Fat embolism syndrome (FES) is a serious clinical disorder occurring in
trauma patients. The diagnosis of
fat embolism syndrome may be difficult to establish clinically. We therefore wanted to investigate the usefulness of bronchoalveolar lavage (BAL) in the diagnostic evaluation of
fat embolism syndrome. We analysed the presence of fat droplets in BAL cells in 32
trauma patients (7 with full diagnostic criteria of
fat embolism syndrome, 17 with incomplete diagnostic criteria, and 8 with no diagnostic criteria at the time of bronchoscopy), 9 nontrauma patients with acute
respiratory failure and radiographic pulmonary infiltrates, and a control group composed of 10 individuals. An increased percentage of
oil red O positive alveolar macrophages (cut-off point > 3%) in BAL was found in 6 out of 7 patients with definite clinical criteria of
fat embolism syndrome, and in 6 out of 20
trauma patients without the clinical diagnosis of
fat embolism syndrome. In two patients with
fat embolism syndrome, sequential BAL showed that the percentage of positive macrophages decreased when the clinical manifestations disappeared. An increased number of BAL macrophages with fat droplets was also observed in two
trauma patients without evidence of
fat embolism syndrome after long-bone surgical intervention. By contrast, all non-
trauma patients had a percentage of positive cells lower than 3%. Our findings suggest that BAL
oil red O positive macrophages are frequently observed in
trauma patients irrespective of the presence of
fat embolism syndrome. Conceivably, a high number of
oil red O positive macrophages could reflect clinically silent fat embolization.