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Updated: Dec 1 2021

Acute Interstitial Nephritis

  • 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
  • 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
  • Prognosis
    • typically resolves after withdrawal of inciting agent
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