I,
or simple CD,
consists of pure cystic dilatations of the intrahepatic bile ducts,
whereas type II,
or complex CD,
also known as Caroli’s syndrome (CD with congenital hepatic fibrosis - CHF),
is associated with hepatic fibrosis,
or even cirrhosis,
portal hypertension and esophageal varices.
Type II CD may be accompanied by cholangiocarcinoma,
calculi of the intrahepatic duct,
cholangitis,
pancreatic cyst,
renal cystic disease or medullary sponge kidney. A significant proportion of Caroli’s disease cases involving CHF are transmitted in an autosomal recessive manner and are associated with autosomal recessive polycystic kidney disease (ARPKD).
The incidence of ARPKD is 1 in 20,000 live births.
Renal failure may be present at birth,
and the disease presentation is not limited to the neonatal period; it can be diagnosed in childhood or even adolescence or adulthood.
It has even been regarded as precancerous and patients with type II CD are reported to have a 2.5–17.5% likelihood of developing cholangiocarcinoma,
which is 100-fold higher than in subjects with normal hepatobiliary ducts and 10-fold higher than in those with calculi.
However,
CD has no specific symptoms or signs,
which makes diagnosis difficult.
Its incidence is extremely low at one case per 1 000 000 people.
The main clinical manifestations are intermittent abdominal pain,
hepatomegaly,
recurrent cholangitis,
and stone formation.
The diagnosis of CD relies on demonstrating the cystic dilatation of intrahepatic bile ducts (IHD) in continuity with the biliary tree by imaging studies.
The central dot sign is suggested as a pathognomonic finding of CD.
These are small foci of strong contrast enhancement within cystic lesions and are detected by CT,
magnetic resonance imaging,
or on an ultrasonogram.
These correspond to fibrovascular bundles containing a portal vein radicle and a branch of the hepatic artery,
bridging the saccule,
and they appear as central dots or a linear streak.
Clinicians should also be aware of the differential diagnosis of CD,
such as the von Meyenburg complex,
a rare condition that is usually asymptomatic and does not cause liver function abnormalities.
It is generally diagnosed incidentally by MRCP,
showing multiple small-sized cystic nodules (<1.5 cm) that do not communicate with the biliary tree.
Other differential diagnosis of CD include primary sclerosing cholangitis,
recurrent pyogenic cholangitis,
polycystic liver disease,
and biliary papillomatosis.
Caroli's disease and hepatic fibrosis is often associated with autosomal recessive polycystic kidney disease (ARPKD).
ARPKD,
known as infantile polycystic kidney disease,
is usually first evaluated with ultrasound in utero.
After birth,
an ultrasound is performed that will show enlarged kidneys with numerous small renal cysts bilaterally.
These three entities have part of "fibropolycystic diseases" which also include several conditions with a variety of intrahepatic bile duct dilatation and associated periportal fibrosis,
autosomal recessive and dominant polycystic kidney disease (ADPKD),
Ivemark,
Jeune,
Joubert,
Bardet-Biedl,
Meckel-Gruber and Arima syndromes.
Most of them are accompanied by progressive cystic degeneration of the kidneys.