A small amount of hydronephrosis in the kidney requires further examination and evaluation for symptomatic treatment: First, if the examination is for extra-renal pelvis or pot-bellied pelvis, there may be a small amount of hydronephrosis, which is a physiological change, and regular follow-up is recommended, without any treatment. Second, if there is a small amount of fluid in the kidney caused by stones or stenosis, the primary cause needs to be treated, such as the presence of a small amount of fluid caused by stones, extracorporeal shock wave lithotripsy or ureteroscopy, percutaneous nephroscopy and other minimally invasive surgical treatment to remove the stones can be self-healing hydronephrosis. If there is a small amount of fluid in the kidney caused by ureteral stenosis urethral stricture, etc., you need to give urethral stricture expansion treatment, urinary tract restoration period patency, hydronephrosis can be cured. Thirdly, excessive bladder filling and holding urine can also cause a small amount of hydronephrosis in the kidneys. It is recommended to avoid holding urine for a long time and excessive holding urine, and then review regularly to observe whether the hydronephrosis is self-healing. For unexplained small amount of hydronephrosis in the kidney and the amount of water accumulation gradually increases during the observation period, it is recommended to conduct ureteroscopy or whole urinary system imaging examination if necessary, give ureteral stent tube for continuous drainage, remove the drainage tube at a later date, and then review regularly.