Learning Center
Asymptomatic Bacteriuria
What is asymptomatic bacteriuria?
Asymptomatic bacteriuria is technically defined as a urine culture growing ≥ 10^5 colony-forming units/mL of a single organism from a clean-catch voided urine sample. In women the recommendation is for this to be repeated as rates of transient bacteriuria are higher. Catheterized specimens more consistently reflect what is happening within the bladder so a repeat sample is not necessary for men or women. In all cases the patient has no signs or symptoms consistent with a urinary tract infection (UTI).
From a practical perspective the magnitude of the bacteriuria is typically of less practical value because in the absence of symptoms the clinical management is the same. Asymptomatic bacteriuria is not associated with significantly greater morbidity or mortality than a sterile bladder, and the treatment of asymptomatic bacteriuria has not been shown to be helpful in the great majority of cases.
What counts as a symptom?
Dysuria, urinary frequency or urgency, suprapubic or flank pain, and costovertebral angle tenderness are common signs and symptoms reported with UTIs. Delirium and cognitive changes in the absence of these and in the absence of fever or hemodynamic instability suggestive of systemic infection are typically not considered symptoms. Guidelines have consistently recommended against up front treatment for patients such as these unless other causes have been ruled out and the cognitive changes persist after a period of observation.
Notably the CDC also explicitly recommends against urine culturing for:
- Malodorous urine
- Cloudy urine
- As a reflex to pyuria alone
Will antibiotic treatment of asymptomatic bacteriuria help my patient?
No. In fact, antibiotic treatment of asymptomatic bacteriuria will only *hurt* your patient. Multiple studies in multiple different patient populations have revealed *no benefit* from the treatment of asymptomatic bacteriuria. Antibiotic treatment did not prevent future UTIs, sepsis, hospitalization, progression of kidney disease, or death. Antibiotic treatment was, however, associated with the selection of more resistant organisms when the next UTI did occur.
The only exceptions to this rule are pregnant women, those about to undergo a urologic procedure, and some patients shortly after kidney transplantation. These individuals *should* be treated for their asymptomatic bacteriuria as in these populations it has been shown to prevent future complications.
What about the pyuria?
Pyuria predicts the presence of bacteriuria, but it does not change the clinical context of the bacteriuria. Although a urinalysis with elevated white blood cells is more likely than one that does not to have a significant amount of bacteria in culture, if the urine was obtained from a patient without signs or symptoms consistent with a UTI its clinical significance is trumped by the absence of symptoms. Asymptomatic bacteriuria has the same prognosis regardless of the presence of urinary white blood cells.
What about nitrites?
Nitrites predict the presence of gram negative, predominately Enterobacteriaceae, bacteriuria, but, as with pyuria, do not change its clinical context. The patient is more likely to have a positive urine culture, but is no more likely to benefit from antibiotics in the absence of symptoms than if their urine was sterile.
How do bladder catheters factor into all this?
Bladder catheters significantly increase the risk for UTIs, but the signs and symptoms indicative of a UTI are largely the same in most patient populations (primarily excluding spinal cord injury patients). Notably, many findings are common and do not consistently indicate a UTI including cloudy urine, foul smelling urine, and urinary sediment. It is unclear to what extent these findings can predict the presence of bacteriuria, but regardless in the absence of clinical signs and symptoms of a UTI there is *no* indication for treatment as there is *no* benefit to be obtained from antibiotic therapy. The Agency for Healthcare Research and Quality, part of the Department of Health and Human Services, has released an excellent webinar regarding UTIs in catheterized patients.
Where can I get more information?
The Infectious Disease Society of America released updated guidelines for the diagnosis and management of asymptomatic bacteriuria this year. They can be referenced at: