Liver cysts (also called hepatic cysts) are fluid-filled sacs that occur in the liver of roughly 5% of the population. They are usually asymptomatic and often discovered by chance during an abdominal imaging procedure, like computed tomography (CT) or magnetic resonance imaging (MRI). Even though most liver cysts are benign, an early diagnosis is critical for proper treatment of the parasitic or cancerous subtypes. In most cases, treatment involves removal via minimally invasive surgical techniques.

Causes and Risk Factors

Liver cysts fall into several categories with varying causes, diagnoses, and treatments.

  • Simple cysts are present from birth and are formed by abnormal bile duct cells during the embryo’s development. Cysts contain a bile-like fluid and are covered with a thin layer of epithelial cells. They are the most common type of liver cyst and generally measure less than 3 cm in diameter.
  • Echinococcosis is an infection by a species of tapeworm that is transmissible between animals and humans. Specifically, the larval stage of the Echinococcus granulosus (E. granulosus) and Echinococcus multilocularis (E. multilocularis) species produces liver cysts in humans. Humans become infected by ingesting the parasite’s eggs, which are found in the excrement of the animal host (e.g. sheep and dogs). Echinococcosis is still not common in the United States, though it has nevertheless become more common over the past several decades in both the U.S. and Europe. It could become gradually more common as wild animals like foxes become more prevalent in areas where people live and keep pets.
  • Cystadenoma and cystadenocarcinoma represent benign and cancerous cystic tumors, respectively. Cystadenomas are similar to simple cysts in that they are of epithelial origin and present from birth. The mechanism by which the cystic tumors become cancerous is not known. Cystadenocarcinomas grow slowly and have a mean diameter of 12 cm.
  • Polycystic liver disease (PLD) is a rare genetic disorder signified by the presence of greater than 20 liver cysts. The cysts are present from birth and cluster together. PLD is closely associated with two other disorders: autosomal dominant polycystic liver disease (PCLD) and autosomal dominant polycystic kidney disease (ADPKD).