Urinary Tract Infection

Aka: Urinary Tract Infection, UTI, Bladder Infection, Acute Cystitis

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II. Causes

  1. Normal Host
    1. Escherichia coli (80-86%)
    2. Staphylococcus saprophyticus (10-15% of young women, 4% overall)
      1. More aggressive and recurrent infections
      2. Associated with Pyelonephritis
    3. Klebsiella (3%)
    4. Proteus (3%)
  2. Nephrolithiasis associated infection
    1. Proteus (urease positive)
    2. Klebsiella
  3. Sexually Transmitted Diseases
    1. Chlamydia
    2. Neisseria gonorrhoeae
    3. Herpes Simplex Virus II (Genital Herpes)

III. Risk factors: Complicated Cystitis

  1. Male gender
  2. Pregnancy
  3. Hospital acquired Urinary Tract Infection
  4. Prolonged urinary tract symptoms (>1 week)
  5. Poorly controlled Diabetes Mellitus
  6. Immunocompromised
  7. Underlying urologic disorder
    1. Vesicoureteral reflux
    2. Recurrent complicated Urinary Tract Infections
    3. Catheter associated Urinary Tract Infection
    4. Neurogenic Bladder dysfunction
    5. Polycystic Kidney Disease
    6. Urologic instrumentation or stenting
    7. Status Renal Transplant
    8. Urinary Tract Obstruction (e.g. Nephrolithiasis)
    9. Men with Prostatitis or BPH

IV. Symptoms

  1. Most suggestive of Urinary Tract Infection
    1. Dysuria (Likelihood Ratio 2.0)
      1. If absent, Likelihood Ratio 0.5
    2. Urinary Frequency (Likelihood Ratio 1.8)
    3. Hematuria (Likelihood Ratio 1.5)
      1. Occurs in 30% of cases
  2. Other symptoms with Urinary Tract Infection
    1. Urinary Urgency
    2. Suprapubic Pain (especially after voiding)

V. Differential Diagnosis

  1. Dysuria
    1. See Dysuria
    2. See Dysuria in Children
    3. See Dysuria in Men
    4. See Dysuria in Women
  2. Urethritis
    1. Pain at onset of urination
  3. Vaginitis
    1. External Dysuria
    2. Vaginal irritation or discharge
  4. Chlamydia trachomatis
    1. Long, insidious onset
    2. Sexually active
  5. Acute Pyelonephritis
    1. Fever, Flank Pain, and Nausea or Vomiting
    2. Risk factors for cystitis with occult Pyelonephritis
      1. Women (30% have subclinical Pyelonephritis)
      2. Pregnancy
      3. Diabetes Mellitus
      4. Immunocompromised patients
      5. Urinary Tract Infection under age 12 years
      6. Genitourinary comorbid condition
  6. Acute Urethral syndrome (Sterile or low urine Bacterial count)
    1. Gonorrhea
    2. Chlamydia
    3. Herpes Simplex Virus
    4. Vaginitis
  7. Sterile Pyuria
    1. Chlamydia (most common)
    2. Genitourinary Tuberculosis (classic sterile pyuria)
  8. Asymptomatic Bacteriuria (organisms isolated on Urine Culture, but often not responsible for cystitis)
    1. Enterococcus
    2. Streptococcus Agalactiae (Group B Streptococcus)
    3. Hooton (2013) N Engl J Med 369(20):1883-91 [PubMed]

VI. Labs

  1. Urinalysis
    1. Urine Leukocyte Esterase (high Test Sensitivity but low Test Specificity)
    2. Urine Nitrite (high Test Specificity, but low Test Sensitivity)
    3. Urine White Blood Cells on microscopy
  2. Urine Culture
    1. Not needed in uncomplicated UTI (young, healthy non-pregnant women)
    2. Recommended in complicated UTI or suspected Pyelonephritis
    3. Positive for >100k organisms
    4. Women with Dysuria have <100k organisms in 30% cases

VII. Diagnosis: Factors suggestive of complicated UTI

  1. Extremes of age (preadolescent, or post-Menopause)
  2. Chronic renal disease
  3. Diabetes Mellitus
  4. Immunodeficiency
  5. Pregnancy
  6. Recent Urinary Tract Instrumentation
    1. Ureteral Stents
    2. Indwelling catheters
  7. Urologic abnormalities
    1. Nephrolithiasis
    2. Neurogenic Bladder
    3. Polycystic Kidney Disease

VIII. Diagnosis: Prediction Rule

  1. Criteria
    1. New onset frequency and Dysuria
    2. Absent Vaginal Discharge and irritation
  2. Efficacy
    1. Pretest probability of UTI based on symptoms: 90%
    2. Probablity of UTI with negative Urinalysis: 23%
    3. Positive Predictive Value: 90%
  3. Interpretation
    1. May be treated without Urinalysis and Urine Culture
    2. Editorial note: I do not recommended this (other Dysuria causes, Antibiotic Overuse)
      1. Alternative: Even dipstick testing alone is reasonably accurate, priced and fast
  4. Reference
    1. Bent (2002) JAMA 287:2701-10 [PubMed]

IX. Diagnosis: Findings suggestive of upper Urinary Tract Infection (Pyelonephritis)

  1. See Pyelonephritis
  2. Fever, chills
  3. Flank Pain
  4. Vomiting
  5. Pregnancy (second and third trimester are higher risk)
  6. Underlying urinary tract disorder
  7. History of Ureteral Stenting or other instrumentation
  8. Male patients
  9. Insulin Dependent Diabetes Mellitus
  10. HIV Infection
  11. Immunosuppressants (Chronic Corticosteroid use, status-post transplant)
  12. Extremes of age (very young or very old)
    1. Underwhelming presentations of upper tract disease

X. Precautions

  1. Consider Sexually Transmitted Infection in Vaginitis or male Dysuria
  2. Consider Nephrolithiasis with Urinary Tract Infection (emergency) when Flank Pain is severe
  3. Empiric antibiotic regimens should be based on local resistance rates
  4. Urine Culture is not needed in occasional, uncomplicated Urinary Tract Infection (young, healthy, non-pregnant women)
  5. Assume upper tract disease in findings listed above
    1. Adjust management strategy to treat upper tract (e.g. avoid Macrobid or Nitrofurantoin)

XI. Management: General

  1. General measures in women
    1. Women should clean perineum wiping front to back
    2. Women should empty Bladder before, after intercourse
    3. Avoid Contraceptive Diaphragm
  2. Antibiotics
    1. Course: Anticipate symptom relief within 36 hours of starting antibiotics
    2. Antibiotic duration
      1. Uncomplicated treatment: 3 days (except noted)
        1. Nitrofurantoin and Macrobid course is 5 days (was 7 days)
      2. Complicated treatment: 10 day course
    3. Antibiotic Resistance increasing
      1. Trimethoprim Sulfamethoxazole (Septra): 18%
      2. Beta Lactams: 20%
      3. Ampicillin: 38%
      4. Nitrofurantoin resistance low (1-2%)
      5. Fluoroquinolone resistance low (2.5%)
        1. Avoid as first line agents if possible (due to other adverse effects)
        2. Consider in areas of high Septra resistance areas
    4. Cure may occur despite resistance to antibiotic used
    5. Risks for resistance
      1. Trimethoprim Sulfamethoxazole within last 3-6 months
      2. Diabetes Mellitus
      3. Recent hospitalization
      4. Travel outside United States
      5. Resistance rates in community >20%
  3. Acute Uncomplicated UTI: First-Line agents
    1. Note that Ciprofloxacin has been demoted from first-line agent due to adverse effects (see below)
    2. Trimethoprim-Sulfamethoxazole (Bactrim) DS one orally twice daily for 3 days
      1. Avoid if local resistance rate >20%
    3. Nitrofurantoin (Macrobid)
      1. Macrobid 100 mg orally twice daily for 5 days
      2. Avoid if GFR <30 ml/min (risk of interstitial pulmonary fibrosis)
    4. Fosfomycin (Monurol) 3 grams for one dose
      1. Consider as a single dose in Emergency Department (e.g. patient non-compliant)
      2. More expensive and may be less effective (58% efficacy compared with 70% for Nitrofurantoin)
        1. Huttner (2018) JAMA 319(17): 781-9 +PMID:29710295 [PubMed]
  4. Acute Uncomplicated UTI with risks for resistance (prior Bactrim use or international travel in last 6 months)
    1. Nitrofurantoin
      1. Avoid if GFR <30 ml/min (risk of interstitial pulmonary fibrosis)
      2. Nitrofurantoin 100 mg orally four times daily for 5 days
      3. Macrobid 100 mg orally twice daily for 5 days
        1. Five days is sufficient course (previously used for 7 days)
        2. Gupta (2007) Arch Intern Med 167(20):2207-12 [PubMed]
    2. Fosfomycin (Monurol) 3 grams for one dose
    3. Also see Fluoroquinolones below
  5. More severe disease or resistant UTI organisms: Fluoroquinolones
    1. Precautions regarding Fluoroquinolones
      1. Risk of Tendinopathy (and Achilles Tendon Rupture) and Peripheral Neuropathy
      2. Avoid if local resistance rate >10%
      3. Renal dose adjustment required if GFR reduced
      4. Although 3 day courses are listed, complicated UTI is treated for 10 days (up to 6 weeks in men)
    2. Ciprofloxacin 250 mg PO bid for 3 days
      1. In healthy older women, 3 days equivalent to 7 days
      2. Vogel (2004) CMAJ 170:469-73 [PubMed]
    3. Levofloxacin 250 mg every 24 hours for 3 days
    4. Norfloxacin 400 mg PO bid for 3 days
    5. Ofloxacin 200 mg PO bid for 3 days
    6. Avoid Moxifloxacin and gemifloxacin (poor penetration into urine)
  6. Antibiotics for UTI in Pregnancy
    1. See Urinary Tract Infection in Pregnancy
  7. Other antibiotics used in Urinary Tract Infection
    1. Precautions
      1. Beta lactams have lower efficacy in UTI
    2. Cephalexin (Keflex) 500 mg orally twice daily for 5-7 days
    3. Amoxicillin-Clavulanate (Augmentin) 875 mg orally twice daily for 5-7 days
    4. Cefdinir 300 mg orally twice daily for 3-7 days
  8. Sexually active young patients
    1. Avoid Nitrofurantoin (Macrobid)
      1. Staphylococcus saprophyticus resistance
    2. Consider Chlamydia sceening
    3. Consider other Sexually Transmitted Disease Testing

XII. Management: Special Circumstances

  1. See Recurrent Urinary Tract Infection
  2. See Ureteral Stent
  3. ESBL (Extended Spectrum Beta-Lactamase) producing E Coli and Klebsiella
    1. Fosfomycin (cystitis)
    2. Ertapenem

XIII. Management: Asymptomatic Bacteriuria

  1. See Asymptomatic Bacteriuria

XIV. Complications: Surgical

  1. Perinephric Abscess
    1. Urinary Tract Infection contiguous spread
    2. Contrast with renal abscess (hematogenous spread)
  2. Emphysematous Pyelonephritis
    1. Seen in Diabetes Mellitus
    2. Requires surgical drainage (otherwise high mortality)

XV. References

  1. (2019) Sanford Guide, accessed on IOS 9/21/2019
  2. Colgan (2011) Am Fam Physician 84(7): 771-6 [PubMed]
  3. Ebell (2006) Am Fam Physician 73:293-6 [PubMed]
  4. Gupta (1999) JAMA 281:736-8 [PubMed]
  5. Gupta (2012) Ann Intern Med 156(5): ITC3-1 [PubMed]
  6. Hooton (1997) Infect Dis Clin North Am 11:551-81 [PubMed]
  7. Michels (2015) Am Fam Physician 92(9): 778-86 [PubMed]

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