Acute Pyelonephritis

1. See Also
   1. Urinary Tract Infection
2. Definition
   1. Upper Urinary Tract Infection involving Kidney
3. Epidemiology
   1. Accounts for 200,000 hospitalizations annually in U.S
   2. Highest Incidence in otherwise healthy women ages 15 to 29 years
4. Causes
   1. Ascending infection via Bladder and ureter (most cases)
   2. Hematogenous spread
      1. Prostatitis or Benign Prostatic Hyperplasia
      2. Serious comorbid chronic illness
      3. Immunocompromised patients
      4. Hematogenous spread of staph. or fungal infection
5. Etiologies
   1. Normal host
      1. Escherichia coli (80%)
      2. KlebsiellaPneumoniae (3-6%)
      3. Staphylococcus saprophyticus (<3%)
      4. Other Gram Negative Bacteria (e.g. Proteus, Enterobacter)
      5. Enterococcus
   2. Elderly
      1. Escherichia coli (60%)
      2. Proteus
      3. Klebsiella
      4. Serratia
      5. Pseudomonas
   3. Urinary Catheter associated infection
      1. Bacteriuria in 50% at 5 days, and 100% at 30 days
      2. Mixed bacterial infection
   4. Diabetes Mellitus
      1. Klebsiella
      2. Enterobacter
      3. Clostridium
      4. Candida
   5. Immunosuppression
      1. Aerobic, Gram Negative Rods (non-enteric)
      2. Candida
6. Risk Factors: Pyelonephritis in women
   1. Frequent sexual intercourse in prior month (3 times weekly)
   2. New sexual partner in the last year
   3. Recent Spermicide use
   4. Family History of Urinary Tract Infections (esp in patient's mother)
   5. Prior Urinary Tract Infections in the last year
   6. Diabetes Mellitus
   7. Stress Incontinence in the last 30 days
7. Risk Factors: Antibiotic Resistance
   1. Frequent medical care
   2. Recent antibiotic use (esp. Fluoroquinolones, Cephalosporins)
   3. Advanced age
   4. Recurrent Urinary Tract Infections
   5. Diabetes Mellitus
8. Risk Factors: Complicated Pyelonephritis (with higher risk of complications such as abscess, Antibiotic Resistance)
   1. Age under 1 or over 60 years
   2. Abnormality (Polycystic Kidney, Vesicoureteral reflux)
   3. Obstruction (Nephrolithiasis, BPH, tumor)
   4. Immunocompromised (Diabetes, HIV, Corticosteroids)
   5. Indwelling Urinary Catheter
   6. Pregnancy
9. Symptoms
   1. Fever
   2. Chills and malaise
   3. Flank pain
   4. Nausea and Vomiting
   5. Acute Cystitis symptoms
      1. Dysuria
      2. Urinary frequency
      3. Urinary urgency
10. Signs
    1. Fever
    2. Tachycardia
    3. Hypotension
    4. Costovertebral angle tenderness
    5. Abdominal tenderness (esp. suprapubic tenderness)
11. Diagnosis
    1. Fever over 100.4 F
       1. May be absent early in course
       2. Not uniformly present in elderly (only in 80%)
       3. Not uniformly present in catheter-associated UTI
    2. Flank pain
    3. Urinalysis with bacteriuria and pyuria
12. Labs
    1. Urinalysis
       1. Leukocyte esterase or nitrite positive
       2. Microscopic Hematuria may be present (contrast with Gross Hematuria in Acute Cystitis)
       3. Microscopic examination may show WBC casts
       4. Consider urine Gram Stain where available
          1. Gram Positive Cocci suggests Enterococcus or Staphylococcus saprophyticus
    2. Urine Culture (positive in 90% of Pyelonephritis)
       1. Manditory in all suspected cases of Pyelonephritis
       2. Diagnosis requires at least 10,000 CFU/mm3
       3. Consider lower threshold in men and in pregnancy
    3. Blood Culture indications (positive in up to 30% cases, obtain in severe infection or hospitalized patients)
       1. Immunocompromised patient
       2. Unclear diagnosis
       3. Hematogenous source suspected
    4. Other labs
       1. Urine Pregnancy Test
       2. Serum Creatinine
       3. Complete Blood Count
       4. Other testing as indicated by differential diagnosis in unclear cases
13. Imaging
    1. Modalities
       1. CT Abdomen with contrast (preferred in non-pregnant patients)
       2. Renal Ultrasound (pregnant patients)
       3. Renal MRI (specific indications as directed by local consultation)
    2. Indications
       1. Not routinely indicated in uncomplicated Pyelonephritis
       2. Reserve for recurrent or refractory infections
14. Differential Diagnosis
    1. Pelvic Inflammatory Disease
    2. Acute Cholecystitis
    3. Appendicitis
    4. Pneumonia
15. Disposition: Hospitalization indications
    1. Inability to stay hydrated and take medications orally
    2. Comorbidity
       1. Diabetes Mellitus
       2. Underlying urologic or renal disorder
       3. Severe liver disease
       4. Severe heart disease
    3. Noncompliance
    4. Uncertain diagnosis
    5. Male gender
    6. Toxic appearance
    7. Severe illness with high fever (>103 F)
    8. Severe flank or Abdominal Pain
    9. Debilitated condition
    10. Pregnancy (some cases may be treated outpatient)
16. Management: Pregnancy
    1. See Pyelonephritis in Pregnancy
17. Management: Oral agents for acute uncomplicated non-pregnant cases
    1. Consider a single initial dose of IV antibiotics if Emesis (see below)
    2. Preferred agents: Fluoroquinolones (if community E. coli resistance rate <10%)
       1. Ciprofloxacin 500 mg orally twice daily for 7 days
       2. Ciprofloxacin XR 1000 mg daily for 7 days
       3. Levofloxacin 750 mg orally daily for 5 days
    3. Alternative agents (higher resistance rates, accompany with initial dose of a broad spectrum IV antibiotic)
       1. Amoxicillin-Clavulanate (Augmentin) bid for 14 days
       2. Trimethoprim-Sulfamethoxazole (Bactrim) bid 14 days
18. Management: IV agents in non-pregnant patients
    1. Duration of treatment
       1. Convert from IV to oral in first 48-72 hours
    2. Preferred agents
       1. Ciprofloxacin 400 mg IV twice daily
       2. Levofloxacin (Levaquin) 250-500 mg IV daily
       3. Ceftriaxone (Rocephin) 1000 mg IV q24 hours
       4. Gentamicin 5 mg/kg IV daily
       5. Imipenem/Cilastatin (Primaxin) 500 mg IV every 6 hours
19. Complications
    1. Perinephric abscess
    2. Emphysematous Pyelonephritis
       1. Occurs in older women with Diabetes Mellitus
       2. Infection produces intraparenchymal gas
       3. Associated with papillary necrosis and Renal Failure
    3. Urinary Tract Infection due to obstruction
       1. Associated with Nephrolithiasis, BPH, or tumor
       2. May result in renal abscess and severe infection
20. References
    1. Escobar in Marx (2002) Rosen's Emergency Med, p. 1401
    2. Colgan (2011) Am Fam Physician 84(5): 519-26
    3. Hooton (2003) Infect Dis Clin North Am 17(2):303-32
    4. Ramakrishnan (2005) Am Fam Physician 71(5):933-42
    5. Roberts (1999) Urol Clin North Am 26:753-63