Asymptomatic bacteriuria is a significant number of bacteria in the urine that occurs without usual symptoms such as burning during urination or frequent urination.

Asympomatic bacteruria may not need treatment, which makes it different from a bacterial urinary tract infection.

Asymptomatic bacteriuria occurs in a small number of healthy individuals. It more often affects women than men. The reasons for the lack of symptoms are not well understood.

Most patients with asymptomatic bacteriuria do not need treatment because the bacteria isn't causing any harm. Persons who have urinary catheters often will have bacteriuria, but most will not have symptoms.

Certain people are at a higher risk for kidney infections if they develop asymptomatic bacteriuria. The following increases your risk:

• Diabetes
• Infected kidney stones
• Kidney transplant
• Older age
• Pregnancy -- up to 40% of pregnant women with untreated asymptomatic bacteriuria will develop a kidney infection
• Vesicoureteral reflux in young children

By definition, asymptomatic bacteriuria causes no symptoms. The symptoms of a urinary tract infection include burning during urination, an increased urgency to urinate, and increased frequency of urination.

Asymptomatic bacteriuria is detected by the discovery of significant bacterial growth in a urine culture taken from a urine sample.

Not all patients with asymptomatic bacteriuria respond to treatment or even need treatment. Pregnant women, kidney transplant recipients, children with vesicoureteral reflux, and those with infected kidney stones appear to be more likely to benefit from treatment with antibiotics.

Giving antibiotics to persons who have long-term urinary catheters in place may cause harm. The bacteria may be more difficult to treat and the patients may develop a yeast infection.

If asymptomatic bacteriuria is found before a urological procedure, it should be treated to prevent complications. The course of treatment in these cases depends on the person's risk factors.

Most individuals with asymptomatic bacteriuria who do not have risk factors for complications do extremely well.

The outlook for those at high-risk is good if the infection is detected early, but it depends on the person's overall health.

Untreated, asymptomatic bacteriuria can lead to a kidney infection in high-risk individuals. In some cases, particularly in those who have had kidney transplants, such infections may lead to the loss of kidney function.

Call your health care provider if the following symptoms occur:

• Difficulty emptying your bladder
• Fever
• Flank or back pain
• Pain with urination

You will need to be evaluated for a bladder or kidney infection.

Lin K, Fajardo K; U.S. Preventive Services Task Force. Screening for asymptomatic bacteriuria in adults: evidence for the U.S. Preventive Services Task Force reaffirmation recommendation statement. Ann Intern Med. 2008 Jul 1;149(1):W20-4.

Smaill F, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy. Cochrane Database Syst Rev. 2007 Apr 18;(2):(CD000490).

Nicolle LE, Bradley S, Colgan R, et al. Infectious Diseases Society of America guidelines for the diagnosis and treatment of asymptomatic bacteriuria in adults. Clin Infect Dis. 2005 Mar 1;40(5):643-54.