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).
Liver cysts generally do not affect liver function and may remain asymptomatic for years. When cysts become enlarged, they can rupture or push against other organs, causing bloating, a feeling of fullness, and a sudden pain in the upper right abdominal region. Parasitic cysts (echinococcosis) may also cause fever, bloody sputum, and severe skin itching. The type of echinococcosis caused by E. multilocularis (called alveolar echinococcosis) can cause symptoms similar to cirrhosis or liver cancer.
Diagnosis and Treatment
Liver cysts are primarily diagnosed (often by chance) using imaging techniques such as a CT scan, ultrasound, or MRI. A physician may also perform a physical exam of the abdomen to feel for cysts. Cystic echinococcosis is diagnosed using immunodiagnostic tests that detect Echinococcus antibodies in the blood.
Most cysts do not require treatment and go away on their own. Symptomatic cysts that become enlarged or malignant are removed surgically. Fluid drainage is also performed, but the effect is only temporary. In some PLD patients, liver transplantation is required.
Surgery. Complete removal of liver cysts is the best method of treatment, especially with cases of cystadenoma and cystadenocarcinoma. This is done using laparoscopy, a minimally invasive surgical procedure where instruments are delivered to the surgery site through thin tubes inserted into the abdomen.
Drug therapy. Parasitic cysts caused by echinococcosis are often treated with a combination of surgery and up to two years of chemotherapy to reduce symptoms. A course of drugs to treat parasitic worms may also be prescribed.
Liver cyst disorders that are congenital (present from birth) or inherited are not preventable. A family history of liver cysts is a good indicator of the likelihood of developing this condition.
Parasitic cysts can be avoided by practicing good hygiene and proper food handling in parts of the world where Echinococcus infections are common, such as Africa, Europe, Asia, the Middle East, and Central and South America. In the United States, such precautions are advisable particularly for those who keep indoor/outdoor pets. Additionally, hunters should always wear gloves when handling wild animals.
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“Liver Cysts”. American Liver Foundation. Oct 2011. Retrieved Apr 28, 2014. http://www.liverfoundation.org/abouttheliver/info/livercysts.
“Echinococcus”. MedlinePlus. NIH. Aug 2012. Retrieved Apr 28, 2014. http://www.nlm.nih.gov/medlineplus/ency/article/000676.htm.
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Macedo, FI. Current management of noninfectious hepatic cystic lesions: A review of the literature. Aliment World J Hepatol. 2013. 5:462-469.
“Alveolar Echinococcosis (AE) FAQs”. Centers for Disease Control and Prevention (CDC). Retrieved May 6, 2014. http://www.cdc.gov/parasites/echinococcosis/gen_info/ae-faqs.html.
Tina is a Life Science Writer for a number of online publications, including Innerbody.com. Her expertise is in conveying complex scientific topics to diverse audiences. Tina earned her PhD in Biochemistry from the University of California, San Francisco and her BS degree in Cell Biology from U.C. Davis. In her spare time, she enjoys drawing science-related cartoons.