Cystic lesions of the liver represent a heterogeneous group of disorders, which differ in etiology, prevalence, and clinical manifestations (table 1). Most liver cysts are found incidentally on imaging studies and tend to have a benign course. A minority can cause symptoms, and rarely may be associated with serious morbidity and mortality [1-3]. Larger cysts are more likely to be symptomatic and cause complications such as spontaneous hemorrhage , rupture into the peritoneal cavity  or bile duct , infection , and compression of the biliary tree [2,7]. Specific types of cysts may have unique complications such as malignant transformation in the case of a mucinous cystic neoplasm (cystadenoma), or anaphylactic shock due to a hydatid cyst. Some of these complications may occasionally mandate surgical intervention.
In some cases, predominantly cystic liver lesions may have solid areas, particularly in the setting malignancy. Conversely, predominantly solid liver lesions may have cystic components, as may be seen with hemangiomas or tumors that have areas that are necrotic.
Considerable controversy still exists regarding the definition and classification of cystic lesions of the liver (table 1). Furthermore, consensus has not been achieved on the optimal treatment of patients with symptomatic cysts, although a number of therapeutic approaches have been described [8,9]. This topic review will provide an overview of the diagnosis and management of cystic lesions in the liver. Detailed discussions on some of the individual causes of cysts are provided on the corresponding topic reviews.
Simple cysts of the liver are cystic formations containing clear fluid that do not communicate with the intrahepatic biliary tree. Although simple cysts are found in approximately 1 percent of autopsied adults, very few become large, and even fewer cause symptoms. Their size ranges from a few millimeters to massive lesions occupying large volumes of the upper abdomen; the largest reported cyst contained 17 liters of fluid .
Simple cysts tend to occur more commonly in the right lobe, and are more prevalent in women. The female-to-male ratio is approximately 1.5:1 among those with asymptomatic simple cysts while it is 9:1 in those with symptomatic or complicated simple cysts . Huge cysts are found almost exclusively in women over 50.