Kidney cysts, also known as renal cystic disease, are divided into many types. There are single and some are multiple. Some kidney cysts are related to genetic factors, such as polycystic kidneys, and in severe cases, the kidneys look like a big bunch of grapes filled with cysts of different sizes. The most common is still common kidney cyst. Patients with kidney cysts may experience discomfort or pain in the lower back and abdomen, some patients may develop kidney stones, and a few patients may develop high blood pressure, bleeding from the cysts, or symptoms due to infection of the cysts. Common cysts are usually not cancerous, but a few kidney cancers may behave like cysts. For patients with suspected cancer, doctors usually need to use imaging tests such as ultrasound, CT or MRI to differentiate. One doctor named Bosniak classified kidney cysts. The cysts are categorized into 4 grades based on the structure of the wall of the kidney cyst on CT, with cancer being considered above grade 3. To make an analogy, a kidney cyst is similar to the house we live in, surrounded by walls and furniture in the room, the difference is that the cyst is airtight, filled with fluid, there is no door, and there is no communication with the outside world. To determine whether there is cancer or not mainly depends on whether the wall structure is uniform, there is no bulge. If the walls of the cyst appear to be unevenly thickened or even bulging, the possibility of cancer should be considered.