Urine is a product of kidney metabolism. The kidneys regulate excess water in the body by producing urine and excrete metabolic waste and toxins produced by the body’s metabolism. The water produced by diet and metabolism in the body every day enters the kidneys with the blood flow. There are many “filters” called glomeruli in the kidneys. The glomeruli are specialized in filtering water and metabolic waste. When blood flows into the “filters,” the excess water in the blood is filtered out along with the metabolic wastes in the body to form urine. Urine enters the bladder through the ureter and is stored in the bladder. Urine is a metabolic product of the body, most of which is not needed by the body, and is constantly being formed. If you hold urine, more and more urine is retained in the bladder, which enlarges and causes damage to the bladder muscles due to expansion. . Some people hold urine for a period of time, even if the discharge will also feel pain in the abdomen, which is the reason for the expansion of the bladder is not fully contracted. In addition, holding urine for too long, the pressure in the bladder increases, which is bound to damage the metabolic function of the kidneys to excrete waste, so that water and metabolic waste accumulate in the body, causing uremia, causing kidney failure and life-threatening. Therefore, except for certain tests that require a short period of holding urine, you should not hold urine in any other case.