Warfarin Related Nephropathy and Beyond. What Renal Pathologists Need To Suspect in A Kidney Biopsy.

We have recently described a new clinical syndrome in patients receiving warfarin for anticoagulation. First, we identified that warfarin therapy can result in acute kidney injury (AKI) by causing glomerular hemorrhage and renal tubular obstruction by red blood cell (RBC) casts in some patients. This syndrome has been named warfarin-related nephropathy (WRN), and patients with chronic kidney disease (CKD) appear to be particularly susceptible. We defined WRN as an acute increase in INR to greater than 3.0, followed by evidence of AKI (defined as a sustained increase in serum creatinine of greater than or equal to 0.3 mg/dl) within a week of the INR increase. We believe that anticoagulant-related kidney injury should be suspected in a patient on an anticoagulation therapy, if there is a disproportion between the number of RBC tubular casts, ATN and the degree of an underlying kidney lesion (such as glomerular immune complex depositions, GBM thickness abnormalities etc) in kidney biopsy. Detailed evaluation of coagulation data and medications is recommended for all patients with RBC casts and AKI.