The total is about a quart and a half of urine each day. The amount of urine varies. It depends on the fluids and foods you eat and drink. The amount formed at night is about half that formed in the daytime.

It contains fluids, salts, and waste products. But it has no bacteria, viruses, or fungi.

Most infections arise from one type of bacteria, Escherichia coli (E. coli). These bacteria normally live in the colon. An infection occurs when bacteria or other microorganisms from the digestive tract, cling to the opening of the urethra. There they begin to grow in number. Germs called chlamydia and mycoplasma may also cause urinary tract infections (UTIs) in both men and women. But these infections tend to stay in the urethra and reproductive system. Unlike E. coli, chlamydia and mycoplasma may be sexually transmitted. These infections require that both partners be treated.

And if the bladder infection is not treated promptly, bacteria may sometimes go up the ureters to infect the kidneys.

A kidney stone, or anything that blocks the flow of urine, sets the stage for an infection. An enlarged prostate gland also can slow the flow of urine. This can raise the risk for infection. A common source of infection is catheters, or tubes, placed in the bladder.

This is because of changes in the immune system. Any disorder that weakens the immune system raises the risk for a urinary infection.

And older women get more UTIs than younger women. Experts are not sure why women have more urinary infections than men. One reason may be that a woman's urethra is short. This lets bacteria reach the bladder more easily. Also, a woman's urethra is near the anus and vagina. Both of these have bacteria in them. For many women, sexual intercourse seems to trigger an infection. Experts don’t know why this is so.

Other symptoms include a frequent urge to pee (urinate). And a painful, burning feeling in the area of the bladder or urethra when peeing. Often, women feel an uncomfortable pressure above the pubic bone. Some men have a fullness in the rectum. The urine itself may look milky, cloudy, or even reddish if blood is present. A fever may mean that the infection has reached the kidneys. Other symptoms of a kidney infection include pain in the back or side below the ribs, nausea, or vomiting.

This is the case if you don’t have a blockage in your urinary tract or a nervous system disorder. Still, many healthcare providers ask their patients to take antibiotics for 1 to 2 weeks to make sure the infection has been cured. It’s important to take all of the medicine you are given even if you start to feel better before you’re done.