Possible reasons for urine becoming less: First, diseases of the kidneys, such as acute renal failure, glomerulonephritis, etc., can lead to less urine, which can be accompanied by water accumulation in the body manifested as edema, such as edema in the face or low hanging limbs, etc. Further examination of kidney function is needed to clarify the presence of nephritis. Second, if there are factors of posterior urethral obstruction, such as bilateral ureteral stones, stones in the urethra, urethral stricture, prostatic hyperplasia, etc., they can lead to urine accumulation in the body, such as causing hydronephrosis or causing urinary retention in the bladder. Indwelling catheterization and timely drainage treatment, or nephrostomy or cystostomy treatment are required. After further examination to determine the primary cause, removal of the primary cause can be cured. Third, less water consumption or the presence of dehydration diseases, such as sweating more or having vomiting, diarrhea, etc. resulting in excessive water loss, can lead to low urine output, and treatment such as hydration needs to be given.