Fat embolism sydrome: a case report

Clinical History

We present a case of an 18-year-old woman with tibial and peroneal fractures, who presented clinical symptoms of confusion, dyspnoea, hypoxaemia, haemoptysis and petechial rash 24 hours after orthopaedic surgery.

Imaging Findings

Chest radiograph showed ill-defined bilateral opacities with symmetrical distribution predominating in the middle and lower fields of both lungs.
Contrast-enhanced chest CT showed ill-defined ground glass opacities associated with interlobular septal thickening with middle and lower lobe predominance. No filling defects were detected in the main lobar or segmental branches of the pulmonary arteries and no pleural effusions were present. Acute pulmonary embolism was therefore ruled out.

Discussion

The concept of fat embolism syndrome (FES) refers to a clinical entity in which neurological, haematological, respiratory and skin symptoms are associated as a result of the release of fat droplets into the bloodstream [1].
Long bone fracture and orthopaedic surgery are often the main cause, although this syndrome may also develop in severe burns, acute pancreatitis, severe infections, acute decompression illness and sickle cell disease [2, 3, 4].
Fat embolism occurs very frequently (up to 90% in bone fractures and orthopedic prosthetic surgery), but only very few patients (~4%) will present with FES with classical symptoms[2, 3, 4].
The pathogenetic mechanism is unclear. There are many theories, but the most widely accepted are two: the mechanical theory which states that fat emboli are released from the intramedullar pressure increased (after trauma or orthopaedic manipulation) and the biochemical theory which postulates that fat embolism are a result of neutral lipids hydrolysis into free fatty acids by lipase activation during some stress situations. In any case, the harmful effect of fat embolism is not due to vascular occlusion, but instead the endothelial damage caused by these fatty acids [3, 4].
Clinical manifestations often appear after a latency period of 24-72 hours, which is the time it takes to develop vasculitis. The respiratory clinical symptoms are usually the first to appear and include dyspnoea, tachypnoea, cyanosis and hypoxaemia. Neurological symptoms can present at the same time, ranging from headache, stupor, drowsiness, seizures or coma. Conjunctival petechiae can appear sometimes in the neck and trunk [1, 3, 4].
The chest radiograph may be normal initially, the most common radiological finding being bilateral ill-defined opacities with a pattern similar to pulmonary edema. These opacities on CT may have variable density, ranging from ground-glass to condensation, but usually tend to clear within 7-14 days. Interlobular septal thickening and centrilobular nodules may also be seen on CT. Sometimes fat embolism is seen as a filling defect in the pulmonary arteries. Pleural effusion is an uncommon finding in fat embolism. In severe cases adult respiratory distress can appear [1, 2, 5].
The diagnosis of FES requires a clinocoradiological correlation [1]. The radiological signs are nonspecific and may occur in other diseases that affect patients with multiple trauma (pulmonary contusion, inhalation of toxic gases etc) [2, 5]. The latency period between the trigger and the onset of clinical and radiological signs is of great importance for the diagnosis [1].

Differential Diagnosis List

Final Diagnosis

Fat embolism syndrom

URL:	https://www.eurorad.org/case/9538
DOI:	10.1594/EURORAD/CASE.9538
ISSN:	1563-4086