Renal cysts, also known as cystic kidney disease, can be of various types. It can present as a single one or some people have multiple ones. Patients with renal cysts may experience discomfort or pain in the lower back and abdomen, some patients may have secondary kidney stones, and a few patients may have secondary hypertension, cyst bleeding or corresponding symptoms due to cyst infection. Once a kidney cyst is detected by examination, it is important to focus on the following questions. First, it is important to determine whether it is a renal cyst. Most physical examinations reveal kidney cysts by ultrasound. Certain other conditions can sometimes be mistaken for a renal cyst, for example, a diverticulum or a duplicated hydronephrosis ultrasound presentation sometimes resembles a renal cyst. Some cysts in specific locations may also be misdiagnosed as other conditions, for example, parapelvic cysts are sometimes seen as hydronephrosis. Whether or not it is a manifestation of a kidney tumor is also one of the key considerations that doctors need to take into account. Common cysts are not usually cancerous, but a few kidney cancers present as a specific type of cyst, previously known as cystic kidney cancer. For patients suspected of cancer, it is usually necessary to grade the kidney cysts through CT and other examinations, so as to distinguish ordinary kidney cysts from cystic kidney cancer. For multiple renal cysts, doctors will also distinguish them from polycystic kidney. Polycystic kidney is a genetic disease and about half of them develop uremia due to progressive impairment of kidney function, requiring lifelong dialysis or kidney transplantation. Early detection of such patients and taking appropriate measures to delay the impairment of kidney function can improve the quality of life of patients.