Causes

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 are not 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

Symptoms

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.

Exams and Tests

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

Treatment

Not all patients with asymptomatic bacteriuria 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 additional problems. 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.

Possible Complications

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.

When to Contact a Medical Professional

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.

References

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;149(1):W20-W24.

Smaill F, Vazquez JC. Antibiotics for asymptomatic bacteriuria in pregnancy. Cochrane Database Syst Rev. 2007;(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;40(5):643-654.

Updated: 4/17/2012

Reviewed by: David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc., Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital.