A CT scan reveals a low-density foci in the liver, indicating that this lesion is cystic fluid and less dense than the liver parenchyma. These foci are usually liver cysts, liver abscesses, hepatic hemangiomas or, less commonly, liver encapsulation disease. Hepatic cysts are the most common benign disease of the liver. The cystic cavity is usually not in communication with the intrahepatic bile duct system, and the cyst is a closed cavity composed of an arrangement of epithelial cells containing fluid, which can be solitary or multiple, varying in size and number from one to dozens of Beden. The vast majority of liver cysts grow slowly and are usually asymptomatic and are only discovered incidentally during physical examination. Huge liver cysts may present with significant compression symptoms. In case of co-infection, symptoms similar to liver abscess such as chills, fever and abdominal pain may appear. Liver abscess: Liver abscess is a serious infectious disease of the liver, which is a purulent lesion of the liver caused by a variety of microorganisms such as bacteria, fungi or lyso-amoeba protozoa, and patients mostly have symptoms such as fever and right upper abdominal pain. If not actively treated, the mortality rate can be as high as 10% to 30%. The rich pipeline system in the liver, including the biliary system, portal system, hepatic arterial system and lymphatic system, greatly increases the probability of microbial parasitism and infection. There are three types of liver abscesses, of which bacterial liver abscesses are often mixed infections due to multiple bacteria, about 80%, amoebic liver abscesses about 10%, and fungal liver abscesses less than 10%. Bacterial liver abscesses require aggressive treatment with intensive nutritional support and strong anti-infective therapy, as well as perforated drainage or surgical drainage. Hepatic hemangioma: Hepatic hemangioma is a relatively common benign tumor of the liver, clinically spongy hemangioma is the most common, the patient mostly has no obvious discomfort symptoms, often found in ultrasound or during abdominal surgery, and generally does not require treatment. According to the pathology, there are 4 types: (1) cavernous hemangioma is the most common; (2) sclerosing hemangioma; (3) vascular endothelial cell tumor; (4) capillary hemangioma. Classification according to tumor size: (1) small hemangioma <5cm; (2) hemangioma 5-10cm; (3) giant hemangioma 10cm-15cm; (4) very large hemangioma >15cm. ? Although hepatic hemangioma is a tumor, it is not a tumor in the ordinary sense. It means that it is caused by abnormal development of blood vessels in the liver, but of course, there are other factors such as infection and hormonal changes. Small hemangiomas, which have no symptoms, do not affect liver function or patient’s life, and therefore do not require treatment. However, when the hemangioma becomes large enough to compress the liver and cause abnormal liver function or if the hemangioma is located on the surface of the liver and is at risk of rupture, active treatment is required. Treatment modality encapsulation intervention local treatment or surgical treatment. Hepatic encysticercosis: Hepatic encysticercosis is a more common parasite in pastoral areas, also known as hepatic echinococcosis. In China, it is mainly prevalent in Xinjiang, Qinghai, Ningxia, Gansu, Inner Mongolia and Tibet, which are provinces with developed animal husbandry. The cause of the disease is larval parasitism in animals (e.g., enough, cattle, etc.) and human infection by swallowing food contaminated with eggs. After the eggs are digested in the intestine, the larvae come out of their shells, cross the intestinal mucosa and enter the portal vein system, and most of them are retained in the liver. After 3 weeks in the body, the larvae develop into encysted worms. The larvae will form large and small enveloped cystic occupations in the liver. In addition, for patients with primary cancer in other areas, if CT suggests hypodense foci in the liver, there is usually nothing to worry about. However, it is important to pay enough attention and it is better to review liver-enhanced MRI to further clarify whether there is a possibility of metastasis. Liver-enhanced MRI is superior to CT in differential diagnosis.