Teaching Case

An 82-year-old man with diabetes, hypertension, dyslipidaemia  and ischemic heart disease was admitted to the intensive care unit for cholangitis and type 2 myocardial infarction. He received a loading dose of antiplatelet therapy. At admission, he had significant hepatic/cholestatic changes, with international normalized ratio (INR) of 1.5. No history of trauma.

An abdominal CT was performed to re-evaluate cholangitis. Included inferior thoracic tomograms showed bilateral pleural effusion and de novo small, slightly convex fluid collection that pushed the extrapleural fat layer centrally within the hemithorax, away from the ribs (Figures 1a and 2) and had higher spontaneous attenuation than pleural fluid (Figure 1b). All ribs were regular, without fracture.

CT scan performed two days earlier showed no convex fluid collection, only a thin pleural effusion.

Background

The extrapleural space (EPS) is located between the thoracic cage and the parietal pleura and contains the extrapleural fat, the endothoracic fascia, and the musculi intercostales intimi. The extrapleural fat includes the intercostal nerve and vessels and separates the pleura from the endothoracic fascia and is located more posterolaterally, from the 4th to the 8th rib. The lymphatic drainage of the parietal pleura is through the EPS.

Imaging Perspective

On CT assessment, the EPS is poorly defined, but when it is displaced away from the inner rib contours, it is useful in distinguishing between intrathoracic or extrathoracic location of a lesion. An extrapleural collection or mass produces the appearance of a fatty streak (low-attenuating layer) that reflects inward displacement of the extrapleural fat and parietal pleura, known as "extrapleural fat sign." [1-4]

The most common cause of this sign is an extrapleural hematoma, usually due to blunt chest trauma, and it can mimic a hemothorax. However, spontaneous hematoma may also occur in cases of coagulopathy [2].

Two cases of spontaneous extrapleural hematoma have been reported in the literature - one in a hemodialysis patient [5] and another in an anticoagulated patient with valvular heart disease [6]. In both cases, the hematoma had an arterial origin and caused larger biconvex collections. In contrast, venous hematomas tend to be non-convex and smaller [7].

Hematoma bleeding can be rapid and cause haemodynamic or respiratory instability, especially if it has an arterial origin, secondary to chest trauma.

Identifying the location of a fluid collection in the extrapleural space is extremely important to differentiate between hematoma and hemothorax, considering they have different management, to avoid incorrect treatment with a chest tube.

Outcome

Management of an extrapleural hematoma depends on its location, size, origin, and impact on laboratory parameters or cardiorespiratory compromise. Biconvex hematomas tend to be larger and require surgery; nonconvex hematomas generally do not require specific treatment [7].

In the present case, based on the presence of the extrapleural fat sign, the features of fluid collection, and its shape, a venous spontaneous extrapleural hematoma was assumed in an ICU patient with coagulopathy, with no effect on blood haemoglobin. He was treated with phytomenadione for INR stabilization. No invasive procedure was required and the hematoma regressed spontaneously with conservative treatment.