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Acute Interstitial Nephritis

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Acute Interstitial Nephritis, Acute Tubulointerstitial Nephritis, Allergic Interstitial Nephritis, Interstitial Nephritis, AIN

  • See Also
  1. Acute Kidney Injury
  2. Acute Prerenal Failure
  3. Acute Postrenal Failure
  4. Acute Kidney Injury Causes
  5. Medication Causes of Acute Kidney Injury
  6. Nephrotoxicity Risk
  7. Intravenous Contrast Related Acute Renal Failure
  8. Chronic Renal Failure
  9. Prevention of Kidney Disease Progression
  • Pathophysiology
  1. Renal interstitial inflammation
  2. T-Cell mediated Hypersensitivity Reaction (Allergic Reaction affecting the Kidney)
  • Causes
  1. See Infectious Causes of Acute Interstitial Nephritis (includes miscellaneous causes)
  2. Medications
    1. See Medication Causes of Interstitial Nephritis
    2. Most common causes
      1. NSAIDs
      2. Antibiotics
      3. Proton Pump Inhibitors
  • Findings
  • Symptoms and Signs
  1. Classic Presentation of rash, fever and urine Eosinophilia in only 10% of patients (within days of starting causative medication)
  2. Classic Symptom Triad (e.g. Methicillin induced Hypersensitivity)
    1. Low grade fever (>70% of cases)
    2. Rash (>30% of cases)
    3. Arthralgia (>15% of cases)
  3. Acute Renal Failure
    1. Oliguria
    2. Malaise
    3. Nausea or Vomiting
  1. Urinalysis
    1. Eosinophiluria
    2. Proteinuria
    3. Fractional Excretion of Sodium >1%
      1. Common to intrinsic Kidney disease (ATN, GN) in which Sodium cannot be retained despite decreased perfusion
  2. Renal Function tests with Renal Insufficiency
    1. Serum Creatinine increased
    2. Blood Urea Nitrogen increased
  3. Miscellaneous
    1. Hyperchloremic Metabolic Acidosis
  • Labs
  • Renal biopsy
  1. Inflammation of renal interstitium
    1. Mononuclear cell and T-Lymphocyte infiltrate
  2. Glomerular and vascular sparing
  • Management
  1. Consider Corticosteroid course
    1. Initial: Prednisone 1 mg/kg/day PO for 2 weeks
    2. Next: Prednisone tapered off over 3-4 weeks
    3. Consider Cyclophosphamide in steroid non-responders
  2. Eliminate possible causes
  3. Optimize fluid status
  4. Manage Hyperkalemia and other Electrolyte abnormalities
  5. Symptomatic relief of fever and Arthralgias
  6. Avoid nephrotoxic medications
  • Prognosis
  1. Recovery in weeks if cause eliminated within 2 weeks
  2. Renal biopsy findings suggestive of poor prognosis
    1. Diffuse inflammation
    2. Neutrophils >1%
    3. Significant interstitial fibrosis
  • Complications
  1. Acute Renal Failure
    1. Responsible for up to 15% of Acute Renal Failure
  • Prevention
  1. See Prevention of Kidney Disease Progression
  • References
  1. Kodner (2003) Am Fam Physician 67(12):2527-34 [PubMed]
  2. Michel (1998) J Am Soc Nephrol 9:506-15 [PubMed]