The human bladder can hold up to 0.5 liters of liquid. A normal person taking 8 glasses of water a day takes 64 ounces (1.9 liters), hence the need to constantly get rid of the excess water. The bladder stores this excess liquid and when half full, sends signals to the brain to let one know that they should pee. This however, is bearable and one may decide to hold the pee for longer.
But how long is long, well it varies with different people. Others can hold it for so long while others can’t hold it in for long. It is however advisable that you hit the head as soon as the urge to do so comes.
While holding it for a short period has no effect apart from the difficulty to concentrate on anything else than your desire to pee, doing so for long and too many times is harmful. It may lead to infections and other numerous side effects. The bacteria on the genital surface is not being flushed out, hence it can enter through the ureter and migrate in to the bladder. The accumulation of these bacteria may cause lower urinary transmitted infection (UTI). In rare cases, the bacteria may walk its way up the ureter, reaching the kidney, causing pyelonephritis, a kidney ailment, whose symptoms include a fever, back pains. If this goes untreated, the bacteria will enter the blood stream causing a systemic disorder that is extremely life threatening.
For pregnant women, these bacteria spread faster, there are other infections that may arise from this. They include:
Kidneys stones a condition where tiny stone like develop in the kidneys due to excess accumulation of calcium and sodium salts along the tract. The stones make it difficult to pass urine as the pain that comes along is unbearable since the stones will be large compared to the tract size.
Cystitis an inflammation of the bladder walls mostly experienced by women. Its symptoms are: pain in the pelvis, burning and pain when urinating and swelling of the bladder.
Voiding dysfunction this occurs mostly in children. It is the inability to retain urine as the sphincter muscles have been weakened and are unable to relax.
The bladder may also swell since it is holding more than its capacity. Too much swelling may call for a surgery.
Other possible diverse effects are anxiety, cramps, shivers and stomach pains.