Acute interstitial nephritis (AIN) is an inflammation of the tubules and interstitium within the kidney, associated with a relatively sudden onset and rapid decline in renal function. It is usually secondary to drugs (antibiotics, nonsteroidal anti-inflammatory drugs, and proton pump inhibitors being most commonly incriminated), with other causes being infections (classically streptococcal, but this is now less common) and immune disorders (systemic lupus erythematosus, sarcoidosis, and tubulointerstitial nephritis with uveitis). Clinical features—the diagnosis of AIN should be considered in any patient with unexplained acute kidney injury. Drug-induced AIN may present with a classic allergic response, including arthralgias, fever, rash, loin pain, and eosinophilia/eosinophiluria, but these are not invariable and their absence does not exclude the diagnosis. The urine typically shows low-grade proteinuria (<1 g/day). Renal biopsy is the only way to confirm or exclude the diagnosis. Management and prognosis—treatment is by ceasing the offending agent, treating the concurrent infectious cause, or managing the immune aetiology with steroids (typically prednisolone 1 mg/kg per day, tapered to zero over 6–8 weeks). Most patients with drug-induced AIN recover renal function, but some are left with chronic renal impairment and a small proportion progress to endstage chronic kidney disease.
Early steroid treatment improves the recovery of renal function in patients with drug-induced acute interstitial nephritis