1

What is a haemothorax (Figure 1)?

A haemothorax is defined as blood within the pleural space, with a haematocrit >50% of the circulating levels to distinguish it from a bloody pleural effusion.

A massive haemothorax is defined as >1500mL of blood within the pleural space.

It may cause secondary collapse of the ipsilateral lung or haemodynamic compromise.

2

What is the aetiology of a haemothorax?

Blunt or penetrating trauma accounts for the majority of haemothoraces and may be caused by:

a)

rib fractures;

b)

lung parenchymal injury;

c)

damage to the lung hila or great vessels of the mediastinum;

d)

injury to the adjacent areas (abdomen, neck or axilla), such as liver laceration, with associated diaphragmatic injury.

Iatrogenic:

a)

central venous line insertion, especially using a subclavian approach;

b)

thoracic or cardiac surgery.

Malignancy (lung or pleural).

Vascular malformation.

Spontaneous bleeding from vascular adhesions or coagulopathy.

Aortic dissection, rupture or transection.

Endometriosis.

3

What is the natural history of a haemothorax?

Blood in the pleural space is agitated by intrathoracic movement of the lungs and diaphragm, resulting in activation of the extrinsic clotting cascade and formation of intrapleural clots.

As the clot organises, it forms a fibrin mesh that adheres to the pleural lining limiting its dynamic properties and ultimately leading to a ‘trapped lung’.

Over the course of 1 week, this fibrin mesh develops from a thin membrane to thick fibrous adhesions.

It is therefore imperative that clotted material in the pleural space is drained or removed to reduce the risk of developing restrictive lung pathology.

Residual clot within the pleural cavity may also become infected, resulting in empyema formation.

4

What are the symptoms of a haemothorax?

Shortness of breath.

Chest pain.

The degree of symptoms vary depending on the volume of blood loss and haemodynamic response.

Symptoms associated with the aetiology, such as concomitant injuries in a trauma patient, may also be present.

5

What are the signs of a haemothorax?

The classic findings on clinical examination of a patient with a haemothorax are:

a)

decreased chest expansion;

b)

dull percussion note;

c)

decreased breath sounds.

In a supine patient or patient with a small haemothorax, these signs may be difficult to elicit and the diagnosis can only be made radiologically.

In an injured patient, bruising, lacerations, penetrating wounds or crepitus may also be present.

Tracheal deviation is rare, except in cases of massive haemothorax.

In patients with significant blood loss, haemodynamic shock may also be present.

6

What are the chest radiographical features of a haemothorax (Figure 2)?

Erect chest radiograph (CXR) – blunting of the costophrenic angle or an air-fluid interface that may track up the pleural margin. As it usually requires approximately 500mL of fluid to obliterate the costophrenic angle, smaller volumes of blood (<250mL) may not be identified.

Supine CXR – diffuse opacification of the hemithorax with preservation of lung markings, as the blood lies on the posterior aspect of the pleural cavity.

Associated rib fractures, pneumothoraces or a widening of the superior mediastinum may also be present.

7

What are the ultrasound features of a haemothorax?

Following trauma, a haemothorax can be identified as a free fluid collection (non-echogenic, black area) above the diaphragm (Figure 3).

Over time, the ‘haematocrit sign’ may also be present, where a bilayer effect is demonstrated secondary to the gravitational effect of the cellular components within the effusion.

The extended focused assessment with sonography for trauma (eFAST) scan may detect smaller haemothoraces (as little as 20mL) than a chest radiograph. The traditional (non-extended) FAST scan does not assess the thoracic cavities.

Although an ultrasound scan does not offer the sensitivity of a computed tomography (CT) scan, it can be performed at the bedside in a more time efficient manner, in a patient who is haemodynamically compromised.

In the presence of a concomitant pneumothorax or subcutaneous emphysema, diagnosis of a haemothorax by ultrasound, however, may be difficult.

8

What are the computed tomography features of a haemothorax (Figure 4)?

A haemothorax can usually be identified on CT as a:

a)

free fluid collection within the pleural cavity – blood usually has an attenuation of 35-70 HU that distinguishes it from simple fluid;

b)

loculations of clotted blood within the pleural cavity.

CT scans are increasingly used as a first-line investigation in the trauma setting as they are excellent at identifying the:

a)

presence of small-volume haemothoraces;

b)

exact location of the haemothorax;

c)

presence of loculations, retained haemothorax, empyema and fibrothorax;

d)

high-flow bleeding sources – which can be visualised as active extravasation of contrast;

e)

associated injuries to nearby structures, including the lung parenchyma, mediastinum, diaphragm, thoracic aorta and abdominal organs.