On October 15, the Department of Urology successfully operated on a patient with severe right hydronephrosis. The patient, a 23-year-old male, had a gradually increasing abdomen with no obvious cause 10 months ago, accompanied by intermittent dull pain in the upper abdomen bilaterally. The examination revealed bilateral hydronephrosis, and the right hydronephrosis was particularly severe. The preoperative diagnosis was congenital stenosis of the pelvic ureteral junction on both sides. In order to protect the patient’s renal function and treat the congenital malformation, a right renal puncture fistula was performed in the urology department 3 months ago to drain the urine to protect the right renal function, and a retroperitoneoscopic pelvic ureteric junction adhesion release was performed on the left side. More than 3 months after the right hydronephrosis was adequately drained, the patient came to our hospital again to undergo right renal pelvis clipping and shaping, and the clipped pelvis was about 30cm3, which successfully released the obstruction, saved the kidney and relieved the patient’s worries about his future life and work. Conventionally, such a serious hydronephrosis requires nephrectomy. Considering that the patient is young and both sides of the kidney have lesions, try to preserve the residual kidney function. After efforts, the surgery was successfully completed. Initial results were seen in the follow-up. The following are the preoperative images. This is a typical case of congenital ureteral stenosis causing hydronephrosis. In addition to congenital developmental factors, urinary tract stones, tumors, and inflammation can cause urinary tract obstruction. Severe obstruction can cause hydronephrosis and impair renal function. If left untreated, it will cause functional insufficiency and even renal failure. If you find hydronephrosis, you should go to the hospital in time to find out the cause and treat it in time.