Review article
Asymptomatic bacteriuria: When to screen and when to treat

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Pathogenesis of bacteriuria

The normal genitourinary tract is sterile, apart from the distal urethra. Asymptomatic bacteriuria occurs following ascension of bacteria up the urethra into the bladder, sometimes with subsequent ascension to the kidneys. Bacteria isolated from the urine of patients with asymptomatic bacteriuria usually originate as colonizing flora of the gut, vagina, or periurethral area. For patients subjected to urinary tract instrumentation, bacteria that contaminate urologic instruments or fluids may be

Indications for screening

Case finding of bacteriuria through screening, and treatment for risk reduction, is appropriate if adverse clinical outcomes are attributable to bacteriuria and prevented with treatment. The costs and potential adverse effects of screening and treatment programs must also be considered. If bacteriuria is benign, or treatment cannot prevent adverse outcomes, screening for bacteriuria has little use. Identification of bacteriuria may, in fact, promote unnecessary antimicrobial use with subsequent

Children

The prevalence of asymptomatic bacteriuria in preschool girls is 1% or less, and subsequently increases slightly with age (Table 2). The prevalence for schoolgirls is less than 2%, although one survey reported a higher prevalence for a group of socioeconomically disadvantaged girls [43]. For boys, bacteriuria is virtually never identified beyond the newborn period (see Table 2).

Comprehensive, long-term screening programs for bacteriuria in schoolgirls undertaken in the 1950s and 1960s found no

Community residents

Asymptomatic bacteriuria is common in older populations (Table 5) [23]. The prevalence is 6% to 7% in women 50 to 60 years of age, 8% to 10% at 70 to 80 years, and increases with age irrespective of sexual activity [56]. Bacteriuria in postmenopausal women is more common in women with a prior history of urinary infection [72]. Variables associated with recurrent symptomatic infection in elderly women, including decreased estrogen effect on the genitourinary mucosa, a genetic predisposition as

Patients with diabetes

The prevalence of bacteriuria in diabetic women is 7% to 13% [107], [108], [109], about three times higher than reported for nondiabetic women (Table 6) [110]. The reported prevalence varies among studies, likely reflecting differences in the diabetic population screened and the definition of bacteriuria [110], [121]. The prevalence of asymptomatic bacteriuria is not increased in diabetic compared with nondiabetic men [110].

The explanation for the increased prevalence of bacteriuria among

Short-term indwelling catheter

From 2% to 7% of patients with a short-term indwelling urethral catheter acquire bacteriuria each day (see Table 6) [149]. The daily incidence is higher in women, and in individuals who do not receive concurrent antimicrobial therapy for the first 4 catheter days [150]. Studies performed early in the antimicrobial era reported no benefits of treatment of asymptomatic bacteriuria in catheterized subjects [151]. Currently, at least 80% of hospitalized patients managed with short-term catheters

Urologic surgery

Genitourinary surgery with trauma and bleeding of the mucosa allows organisms in the urinary tract to invade the systemic circulation. If antimicrobial therapy is not given, from 25% to 80% of patients with bacteriuria undergoing a traumatic urologic procedure will have bacteremia [165]. Antimicrobial treatment before the intervention can prevent bacteremia and sepsis [165], [166]. Urine cultures obtained before treatment identify the specific infecting organism and allow optimal

Summary

Asymptomatic bacteriuria is common. Populations with structural or functional abnormalities of the genitourinary tract may have an exceedingly high prevalence of bacteriuria, but even healthy individuals frequently have positive urine cultures. Asymptomatic bacteriuria is seldom associated with adverse outcomes. Pregnant women and individuals who are to undergo traumatic genitourinary interventions are at risk for complications of bacteriuria and benefit from screening and treatment programs.

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