Treatment of UTI with Positive Leukocytes and Nitrites
For a patient with urinalysis showing leukocytosis and positive nitrites, initiate empiric antibiotic therapy immediately, as this combination confirms urinary tract infection and warrants prompt treatment. 1
Immediate Management
Obtain a urine culture before starting antibiotics to guide subsequent therapy adjustments based on susceptibility results. 1, 2 A positive urinalysis (leukocyte esterase or nitrites positive) indicates UTI and justifies empiric treatment while awaiting culture results. 1
Empiric Antibiotic Selection
The choice of empiric therapy depends on whether this is uncomplicated cystitis versus pyelonephritis/complicated UTI:
For Uncomplicated Cystitis (Lower UTI)
Nitrofurantoin is the recommended first-line agent for uncomplicated cystitis due to robust efficacy evidence and its ability to spare broader-spectrum agents. 1
- Nitrofurantoin: 5 days 1
- Fosfomycin: Single 3-gram dose 1
- Trimethoprim-sulfamethoxazole (TMP/SMX): 3 days 1, 3 - only if local resistance rates are <20% 4
Important caveat: Fluoroquinolones should be avoided as first-line empiric therapy due to increasing resistance rates and should be reserved for situations where other options are unsuitable. 5, 6
For Pyelonephritis or Complicated UTI (Upper UTI/Febrile)
Do NOT use nitrofurantoin for febrile UTIs or suspected pyelonephritis, as it does not achieve adequate serum/parenchymal concentrations to treat upper tract infections. 2
For empiric treatment of pyelonephritis:
- TMP/SMX or first-generation cephalosporin (e.g., cephalexin) are reasonable first-line oral agents if local resistance rates are favorable 1
- Ceftriaxone is the recommended empirical choice for patients requiring intravenous therapy, unless risk factors for multidrug resistance exist 1
- Duration: 7 days for β-lactams; 5-7 days for fluoroquinolones 1
Pediatric Considerations
For children with UTI (positive urinalysis with leukocytes and nitrites):
- Oral antibiotics are as effective as parenteral treatment for most children 1, 2
- First-line options: Cephalosporins, amoxicillin-clavulanate, or TMP/SMX 2
- Duration: 7-14 days for febrile UTIs 2; shorter courses (1-3 days) are inferior 2
- Reserve parenteral therapy for toxic-appearing children, those unable to retain oral intake, or with uncertain compliance 2
Treatment Duration by Syndrome
- Adult cystitis: 3-5 days depending on agent 1
- Adult pyelonephritis: 5-7 days (fluoroquinolones) or 7 days (β-lactams) 1
- Pediatric febrile UTI: 7-14 days 2
- Complicated UTI: 7-14 days (14 days for males where prostatitis cannot be excluded) 7
Adjusting Therapy
Tailor antibiotics based on culture and sensitivity results once available, typically within 48-72 hours. 1, 7 Consider local resistance patterns when selecting empiric therapy, as resistance to TMP/SMX and fluoroquinolones varies significantly by region. 1, 5
Critical Pitfalls to Avoid
- Never use nitrofurantoin for febrile UTIs/pyelonephritis - inadequate tissue penetration 2
- Do not treat for less than 7 days for febrile/upper UTIs - associated with treatment failure 2
- Avoid fluoroquinolones as first-line empiric therapy - reserve for resistant organisms or when other options fail 1, 5
- Do not fail to obtain culture before starting antibiotics - essential for guiding definitive therapy 2, 7
- Do not ignore local antibiotic resistance patterns - resistance rates >20% for TMP/SMX preclude its use as empiric therapy 4
Special Considerations
Positive nitrite test has high specificity (94%) and positive predictive value (96%) for UTI, making it highly reliable for confirming infection. 4 However, nitrite results should not guide specific antibiotic selection (e.g., choosing agents based on nitrite-reducing organisms), as this does not reliably predict TMP/SMX susceptibility. 8