Most normal urine is a pale yellow liquid, the main component is water, accounting for about 96% of urine, and other components are nitrogenous substances such as urea, uric acid and creatinine. The amount of urine excreted by a normal person is about 1000-2000 ml per day and night.
The bladder is located in the pelvis and is an organ that stores urine with a capacity of 300-500 ml. There is a limit to the capacity of the bladder to hold urine. By holding urine, we mean that the urine held in the bladder exceeds the capacity of the bladder itself, but we consciously hold it back. Sitting for a long time without holding urine is not good for your health and can lead to urinary tract diseases. Normal urination not only removes metabolic products from the body, but also has a self-cleaning flushing effect on the urinary system and urinary tract.
When 200 ml of urine accumulates in the bladder, the body will begin to have the urge to urinate, at this time, if you do not urinate, the bladder can still hold urine, but if the accumulation continues to 500-600 ml, If you do not urinate in a timely manner for a long time, the bladder will become overloaded, and in severe cases, it will lead to urinary retention and inability to urinate on your own.
When a large amount of urine is stored in the bladder, precipitates concentrate, increasing the saturation of calcium salts in the urine and increasing the likelihood of urinary stone formation. When urine is held, the bladder volume increases, blood vessels are compressed, and the mucous membrane becomes ischemic, leading to a decrease in resistance. At this time, bacteria take advantage of the situation (retrograde infection of the urinary tract) and grow and multiply, easily causing urethritis, cystitis and other diseases of the urinary system.
There is a good “anti-reflux” physiological anatomical mechanism for urine to drain from the ureter into the bladder, and the ureter is submerged by “tunneling” through the bladder wall. However, holding urine can cause urine to “reflux” because the pressure in the bladder continues to increase, even more than the pressure at the ureteral orifice. Holding urine can even lead to pyelonephritis. Urine retention can cause the pressure in the bladder to rise and urine to reflux along the ureter, resulting in pelvic effusion, followed by pressure on the renal parenchyma, ischemia, and even necrosis. This is reflux nephropathy.
Holding urine can also cause physical and psychological stress. The continuous increase in bladder capacity causes an increase in intra-abdominal pressure, which increases blood pressure in patients with hypertension; patients with coronary artery disease experience arrhythmias and even angina pectoris. Therefore, holding urine is more likely to lead to serious consequences such as sudden cardiac death in most elderly patients with underlying conditions such as hypertension, coronary artery disease, and diabetes.
If an elderly person urinates suddenly after holding urine for a long time, the rapid emptying of the bladder, the drop in intra-abdominal pressure, and the slowing of the amount of blood returning to the heart will cause excitation of the vagus nerve, insufficient blood supply to the brain, lower blood pressure, slower heart rate, and even urinary syncope. Rapid urination after urine retention can also cause hematuria to the naked eye.