What Is a Hemothorax?

This buildup of blood can eventually cause your lung to collapse

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A hemothorax is when there is an accumulation of blood between the membranes lining the lungs (the pleura). The most common cause is trauma, but lung infections, heart and lung surgery, cancer, or even excess doses of blood thinners may also be responsible.

When a hemothorax develops, there is often confusion at first because there are so many similarities in the symptoms of a hemothorax and other respiratory complications.

Prompt treatment of a hemothorax is important to reduce the risk of developing long-term respiratory problems like troubled breathing.

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Hemothorax Symptoms

Hemothorax symptoms can be difficult to distinguish from those of other conditions at first and may include:

  • Severe shortness of breath
  • Anxiety and extreme restlessness
  • Symptoms of shock such as a rapid heart rate, low blood pressure, pale, cold extremities, and weakness
  • Chest pain which is often sharp and may vary with position. Pain with deep breathing may also occur
  • A feeling of impending doom

Causes of a Hemothorax

There are many hemothorax causes. Depending on the cause, the blood may originate from the lungs, the heart, the chest wall, or the large blood vessels present in the chest. Some of these include:

  • Trauma to the chest (this is the most common cause of a hemothorax).
  • Emphysema
  • Lung cancer
  • Pleural mesothelioma (a cancer that involves the pleura)
  • Cancers that are metastatic (spread) to the lung such as breast cancer and colon cancer
  • Chest surgery (most commonly following lung and heart surgery)
  • Biopsy of lung masses
  • Lung infections such as tuberculosis
  • Bleeding disorders that result in prolonged clotting, or excess doses of blood thinners
  • Pulmonary embolism and infarcts
  • Spontaneous


It's thought that close to 300,000 cases of hemothorax occur in the United States each year due to trauma alone, with chest injuries present in roughly 60% of patients with multiple trauma injuries.

Risk Factors

Driving, in general, might be the most common risk factor for a hemothorax, as motor vehicle crashes account for up to 70% of high-impact trauma to the chest. There is a risk of developing a hemothorax for those who participate in sports that can result in repetitive trauma to the chest, such as boxing, mixed martial arts, and rugby.

Those with underlying conditions that include lung cancer, blood clotting defects, and tuberculosis are at an increased risk for a hemothorax as well.


A careful history may give some clues to the cause and presence of a hemothorax. On the side affected, lung sounds may be diminished or absent.

An upright chest X-ray may help to diagnose a hemothorax. A chest CT or further testing may then be considered. When a chest tube is placed, the fluid may be evaluated to confirm the presence of blood in the pleural cavity and further look for possible causes.

Evaluation of the pleural fluid can be helpful as well. For this fluid to be classified as a hemothorax, the hematocrit of the pleural fluid should be at least 50% of the hematocrit of the peripheral blood (blood examined by taking a sample from a vein).

Differential Diagnoses

A hemothorax is different than some other conditions involving the thorax, such as:

Hemothorax Treatment

Initial treatment for a hemothorax usually involves stabilizing the person and then inserting a chest tube to drain the blood and air that has built up or is building up between the lung membranes in the pleural cavity.

Often, a hemothorax is a result of blunt or penetrating trauma to the chest. When it occurs without trauma, it's very important to find and treat the underlying cause.

Treatment usually involves inserting a chest tube as part of a video-assisted thoracostomy (a minimally invasive surgery in which small incisions are made in the chest and a surgery is done through these small incisions with the use of a camera).

For some people surgery, a thoracotomy (open chest surgery in contrast to minimally invasive surgery) is needed to get to the source and control the bleeding, especially in the setting of large hemothorax or when the source of the bleeding is uncertain.


The outcome of a hemothorax is determined by both the extent of the bleeding, and the underlying cause.

For people who sustain a hemothorax as a result of chest trauma, the overall prognosis is actually quite good, and excellent if the hemothorax can be adequately treated.

Prognosis may also be good when the hemothorax occurs as a complication of a biopsy or chest surgery.

When a hemothorax occurs in the presence of cancer (due to growth of the tumor through the lung lining) or a pulmonary infarct, however, the prognosis is more guarded.

Complications After Treatment

For those people who receive treatment, a small number are left with an empyema (a collection of pus between the membranes lining the lungs) or some scarring of the pleura (pleural fibrosis).

With an empyema, further surgeries may be done to remove the pus and to prevent further fluid and bacteria from entering the chest.

Treatments for fibrosis are primarily supportive as fibrosis is usually irreversible. That said, treatments ranging from pulmonary rehabilitation to breath training can be helpful in restoring the best quality of life possible.

Fibrosis may result in long-term respiratory symptoms for some people.


Depending on the cause, a hemothorax may or may not be preventable. Since trauma is the most common cause, taking safety measures when doing activities may decrease the chance of trauma to the chest. Examples include wearing a seat belt when driving or wearing chest protection garments if involved in contact sports.

Additionally, a hemothorax may occur from lung cancer, and it's known that smoking tobacco is the leading cause of lung cancer. Smoking cessation can decrease the risk of developing lung cancer which reduces the chance of complications of lung cancer, such as a hemothorax.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading

By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."