Pulmonary fat embolism
Pulmonary fat embolism is a specific subtype of pulmonary embolism where the embolic particles are composed of fat.
It usually occurs in the context of a long bone fracture and may occur in 1-3% of patients with simple tibial or femoral fractures and up to 20-33% of individuals with more severe trauma.
Other less common causes include:
- soft tissue trauma
- major burns
- overwhelming infection
- blood transfusion
The exact pathophysiology is not entirely clear but presumably occurs by one of two mechanisms or a combination thereof:
- production of free fatty acids, which initiates a toxic reaction in the endothelium. This process is further complicated by the accumulation of neutrophils and other inflammatory cells, which cause damage to the vasculature.
- mechanical obstruction of the pulmonary vasculature by fat globules, aggregates of red blood cells, and platelets.
Urinalysis for fat globules may be useful in the setting of large a pulmonary fat embolism.
Imaging findings typically become evident ar around 24-48 hours after the traumatic insult.
Non-specific but can resemble those in acute respiratory distress syndrome from any cause, and shows widespread homogeneous and heterogeneous areas of increased opacity. A normal heart size and the absence of other features of cardiogenic oedema (septal lines, pleural effusion, and pulmonary venous hypertension) may aid in the differentiation from noncardiogenic pulmonary oedema.
Commonly reported findings include:
- may show areas of consolidation
- ground-glass opacities: can occur with a geographic distribution and or in association with interlobular septal thickening 7
- small (<1 cm) nodules of various sizes: presumed to represent alveolar oedema or haemorrhage secondary to the fat embolism syndrome 5,6
- fat attenuating filling defects in pulmonary arteries: rarely described in non-fulminant fat embolism syndrome
Treatment and prognosis
Prophylactic treatment consists of prompt treatment of the causative factor, e.g. fracture fixation. Treatment is largely supportive and involves fluid resuscitation, maintaining good arterial oxygenation and sufficient intravascular volume. Adding albumin to the electrolyte solution used for volume resuscitation can help bind the free fatty acids 8. Mechanical ventilation and PEEP may be required in certain cases. Symptoms are often transient with good prognosis.
- some imaging features can resemble those of acute respiratory distress syndrome 11
- other considerations for multifocal ground glass changes include
- multifocal infective inflammatory changes
- 1. Han D, Lee KS, Franquet T et-al. Thrombotic and nonthrombotic pulmonary arterial embolism: spectrum of imaging findings. Radiographics. 2003;23 (6): 1521-39. Radiographics (full text) - doi:10.1148/rg.1103035043 - Pubmed citation
- 2. Nucifora G, Hysko F, Vit A et-al. Pulmonary fat embolism: common and unusual computed tomography findings. J Comput Assist Tomogr. 2007;31 (5): 806-7. doi:10.1097/rct.0b013e318032566e - Pubmed citation
- 3. Van den Brande FG, Hellemans S, De Schepper A et-al. Post-traumatic severe fat embolism syndrome with uncommon CT findings. Anaesth Intensive Care. 2006;34 (1): 102-6. Pubmed citation
- 4. Fulde GW, Harrison P. Fat embolism-a review. Arch Emerg Med. 1992;8 (4): 233-9. Free text at pubmed - Pubmed citation
- 5. Heyneman LE, Müller NL. Pulmonary nodules in early fat embolism syndrome: a case report. J Thorac Imaging. 2000;15 (1): 71-4. Pubmed citation
- 6. Gallardo X, Castañer E, Mata JM et-al. Nodular pattern at lung computed tomography in fat embolism syndrome: a helpful finding. J Comput Assist Tomogr. 2006;30 (2): 254-7. Pubmed citation
- 7. Malagari K, Economopoulos N, Stoupis C et-al. High-resolution CT findings in mild pulmonary fat embolism. Chest. 2003;123 (4): 1196-201. Pubmed citation
- 8. Shaikh N. Emergency management of fat embolism syndrome. J Emerg Trauma Shock. 2009;2 (1): 29-33. J Emerg Trauma Shock (full text) - doi:10.4103/0974-2700.44680 - Free text at pubmed - Pubmed citation
- 9. Sidney Ching Liang Ong, Viknesh Balasingam. Characteristic imaging findings in pulmonary fat embolism syndrome (FES). (2017) BMJ Case Reports. 2017: bcr-2017-223007. doi:10.1136/bcr-2017-223007 - Pubmed
- 10. Arakawa H, Kurihara Y, Nakajima Y. Pulmonary fat embolism syndrome: CT findings in six patients. (2000) Journal of computer assisted tomography. 24 (1): 24-9. Pubmed
- 11. Alla Khashper, Federico Discepola, John Kosiuk, Salah-Dine Qanadli, Benoît Mesurolle. Nonthrombotic Pulmonary Embolism. (2012) American Journal of Roentgenology. 198 (2): W152-9. doi:10.2214/AJR.11.6407 - Pubmed