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Acute Interstitial Nephritis

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Topic updated on 07/30/17 5:02pm

Snapshot
  • A 65-year-old man presents to urgent care with a sudden-onset of fever and rash. His review of systems is negative. He was recently started on omeprazole for acid reflux approximately 2 weeks ago. Routine laboratory tests reveal a serum creatinine of 3.5 mg/dL and eosinophilia. Urine studies showed white blood cell casts.
Introduction
  • Clinical definition
    • acute interstitial nephritis (AIN), also known as tubulointerstitial nephritis, is an acute immune-mediated interstitial inflammation of the kidneys
  • Epidemiology
    • demographics
      • male:female ratio is 3:1 in methicillin-induced AIN
      • middle-aged adults
  • Etiology
    • drug-induced hypersensitivity (majority of cases)
      • typically developed between 1 week to 9 months
      • 5 Ps
        • Pee (diuretics, especially sulfa ones)
        • Pain-free (NSAIDs)
        • Penicillins and cephalosporins
        • Proton pump inhibitors
        • rifamPin
    • systemic infections
      • mycoplasma
    • autoimmune diseases
      • systemic lupus erythematosus
      • sarcoidosis
  • Pathogenesis
    • type IV hypersensitivity reaction
    • T-cell-mediated attack on tubular cells
  • Prognosis
    • typically resolves after withdrawal of inciting agent
Presentation
  • Symptoms
    • primary symptoms
      • fever
      • minimal hematuria
      • flank pain
      • arthralgias
      • can be asymptomatic
    • defining characteristics
      • development of rash after administration of drug
  • Physical exam
    • rash
      • diffuse
      • maculopapular
    • flank/costovertebral angle tenderness
Studies
  • Labs
    • serum eosinophilia
    • elevated serum creatinine
  • Urinalysis with microscopy and sediment analysis
    • white blood cell casts
    • hematuria
    • eosinophiluria
      • seen with Hansel or Wright stain
        • recall that urinalysis can only detect white blood cells, red blood cells, and protein
      • most accurate test
  • Renal biopsy
    • not usually indicated
    • indications
      • patients with suspected AIN but no obvious etiology
    • only definitive method of diagnosis
  • Histology
    • severe tubular damage
    • interstitial edema
    • T-cell and eosinophilic infiltration
  • Diagnostic criteria
    • elevated creatinine
    • urinalysis with white cell casts and eosinophiluria
Differential
  • Acute tubular necrosis from NSAIDs
    • no rash or eosinophils
  • Renal atheroemboli
    • also presents with eosinophiluria, eosinophilia, and skin rash
    • rash is typically livedo reticularis with digital infarcts, not maculopapular
Treatment
  • Conservative
    • discontinue inciting drug
      • indications
        • for all drug-induced hypersensitivity cases
  • Medical
    • glucocorticoids      
      • indications
        • if creatinine continues to rise after stopping drugs
        • if etiology is sarcoidosis
Complications
  • Renal failure requiring dialysis



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