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USMLE – Fibropolycystic Disease

Fibropolycystic diseases of the liver and biliary system constitute a heterogeneous group of rare disorders, some of which are inherited. They are not distinct entities, as combined lesions occur.

ADULT HEPATORENAL POLYCYSTIC DISEASE
The kidneys are predominantly affected in this condition, which is inherited as an autosomal dominant trait. Hepatic cysts which do not communicate with the biliary system are present in over half the patients with renal cysts, and cysts can also be found in other organs. Cerebrovascular aneurysms sometimes develop too. Cysts restricted to the liver constitute a separate rare genetic disorder.

Hepatic cysts are often discovered by chance; complications are rare, but include pain or jaundice from cyst enlargement, hemorrhage into cysts, or cyst infection. Portal hypertension and bleeding from varices are very rare.

Diagnosis is made best by ultrasonography. Resection of a large cyst or groups of cysts is only required if symptoms are troublesome and the prognosis is excellent as liver function is good. Cholangiocarcinoma is a rare complication.

CONGENITAL HEPATIC FIBROSIS
This is characterized by broad bands of fibrous tissue linking the portal tracts in the liver, abnormalities of the interlobular bile ducts and sometimes a lack of portal venules. The renal tubules may show cystic dilatation (medullary sponge kidney) and eventually renal cysts may develop. The condition can be inherited as an autosomal recessive trait. Liver involvement causes portal hypertension with splenomegaly and bleeding from esophageal varices that usually presents in adolescence or in early adult life. The prognosis is good because liver function remains good. Treatment is required for variceal bleeding and occasionally cholangitis. Patients can present during childhood with renal failure if the kidneys are severely affected.

CHOLEDOCHAL CYSTS
This term applies to cysts anywhere in the biliary tree. The great majority cause diffuse dilatation of the common bile duct (type I), but others take the form of biliary diverticula (type II), dilatation of the intraduodenal bile duct (type III) and multiple biliary cysts (type IV). The last type merges with Caroli’s syndrome. Recurrent jaundice and abdominal pain and an abdominal mass are typical but these occur together in only a minority of patients. Prolonged biliary obstruction predisposes to cholangitis, liver abscess and eventually biliary cirrhosis and there is an increased incidence of cholangiocarcinoma. Excision is the treatment of choice if this is possible; otherwise a biliary bypass operation is performed.

CAROLI’S SYNDROME
This is very rare and is characterized by segmental saccular dilatations of the intrahepatic biliary tree. The whole liver is usually affected and extrahepatic biliary dilatation occurs in about one-quarter of patients. Recurrent attacks of cholangitis occur and may cause hepatic abscesses. Complications include biliary stones and cholangiocarcinoma. Antibiotics are required for episodes of cholangitis, and occasionally localized disease can be treated by segmental liver resection.

OTHER HEPATIC CYSTS
Isolated single cysts in the liver are quite common. They rarely cause symptoms and are usually found incidentally when imaging is performed.

Non-parasitic cysts
Most non-parasitic liver cysts are congenital in origin and the majority are solitary. They rarely communicate with the biliary tree. They are usually asymptomatic but can cause abdominal pain, nausea or vomiting and if the cysts become big enough, they may be palpable. Jaundice occasionally results from biliary compression and infection, hemorrhage and rupture are other rare complications. Other non-parasitic hepatic cysts include traumatic and neoplastic cysts.

Parasitic cysts
These cysts are caused by Echinococcus granulosus infection. They have an outer layer derived from the host, an intermediate laminated layer, and an inner germinal layer. They can be single or multiple. Chronic cysts become calcified. The cysts may be asymptomatic or may cause abdominal pain or a mass. There is a peripheral blood eosinophilia, radiographs may show calcification, imaging shows the cyst(s), and serological tests are positive. Rupture or secondary infection of cysts can occur and other organs may be involved. Surgical removal of the intact cyst after sterilization with alcohol or formalin is necessary.

Lillian Thompson By Lillian Thompson

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