What is asymptomatic bacteriuria?

Asymptomatic bacteriuria is a condition in which bacteria are in a person's urine, although the person has no symptoms of infection.

How does it occur?

Urine is normally sterile, which means that it contains no bacteria. However, a small number of bacteria may be found in the urine of many healthy people. The presence of a small number of bacteria in the urine is usually considered to be harmless. If the number of bacteria reaches a certain level, however, it may mean that the bladder, urethra, or kidneys are infected.

Anything that blocks the flow of urine (such as a stone or tumor in men or women, or prostate enlargement in men) or causes incomplete emptying of the bladder provides a place where bacteria can grow in the urine.

After 1 year of age, asymptomatic bacteriuria occurs more commonly in females than males because the urethra is shorter in females. The short urethra makes it easier for bacteria to travel from the anus or genital area up the urethra and into the bladder during normal activities such as wiping or sexual intercourse. Most bacterial infections of the urinary tract are caused this way. Bacteria can also enter the urine through the bloodstream, but this is rare.

Elderly women and pregnant women, particularly pregnant women with diabetes or sickle cell trait, have an increased risk of getting asymptomatic bacteriuria.

Men can also develop asymptomatic bacteriuria. In younger men, it is usually due to an inflammation or infection of the prostate gland (prostatitis). In older men it is usually due to an enlargement of the prostate gland that blocks the flow of urine.

What are the symptoms?

Asymptomatic bacteriuria has no obvious symptoms.

How is it diagnosed?

To diagnose asymptomatic bacteriuria, your doctor may examine you and ask you to provide a clean-catch urine specimen at two different times, about a week apart. Your doctor may also order some blood tests.

For a clean-catch specimen you will be asked to clean the genital area from front to back with a special antiseptic wipe and urinate a small amount into the toilet. Then you urinate into a sterile container. When the sterile container is about half full or you are almost done urinating, finish urinating into the toilet. This is also called a midstream urine specimen. The urine sample will be cultured and tested in the lab to see if there are any bacteria in the urine and to determine which antibiotics will kill the bacteria. There is a possibility of a false positive culture due to contamination of the specimen.

If you get bacteriuria more than once, your doctor may order additional blood tests or a special x-ray of the kidneys called an intravenous pyelogram (IVP). The IVP shows any abnormalities in the urinary tract. Your doctor may order a sonogram instead of IVP. A sonogram is a painless technique that is useful in looking at soft tissue such as the urinary tract that does not x-ray well.

How is it treated?

Asymptomatic bacteriuria may or may not be treated with an antibiotic. If your doctor prescribes an oral antibiotic, take all of the prescribed medication, even though you have no symptoms.

You may need to return to your doctor's office after you have taken all of the antibiotic to give another sample of your urine. The urine will be cultured and analyzed by the lab to see if there are still bacteria in your urine. Your doctor may recommend periodic tests of your urine to see if the bacteriuria recurs.

In some cases periodic urine testing rather than antibiotic treatment may be the best course. Your doctor will determine which course of action is best for you, based on your lab results and your medical history.

How long will the effects last?

Asymptomatic bacteriuria usually clears up after a short course of treatment with antibiotics. However, it could recur.

If asymptomatic bacteriuria is not treated, it could possibly develop into a full-blown urinary tract infection. If the infection is not then treated with antibiotics, the kidneys could be damaged.

How can I take care of myself?

• Take all of the antibiotic medication that your doctor prescribes, even if you have no symptoms. Do not take medication left over from previous infections.

• Drink six to eight glasses of fluid each day to cleanse the bladder and the rest of the urinary tract.

• Return to your doctor for a follow-up urine test within 1 week after you finish your antibiotic treatment.

• Follow your doctor's recommendation for periodic urine testing to check for recurrence.

What can be done to help prevent asymptomatic bacteriuria?

Women can take the following steps to help prevent bacteriuria from recurring:

• Drink plenty of fluids (six to eight glasses each day).

• Be sure that you urinate regularly during the day and that your bladder is completely emptied each time. Avoid long waits.

• Keep the vaginal area clean and wipe from front to back after a bowel movement.

• Urinate before and after intercourse.

• Wear cotton underwear, which allows better air circulation than nylon. Wear pantyhose that have a cotton crotch.

• Avoid tight clothes in the genital area, such as control-top pantyhose and tight jeans. Do not wear a wet bathing suit for long periods of time.

• Use tampons instead of sanitary pads during your menstrual periods. Change tampons every 3 to 4 hours. Sanitary pads can act as a breeding ground for bacteria, which can enter the urethra and the bladder.

If you have a history of recurrent urinary tract problems, your doctor may prescribe small doses of antibiotics to be taken continually to prevent bacteriuria from recurring.