J Thorac Cardiovasc Surg 2008;135:225-226
© 2008 The American Association for Thoracic Surgery
The extrapleural fat sign
Elena Alventosa Fernández, MDa,
Luisa Elena Rodríguez Delgado, MDa,
Emilio Martín Díaz, MDb
a Diagnostic Imaging Department, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
b Thoracic Surgery Department, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
To the Editor:
We read with great interest the communication on extrapleural hematoma by Dr Kabiri and colleagues in the August 2006 issue.1
We would like to contribute to the diagnosis value of this report with the explanation of the pathognomonic radiologic sign they mentioned, known as the "extrapleural fat sign." We report a similar case demonstrating this sign.
A 61-year-old man with shortness of breath and thoracic pain with respiratory movements after a blunt trauma was admitted to our institution. Initial x-ray evaluation showed diffuse increased density in the left hemithorax with 5th to 10th posterior rib fractures. The diagnosis was multiple left rib fractures associated with ipsilateral hemothorax. A pleural tube was seemingly successfully placed as hematic fluid was drained. The initial hemogram and vital signs were within normal limits. During the next 4 days, the patient’s systolic blood pressure, hemoglobin, and hematocrit levels decreased, and a decreased quantity of serosanguinolent fluid was obtained by the pleural drainage. The lack of abdominal symptoms and normal ultrasound ruled out abdominal traumatic lesions. Chest x-ray follow-up showed radiologic findings that were suggestive of extraparenchymatous lesion, either pleural or extrapleural. Thorax computed tomography (CT) was ordered to assess for loculated pleural hemothorax versus extrapleural location, because plain x-rays cannot differentiate between these locations. Contrast-enhanced CT images (Figure 1) revealed a large collection of increased attenuation, which contained the chest tube, separated from the enhanced, partially collapsed left lower lobe by a fat attenuation stripe. The large outer high-density collection was interpreted as an extrapleural hematoma, which was separated from the lower lobe atelectasis by the parietal pleura and extrapleural fat. The patient underwent an open thoracotomy, and a large extrapleural hematoma was found and removed.
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Figure 1. Contrast-enhanced axial CT image demonstrates a large collection of increased attenuation, interpreted as a hematoma, that contains the chest tube separated from the enhancing partially collapsed left lower lobe by a fat attenuation stripe. This fat ribbon is known as the extrapleural fat sign and establishes the extrapleural location of the lesion.
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The extrapleural fat sign2 refers to the fat layer outside the pleura in the chest wall between the parietal pleura and the endothoracic fascia. Recognition of this finding on CT scan is useful to determine the extrapleural location of a lesion, as it is outlined by a fat ribbon that represents the extrapleural fat medially displaced.3 In our case, the extrapleural fat sign was useful in distinguishing an extrapleural hematoma from the initially diagnosed pleural hemothorax. Extrapleural hematomas are rare and known to occur as a result of blunt trauma or placement of medical devices. When the hematoma is traumatic, it can be associated with rib fracture, hemothorax, lung contusion, or pneumothorax.4 A formal or minithoracotomy is the recommended procedure in cases of large hematomas or unstable patients.5 This sign has also been described secondary to thoracic wall tumor and edema.
Plain x-ray semiology suggests the extraparenchymatous location of the lesion. It is the recognition of medially displaced extrapleural fat on CT that helps to establish a differential diagnosis on the basis of an extrapleural lesion.
References
- Kabiri EH, Arsalane A, Zidane A, Aoini F. Extrapleural hematoma as a complication of spontaneous pneumothorax. J Thorac Cardiovasc Surg 2006;132:423-424.[Free Full Text]
- Hammerman AM, Susman N, Strzembosz A, Kaiser LR. The extrapleural fat sign: CT characteristics. J Comput Assist Tomogr 1990;14:345-347.[Medline]
- Aquino SL, Chiles C, Oaks T. Displaced extrapleural fat as revealed by CT scanning: evidence of extrapleural hematoma. AJR Am J Roentgenol 1997;169:687-689.[Free Full Text]
- Goh BK, Koong HN. Massive traumatic extrapleural hematoma mimicking hemothorax: a potential pitfall of penetrating chest trauma. J Trauma 2006;61:995-997.[Medline]
- Poyraz AS, Kilic D, Gultekin B, Ozulku M, Hatipglu A. Extrapleural hematoma: when is surgery indicated?. Monaldi Arch Chest Dis 2005;63:166-169.[Medline]
