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asymptomatic bacteriuria



How does one approach a patient who has significant bacteriuria but is asymptomatic? Significant bacteriuria is defined as more than 105 bacteria per milliliter of urine obtained by sterile technique on consecutive samples. Patients with significant bacteriuria who have urinary tract symptoms require antimicrobial therapy.
In some patients with asymptomatic bacteriuria, including pregnant women and patients with obstructive uropathy, treatment is recommended. Elderly men and women have a higher incidence of bacteriuria than younger adults, for the following reasons: (a) prostatic hypertrophy in men, (b) loss of bactericidal prostatic secretions in men, (c) perineal soiling in women, (d) bladder dysfunction and genitourinary instrumentation, and (e) loss of hormone-dependent protection against introital colonization in postmenopausal women. The incidence of bacteriuria increases with the degree of debility and institutionalization, from 2% in some ambulatory elderly to 59% in some hospitalized patients.
Because of the high incidence in this setting, the role of antimicrobial therapy has become an area of interest and controversy. In at least two studies, elderly nursing home patients with asymptomatic bacteriuria died earlier than those with sterile urine. Other studies have found no correlation of bacteriuria with longevity. The concern that chronic bacteriuria will cause chronic pyelonephritis is not supported by longitudinal studies. Patients with chronic pyelonephritis have underlying uropathy, hypertension, or diabetes mellitus, but not bacteriuria alone. Progressive abnormalities do not develop on IV pyelogram in patients with asymptomatic bacteriuria. Randomized, controlled trials of antimicrobial therapy for asymptomatic bacteriuria in elderly men and women could demonstrate no effect on mortality. Prospective, randomized studies of therapy for asymptomatic bacteriuria have not benefited elderly men or women, whether bedridden or ambulatory. Recent studies, however, have shown that in patients with asymptomatic bacteriuria studied by a bladder washout technique, localization of bacteria to the kidney is commonly found. Patients with asymptomatic bacteriuria treated with antimicrobials do not maintain urine sterility. Such therapy is associated with side effects, cost, and the development of resistant organisms. Hence, antimicrobials are generally not recommended for asymptomatic bacteriuria in the elderly.
There is no evidence to support the treatment of bacteriuria based on the symptom of foul-smelling urine. The unpleasant odor of urine may be caused by polyamine production of bacteria, but urine may be foul-smelling for other reasons.
Asymptomatic bacteriuria is not in itself an indication for anatomic assessment of the urinary tract. Patients with asymptomatic bacteriuria and obstructive uropathy, as well as patients with asymptomatic bacteriuria, should receive antimicrobial therapy before undergoing genitourinary instrumentation.
In the elderly patient with bacteriuria whose general condition has acutely deteriorated, the term asymptomatic bacteriuria loses its usefulness. Urinary tract infection can present in a more subtle manner in the elderly, and patients with urosepsis may remain afebrile or present only with mental status changes. A patient with a history of bacteriuria who becomes septic will often need to be treated for urosepsis if no definite focus of infection can be found.
Patients who require external condom catheters have a bacteriuria rate of as high as 87%. In patients with long-term Foley catheters, bacteriuria is inevitable.
The pregnant woman with asymptomatic bacteriuria represents a special situation in which benefits of treatment outweigh risks. Reflux and resulting pyelonephritis occur in this group. Preterm delivery and low birth weight appear to be bona fide associations with asymptomatic bacteriuria.
The consequences of asymptomatic bacteriuria in patients with diabetes mellitus are not so well defined. The rates of asymptomatic bacteriuria are threefold higher in diabetic women than in nondiabetic women. However, rates for diabetic versus nondiabetic men are similar. In diabetic patients, a 2-week course of antimicrobials is equivalent to a 6-week course for initial eradication of bacteriuria. Reinfection often occurs. The overall benefits of treatment remain unproven.
Screening children for asymptomatic bacteriuria is widely recommended in the hope of preventing pyelonephritis. However, such detection has not been proved to prevent pyelonephritis or renal scarring and is now controversial. (S.L.B.)
Abrutyn E, et al. Does asymptomatic bacteriuria predict mortality and does antimicrobial treatment reduce mortality in elderly, ambulatory women? Ann Intern Med 1994;120:827.
No beneficial outcome in the treated group was noted.
Baldassarre JS, Kaye D. Special problems of urinary tract infection in the elderly. Med Clin North Am 1991;75:375.
Describes rationale for conservative management of asymptomatic bacteriuria.
Bendall MJ. A review of urinary tract infection in the elderly. J. Antimicrob Chemother 1984;13 (Suppl B):69.
Excellent review of the international literature, particularly with respect to patterns of bacteriuria over time.
Boscia JA, et al. Epidemiology of bacteriuria in an elderly ambulatory population. Am J Med 1986;80:208.
Different patterns of bacteriuria occur in the elderly. Bacteriuria may be persistent or episodic.
Dontas AS, et al. Bacteriuria and survival in old age. N Engl J Med 1981;304:939.
In a Greek nursing home, survival is shortened by the presence of asymptomatic bacteriuria.
Kemper KJ, Avner ED. The case against screening urinalyses for asymptomatic bacteriuria in children. Am J Dis Child 1992;146:343.
Screening children for asymptomatic bacteriuria is considered costly and ineffective in this review.
Mims AD, et al. Clinically inapparent (asymptomatic) bacteriuria in ambulatory elderly men: epidemiological, clinical and microbiological findings. J Am Geriatr Soc 1990;38:1209.
Of 238 ambulatory elderly men, 29 had asymptomatic bacteriuria. Patients were followed from 1 to 4.5 years. Gram-positive organisms were commonly isolated.
Mittendorf R, Williams MA, Kass EH. Prevention of preterm delivery and low birth weight associated with asymptomatic bacteriuria. Clin Infect Dis 1992;14:927.
Meta-analysis is used to confirm association of bacteriuria in pregnant women with preterm delivery and low birth weight infants.
Nicolle LE. Consequences of asymptomatic bacteriuria in the elderly. Int J Antimicrob Agents 1994;4:107.
Foul odor of urine is not an indication for the treatment of bacteriuria.
Nicolle LE. Asymptomatic bacteriuria in the elderly. Infect Dis Clin North Am 1997; 11:647.
Recent review summarizes outcome data from five of the more recent randomized studies of treatment of asymptomatic bacteriuria. Again, no differences are noted in a comparison of the treatment and nontreatment groups.
Nicolle LE, Mayhew WJ, Bryan L. Prospective randomized comparison of therapy and no therapy for asymptomatic bacteriuria in institutionalized elderly women. Am J Med 1987;83:27.
A randomized trial of antimicrobial therapy in elderly women with asymptomatic bacteriuria. Despite a lowered prevalence of bacteriuria, no difference in genitourinary morbidity or mortality was found. Antimicrobial therapy was associated with recurrent infection, adverse drug effects, and increasingly resistant organisms.
Nicolle LE, et al. The association of bacteriuria with resident characteristics and survival in elderly institutionalized men. Ann Intern Med 1987;106:682.
No difference was found in the survival of bacteriuric versus nonbacteriuric elderly men.
Nicolle LE, et al. Localization of urinary tract infection in elderly, institutionalized women with asymptomatic bacteriuria. J Infect Dis 1988;157:65.
By means of bladder washout technique, it was found that 67% of women with asymptomatic bacteriuria had upper tract infection.
Ouslander JG, Greengold B, Chen S. External catheter use and urinary tract infections among incontinent male nursing home patients. J Am Geriatr Soc 1987;35:1063.
A high incidence of bacteriuria is reported in patients with external condom catheters.
Pels RJ, et al. Dipstick urinalysis screening of asymptomatic adults for urinary tract disorders. II. Bacteriuria. JAMA 1989;262:1221.
Recommends that urine culture alone be used to screen pregnant women for bacteriuria. Dipstick screening may be adequate with diabetic patients.
Ronald AR, Pattullo ALS. The natural history of urinary infection in adults. Med Clin North Am 1991;75:299.
Reviews definitions and data on asymptomatic bacteriuria and renal function.
U.S. Preventive Services Task Force. Screening for asymptomatic bacteriuria, hematuria and proteinuria. Am Fam Physician 1990;42:389.
Recommends leukocyte esterase and nitrate tests for bacteriuria screening in pregnant women, diabetic patients, and perhaps schoolchildren.
Zhanel GG, Harding GK, Guay DR. Asymptomatic bacteriuria. Which patients should be treated? Arch Intern Med 1990;150:1389.
An excellent review. The authors recommend that neonates, preschool children, pregnant women, and nonelderly men be treated for asymptomatic bacteriuria.
Zhanel GG, Harding GK, Nicolle LE. Asymptomatic bacteriuria in patients with diabetes mellitus. Rev Infect Dis 1992;13:150.
Excellent review of the implications of bacteriuria in diabetic patients. A 2-week course of antimicrobials is effective in initial eradication.

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