Overview
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).