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Infections of the urinary tract are common-only respiratory infections occur more often. Each year, urinary tract infections (UTI's) account for about 8 million doctor visits. Women are especially prone to UTI's for reasons that are poorly understood. One woman in five develops a UTI during her lifetime.

The urinary system consists of the kidneys, ureters, bladder, and urethra. The key players in the system are the kidneys, a pair of purplish-brown organs located below the ribs toward the middle of the back. The kidneys remove liquid waste from the blood in the form of urine, keep a stable balance of salts and other substances in the blood, and produce a hormone that aids the formation of red blood cells. Narrow tubes called ureters carry urine from the kidneys to the bladder, a triangle- shaped chamber in the lower abdomen. Urine is stored in the bladder and emptied through the urethra.




In most cases, bacteria first begin growing in the urethra. An infection limited to the urethra is called urethritis. From there bacteria often move on to the bladder, causing a bladder infection (cystitis). If the infection is not treated promptly, bacteria may then go up the ureters to infect the kidneys (pyelonephritis). Microorganisms called chliamydia and mycoplasma may also cause UTI's in both men and women, but these infections tend to remain limited to the urethra and reproductive system.

Unlike E. coli, chlamydia and mycoplasma may be sexually transmitted, and infections require treatment of both partners.

The urinary system is structured in a way that helps ward off infection. The ureters and bladder normally prevent urine from backing up toward the kidneys, and the flow of urine from the bladder helps wash bacteria out of the body. In men, the prostate gland produces secretions that slow bacterial growth. In both sexes, immune defenses also prevent infection. Despite these safeguards, though, infections still occur.

Who Is at Risk

A common source of infection is catheters, or tubes, placed in the bladder. A person who cannot void, is unconscious or critically ill, often needs a catheter that stays in place for a long time. Some people, especially the elderly or those with nervous system disorders who lose bladder control, may need a catheter for life. Bacteria on the catheter can infect the bladder, so hospital staff take special care to keep the catheter sterile and remove it as soon as possible.

People with diabetes have a higher risk of a UTI because of changes of the immune system. Any disorder that suppresses the immune system raises the risk of a urinary infection.

UTI's may occur in infants who are born with abnormalities of the urinary tract, which sometimes need to be corrected with surgery. UTI's are rarely seen in boys and young men. In women, though, the rate of UTI's gradually increases with age. Scientists are not sure why women have more urinary infections than men. One factor may be that a woman's urethra is short, allowing bacteria quick access to the bladder. Also, a woman's urethral opening is near sources of bacteria from the anus and vagina. For many women, sexual inter- course seems to trigger an infection, although the reasons for this linkage are unclear.

Recurrent Infections

Many women suffer from frequent UTI'S. Nearly 20 percent of women who have a UTI will have another, and 30 percent of those will have yet another. Of the last group, 80 percent will have recurrences.

Usually, the latest infection stems from a strain or type of bacteria that is different from the infection before it, indicating a separate infection. (Even when several UTI's in a row are due to E. coli, slight differences in the bacteria indicate distinct infections.)

Infections in Pregnancy

Pregnant women seem no more prone to UTI's than other women. However, when a UTI does occur, it is more likely to travel to the kidneys. According to some reports, about 2 to 4 percent of pregnant women develop a urinary infection. Scientists think that hormonal changes and shifts in the position of the urinary tract during pregnancy make it easier for bacteria to travel up the ureters to the kidneys. For this reason, many doctors recommend periodic testing of urine.


Not everyone with a UTI has symptoms, but most people get at least some. These may include a frequent urge to urinate and a painful, burning feeling in the area of the bladder or urethra during urination. It is not unusual to feel bad all over-tired, shaky, washed out-and to feel pain even when not urinating. Often, women feel an uncomfortable pressure above the pubic bone, and some men experience a fullness in the rectum.


In children, symptoms of a urinary infection may be overlooked or attributed to another disorder. A UTI should be considered when a child or infant seems irritable, is not eating normally, has an unexplained fever that does not go away, has incontinence or loose bowels, or is not thriving. The child should be seen by a doctor if there are any questions about these symptoms, especially if there is a change in the child's urinary pattern.


