The majority of normal urine is light yellow liquid, the main component is water, accounting for about 96% of the urine, and other components are urea, uric acid, creatinine and other nitrogen-containing substances. The urine output of normal people every day and night is about 1000-2000 ml. The bladder is located in the pelvis and is an organ for storing urine. Its capacity is 300-500 ml. The capacity of the bladder to hold urine is limited. The so-called suffocation is that the urine contained in the bladder exceeds the capacity of the bladder itself, but consciously endure not to discharge. Sitting and holding urine for a long time is not conducive to health, and it will also lead to diseases of the urinary system. Normal urination can not only excrete metabolic products in the body, but also have self-cleaning scouring effect on the urinary system and urinary tract. When 200ml of urine accumulates in the bladder, the human body will begin to feel the urge to urinate. At this time, if there is no urination, the bladder can still retain urine, but when it continues to accumulate to 500-600ml, the bladder will appear excessive expansion, and make the muscles that control urination expand. If the bladder does not urinate in time for a long time, the bladder will be overloaded. In serious cases, it will lead to urinary retention and cannot urinate autonomously. When a large amount of urine is stored in the bladder, the sediment is concentrated, resulting in an increase in the saturation of calcium salts in urine, and an increase in the probability of formation of urinary calculus. When holding urine, bladder volume swells, blood vessels compress, and mucosa ischemia, resulting in reduced resistance. At this time, bacteria will take advantage of the opportunity to enter (retrograde infection of the urinary tract) and multiply in a large scale, which is easy to cause diseases of the urinary system such as urethritis and cystitis. Urine is discharged into the bladder from the ureter, which has a good physiological and anatomical mechanism of "anti reflux". The ureter is a "tunnel" that sneaks into the bladder wall. However, when holding urine, the pressure in the bladder continues to increase, even greater than the pressure of the ureter opening, which will lead to urine "reflux". Holding urine can even induce pyelonephritis. Urinary retention can increase the internal pressure of the bladder, and urine flows back along the ureter, resulting in hydronephrosis, followed by renal parenchyma compression, ischemia, or even necrosis. This is reflux nephropathy. Holding urine can also cause physical and psychological tension. The continuous increase of bladder volume leads to the increase of intraperitoneal pressure and the increase of blood pressure in hypertensive patients; Patients with coronary heart disease have arrhythmia, even angina pectoris. Therefore, suffocation is more likely to lead to sudden cardiac death and other serious consequences for most elderly patients with basic diseases such as hypertension, coronary heart disease and diabetes. If the old man urinates suddenly after holding urine for a long time, because of the rapid emptying of the bladder, the pressure in the abdominal cavity decreases, and the amount of blood returning to the heart slows down, the vagus nerve will be excited, the blood supply to the brain will be insufficient, the blood pressure will decrease, the heart rate will slow down, and even urination syncope will occur. Rapid urination after holding urine will also cause gross hematuria. (Xinhua News Agency)