Fat embolization is most often associated with severe bone trauma, but may also occur in fatty liver, diabetes, and other conditions. Symptoms may be immediate or delayed. If they are immediate, shock is frequent. Delayed symptoms occur 2 – 3 days after injury, and pulmonary or cerebral manifestations are most prominent. Frequent signs are fever, tachycardia, tachypnea, upper body petechiae (50% of patients), and decreased hemoglobin values. Laboratory diagnosis includes urine examination for free fat, results of which are positive in 50% of cases during the first 3 days; and serum lipase, results of which are elevated in nearly 50% of patients from about day 3 to day 7. Fat in sputum is unreliable; there are many false positive and negative results. Chest x-ray films sometimes demonstrate diffuse tiny infiltrates, occasionally coalescing, described in the literature as having a “snowstorm” appearance. Some patients have a laboratory picture suggestive of disseminated intravascular coagulation. One report has indicated that diagnosis by cryostat frozen section of peripheral blood clot is sensitive and specific, but adequate confirmation of this method is not yet available. The most sensitive test for fat embolism is said to be a decrease in arterial PO2, frequently to levels less than 60%. However, patients with chronic lung disease may already have decreased PO2.