After hydronephrosis, you need to improve the relevant tests to find the cause of the hydronephrosis and then consider how to proceed with the follow-up treatment. Common causes of hydronephrosis are still problems at the junction of the renal calyx and ureter, such as loss of muscle function, stone obstruction, and compression by tumor tissue. It is important to choose the treatment according to the cause of the obstruction and to select the drainage method according to the condition. In the case of congenital developmental problems that result in local loss of muscle function or incomplete obstruction, it is important to consider whether to treat the problem surgically by removing the local diseased tissue and reanastomosing it to restore function. In the case of stone obstruction, the appropriate treatment plan should be selected according to the size of the stone. If the stone is small, oral medication can be considered to promote stone discharge, and if the stone is large, percutaneous nephrolithoscopy or ureteroscopy should be selected according to the actual situation of the patient to perform surgical treatment to remove the stone. If it is a tumor factor, we should improve the relevant examination and choose the appropriate treatment plan according to the specific size and location of the tumor, such as surgical removal or local radiotherapy. In addition to the etiological treatment, the drainage method should be selected according to the condition. For example, percutaneous nephrostomy under ultrasound guidance, permanent nephrostomy, double J-tube via bladder placement, etc. Severe infection and severe loss of renal function, while the contralateral kidney function is normal can be removed from the affected kidney. If the obstruction cannot be relieved, if the symptoms are not relieved after adequate drainage, or if there is significant hyperkalemia, hemodialysis treatment should be performed. In conclusion, if hydronephrosis is found, it is important to improve the examination, such as urological ultrasound, CT, and contrast examination, to clarify the cause of hydronephrosis and choose an efficient treatment plan according to the actual situation of the patient, and while treating it, attention should be paid to protect the kidney function to avoid renal insufficiency or uremia.