[1673] The Clinico-Pathologic Spectrum of Rhabdomyolysis and KIM-1 Immunohistochemistry in Patients with Acute Kidney Injury

Hope E Karnes, Joseph P Gaut, Osamu Takasu, Helen Liapis. Washington University in St. Louis, St. Louis, MO

Background: Rhabdomyolysis is associated with acute kidney injury (AKI) and can be lethal. Small decrements in renal function are thought to contribute to increased mortality. Therefore, early AKI detection is crucial. Pathologic changes on renal biopsy may be subtle, underestimating the degree of acute tubular injury (ATI). Previous studies have demonstrated upregulation of kidney injury molecule-1 (KIM-1) within the proximal tubule brush border in patients with AKI. We aimed to investigate whether KIM-1 immunohistochemistry in renal biopsies of patients with rhabdomyolysis may improve assessment of AKI.
Design: A retrospective review of patients at our institution with clinical diagnoses of rhabdomyolysis and renal biopsies performed between 1/1/1989 and 9/1/2011 was conducted. Formalin-fixed paraffin-embedded tissue sections stained with H&E, myoglobin, and KIM-1 were evaluated. The extent of immunohistochemical staining was semiquantitated as follows: 1+ = 1-25% of tissue section staining; 2+ = 25-50%, and 3+ = >50%. Myoglobin and KIM-1 scores were calculated. Clinical follow up at the time of release from the hospital or at autopsy was recorded.
Results: Ten cases were identified with clinical evidence of rhabdomyolysis secondary to HIV (n=1), cocaine use (n=2), membranous glomerulonephritis (n=2), polymyositis (n=1), acute renal failure (n=2), chemotherapy (n=1), heat exhaustion (n=1), and pulmonary hemorrhage (n=1). Apparent ATI was identified in 2/10 (20%) cases. Myoglobin casts were present in 4/10 (40%) biopsies. Eight cases had tissue remaining for KIM-1 immunostaining. KIM-1 (3+) was present in all 4 cases with myoglobin casts, as well as 3 additional cases without casts for a total of 7/8 (88%). The case without KIM-1 staining showed no ATI by light microscopy. Of the patients with 3+ KIM-1 staining, 2 ended up on dialysis, 1 showed progressive decline in renal function and is awaiting transplantation, and 1 died.
Conclusions: Of the patients with clinical rhabdomyolysis, ATI was only identified in 20% of cases. Strikingly, KIM-1 revealed extensive AKI, even when only subtle changes were observed by light microscopy. Diffuse KIM-1 immunoreactivity was associated with a worse clinical outcome. We suggest that KIM-1 is a useful tool for AKI diagnosis and in determining severity in patients with rhabdomyolysis.
Category: Kidney (does not include tumors)

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 255, Monday Morning


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