Hydronephrosis is a condition in which the human body has difficulty in urination due to various reasons, and the pressure in the kidney gradually increases, resulting in an abnormally dilated state of the renal pelvis and calyces, with an enlarged renal shadow, enlarged renal pelvis and calyces, and atrophied and thinned renal parenchyma on abdominal X-ray plain film and urological ultrasound. There are many causes of hydronephrosis, which can be related to obstruction or can exist independently. Common clinical causes include congenital pelvic ureteral junction stenosis, duplicated kidney, horseshoe kidney, urological tuberculosis, stones, tumors, etc. It may also lead to hydronephrosis due to long-term lower urinary tract obstruction, such as prostatic hyperplasia, diabetes mellitus and neurogenic bladder due to nerve injury. Severe hydronephrosis can lead to renal failure and other comorbidities, followed by significant back pain secondary to infection, and individual patients can be combined with sepsis, which requires active response to determine the cause of hydronephrosis, such as the location and extent of the lesion and kidney damage, and treatment for the cause, including surgery, pyelostomy, etc.