Hydronephrosis is the obstruction of urine discharge and accumulation in the kidney, thus affecting the kidney function. There are many causes of hydronephrosis, and the severity usually depends on the amount and time of hydronephrosis. If the amount of hydronephrosis is small, the time is short and the obstruction is released in time, the condition is mostly mild and the prognosis is good; if the condition is delayed for a long time or a large amount of hydronephrosis is accumulated in the kidney, it can lead to organic lesions of the kidney, renal function decreases, or even develop into renal failure, which is usually more serious. Common clinical causes include: 1, urinary tract stones: upper and lower urinary tract stones block the ureter, bladder or urethra and other parts of the obstruction, which can cause urine reflux, resulting in patients with hydronephrosis; 2, prostate disease: such as prostate hyperplasia and other diseases caused by prostate hypertrophy, will compress the urethra to form an obstruction, patients can have difficulty urinating, urinary weakness, and even urinary retention, which causes hydronephrosis; 3, infection and Trauma: such as inflammatory infections of the urinary system, urological tuberculosis, recovery from trauma, etc., can cause ureteral and urethral stenosis or bladder atrophy, leading to hydronephrosis; 4, congenital developmental abnormalities: some patients have abnormal embryonic development, resulting in narrowing of the pelvic ureteral junction, posterior urethral valves, ectopic ureteral openings or horseshoe kidneys, etc., which can obstruct urine discharge, thus forming hydronephrosis; 5, urinary system polyps The cause is similar to that of stones, and compression of the ureter and urinary nerve can lead to inability to urinate, thus forming hydronephrosis; 6, nerve damage: such as cerebral infarction, diabetes, spinal cord injury, etc., can cause neuropathy, resulting in bladder nerve damage, resulting in urine retention and hydronephrosis; 7, medically induced injury: ureteroscopy The ureter may be accidentally damaged during surgery of the urological system and reproductive system, resulting in stricture or even occlusion. Patients may have urinary obstruction, thus causing hydronephrosis; 8. Compression of neighboring organs: such as colon cancer, rectal cancer, retroperitoneal fibrous degeneration and other gastrointestinal lesions, cervical cancer, ovarian cancer, pelvic tumors and other reproductive system lesions, as well as pregnancy, can lead to ureteral, bladder and other parts of the compression or invasion, which can cause obstruction, resulting in hydronephrosis.