Liver cysts are one of the most common benign diseases of the liver and are not tumors, although they are an occupying lesion. Liver cysts are divided into two categories: parasitic cysts and nonparasitic cysts. Parasitic liver cysts are caused by parasites, such as encapsulated cysticercosis in pastoral areas. Non-parasitic liver cysts are the most common and clinically referred to as non-parasitic liver cysts, both congenital and acquired. Acquired hepatic cysts are: (1) hematoma and degenerative cysts; (2) lymphatic cysts; (3) retention cysts due to bile duct obstruction; and (4) cystic adenomas. Of these, retention cysts are the most common and are mostly due to inflammation, edema, scarring, trauma, and puncture. The majority of congenital liver cysts seen clinically are due to abnormal development of intrahepatic bile ducts or lymphatic vessels during the embryonic period. Liver cysts are also classified as monogenic or multiple. Solitary hepatic cysts are often located in the right lobe of the liver and are more commonly seen in women. Multiple hepatic cysts are more common and may invade the left and right hepatic lobes and may be combined with polycystic kidneys. Liver cysts grow slowly and may be asymptomatic for a long time or for life, and their clinical manifestations vary with the location, size, number and presence of complications. When the cyst increases to a certain extent, it may compress adjacent organs, such as stomach, duodenum and colon. Symptoms usually appear after 40-50 years of age, most of them are mild, with occasional painless masses in the upper abdomen, or distension and pain in the liver area, loss of appetite, belching, nausea, vomiting and wasting. If the cyst enlarges and presses on the common bile duct, there is jaundice, rupture may have intracapsular bleeding, and torsion of the cyst with tip may have acute abdominal pain, mostly in the upper abdomen or right rib area, sometimes radiating to the shoulder, back or chest. The liver is enlarged but no pressure pain. About half of the patients have polycystic lesions of kidney, spleen, ovary and lung. There is chills, fever, and elevated white blood cells in case of intracapsular infection. Liver cysts mainly rely on imaging diagnosis, with ultrasonography being the most important. b-mode ultrasonography has a detection rate of up to 98% for liver cysts. In terms of characterization, ultrasonography is more accurate than CT; however, CT is superior to B-mode ultrasonography in fully understanding the size, number and location of cysts and related organs in the liver and around the liver, especially for huge liver cysts that require surgical treatment. Simple and non-invasive B-mode ultrasonography should be performed first, which can also identify liver cysts. Next, X-rays should be selected as needed, including abdominal plain film, abdominal arteriography, gastrointestinal imaging, CT and MRI. Liver cysts usually do not lead to liver function abnormalities, and laboratory tests are of little value for the diagnosis of liver cysts. ultrasound or CT is very reliable for the diagnosis of liver cysts, and there is generally no need to do too many tests. After liver cysts are found, blood should be taken to check for alpha-fetoprotein to exclude liver cancer. Liver cysts are not tumors. Cyst is a fluid occupancy while tumor is a substantial occupancy, which can be easily distinguished when ultrasound examination is performed. One should be alert to the fact that liver cysts can exist in combination with liver cancer. Those found to have liver cysts should not forget to test blood AFP. Liver cysts are completely different from hepatic hemangioma. Hepatic hemangioma is one of the most common benign tumors of the liver, with hepatic cavernous hemangioma being the most common. It is usually solitary, mostly occurring in the right lobe of the liver, and about 10% are multiple, and can be distributed in one or both lobes of the liver. Hemangiomas present in the liver as dark red or blue-purple cystic elevations, lobulated or nodular, soft, compressible, and mostly clearly demarcated from adjacent tissues. The tumor consists of blood-filled vessels with markedly enlarged lumens. The cause of hemangioma formation is unknown, but some believe it is due to abnormal development of intrahepatic vascular structures, while others believe it is related to estrogen levels. The disease is asymptomatic and presents only as an intrahepatic occupying lesion, so clinical attention should be paid to differentiate it from hepatocellular carcinoma. About 10% of patients may have liver cysts as a complication. Liver cysts are also a completely different concept from liver abscesses. The fluid of a liver cyst is thin, sterile, and free of cellular components; however, the fluid of a liver abscess is thick, bacterial, and has white blood cells and necrotic cells. Liver abscesses may not only produce localized pain in the liver area, but also cause systemic inflammatory reactions, such as fever and elevated blood leukocytes. Imaging liver abscesses have characteristic manifestations and are easily distinguished. The number of cysts found during ultrasound or CT examination is sometimes high and sometimes low because of the limitations of the examination equipment or the degree of care of the examiner. Liver cysts do not become malignant. So far, the formation of liver cysts has not been found to be related to certain foods, so patients with liver cysts do not need to avoid eating. It is also not found that doing housework, sports and work have a promoting effect on the growth of liver cysts, so patients with liver cysts do not need to change their living habits and working environment, they can work and exercise, and there is nothing to pay special attention to in their life. Most liver cysts do not require special treatment. Those with single or multiple cysts without clinical symptoms should undergo regular ultrasound examination, and those with cysts over 5 cm can be treated with injection of sclerosing agent after aspiration of cyst fluid by ultrasound-guided puncture. Usually, the liver area should be avoided to be hit by external force to avoid cyst rupture. Special treatment should be considered for those with the following conditions: (1) Giant liver cysts: A few liver cysts grow faster and when the diameter exceeds 10 cm, they are called giant liver cysts. Giant liver cysts can cause compression symptoms and affect life and work, and should be considered for treatment. (2) Secondary infection of cysts: liver cysts usually rarely become secondary to infection, but a few liver cysts can become secondary to infection. These patients may have inflammatory manifestations such as pain in liver area, fever, elevated blood leukocytes, etc. Ultrasound examination may show thickened cyst wall, liquid dark area and mixed enhanced light spots (suggesting pus). These patients should be treated promptly. (3) Cyst secondary hemorrhage: a few liver cysts with cyst wall vessels can rupture spontaneously leading to intracapsular hemorrhage, some without obvious symptoms, some with severe pain in liver area, such as conservative treatment without effect surgical treatment. (4) Cyst torsion: overhanging cysts produce severe pain when torsion occurs, and surgery may be the only treatment method.