Urinary Tract Infections

Kalpana Gupta, MD, MPH
Walter E. Stamm, MD

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 sporadic or recurrent (repeated infections with the same or different organisms), and/or complicated
• Affects more females than males at most age groups
• 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
• Back or flank pain
• Nausea and vomiting
• Symptoms often follow cystitis symptoms

Prostatitis

• Acute
• Fever
• Chills
• Dysuria
• Frequency, urgency
• Perineal, back, or pelvic pain
• Difficulty urinating
• Prostate is enlarged, tender, and indurated
• Chronic
• Recurrent UTI
• Prostate exam may be normal

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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 with symptoms
• Minimum diagnostic level is 10³ organisms/ml
• In women with symptoms
• Minimum diagnostic level is 10² 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 75–90% sensitivity and 70–82% 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

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Best Therapy

Acute Uncomplicated Cystitis

Empirical Regimens

• Otherwise-healthy women
  • 3-day regimens
    • Oral TMP-SMX
    • TMP
    • Fluoroquinolone
  • 7-day regimens
    • Nitrofurantoin monohydrate/macrocrystals
    • Nitrofurantoin macrocrystals (see Oral Regimens, below)
    • Amoxicillin
    • Cephalexin or other cephalopsorin
  • If symptomatic after therapy, order urinalysis and urine culture
    • If no pyuria or bacteriuria are present, treat with a 2-day course of pyridium, evaluate for vaginitis or urethritis, close clinical follow-up
    • 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
    • Cephalexin or other cephalosporin
    • TMP-SMX (use with caution; avoid in 1st and 3rd trimesters) (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
    • Cephalexin or other cephalosporin (see Oral Regimens, below)

Oral Regimens

• TMP-SMX
  • Efficacy: > 90%
  • Can be used with caution in the 2nd trimester of pregnancy
  • High resistance in some communities
• Fluoroquinolones
  • Efficacy: > 90%
  • Avoid in pregnancy
  • Men: 7–14 days
    • Ciprofloxacin
      • Dose: 100–250 mg q. 12 hr or 500 mg q.d. (Cipro XR)
    • Levofloxacin
      • Dose: 250 mg q.d.
• Cephalexin
  • Efficacy: > 75%
  • Dose: 250 mg q.6 hr
  • High resistance rates in some areas
• Nitrofurantoin monohydrate/macrocrystals
  • Efficacy: > 75%
  • Men: 7–14 days (no prostatic activity)
  • Dose: 100 mg q. 12 hr
• Amoxicillin
  • Efficacy: >75%
  • Dose: 100 mg q. 12 hr

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 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.
  • 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 or 1000 mg q.d.(cipro XR) x 7–14 days
    • I.V.: initially, 400 mg q. 12 hr
• 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 an initial dose of parenteral therapy with ceftriaxone 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
  • Ceftriaxone
    • Dose: 1-2 gm I.V. q.d. x 7–14 days
• Imipenem/cilastatin
  • Reduce dose with renal failure
  • Efficacy: high
  • Useful in complicated UTI
• Dose: initially 500 mg I.V. q. 6 hr

UTI in Pregnancy

• Asymptomatic bacteriuria should be diagnosed and treated
• The following are safe in early pregnancy
  • Nitrofurantoin
  • Ampicillin
  • Cephalosporins
• TMP/SMX can be used with caution in the 2nd trimester
• Avoid 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 2–4 wks

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Best References

Warren JW, Abrutyn E, Hebel JR, et al: Clin Infect Dis 29:745, 1999 [PMID 10589881]

Gupta K, Hooton TM, Stamm WE: Ann Intern Med 135:41, 2001 [PMID 11434731]

Patterson TF, Andriole VT: Infect Dis Clin North Am 11:593, 1997 [PMID 9378925]

Talan DA, et al: JAMA 283:1583, 2000 [PMID 10735395]

Lipsky BA: Am J Med 106:327, 1999 [PMID 10190383]

April 2008

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