Warfarin: A double-edged sword.

Warfarin is the commonest anticoagulant used in today's practice; it has a very narrow therapeutics window. Under and overdosing results in various life-threatening complications. Warfarin-related nephropathy (WRN) is a rare cause of acute kidney injury (AKI) in patients on long-term anticoagulation, as a result of supratherapeutic anticoagulation. Warfarin causes AKI by inducing glomerular hemorrhage with subsequent tubular obstruction by red blood cell (RBC) casts. WRN has been associated with irreversible kidney injury and increased risk of mortality. Despite a better understanding of pathophysiology and histopathology of WRN, its preventive measures and clinical outcome are not well known. We report here the case of a 62-year-old male, who was on a long-term warfarin therapy due to chronic atrial fibrillation with a history of old ischemic stroke and dilated cardiomyopathy. He was presented with AKI and his renal biopsy was suggestive of WRN. He was managed by withholding warfarin for a few days until the therapeutic range of international normalized ratio was achieved and steroids and N-acetylcysteine (NAC) recovered. WRN is a diagnosis of exclusion; other causes of AKI must be ruled out. Renal biopsy is the gold standard for diagnosis. Patients on chronic anticoagulant therapy should be monitored periodically for the therapeutic range of anticoagulants, deterioration of renal function, and hematuria.