Tubulointerstitial Disease

The answer first

Acute interstitial nephritis (AIN) is the great mimic of acute kidney injury — an immune-mediated inflammation of the renal interstitium that presents as a quiet, subacute creatinine drift with unimpressive urine, and that is caused by a drug until proven otherwise ^[1]. Three rules carry you through the DWE and the long case ^{[1] [5]}:

1. Suspect it in every unexplained AKI. The textbook allergic syndrome — fever, rash, eosinophilia — is the exception, not the rule. Modern drug-induced AIN is usually just a creatinine that will not stop rising, and the triad appears together in only a small minority of biopsy-proven cases ^{[3] [4]}.
2. Stop the culprit drug immediately. Withdrawal of the offending agent is the one intervention with consistent outcome data, and delay in withdrawal is associated with worse renal recovery — the steroid question always comes second ^[2].
3. Steroids are a decision, not a default. The evidence is entirely retrospective; benefit concentrates in patients treated early after biopsy confirmation with no contraindication. In an elderly polypharmacy patient with modest AKI, watchful waiting after drug withdrawal is a defensible, examinable position ^{[2] [13]}.

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References22ShowHide

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