Post-renal oliguria, also called obstructive nephropathy, refers to oliguria caused by poor urinary discharge in the urinary tract. Common causes include inflammation, stones, tumors, prostatic hyperplasia, neuromuscular disorders, and renal prolapse. Inflammatory causes are commonly due to repeated inflammatory infections of the renal pelvis and ureter, resulting in hyperplasia and narrowing of the ureteral mucosa. Patients with tumors often suffer from an enlarged, occupying lesion in the mucosa of the ureter or renal pelvis that causes narrowing of the lumen, resulting in poor urinary drainage. In other patients with stones, the stones become lodged in three narrowed parts of the ureter, causing luminal narrowing. Some patients with tumors are abdominal organs, and if there is an occupying lesion in an organ other than the ureter, its enlargement and enlargement will compress the ureter from the outside, resulting in narrowing of the lumen. Prostate enlargement belongs to the glandular enlargement after the compression of the urethra, resulting in poor urinary discharge and retention of urine in the bladder. There are also patients with sequelae of cerebrovascular disease, there will be dysfunction of the sensory and motor nerves of the bladder, resulting in decreased diastolic function of the bladder muscles, and the patient is unable to stretch the smooth muscles of the bladder in time for urination. For patients with prolapsed kidneys, the normal kidney is fixed in the posterior wall of the abdominal cavity by adipose tissue. Young people who are very thin may have a weakened fixation of the kidney due to the low adipose tissue, and the kidney will have downward displacement and sagging, which will cause the ureter to fold, and likewise cause poor urinary discharge, leading to hydronephrosis. Therefore, postrenal oliguria is mainly the cause of obstruction and needs to be treated accordingly after examination.