Home » Diseases » In dogs » Hemothorax (Blood Accumulation in the Chest)

Hemothorax (Blood Accumulation in the Chest) in Dogs

Occurrence: rarer
Location of disease: Chest

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026

When to visit the vet?

Emergency see a veterinarian immediately

Definition

A hemothorax, also called hematothorax, is the accumulation of blood in a dog’s chest. This blood accumulation occurs in the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing., the space between the lung and the chest wall.

The most important facts at a glance

Hemothorax in dogs is a blood accumulation in the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing. of the chest. This space normally contains only a small amount of fluid that supports lung movement. Causes of hemothorax can be traumatic, such as car accidents or injuries from sharp objects, and non-traumatic, such as tumors, blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders, or lungworm infestation. Certain medications or poisonings can also increase the risk. Symptoms include shortness of breath, pale mucous membranes, weakness, and increased heart and respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. rate. For diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., a clinical examination is performed, supplemented by X-rays and possibly thoracocentesisThoracocentesis is a medical procedure in which fluid or air is removed from the chest using a needle or catheter. This may be necessary to relieve shortness of breath in dogs and cats caused by fluid accumulation or air in the chest.. Blood tests and ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. can provide additional information. Treatment aims to address the cause of bleeding and relieve symptoms. If necessary, blood can be drained from the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing.. For traumatic causes, surgery may be required to repair damaged blood vessels. Blood transfusions and medications to stabilize blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. may also be necessary. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. depends on the cause and severity of the condition but is often favorable with early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. PreventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. includes regular veterinary examinations and avoiding risks. Research focuses on improved diagnostic and treatment procedures as well as preventive measures to reduce the risk of hemothorax.

Causes

The pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing. is a potential space that normally contains only a small amount of fluid, which allows smooth movement of the lungs during breathing. When blood enters this space, it is called a hemothorax.

The causes of hemothorax in dogs are varied and can be both traumatic and non-traumatic. The most common traumatic causes include car accidents, falls from great heights, or injuries from sharp objects that can damage blood vessels in the chest cavity.

Non-traumatic causes include tumors that invade the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing., blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders, or certain diseases such as lungworm infestation. Tumors can infiltrate or compress blood vessels due to their size and location, causing bleeding.

Certain medications or poisonings can also impair blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. and thus increase the risk of hemothorax. A systemic disease such as von Willebrand disease, a hereditary condition that impairs blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound., can also lead to hemothorax.

Symptoms

Very common symptoms:

Common symptoms:

The symptoms of hemothorax in dogs can vary depending on the severity of the blood accumulation. Common signs include shortness of breath, as the lungs are compressed by the blood in the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing.. The dog may show rapid, shallow breaths.

Other symptoms include weakness, lethargy, and pale gums due to blood loss and oxygen deficiencyDeficiency means a lack or absence of a necessary substance required for normal bodily functions or health, such as vitamins, minerals, or hormones.. Sometimes coughing may also occur, especially when the dog tries to clear the airways of blood.

In severe cases, the dog may show signs of shock, including rapid heart rate, low blood pressure, and collapse. These symptoms require immediate veterinary care.

Diagnosis

DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of hemothorax typically begins with a thorough clinical examination and detailed medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. to identify possible traumatic events or underlying conditions.

X-rays of the chest are crucial to confirm the presence of fluid in the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing.. On X-rays, the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing. appears enlarged and the lungs may appear compressed.

A thoracocentesisThoracocentesis is a medical procedure in which fluid or air is removed from the chest using a needle or catheter. This may be necessary to relieve shortness of breath in dogs and cats caused by fluid accumulation or air in the chest., in which a needle is inserted into the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing., can be performed to determine the type of fluid. If blood is withdrawn from the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing., this confirms the diagnosis of hemothorax.

Blood tests can be performed to assess the dog’s overall health and obtain clues about blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders or other systemic problems. An ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. examination can also be helpful in identifying tumors or other structural abnormalities.

Therapy

Treatment of hemothorax aims to identify and address the cause of the bleeding and to relieve symptoms. In emergencies, it may be necessary to drain the blood from the pleural cavityThe pleural cavity is the narrow space between the two pleural layers, filled with pleural fluid, that allows the lungs to move smoothly during breathing. to reduce pressure on the lungs and facilitate breathing.

In traumatic causes, surgical intervention may be required to repair damaged blood vessels or remove foreign objects. If a tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. is the cause, surgical removal or other targeted therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. may be considered.

Blood transfusions may be necessary if the dog has suffered significant blood loss. Additionally, medications to stabilize blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. may be used if a coagulationCoagulation is the process of blood coagulation, in which liquid blood is transformed into a solid clot. This process is crucial for stopping Bleeding and promoting wound healing. disorder is present.

SupportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. care includes administering oxygen and monitoring vital functionsVital functions are essential bodily functions necessary to sustain life. These include breathing, heart rate, blood pressure, body temperature, and level of consciousness. to ensure the dog remains stable and can recover.

Prognosis and follow-up care

The prognosis of hemothorax in dogs depends on the cause of the bleeding and the severity of the condition. With early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and appropriate treatment, the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. can be favorable, especially if the cause can be treated.

In cases of traumatic injuries that are successfully repaired, the prognosis is generally good. For non-traumatic causes, such as tumors, the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. depends on the type and stage of the tumor.

Blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders can complicate the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. as they increase the risk of recurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. bleeding. Long-term monitoring and treatment of underlying conditions may be necessary to reduce the risk of recurrentRecurrent refers to a disease that repeatedly returns or worsens after a temporary remission or improvement. hemothorax.

Prevention

PreventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of hemothorax focuses on minimizing risks and early detection of problems. Regular veterinary examinations can help detect and treat underlying conditions early.

For dogs with known blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders, special precautions should be taken to avoid injuries. This includes avoiding rough play or dangerous environments where the dog could get injured.

Castration or neutering can reduce the risk of certain tumors that can lead to hemothorax. Good general care and nutrition also contribute to the dog’s health and can reduce the risk of diseases that lead to hemothorax.

In case of poisonings or medication side effects that can cause blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders, it is important to avoid exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. and use medications only under veterinary supervision.

Outlook on current research

Current research on hemothorax in dogs focuses on developing improved diagnostic and treatment procedures. A significant advancement is the use of imaging techniques such as X-ray and ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. examinations, which enable more efficient identification of blood accumulations in the chest. Researchers are working to improve the accuracy of these technologies to enable faster and more accurate diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

Another area of research is investigating the causes of hemothorax in dogs. While traumatic injuries, such as traffic accidents or bites, are common causes, the role of blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders is also being examined more closely. Genetic studies aim to identify specific genetic markers that could increase the risk of such disorders.

There is also growing interest in developing new therapeutic approaches. Researchers are investigating the use of medications that can promote blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. or stop bleeding without increasing the risk of thrombosisThrombosis is the formation of a blood clot in a blood vessel that can obstruct or block blood flow. Thromboses can occur in veins (venous thrombosis) or arteries (arterial thrombosis).. Additionally, regenerative therapies, such as the use of stem cells to promote healing of injured tissue, are being explored.

PreventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. of hemothorax is also an important research topic. The development of protective clothing for dogs working in dangerous environments, such as search and rescue dogs, could help reduce the risk of chest injuries. Furthermore, the importance of nutritional and lifestyle factors in preventing blood coagulationBlood coagulation is a process that helps stop Bleeding when a blood vessel is damaged. Platelets and certain proteins in the plasma form a blood clot that seals the wound. disorders is being investigated.

In summary, research aims for more comprehensive and effective treatment of hemothorax in dogs. By combining advanced diagnostics, innovative therapies, and preventive measures, scientists hope to improve the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. for affected dogs and enhance quality of life.

Frequently asked questions (FAQs)

What is a hemothorax?

A hemothorax is an accumulation of blood in the chest, specifically in the pleural space surrounding the lung. This can lead to respiratory distress and other health problems. -

What causes hemothorax in dogs?

Common causes are traumatic injuries such as car accidents or bite wounds. Internal bleeding due to blood coagulation disorders or tumors can also cause hemothorax. -

How is a hemothorax diagnosed?

Diagnosis is usually made through imaging procedures such as X-ray or ultrasound examinations. A thoracocentesis, in which fluid is removed from the chest, may also be necessary. -

What symptoms does a dog with hemothorax show?

Symptoms can include shortness of breath, pale mucous membranes, cough, weakness, and in severe cases, collapse. These symptoms require immediate veterinary examination. -

How is a hemothorax treated?

Treatment may include draining the blood from the chest, administering blood coagulation agents, or surgical intervention to stop the bleeding. -

Can a hemothorax heal on its own?

In some mild cases, the body may heal itself, but in most cases, veterinary treatment is necessary to avoid serious complications. -

How can you prevent hemothorax in dogs?

Prevention includes avoiding traumatic injuries through leash control and protective measures for dogs working in dangerous environments. Treatment of underlying blood coagulation disorders is also important. -

How quickly should a dog suspected of having hemothorax be treated?

A hemothorax is a medical emergency that requires immediate veterinary care to minimize the risk of life-threatening complications. -

What is the prognosis for dogs with hemothorax?

The prognosis depends on the cause and severity of the hemothorax. Early diagnosis and treatment significantly improve the chances of complete recovery. -

Can all dogs develop hemothorax?

Yes, theoretically all dogs can be affected, but the risk is higher in dogs prone to traumatic injuries or with existing health problems such as blood coagulation disorders.