What is the recommended approach for diagnosing and treating asymptomatic bacteriuria in patients with a history of urinary tract infections or underlying medical conditions?

Diagnosis and Management of Asymptomatic Bacteriuria

In most patients with asymptomatic bacteriuria, screening and treatment should NOT be performed, as treatment provides no benefit and causes harm through antimicrobial resistance, adverse drug effects, and unnecessary costs. 1, 2

Diagnostic Criteria

Asymptomatic bacteriuria is defined as isolation of bacteria in urine without any urinary symptoms (no dysuria, frequency, urgency, suprapubic pain, or costovertebral angle tenderness). 1

Specific Diagnostic Thresholds for Women:

• Two consecutive voided urine specimens with the same bacterial strain at ≥10⁵ CFU/mL 3
• OR a single catheterized specimen with ≥10² CFU/mL 3
• Must have complete absence of urinary symptoms 3

Common Pitfall to Avoid:

• Do NOT interpret cloudy or smelly urine as symptomatic infection - these observations alone should not trigger treatment in elderly or catheterized patients 1
• Pyuria (white blood cells in urine) does NOT change management - pyuria accompanying asymptomatic bacteriuria is not an indication for treatment 2

Populations Where Treatment is NOT Recommended

The following groups should NOT be screened or treated for asymptomatic bacteriuria: 1, 2

• Premenopausal, nonpregnant women 1
• Postmenopausal women 2
• Patients with well-controlled diabetes mellitus 2
• Elderly patients in community or long-term care facilities 2
• Patients with spinal cord injuries 1
• Patients with indwelling catheters (short-term or long-term) 1
• Renal transplant recipients 1
• Patients undergoing non-urologic surgery (including orthopedic, cardiac, vascular, or cataract surgery) 4

Evidence Supporting Non-Treatment:

• Treatment does not prevent symptomatic UTIs, kidney damage, or progression of kidney disease 2
• In 3,167 preoperative patients, treating asymptomatic bacteriuria did not reduce postoperative complications 4
• Patients who developed orthopedic implant infections had different pathogens in surgical sites compared to their preoperative urine, proving urine was not the infection source 4
• 45% of women with asymptomatic bacteriuria remain asymptomatic even after 15 years 3

Only TWO Populations Requiring Screening and Treatment

1. Pregnant Women (Strong Recommendation, A-I)

Pregnant women are the primary exception and MUST be screened and treated. 3, 2

• Untreated asymptomatic bacteriuria carries a 20-35% risk of developing pyelonephritis 3
• Treatment reduces pyelonephritis risk to 1-4% 3
• Treatment also reduces premature delivery and low birth weight 3
• This represents a 20-30-fold increased risk if left untreated 3

2. Patients Undergoing Urologic Procedures with Mucosal Bleeding (Strong Recommendation, A-I)

Screen and treat before transurethral resection of the prostate and other urologic procedures that breach the mucosa. 1

Specific Protocol:

• Obtain urine culture so results are available before the procedure 1
• Initiate antimicrobial therapy the night before or immediately before the procedure (NOT 72 hours before, which allows superinfection) 1
• Discontinue antimicrobials immediately after the procedure if no indwelling catheter remains 1
• Continue antimicrobials only until catheter removal if indwelling catheter remains post-procedure 1

Do NOT treat before catheter replacement - this carries low bacteremia risk and treatment is not beneficial 1

Harms of Unnecessary Treatment

Treating asymptomatic bacteriuria causes measurable harm: 4, 2

• Promotes antimicrobial resistance, making future infections harder to treat 2
• Increases risk of Clostridioides difficile infection 4
• Causes adverse drug effects 4, 2
• Increases healthcare costs without benefit 4, 2
• May eliminate protective bacterial strains that prevent colonization with more virulent organisms 2

Practical Clinical Approach

Do NOT order routine urinalysis or urine cultures in asymptomatic patients - this leads to unnecessary findings that prompt inappropriate treatment 4

If asymptomatic bacteriuria is discovered incidentally on preoperative testing, do NOT treat unless the patient is pregnant or undergoing urologic procedures with mucosal trauma. 4

E. coli strains causing asymptomatic bacteriuria have fewer virulence characteristics than symptomatic UTI strains - they are fundamentally different organisms 3