Urinary Tract Infection

Kalpana Gupta, M.D., M.P.H.
Walter E. Stamm, M.D.
University of Washington School of Medical

Definition/Key Clinical Features
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

General

• Includes the following:
  • Asymptomatic bacteriuria
  • Cystitis
  • Prostatitis
  • Pyelonephritis
• Clinical symptoms do not always correlate with site of infection (bladder vs. kidney) or with degree of bacteriuria
• No test differentiates bladder infections from kidney infections
• May be acute, recurrent (repeated infections with the same or different organisms), or complicated
• Usually affects females
• Usually caused by gram-negative bacilli

Cystitis

• Dysuria
• Urinary frequency
• Urgency
• Nocturia
• Suprapubic or back pain
• Urine cloudy, malodorous, or bloody

Acute Pyelonephritis

• Fever
• Shaking chills
• Nausea and vomiting
• Symptoms often follow cystitis symptoms

Prostatitis

• Fever
• Chills
• Dysuria
• Frequency, urgency
• Perineal, back, or pelvic pain
• Difficulty urinating
• Prostate is enlarged, tender, and indurated

Clinical Pearls

• In men of any age with acute febrile UTI
  • Perform prostatic exam
  • Assess postvoiding residual urine volume
• In women
  • Restrict evaluations to those with frequently recurring infection and recurrent pyelonephritis despite adequate therapy
    

Best Tests

• No culture required before treatment in otherwise healthy women with typical symptoms of acute cystitis
• Cultures should be obtained in all other patient groups

Urine Culture

• In men or women with asymptomatic bacteriuria
  • Growth of >10⁵ colonies/ml of single bacterial species in 2 consecutive samples is diagnostic
• In children
  • >10⁵ colonies/ml also used
• In men,
  • Minimum diagnostic level is 10³ organisms/ml
• Negative Gram stain does not rule out infection
• Cultures growing mixed bacterial species should be repeated

Urinalysis

• Presence of squamous epithelial cells suggests contamination
• Dipstick for leukocyte esterase, nitrite, or both has about 90% sensitivity and 70% specificity for infection

Imaging Studies

• Rarely needed for the following:
  • Acute cystitis
  • Acute pyelonephritis
• Reserve for evaluation of the following:
  • Abscess
  • Tumor
  • Stones
  • Obstruction
  • Relapsing infections
• For I.V. pyelography, ultrasound, or CT
  • Use to rule out obstruction in urosepsis or acute pyelonephritis unresponsive to antimicrobial
  • Ultrasound is preferred test
• For contrast-enhanced helical CT
  • First choice for evaluating renal infections
  • Use noncontrast CT when renal calculi suspected
• I.V. pyelography + voiding cystourethrography:
  • Use to delineate surgically correctable lesions that might predispose to recurrent UTI or progressive renal disease
  • Obligatory to look for congenital anomalies in young children

Best Therapy

Acute Uncomplicated Cystitis

Empirical Regimens

• Otherwise-healthy women
  • 3-day regimens
    • Oral TMP-SMX
    • TMP
    • Fluoroquinolone
    • Cefixime
    • Cefpodoxime
  • 7-day regimens
    • Nitrofurantoin monohydrate/macrocrystals
    • Nitrofurantoin macrocrystals (see Oral Regimens, below)
  • Follow up after 3–7 days; if symptomatic, order urinalysis and urine culture
    • If pyuria is present with no bacteriuria, evaluate for cystitis or urethritis
    • If bacteriuria is present, treat with a fluoroquinolone or TMP-SMX for 14 days
• Pregnancy
  • 7-day regimen
    • Oral amoxicillin
    • Nitrofurantoin monohydrate/macrocrystals
    • Nitrofurantoin macrocrystals
    • Cefixime
    • Cefpodoxime proxetil
    • TMP-SMX (see Oral Regimens, below)
• For patients who have diabetes, who have symptoms for greater than 7 days, who have recently used antimicrobials, who are older than 65 yr, or who are male
  • 7-day regimen
    • Oral TMP-SMX
    • Fluoroquinolone
    • Cefixime
    • Cefpodoxime proxetil (see Oral Regimens, below)

Oral Regimens

• TMP-SMX
  • Efficacy: > 90%
  • Can be used in pregnancy
  • High resistance in some communities
• Fluoroquinolones:
  • Efficacy: > 90%
  • Avoid in pregnancy
  • Men: 7–14 days
    • Ciprofloxacin
      • Dose: 100–250 mg q. 12 hr
      • Cost/mo: $257.48 (250 mg)
    • Levofloxacin
      • Dose: 250 mg q.d.
      • Cost/mo: $222.98
    • Ofloxacin
      • Dose: 200 mg q. 12 hr
      • Cost/mo: $218.65
    • Norfloxacin
      • Dose: 400 mg q. 12 hr
      • Cost/mo: $235.97
• Cefixime
  • Efficacy: > 90%
  • Dose: 400 mg q.d.
  • Cost/mo: not available
• Nitrofurantoin monohydrate/macrocrystals
  • Efficacy: > 75%
  • Avoid in pregnancy
  • Men: 7–14 days
  • Dose: 100 mg q. 12 hr
  • Cost/mo: $108.98
• Amoxicillin:
  • Efficacy: >75%
  • Dose: 100 mg q. 12 hr
  • Cost/mo: $15.10
    

Prophylaxis for recurrent UTI in women

• If more than 3 symptomatic episodes a year, suggest
  • Voiding after sexual intercourse,
  • Use of contraception other than diaphragm + spermicide,
  • Drinking cranberry/lingonberry juice
• Prescribe continuous or postcoital low-dose antimicrobial prophylaxis for 6 mo, then discontinue and observe response
  • Single-dose TMP-SMX
    • Efficacy: high
    • Dose: half a 20/300 mg tablet
  • Ciprofloxacin
    • Efficacy: high
    • Dose: 250 mg q.d.
    • Cost/mo: $128.74
  • Nitrofurantoin
    • Efficacy: high
    • Dose: 50 mg or 100 mg macrocrystals
      
      

Acute Uncomplicated Pyelonephritis

• Immediate treatment with oral or parenteral antimicrobial agent to which invading organism is presumed or known to be sensitive, followed by
  • Oral therapy to eradicate residual tissue infection

Antimicrobial Agents for Pyelonephritis

• Ciprofloxacin:
  • Can be given orally or I.V. followed by oral
  • Resistance rare
  • Efficacy: high
  • Dose
    • Oral: 500 mg q. 12 hr x 7–14 days
    • I.V.: initially, 400 mg q. 12 hr
  • Cost/mo: $297.98
• Ampicillin + gentamicin
  • Particularly useful if urine Gram stain shows 6PC (enterococci) or in complicated UTI
  • Reduce dose with renal failure
  • Efficacy: high
  • Dose:
    • Initially, ampicillin 1 g I.V. q. 6 hr
    • Gentamicin, 1 mg/kg I.V. q. 8 hr
• TMP-SMX
  • Reduce dose with renal failure
  • Efficacy: high
  • Entire course of therapy for patients with mild disease who can tolerate oral
  • 14-day course following initial parenteral therapy is very effective
  • Resistance high enough in some areas to preclude empiric use
  • Dose: 160/800 mg q. 12 hr x 14 days
• Third-generation cephalosporins
  • Reduce dose with renal failure
  • Efficacy: high
  • Less published clinical experience
  • Cefixime
    • Dose: Oral: 400 mg q.d. x 7–14 days
  • Ceftazidime
    • Dose: I.V.: initially 500 mg q. 12 hr
• Imipenem/cilastatin:
  • Reduce dose with renal failure
  • Efficacy: high
  • Useful in complicated UTI
• Dose: I.V.: initially 500 mg q. 6 hr
  
  

UTI in Pregnancy

• Asymptomatic bacteriuria should be diagnosed and treated
• The following are safe in early pregnancy
  • Sulfonamides
  • Nitrofurantoin
  • Ampicillin
  • Cephalosporins
• Avoid trimethoprim and fluoroquinolones

Prostatitis

• Treatment of acute prostatitis
  • TMP-SMX, 160/800 mg b.i.d. for at least 4 wk
  • Ciprofloxacin, 250 mg b.i.d. for 2 wk

   

Best References

Kontiokari, et al: BMJ 322:1571, 2001

McCarty, et al: Am J Med 106:292, 1999

Talan, et al: JAMA 283:1583, 2000

Wing, et al: Obstet Gynecol 92: 249, 1998

July 2004