Identification at Autopsy of Clinically Unsuspected Pulmonary And/Or Systemic Fat Embolism

Abstract

Systemic or pulmonary fat embolism (SFE,PFE) is typically associated with bone fractures and can be diagnosed only at autopsy using a lipophilic stain on frozen tissue sections. PFE also has been found as a cause of death following liver transplantation. We asked whether PFE or SFE could be found in other autopsies in cases of unexpected death. In hospital autopsy cases assigned to one of us (B.G.), 2009-2011, oil red O (ORO) staining on frozen sections of formalin-fixed lung, kidney, brain, and/or liver tissues was performed to confirm PFE and/or SFE in cases of unexpected death when light microscopic features of lung showed vacuoles suggestive of fat emboli. We similarly studied 10 control autopsy cases of sudden death due to other known causes. In all cases, identification of PFE/SFE was correlated with autopsy findings of rib or other fracture, pulmonary bone marrow emboli, obesity, and/or hepatic steatosis; postmortem interval; and history of hyperlipidemia and/or CPR. Of 197 autopsy cases in the 3-year period, 11 (5.6%) were diagnosed with PFE; in 7 of these (3.6% of total) renal capillary ORO positivity indicative of SFE also was found. Causes of PFE/SFE at autopsy included traumatic fracture (n = 3), rib fracture associated with CPR (n = 3), acute pancreatitis (n = 2), fatty liver disease (n = 1), and undetermined (n = 1). Fat embolism at autopsy was deemed the immediate cause of death in 6 cases (4 with traumatic fracture, 2 with acute pancreatitis); SFE was identified in 1 of 3 cases associated with CPR. In none of the 11 PFE/SFE cases was the diagnosis of PFE or SFE made before death. No PFE or SFE was found in the control cases. Clinically unsuspected PFE or SFE can be found at autopsy with traumatic fracture and in association with other medical disease, and PFE/SFE may represent the immediate cause of death in many of these cases. The identification of SFE following CPR suggests that SFE may sometimes prevent successful resuscitation from cardiopulmonary arrest. ORO staining of lung and kidney samples may be helpful in determining cause of death at autopsy.