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A liver cyst is a closed, sac-like pocket of tissue formed in the liver that may be filled with fluid, air, pus, parasites, or other materials.
People with liver cysts can either have a single cyst or multiple. Cystic lesions of the liver are extremely heterogeneous and can be caused by various etiologies.
Simple cysts are the most common. Simple cysts contain clear fluid and do not communicate with the intrahepatic biliary tree. In most cases, people are born with these, and they are caused by biliary ducts that fail to connect to the biliary system. Some people have polycystic disease, characterized by multiple cysts affecting the whole organ.
Liver cysts are very common. They affect between 15–18% of people in the US, although most don’t have symptoms.¹
Most of the time, liver cysts do not have symptoms. This is especially the case for simple cysts. Frequently, liver cysts are incidental, meaning they’re discovered when someone is getting a scan for an unrelated health issue.
In cases with symptoms, this often depends on the size and cause of the cyst. Large cysts can cause pain or upper abdominal discomfort as well as complications such as hemorrhage (although this is rare), rupture, infection, or even compression of the biliary tree. The following section will break down liver cyst symptoms based on the type of cyst.
Simple cysts do not usually cause symptoms, but in a minority of people, they can cause pain, nausea, and vomiting.
In rarer cases, a parasite called Echinococcus can cause hydatid cysts in the liver, among other organs. Although these are common in some parts of the world, they’re uncommon in the US. Hydatid cysts are caused by the larva of Echinococcus granulosus, typically from infected dogs.
Patients are usually asymptomatic, and if they’re symptomatic, this is typically secondary to mass effect from an enlarging cyst. However, these cysts can rupture and cause serious complications.
Though uncommon, liver metastases may appear as cysts due to central necrosis, typically from metastasis of pancreatic, colon, kidney, or ovarian tumors.
Another cyst-related condition is polycystic liver disease, which affects the whole organ with multiple cysts. This condition is genetic and occurs mainly in patients with polycystic kidney disease. Again, most patients do not have symptoms. However, when present, symptoms/complications include pain (very common), hepatic function impairment, and cyst infection, but this is rare.
Most people with a liver cyst or cysts do not develop symptoms. In fact, only 5% of people with a liver cyst experience any symptoms. Of this 5%, most will need treatment, and some will experience complications.²
In most cases, there is no known cause for liver cysts. People are sometimes born with them, and they sometimes develop during life. There is a significant increase in liver cysts with age. This is likely because they grow slowly and are often undetected for a long time. Different forms of liver cysts have different causes. Here is a breakdown:
Simple cysts form from biliary ducts that do not connect to the biliary system. However, as mentioned, simple cysts are usually asymptomatic and do not cause problems.
Hydatid cysts are caused by the tapeworm Echinococcus granulosus. The parasite spreads from an intermediate host, such as sheep, goats, cervids etc., to a definitive host, such as dogs or related species. Humans are incidental hosts and do not play a role in the transmission cycle.
Cystic hydatidosis is still a public health problem in many parts of the Mediterranean and has shown a re-emergence in Wales and Bulgaria.
Liver metastasis (also known as cystadenomas) can sometimes be cystic or cystic looking due to central necrosis. The most common cancers implicated are pancreas, ovarian, and colon.
Polycystic liver disease is a genetic condition associated with a gene mutation, which can cause progressive dysfunction over time. It is most commonly seen in the context of polycystic kidney disease.
As mentioned, liver cysts usually do not have symptoms and are often diagnosed when undertaking an ultrasound or CT scan for another reason. However, if you do have symptoms, liver cysts are usually diagnosed by an abdominal CT scan of the liver, sometimes using a special contrast agent to help show the different features the doctor is looking for.
Blood tests are used to differentiate the causes of liver cysts, particularly parasitic causes.
While liver cysts are often uncomplicated and lack symptoms, complications develop in some cases. Complications of liver cysts can include:
Compression of the biliary tree
Usually, liver cysts do not need to be treated. This is because they often don't have symptoms. Complicated or large cysts may need to be surgically removed or drained.
In most cases, the cysts are drained and then surgically removed with a laparoscopic (keyhole) procedure. It is sometimes possible to drain the cyst without operating, but this often leads to the cyst returning.
It is best to see a doctor if you have experienced any symptoms that may indicate a liver cyst. For instance, if you have nausea, vomiting, or abdominal pain that doesn’t seem to be going away.
If you have been diagnosed with a liver cyst or polycystic liver disease, see your doctor if you experience any signs of complications, such as worsening abdominal pain or fluid collecting in your abdomen.
Liver cysts are common and, in most cases, do not cause any issues or require treatment. Symptoms vary based on the type or cause of the cyst. There are simple cysts, parasitic cysts, cystic tumors, and cysts related to polycystic kidney disease.
Cysts are commonly diagnosed via imaging such as ultrasound; in some cases, a blood test is also needed. Treatments available include drainage, surgery, and antibiotics for parasitic cysts.
If you are concerned about potential symptoms of a liver cyst, it is best to see a doctor.
Liver cysts | American Liver Association
Complications of liver disease | American Liver Foundation