AJKD Atlas of Renal Pathology: Cholesterol Emboli

Renal atheroembolic disease is a vascular injury caused by cholesterol emboli from atherosclerotic plaques. It is commonly seen in patients older than 50 years with cardiovascular risk factors. In most cases, it is iatrogenic following cardiovascular procedures or initiation of anticoagulant therapy. In approximately 25% of patients, it happens spontaneously. The presentation is variable and can range from acute kidney injury to chronic kidney disease, with skin lesions, transient eosinophilia, gastrointestinal symptoms, retinal emboli, and proteinuria. A kidney biopsy is usually performed if the etiology of kidney failure is unclear.

On light microscopy, the disease is most commonly characterized by the presence of needle-like or slit-like clefts within arterioles and occasionally glomerular capillaries. This appearance is due to the fact that cholesterol crystals are dissolved by formalin fixation, leaving cleft-like spaces (Figure 1).  The morphology of the cholesterol cleft depends on the age of the lesion. Acute lesions are accompanied by red blood cells, fibrin, and acute inflammatory cells, while chronic lesions are surrounded by intimal fibrosis and chronic inflammatory cells (Figure 2). On immunofluorescence, there are no specific staining patterns, but the cholesterol crystals can sometimes be seen (Figure 3) and polarized (Figure 4). On electron microscopy, the clefts appear within blood vessels or glomeruli (Figure 5). Tubular injury, ischemia, or other pre-existing conditions (e.g., hypertension, diabetes, focal segmental glomerulosclerosis, and immune complex disease) can also be found on biopsy.

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The main differential diagnosis on the biopsy are artifacts, severe arteriosclerosis (severe luminal narrowing or vascular branching points can look like clefts), vasculitis (because of the presence of surrounding inflammation and clinical presentation), and thrombotic microangiopathy (due to the presence of surrounding fibrin in acute lesions).

Post prepared by guest contributor Shree G. Sharma, MD. Figures from Lusco et al, AJKD, © National Kidney Foundation.

Please visit the Atlas of Renal Pathology II (freely available) at AJKD.org for related installments on this and other topics.

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