Objective: Fat embolism syndrome (FES) is rare and diagnosis is challenging. Clinical manifestations are non-specific and no biochemical tests are reliable for diagnosis, highlighting the importance of thoracic CT. Our goal was to describe the CT manifestations of FES and assess whether imaging findings, time of onset of symptoms and time of surgery correlate with clinical course and severity of the disease.
Methods: Retrospective review of 49 patients with respiratory distress after trauma/intramedullary nail fixation over a 10 year period; 12 patients met clinical criteria and were categorized as non-fulminant (NF-FES) or fulminant FES (F-FES). CT images were analyzed and electronic records reviewed for clinical findings, timeline from trauma to surgery and onset of symptoms. Pearson Chi-square and Levene's test were used and results considered significant when p<0.05.
Results: All patients were men (18-80 years, mean 38 years), 5 (42%) suffered F-FES and 7 (58%) NF-FES. The most common CT finding was ground-glass opacities (8/12, 67%), often with lobular sparing. Consolidation occurred in 4/12 (33%), all in F-FES patients (p=0.004). In 5/5 F-FES, lung involvement was extensive (>75%) whereas most NF-FES had limited involvement (p<0.01). Centrilobular nodules were the predominant finding in 3/12 (16%). Median time between fracture and onset of symptoms was 43h, in 9/12 patients manifesting after surgery. Mean time between trauma and surgery was 20h in NF-FES and 52h in F-FES (p=0.02).
Conclusions: The most common CT features of FES were ground-glass opacity and consolidation, less commonly, centrilobular nodules. The extent of ground-glass opacities and the presence of consolidation correlated with disease severity. Significant difference was found from time of trauma to surgery in the two groups however is uncertain whether delayed surgery truly increased the risk of F-FES.
Keywords: Computed tomography; Fat embolism; Fat embolism syndrome.
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