Acute Interstitial Nephritis

Key points

• Acute interstitial nephritis (AIN) accounts for about 25% of drug-induced AKI.
• Causes — drugs (commonest): antibiotics (penicillins, cephalosporins, rifampicin), NSAIDs, allopurinol, furosemide, proton pump inhibitors; also infections and systemic disease (SLE, sarcoidosis, Sjogren's).
• Presentation: fever, rash and arthralgia with AKI; eosinophilia and eosinophiluria; sterile pyuria and white-cell casts.
• Histology: marked interstitial oedema and an inflammatory infiltrate (lymphocytes and eosinophils) between the renal tubules.
• Management: stop the causative drug (the mainstay); corticosteroids are often used if renal function does not recover. Tubulointerstitial nephritis with uveitis (TINU) is a recognised variant.