Clinically, 24h urine volume less than 400mL is called oliguria, 24h urine volume less than 100mL or 12h urine volume of 0mL is called anuria, if oliguria occurs, further examination in hospital is needed, often due to pre-renal or renal or post-renal factors. 1, pre-renal oliguria, mostly seen in hemorrhagic shock, dehydration or insufficient rehydration, etc., which leads to a decrease in blood volume filtered through the kidneys, can cause oliguria. It can cause oliguria, and after rehydration treatment or replenishment of blood volume, the urine volume can be restored to normal. 2, renal oliguria, which is damage to the kidneys themselves, such as glomerulonephritis, nephrotic syndrome or acute renal failure, etc., the filtration function of the kidneys stops, that is, the kidneys do not work, so they do not produce urine volume, and often need to give dialysis treatment, and the treatment course time is relatively long. 3, post-renal obstruction, that is, the kidneys work normally, but the urine produced by the kidneys stays in the kidneys, ureter or bladder and cannot be discharged, such as kidney stones, ureteral stones causing ureteral blockage, or prostate enlargement leading to urethral blockage of urine can not be discharged, surgical treatment is needed to restore the patient’s urine volume.