Risks for Urinary Tract Infection (UTI)

Some people are more prone to getting a UTI than others. Any abnormality of the urinary tract that obstructs the flow of urine (a kidney stone, for example) sets the stage for an infection. An enlarged prostate gland also can slow the flow of urine, thus raising the risk of infection.

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 that 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 intercourse seems to trigger an infection, although the reasons for this linkage are unclear.

According to several studies, women who use a diaphragm are more likely to develop a UTI than women who use other forms of birth control. Recently, researchers found that women whose partners use a condom with spermicidal foam also tend to have growth of E. coli bacteria in the vagina.

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.)

Research funded by the National Institutes of Health (NIH) suggests that one factor behind recurrent UTI's may be the ability of bacteria to attach to cells lining the urinary tract. A recent NIH-funded study has also shown that women with recurrent UTI's tend to have certain blood types. Some scientists speculate that women with these blood types are more prone to UTI's because the cells lining the vagina and urethra may allow bacteria to attach more easily. Further research will show whether this association is sound and proves useful in identifying women at high risk for UTI's.

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 tract 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.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.