Urinary Tract Infections

URINARY TRACT INFECTIONS

OUTLINE

Ð'* Background information

Ð'* What are the causes of UTI?

Ð'* Who is at risk?

1. Recurrent Infections

2. Infections in pregnancy

Ð'* What are the symptoms of UTI?

Ð'* How is UTI diagnosed?

Ð'* How is UTI treated?

1. Recurrent Infections in women

2. Infections in pregnancy

3. Complicated Infections

Ð'* Is there a vaccine to prevent recurrent UTIs?

Background Information

Urinary tract infections are a serious health problem affecting millions of people each year. Infections of the urinary tract are commonÐ'--only respiratory infections occur more often. In 1997, urinary tract infections (UTIs) accounted for about 8.3 million doctor visits.* Women are especially prone to UTIs for reasons that are poorly understood. One woman in five develops a UTI during her lifetime. UTIs in men are not so common, but they can be very serious when they do occur.

The urinary system consists of the kidneys, ureters, bladder, and urethra. The key elements 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 excess liquid and wastes 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.

The average adult passes about a quart and a half of urine each day. The amount of urine varies, depending on the fluids and foods a person consumes. The volume formed at night is about half that formed in the daytime.

What are the causes of UTI?

Normal urine is sterile. It contains fluids, salts, and waste products, but it is free of bacteria, viruses, and fungi. An infection occurs when microorganisms, usually bacteria from the digestive tract, cling to the opening of the urethra and begin to multiply. Most infections arise from one type of bacteria, Escherichia coli (E. coli), which normally lives in the colon. 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 Chlamydia and Mycoplasma may also cause UTIs 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. But despite these safeguards, infections still occur.

Who is at risk?

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 or who 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 takes 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 in the immune system. Any disorder that suppresses the immune system raises the risk of a urinary infection. UTIs may occur in infants who are born with abnormalities of the urinary tract, which sometimes need to be corrected with surgery. UTIs are rarely seen in boys and young men. In women, though, the rate of UTIs 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 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