In the process of kidney development, there may be abnormalities or deformities in shape, position and quantity. Common ones are: ① horseshoe kidney: the lower ends of the left and right kidneys are connected with each other to form a horseshoe shape; ② Polycystic kidney: Because the renal tubule is not connected with the collecting duct during the embryo, the fluid is stored in the renal tubule, which causes the kidney to swell into cysts; (3) Double renal pelvis and double ureter: If there are two branches at the bud end of ureter, double renal pelvis will be formed; ④ Single kidney: One kidney is called single kidney if it is missing or underdeveloped; ⑤ Low kidney: In the early embryo, the kidney is located in the pelvis and gradually rises to the waist with the development of the fetus. If the development is stagnant, it can become a low kidney, which can be located in iliac fossa or pelvic cavity. If the renal area is often painful, it is recommended to have a renal function examination.