As a gastroenterologist and hepatologist, it is quite common for me to see patients with liver cyst(s) in my outpatient clinic every day. Most of them were diagnosed during their medical checkup as an incidental finding on ultrasound scan.
What is a liver cyst?
A liver cyst is a fluid-filled cavity – sort of like a water balloon – that forms in the liver. Most liver cysts are benign, which means they are not cancerous. A small liver cyst rarely causes symptoms; therefore, it might go undetected until later when symptoms arise due to mass effect, complications, or when discovered during a medical checkup.
Liver cysts can be developmental, inflammatory, neoplastic or trauma-related lesions. The simple liver cyst is the commonest type. The cause of simple liver cysts is unknown, but they may be the result of a malformation at birth.
Some rare medical diseases, such as autosomal dominant polycystic kidney disease (ADPKD), can also cause cysts to form in the liver. This is a genetic condition and the cysts can recur even if surgical removal is done. Polycystic liver disease (PLD) is defined as the presence of 20 or more cysts in the liver.
A pseudocyst (false cyst) can occur after ongoing chronic inflammation of the pancreas, which is a common complication of acute alcoholic pancreatitis. Biloma is a hepatic bile collection outside the biliary tree, which occurs as a result of an iatrogenic biliary injury such as cholecystectomy or blunt abdominal injury. A parasite called Echinococcus, which can be spread by faecal-oral route from infected dogs, can cause hydatic liver cysts. Rarely, a liver cyst could turn out to be a cystic liver tumour.
How common are liver cysts?
They are very common! About one in 20 people are found to have at least one cyst in their liver. According to Lantiga et al, a study conducted between 1954-1971 found the incidence of liver cysts to be 17 in 10,000.(1) Another study by Seoul National University College of Medicine showed that simple liver cyst had a prevalence of 2.5-5.0%, with a slight female predominance.(2)
Most simple cysts can be confidently diagnosed by ultrasound scan alone. Occasionally, contrast-enhanced computed tomography (CECT) or magnetic resonance imaging (MRI) if other differential diagnoses are considered. Although genetic testing for ADPKD and PLD is available, they are seldom performed on a regular basis as the results do not influence our management. The measurement of serum and cyst fluid CA 19-9 levels could be useful in differentiating between a bleeding simple liver cyst and malignant cyst.
How do I deal with liver cysts?
Majority of patients do not have any discomfort until the cyst grows big enough to cause mass effect such as right upper abdominal discomfort or pain, early satiety, nausea and vomiting. Complications such a bleeding and rupture are uncommon, and more likely to happen in larger cysts.
Management is dependent on the underlying cause. Asymptomatic, small liver cysts are managed with a “wait and see” policy, while large, symptomatic or cancerous cysts need further treatment. Those without symptoms just need to be followed up with periodic ultrasound scans and blood tests, especially for those with large cysts ⩾4 cm in diameter.(3)
Symptomatic cysts are treated either with percutaneous aspiration, with or without a sclerosant; or surgical intervention, preferably done laparoscopically. Antibiotics are indicated when there are signs of infection. Chemotherapy and antiparasitic drugs are required for those with hydatic liver cysts.
References:
- Lantinga MA, Gevers TJ, Drenth JP. Evaluation of hepatic cystic lesions. World J Gastroenterol. 2013;19:3543–3554.
- Seo JK, Kim SH, Lee SH, et al. Appropriate diagnosis of biliary cystic tumors: comparison with atypical hepatic simple cysts. Eur J Gastroenterol Hepatol. 2010;22:989–996.
- Antunes H, Braga-Tavares H, Cunha I, et al. Congenital simple hepatic cyst: a diagnostic and management challenge. Gastroenterol Hepatol. 2009;32:92–96.