Simple renal cysts are divided into single and multiple (more than 2 on one kidney), and the size is usually 0.5cm~10+cm (too small to be detected by ultrasound). Most kidney cysts are found during physical examination and ultrasound is the preferred method of diagnosis. If the nature of the cyst (simple or complex, such as cancer) cannot be confirmed by ultrasound, CT examination is used. Simple renal cysts are mostly single-chambered, with smooth cyst walls and thin and uniform cyst fluid. If the cyst wall is of variable thickness and has burrs, the possibility of carcinoma is to be considered. Kidney cysts usually do not disappear on their own and are not controlled by drugs, most of them will gradually increase, of course the rate of increase varies, usually 0.2cm~1.5cm per year. simple kidney cysts usually have little effect on human health and do not affect kidney function, so no treatment is needed. If the following conditions occur, treatment needs to be considered (1) the cyst is too large (more than 7cm~8cm), especially positioned in the lower level of the kidney and prone to rupture; (2) the cyst is too large and develops high blood pressure; (3) there are changes inside the cyst, such as the cyst wall is not smooth; (4) the cyst is too large and develops back pain, which is considered to be related to the cyst. There are three treatments for renal cysts: (1) puncture and drainage + injection of sclerosing agent; (2) open cystotomy; (3) laparoscopic cystotomy. Each of the three treatments has advantages and disadvantages, with a high recurrence rate for puncture, a high trauma for open surgery, and a higher cost for laparoscopy. Those who have problems need to discuss in detail with their doctors and choose after weighing the pros and cons. There is a genetic disease, polycystic kidney, which is completely different from renal cyst. However, it is often confused with polycystic kidney cyst by doctors and patients. Polycystic kidney often runs in families and manifests as multiple cystic changes in both kidneys, which can be accompanied by hypertension and renal insufficiency, and in severe cases, uremia. Renal cysts are one of the most common kidney diseases with unknown etiology, probably related to renal tubular stasis. The vast majority of renal cysts are benign lesions, i.e. simple renal cysts. Malignant renal cysts are also known as cystic kidney cancer, and some may be transformed from simple renal cysts.