Acute Interstitial Nephritis

Background / Epidemiology

  • Characterised by acute inflammation affecting the tubulo-interstitium of the kidney
  • Usually drug-induced (in particular- Penicillins; Cephalosporins; NSAIDs; PPIs; diuretics); but can be caused by other renal toxins and complicate other diseases/infections (e.g. pyelonephritis, renal tuberculosis; sjogren’s, SLE, Wegener’s)

Presentation

  • Renal impairment
    • Proteinuria usually modest; there may be haematuria and leucocytes (although these are rarer); eosinophilia in the urine is a classic finding (although not present in all cases)
    • Acute kidney injury¬†(although often without oligouria)
      • Raised creatinine/low eGFR; U&Es may show abnormal potassium
  • There may also be features of drug hypersensitivity
    • e.g. generalised rash, fever, eosinophilia; arthralgia

Management and Investigations

  • Urinalysis, FBCs, U&Es, LFTs should also be used
    • May show eosinophilia, raised ALT (if drug-induced)
  • Remove any potentially causative medications- this usually resolves the problem
  • If there is no improvement and no contraindications, renal biopsy will provide a pathological diagnosis if uncertain clinically
    • Nuclear imaging may be of use if biopsy is contraindicated
  • Steroid therapy may be used and dialysis may be required for severe cases causing acute renal failure
  • Treat any underlying causes e.g infections, systemic connective tissue diseases; as appropriate

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