Urinary Tract Infection: Definition and Treatment Guidelines
A urinary tract infection (UTI) is a bacterial infection of the urinary system that requires prompt diagnosis through clinical symptoms and urinalysis, with treatment tailored to whether the infection is uncomplicated cystitis, pyelonephritis, or complicated UTI, using antimicrobial stewardship principles to combat rising resistance. 1
What is a Urinary Tract Infection?
UTIs are among the most frequent bacterial infections, ranging from benign uncomplicated cystitis to severe conditions including pyelonephritis and urosepsis 1. The infection occurs when bacteria (predominantly Escherichia coli in >90% of cases) ascend through the urethra into the bladder or kidneys 2, 3.
Clinical Presentation
Key symptoms to identify:
- Acute-onset dysuria (>90% accuracy for UTI in young women without vaginal symptoms) 1
- Urinary frequency and urgency 1, 4
- Hematuria 4
- Suprapubic pain 2
- New or worsening incontinence 1
Critical distinction: Dysuria with vaginal discharge or irritation significantly decreases UTI probability (likelihood ratio 0.2-0.3), suggesting alternative diagnoses like vaginitis 4.
Diagnostic Approach
When to Obtain Urine Culture
Mandatory urine culture before treatment in: 5
- Suspected acute pyelonephritis 5
- Symptoms not resolving or recurring within 4 weeks after treatment 5
- Pregnant women 5
- All cases of recurrent UTI 1, 5
- Women with atypical symptoms 5
For uncomplicated cystitis in otherwise healthy women: History, physical examination, and urinalysis (including nitrite and leukocyte esterase) typically suffice without culture 2, 6. However, continued documentation of cultures during symptomatic periods is essential for recurrent UTI patients to establish baseline patterns and guide therapy 1.
Imaging Indications
Do NOT routinely perform cystoscopy or upper tract imaging in women <40 years with recurrent UTI and no risk factors 1.
Obtain upper urinary tract ultrasound in pyelonephritis patients with: 1
- History of urolithiasis
- Renal function disturbances
- High urine pH
Obtain contrast-enhanced CT scan if patient remains febrile after 72 hours of treatment or experiences clinical deterioration 1, 7.
Treatment Guidelines by UTI Type
Uncomplicated Cystitis in Women
First-line therapy (choose based on local antibiogram): 5
- Fosfomycin trometamol: 3g single dose 5
- Nitrofurantoin: 100mg twice daily for 5 days 5
- Pivmecillinam: 400mg three times daily for 3-5 days 5
Alternative when resistance <20%:
Treatment duration: 3-7 days maximum 1. Three-day therapy is optimal—it eradicates simple UTIs while identifying treatment failures who likely have occult upper tract infection 2.
Critical pitfall: Fluoroquinolones should be reserved for more invasive infections due to "collateral damage" (selection of multi-resistant pathogens) 5.
Uncomplicated Pyelonephritis
Oral therapy options: 5
- Ciprofloxacin: 500-750mg twice daily for 7 days 5
- Levofloxacin: 750mg once daily for 5 days 5
- Trimethoprim-sulfamethoxazole: 160/800mg twice daily for 14 days 5
Parenteral therapy (for hospitalized patients): 5, 9
- Fluoroquinolones, aminoglycosides, extended-spectrum cephalosporins, or penicillins 5
- Ciprofloxacin IV: 400mg every 8-12 hours, infused over 60 minutes 9
- Monitor for clinical improvement within 72 hours 7
Important caveat: Oral cephalosporins achieve significantly lower blood concentrations than fluoroquinolones and should be used cautiously 1.
UTI in Men
Treatment regimen: 5
- Trimethoprim-sulfamethoxazole: 160/800mg twice daily for 7 days 5
- Fluoroquinolones: According to local susceptibility testing 5
- Duration: 7-14 days (14 days when prostatitis cannot be excluded) 5
Complicated UTI
Definition: UTI with host-related factors (diabetes, immunosuppression, pregnancy) or anatomic/functional abnormalities (obstruction, foreign bodies, incomplete voiding, vesicoureteral reflux, recent instrumentation) 7, 5.
Treatment approach: 5
- Duration: 7-14 days (14 days for men when prostatitis cannot be excluded) 5
- Mandatory: Appropriate management of underlying urological abnormality 5
- Avoid fluoroquinolones empirically in patients from urology departments or with fluoroquinolone use in last 6 months due to increasing resistance 7
Recurrent UTI (≥3 UTIs/year or 2 UTIs in 6 months)
Diagnosis requires: Documented positive urine cultures with prior symptomatic episodes 1.
Prevention strategies (attempt in this order): 1, 5
Non-antimicrobial measures:
- Increased fluid intake in premenopausal women 1, 5
- Vaginal estrogen replacement in postmenopausal women (strong recommendation) 1, 5
- Immunoactive prophylaxis (strong recommendation) 1, 5
- Methenamine hippurate for women without urinary tract abnormalities (strong recommendation) 1, 5
- Probiotics containing strains proven for vaginal flora regeneration 1
- Cranberry products (weak evidence, contradictory findings) 1
- D-mannose (weak and contradictory evidence) 1
- Endovesical instillations of hyaluronic acid or hyaluronic acid/chondroitin sulfate (when less invasive approaches fail) 1
Antimicrobial prophylaxis (when non-antimicrobial interventions fail):
- Continuous or postcoital antimicrobial prophylaxis (strong recommendation) 1, 5
- Self-administered short-term antimicrobial therapy for patients with good compliance (strong recommendation) 1, 5
Pediatric UTI (Complicated UTI/Pyelonephritis, Ages 1-17)
IV therapy: 9
- Ciprofloxacin: 6-10 mg/kg every 8 hours (maximum 400mg per dose), infused over 60 minutes 9
- May switch to oral therapy (10-20 mg/kg every 12 hours, maximum 750mg per dose) at physician discretion 9
- Total duration: 10-21 days 9
Important warning: Increased incidence of joint-related adverse events compared to controls 9.
Treatment Failure Management
If symptoms don't resolve by end of treatment or recur within 2 weeks: 5
- Perform urine culture with antimicrobial susceptibility testing 7, 5
- Assume infecting organism is not susceptible to original agent 5
- Use 7-day regimen with different antimicrobial agent 5
Do NOT perform routine post-treatment urinalysis or cultures in asymptomatic patients 7, 5.
Special Populations
Pregnancy
- Always treat asymptomatic bacteriuria 5, 3
- Safe options: Beta-lactams, nitrofurantoin, fosfomycin, trimethoprim-sulfamethoxazole 6
- Use ultrasound or MRI (not CT) for imaging to avoid fetal radiation 1
Asymptomatic Bacteriuria
Do NOT treat except in: 5
Critical pitfall: Asymptomatic bacteriuria is common in older women and should not be treated with antibiotics 6.
Safety Netting
Advise patients to seek immediate medical attention if: 7
- Symptoms do not resolve within 4 weeks after treatment completion 7
- Symptoms recur within 2 weeks 7
- Development of pyelonephritis signs: fever, chills, flank pain, nausea, vomiting, or costovertebral angle tenderness 7
Antimicrobial Stewardship Principles
Key strategies to combat rising resistance: 1