What Is a Liver Cyst?

Ultrasound shows a liver cyst.

A cyst is a small sac or capsule packed with fluid, cells, or other material -- sort of like a balloon.

Cysts normally show up on or just beneath your skin. The back of the neck and wrists are common cyst sites. But cysts can also show up in organs, breast tissue, ovaries, or other places inside your body. 

Liver cysts form on or in your liver. They’re very common; about one in every 20 people is walking around with at least one cyst. But most people who have a liver cyst don’t know it. 

Most liver cysts are benign, meaning not cancerous.

Most liver cysts cause no symptoms at all. That’s why most people who have one don’t know it. But in some cases, usually when the cyst is large, a liver cyst can cause the following symptoms:

• Bloating
• Pain in the upper-right part of your stomach or abdomen
• An abdomen that feels full or uncomfortable
• Pain in your right shoulder

When a liver cyst causes pain, that pain tends to be minor and dull. Sudden, severe pain could mean that you are bleeding into the cyst.

In most cases, doctors aren’t sure. But they think birth defects may cause a liver cyst to form. 

In some parts of the world, swallowing a parasite called Echinococcus -- that infected dogs can spread -- can cause liver cysts. Some rare medical conditions, such as polycystic liver disease, can also cause cysts to form. 

Finally, some liver tumors can cause cyst-like growths to form. 

Usually, doctors use ultrasound or some other form of imaging to identify a cyst. In some cases, the doctor will also perform a blood test to rule out a parasite as the cause of a person’s liver cyst.

Unlike simple liver cysts, cystic liver tumors are not very common. These tumors contain both liquid and solid parts. Most are noninvasive and harmless. But they can transform into cancers called cystadenocarcinomas or mucinous cystic neoplasms with invasive carcinoma. Doctors call these tumors cystadenomas or, more recently, mucinous cystic neoplasms. 

In very rare cases, people who have ongoing inflammation of the pancreas (pancreatitis) can develop a pseudocyst in the liver. Pseudo means “not real,” and this is not a real cyst. It is waste and fluid from the pancreas that can collect in the liver. If you have one, you may need drainage and surgery. 

If your doctor identifies something on your liver, he will be able to tell you if it’s a cyst or a tumor.

If your liver cyst isn’t causing symptoms, your doctor may not treat it at all. If you do have symptoms, the doctor may choose to simply drain the fluid from your cyst. 

In some cases, the doctor might also want to perform surgery to remove part of the cyst so that it can’t fill with fluid again. This surgery is usually laparoscopic, which means it requires just a few small cuts and a night or two in the hospital.

In most cases, you’ll be back to normal within two weeks of surgery. After surgery, liver cysts almost never come back.  

If you have a cystic liver tumor, the only way to know whether it is benign or cancerous is to surgically remove the entire growth and examine it carefully. People do very well when the surgeon is able to remove the entire tumor during surgery.

In very rare cases, noncancerous liver cysts called cystadenomas can become cancerous. When they become cancerous, doctors call them cystadenocarcinomas. Their symptoms, similar to those of a simple cyst, are feeling full in your belly and dull pain or discomfort in the upper right side of your abdomen. Unlike with simple cysts, images will show that cystadenocarcinomas have both liquid and solid areas. 

Rarely, liver cysts may mean that you have polycystic liver disease. This is a genetic condition, and it can cause cysts to return even if your doctor removes them. Not all people with polycystic liver disease have symptoms. But those who do have symptoms require treatment -- which could include a liver transplant, though that’s uncommon. 

Finally, cysts can cause blockages that lead to infections or duct problems. 

To avoid these complications, see your doctor sooner rather than later if you have symptoms that could point to a liver cyst.