II. Causes
- Normal Host
- Escherichia coli (80-86%)
- Staphylococcus saprophyticus (10-15% of young women, 4% overall)
- More aggressive and recurrent infections
- Associated with Pyelonephritis
- Klebsiella (3%)
- Proteus (3%)
-
Nephrolithiasis associated infection
- Proteus (urease positive)
- Klebsiella
- Sexually Transmitted Diseases
III. Risk factors: Complicated Cystitis
- Male gender
- Pregnancy
- Hospital acquired Urinary Tract Infection
- Prolonged urinary tract symptoms (>1 week)
- Poorly controlled Diabetes Mellitus
- Immunocompromised
- Underlying urologic disorder
- Vesicoureteral reflux
- Recurrent complicated Urinary Tract Infections
- Catheter associated Urinary Tract Infection
- Neurogenic Bladder dysfunction
- Polycystic Kidney Disease
- Urologic instrumentation or stenting
- Status Renal Transplant
- Urinary Tract Obstruction (e.g. Nephrolithiasis)
- Men with Prostatitis or BPH
IV. Symptoms
- Most suggestive of Urinary Tract Infection
- Dysuria (Likelihood Ratio 2.0)
- If absent, Likelihood Ratio 0.5
- Urinary Frequency (Likelihood Ratio 1.8)
- Hematuria (Likelihood Ratio 1.5)
- Occurs in 30% of cases
- Dysuria (Likelihood Ratio 2.0)
- Other symptoms with Urinary Tract Infection
- Urinary Urgency
- Suprapubic Pain (especially after voiding)
V. Differential Diagnosis
-
Dysuria
- See Dysuria
- See Dysuria in Children
- See Dysuria in Men
- See Dysuria in Women
-
Urethritis
- Pain at onset of urination
-
Vaginitis
- External Dysuria
- Vaginal irritation or discharge
-
Chlamydia trachomatis
- Long, insidious onset
- Sexually active
-
Acute Pyelonephritis
- Fever, Flank Pain, and Nausea or Vomiting
- Risk factors for cystitis with occult Pyelonephritis
- Women (30% have subclinical Pyelonephritis)
- Pregnancy
- Diabetes Mellitus
- Immunocompromised patients
- Urinary Tract Infection under age 12 years
- Genitourinary comorbid condition
- Acute Urethral syndrome (Sterile or low urine Bacterial count)
- Sterile Pyuria
- Chlamydia (most common)
- Genitourinary Tuberculosis (classic sterile pyuria)
- Asymptomatic Bacteriuria (organisms isolated on Urine Culture, but often not responsible for cystitis)
VI. Labs
-
Urinalysis
- Urine Leukocyte Esterase (high Test Sensitivity but low Test Specificity)
- Urine Nitrite (high Test Specificity, but low Test Sensitivity)
- Urine White Blood Cells on microscopy
-
Urine Culture
- Not needed in uncomplicated UTI (young, healthy non-pregnant women)
- Recommended in complicated UTI or suspected Pyelonephritis
- Positive for >100k organisms
- Women with Dysuria have <100k organisms in 30% cases
VII. Diagnosis: Factors suggestive of complicated UTI
- Extremes of age (preadolescent, or post-Menopause)
- Chronic renal disease
- Diabetes Mellitus
- Immunodeficiency
- Pregnancy
- Recent Urinary Tract Instrumentation
- Ureteral Stents
- Indwelling catheters
- Urologic abnormalities
VIII. Diagnosis: Prediction Rule
- Criteria
- New onset frequency and Dysuria
- Absent Vaginal Discharge and irritation
- Efficacy
- Pretest probability of UTI based on symptoms: 90%
- Probablity of UTI with negative Urinalysis: 23%
- Positive Predictive Value: 90%
- Interpretation
- May be treated without Urinalysis and Urine Culture
- Editorial note: I do not recommended this (other Dysuria causes, Antibiotic Overuse)
- Alternative: Even dipstick testing alone is reasonably accurate, priced and fast
- Reference
IX. Diagnosis: Findings suggestive of upper Urinary Tract Infection (Pyelonephritis)
- See Pyelonephritis
- Fever, chills
- Flank Pain
- Vomiting
- Pregnancy (second and third trimester are higher risk)
- Underlying urinary tract disorder
- History of Ureteral Stenting or other instrumentation
- Male patients
- Insulin Dependent Diabetes Mellitus
- HIV Infection
- Immunosuppressants (Chronic Corticosteroid use, status-post transplant)
- Extremes of age (very young or very old)
- Underwhelming presentations of upper tract disease
X. Precautions
- Consider Sexually Transmitted Infection in Vaginitis or male Dysuria
- Consider Nephrolithiasis with Urinary Tract Infection (emergency) when Flank Pain is severe
- Empiric antibiotic regimens should be based on local resistance rates
- Urine Culture is not needed in occasional, uncomplicated Urinary Tract Infection (young, healthy, non-pregnant women)
- Assume upper tract disease in findings listed above
- Adjust management strategy to treat upper tract (e.g. avoid Macrobid or Nitrofurantoin)
XI. Management: General
-
General measures in women
- Women should clean perineum wiping front to back
- Women should empty Bladder before, after intercourse
- Avoid Contraceptive Diaphragm
- Antibiotics
- Course: Anticipate symptom relief within 36 hours of starting antibiotics
- Antibiotic duration
- Uncomplicated treatment: 3 days (except noted)
- Nitrofurantoin and Macrobid course is 5 days (was 7 days)
- Complicated treatment: 10 day course
- Uncomplicated treatment: 3 days (except noted)
- Antibiotic Resistance increasing
- Trimethoprim Sulfamethoxazole (Septra): 18%
- Beta Lactams: 20%
- Ampicillin: 38%
- Nitrofurantoin resistance low (1-2%)
- Fluoroquinolone resistance low (2.5%)
- Avoid as first line agents if possible (due to other adverse effects)
- Consider in areas of high Septra resistance areas
- Cure may occur despite resistance to antibiotic used
- Risks for resistance
- Trimethoprim Sulfamethoxazole within last 3-6 months
- Diabetes Mellitus
- Recent hospitalization
- Travel outside United States
- Resistance rates in community >20%
- Acute Uncomplicated UTI: First-Line agents
- Note that Ciprofloxacin has been demoted from first-line agent due to adverse effects (see below)
- Trimethoprim-Sulfamethoxazole (Bactrim) DS one orally twice daily for 3 days
- Avoid if local resistance rate >20%
- Nitrofurantoin (Macrobid)
- Macrobid 100 mg orally twice daily for 5 days
- Avoid if GFR <30 ml/min (risk of interstitial pulmonary fibrosis)
- Fosfomycin (Monurol) 3 grams for one dose
- Consider as a single dose in Emergency Department (e.g. patient non-compliant)
- More expensive and may be less effective (58% efficacy compared with 70% for Nitrofurantoin)
- Acute Uncomplicated UTI with risks for resistance (prior Bactrim use or international travel in last 6 months)
- Nitrofurantoin
- Avoid if GFR <30 ml/min (risk of interstitial pulmonary fibrosis)
- Nitrofurantoin 100 mg orally four times daily for 5 days
- Macrobid 100 mg orally twice daily for 5 days
- Five days is sufficient course (previously used for 7 days)
- Gupta (2007) Arch Intern Med 167(20):2207-12 [PubMed]
- Fosfomycin (Monurol) 3 grams for one dose
- Also see Fluoroquinolones below
- Nitrofurantoin
- More severe disease or resistant UTI organisms: Fluoroquinolones
- Precautions regarding Fluoroquinolones
- Risk of Tendinopathy (and Achilles Tendon Rupture) and Peripheral Neuropathy
- Avoid if local resistance rate >10%
- Renal dose adjustment required if GFR reduced
- Although 3 day courses are listed, complicated UTI is treated for 10 days (up to 6 weeks in men)
- Ciprofloxacin 250 mg PO bid for 3 days
- In healthy older women, 3 days equivalent to 7 days
- Vogel (2004) CMAJ 170:469-73 [PubMed]
- Levofloxacin 250 mg every 24 hours for 3 days
- Norfloxacin 400 mg PO bid for 3 days
- Ofloxacin 200 mg PO bid for 3 days
- Avoid Moxifloxacin and gemifloxacin (poor penetration into urine)
- Precautions regarding Fluoroquinolones
- Antibiotics for UTI in Pregnancy
- Other antibiotics used in Urinary Tract Infection
- Precautions
- Beta lactams have lower efficacy in UTI
- Cephalexin (Keflex) 500 mg orally twice daily for 5-7 days
- Amoxicillin-Clavulanate (Augmentin) 875 mg orally twice daily for 5-7 days
- Cefdinir 300 mg orally twice daily for 3-7 days
- Precautions
- Sexually active young patients
- Avoid Nitrofurantoin (Macrobid)
- Staphylococcus saprophyticus resistance
- Consider Chlamydia sceening
- Consider other Sexually Transmitted Disease Testing
- Avoid Nitrofurantoin (Macrobid)
XII. Management: Special Circumstances
- See Recurrent Urinary Tract Infection
- See Ureteral Stent
- ESBL (Extended Spectrum Beta-Lactamase) producing E Coli and Klebsiella
- Fosfomycin (cystitis)
- Ertapenem
XIII. Management: Asymptomatic Bacteriuria
XIV. Complications: Surgical
-
Perinephric Abscess
- Urinary Tract Infection contiguous spread
- Contrast with renal abscess (hematogenous spread)
-
Emphysematous Pyelonephritis
- Seen in Diabetes Mellitus
- Requires surgical drainage (otherwise high mortality)
XV. References
- (2019) Sanford Guide, accessed on IOS 9/21/2019
- Colgan (2011) Am Fam Physician 84(7): 771-6 [PubMed]
- Ebell (2006) Am Fam Physician 73:293-6 [PubMed]
- Gupta (1999) JAMA 281:736-8 [PubMed]
- Gupta (2012) Ann Intern Med 156(5): ITC3-1 [PubMed]
- Hooton (1997) Infect Dis Clin North Am 11:551-81 [PubMed]
- Michels (2015) Am Fam Physician 92(9): 778-86 [PubMed]