Case Report
Acute Kidney Injury During Warfarin Therapy Associated With Obstructive Tubular Red Blood Cell Casts: A Report of 9 Cases

https://doi.org/10.1053/j.ajkd.2009.04.024Get rights and content

Acute kidney injury (AKI) during warfarin therapy usually is hemodynamic secondary to massive blood loss. Here, we report pathological findings in kidney biopsy specimens from 9 patients with warfarin overdose, hematuria, and AKI. Kidney biopsy specimens from patients on warfarin therapy with AKI were identified in our database within a 5-year period. Each kidney biopsy specimen was evaluated by using semiquantitative morphometric techniques, and medical history was reviewed for conditions explaining AKI. Biopsy specimens with morphological findings of active glomerulonephritis and active inflammatory lesions were excluded from the study. Biopsy specimens from 9 patients were selected. At presentation with AKI, each patient had an abnormal international normalized ratio (mean 4.4 ± 0.7 IU) and increased serum creatinine level (mean, 4.3 ± 0.8 mg/dL). Morphologically, each biopsy specimen showed evidence of acute tubular injury and glomerular hemorrhage: red blood cells (RBCs) in Bowman space and numerous occlusive RBC casts in tubules. Each biopsy specimen showed chronic kidney injury. Six of 9 patients did not recover from AKI. These data suggest that warfarin therapy can result in AKI by causing glomerular hemorrhage and renal tubular obstruction by RBC casts. Our experience suggests that this may be a potentially serious complication of warfarin therapy, especially in older patients with underlying chronic kidney injury.

Section snippets

Case Reports

We searched the kidney biopsy files at the Department of Pathology, The Ohio State University Medical Center, Columbus, OH, for a 5-year period. We focused on biopsy specimens from patients who presented with unexplained AKI and hematuria while on warfarin therapy. We identified 2,801 native kidney biopsy specimens. Of these, 61 biopsy specimens were from patients on warfarin treatment (according to clinical information provided). AKI was noted in the clinical history for 35 biopsies. Only

Discussion

In the present study, we summarize pathological findings in kidney biopsy specimens obtained from patients on warfarin treatment who developed unexplained AKI. We identified RBCs in Bowman space, RBCs in tubules, and occlusive RBC casts predominantly in distal nephron segments. In addition, all patients had underlying chronic kidney injury, but no active proliferative glomerular lesions.

The association of hematuria with warfarin treatment in the absence of acute kidney disease has been reported

Acknowledgements

The authors thank Drs Stephen Silver, Ashutosh Singh, Ganesh Shidham, Paul Kovach, and John Panos for help in providing follow-up data.

This work was presented in part at the 2009 United States and Canadian Academy of Pathology Annual Meeting, March 7-13, 2009, Boston, MA.

Support: None.

Financial Disclosure: None.

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Originally published online as doi:10.1053/j.ajkd.2009.04.024 on July 6, 2009.

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