alveolar macrophages fat stain in early diagnosis of fat embolism syndrome the aim of this study was to assess the contribution of bronchoalveolar lavage bal in the diagnosis of fat embolism syndrome fes the presence of fat droplets in alveolar macrophages was addressed in 13 trauma patients with bone fractures and 10 nontrauma patients with acute respiratory distress syndrome ards the control group was composed of 5 anesthesized patients with ischemic heart disease immediately prior to cardiac surgery two patients with suggestive clinical and laboratory signs of fes had 40 and 24 fatcontaining alveolar cells respectively the trauma patients without signs of fes displayed a wide variation in the percentage of fatcontaining macrophages from 3 to 95 most of the patients with ards who were receiving lipid emulsion as part of their parenteral nutrition had a high percentage 85 of fatcontaining macrophages patients with normal lungs had no fatcontaining macrophages our findings suggest that bal oil red opositive macrophages are frequently observed in trauma patients irrespective of the presence of fes therefore estimation of the percentage of fatcontaining macrophages from bal is an unreliable marker of fes