By Robert Leventhal, MD
The liver is the largest internal organ, weighing about 3-4 lbs. in adults, and situated in the right upper quadrant of the abdomen under the diaphragm. The liver receives 25% of its blood from the hepatic artery and 75% from the portal vein. All products of digestion and absorption flow through the liver and are stored or excreted by the liver for transport. The liver produces bile, which is needed for absorption of fat and fat soluble vitamins. The bile ducts in the liver are like branches of a tree and come together just below the stomach into the small intestine. A side branch of the “biliary tree” is the sac-like gall bladder.
A liver cyst is typically a small and often fluid-filled collection that develops in the liver. Cystic disease in the liver is rare but comes in many forms. Simple cysts are most commonly found incidentally during imaging studies and are usually benign, do not cause symptoms, and do not require specific therapy. Women tend to have them more than men. They are not associated with the bile ducts. Only in cases where they are large can complications possibly occur such as infection, rupture, bleeding, and possible transformation to cancer.
Polycystic liver disease refers to the presence of multiple cysts within the liver and usually in patients with kidney cysts as well (polycystic kidney disease).
Echinococcal cysts are uncommon in the US but occur as a result of a parasitic infection (Echincoccus granulosus) from infected dogs. Symptoms (which may not present for many years) such as abdominal pain and fever develop as the cysts enlarge and can rupture which can lead to anaphylactic shock and death. Treatment involves the use of antiparasitic drugs and possibly surgery.
Cystadenomas are rare benign cysts but can become cancerous. Cystadenocarcinomas are cancerous cysts often seen in the elderly. Both types often require surgical resection.
Metastatic spread of cancer from elsewhere in the body can rarely appear as a cystic lesion, usually due to central necrosis. These include metastases from colon, pancreas, ovarian, kidney carcinoma and also neuroendocrine carcinomas.
Cysts can also arise from the biliary system and can be located at any level of the biliary tree. Most of these biliary cysts occur in the main trunk of the biliary tree (i.e., choledochal cysts). These types of cysts are congenital and can be associated with a variety of symptoms such as abdominal pain and jaundice (usually in childhood) and can also be associated with an increased risk of cancer as well (cholangiocarcinoma). Most biliary cysts require surgery.
Distinguishing between a simple cyst, cystadenoma, cystadenocarcinoma and Echinococcal cyst as well as primary or metastatic cystic tumors is extremely important and occasionally very difficult. These different entities have distinct differences in terms of treatment and management making accurate diagnosis imperative.
Ultrasonography is the safest and cost effective way of differentiating simple cysts from other more complex cystic lesions. Symptoms and ultrasound findings are usually enough to differentiate simple cyst from more significant pathology. Contrast CT and MRI are very useful alternatives to differentiating more serious cystic lesions. The differentiation can usually be made with radiographic tools along with clinical findings. Aspiration of a cyst is usually not required for diagnosis unless in cases of possible infection or need to exclude cancer.
The majority of cysts need no treatment. It may be necessary to monitor large cysts (> 4 cm) with periodic ultrasonography usually repeated in 3 months and then again at 6 – 12 months. If there is no change in the cyst size over one year, further evaluation or treatment will not be needed. The presence of symptoms or increasing size of the cyst should raise concern that it could be a cystadenoma, cystadenocarcinoma or other cystic neoplasm. Since most cysts are not associated with digestive symptoms, it is important to consider other diseases that could be causing symptoms such as gallstones, peptic ulcer disease, gastroesophageal reflux disease, gastric motility disturbance, or even functional dyspepsia before attributing them to liver cysts.
Therapeutic options for symptomatic cysts include needle aspiration with or without sclerosing agents (performed by interventional radiologists) and surgical therapies such as internal drainage with cyst-jejunostomy, unroofing cysts, and partial/segmental liver resection. Treatment options need to be individualized to each case as they can be associated with significant risks and complications.