Cholesterol embolism (often cholesterol crystal embolism or atheroembolism, sometimes blue toe or purple toe synrome or trash foot) occurs when cholesterol is released, usually from an atherosclerotic plaque, and travels along with the bloodsteam (embolism) to other places in the body, where it obstructs blood vessels. Most commonly this causes skin symptoms (usually livedo reticularis), gangrene of the extremities and sometimes renal failure; problems with other organs may arise, depending on the site at which the cholesterol crystals enter the bloodstream. When the kidneys are involved, the disease is referred to as atheroembolic renal disease (AERD). The diagnosis usually involves biopsy (removing a tissue sample) from an affected organ. Cholesterol embolism is treated by removing the cause and with supportive therapy; statin drugs have been found to improve the prognosis.