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Blood Clot in the Lungs in Dogs

Pulmonary Thromboembolism in Dogs

Pulmonary thromboembolism (PTE) manifests when a blood clot becomes lodged in one of the arteries supplying blood to the lungs. Factors such as sluggish blood flow, vascular damage, and a propensity for clot formation contribute to the likelihood of thrombus development in dogs. Typically, PTE arises as a complication of an underlying health condition.

Blood clots leading to pulmonary thromboembolism may originate from the right atrium of the heart or various major veins in the body. As the dog’s circulatory system transports oxygen-rich blood to the heart and lungs, these clots travel through the bloodstream toward the lungs. There, they obstruct narrow segments of the arterial network responsible for delivering oxygenated blood. Consequently, blood flow in the affected artery is impeded, compromising the lung’s oxygenation process. The severity of the condition correlates, to some extent, with the size of the blood clot.

It’s important to note that pulmonary thromboembolism can affect both dogs and cats.

Symptoms and Types

  • Fatigue
  • Cough
  • Lack of appetite (anorexia)
  • Sudden difficulty breathing
  • Inability to sleep or get comfortable
  • Increased breathing rate
  • Spitting up blood
  • Exercise intolerance
  • Pale or bluish-colored gums


Potential causes of pulmonary thromboembolism include:

  • Cancer
  • Heart disease
  • Liver disease
  • Heartworm disease
  • Cushing’s disease
  • Pancreatitis (inflammation of the pancreas)
  • Protein-losing kidney disease or intestinal disease
  • Immune-mediated hemolytic anemia (red blood cell destruction)
  • Musculoskeletal trauma
  • Recent surgery
  • Bacterial bloodstream infection
  • Disseminated intravascular coagulopathy (DIC), characterized by extensive blood thickening and clot formation throughout the blood vessels.


Your veterinarian will conduct a comprehensive physical examination, which includes analyzing a chemical blood profile, complete blood count, urinalysis, and electrolyte panel. These tests help in identifying any underlying diseases contributing to the condition.

Providing a detailed history of your dog’s health, symptoms, and potential triggering events is crucial. This information assists the veterinarian in understanding the origin of the clot.

Arterial blood gases will be assessed to determine oxygen levels in the blood. Additionally, a coagulation profile will be conducted to detect any clotting disorders, involving tests such as the one-stage prothrombin time (OSPT) and activated partial thromboplastin time (APTT). Heartworm serology testing may also be performed.

X-ray imaging of the dog’s chest enables the veterinarian to visually inspect for abnormalities in the pulmonary artery, heart enlargement, lung patterns, or signs of fluid accumulation in the lungs. An echocardiogram, a more sensitive imaging technique, may be chosen to examine the heart’s motion and size, especially when a thrombus is suspected in the right heart chamber or main pulmonary artery.

Electrocardiogram (ECG) readings can reveal cor pulmonale, which signifies right ventricular enlargement due to elevated lung blood pressure. Serious heart rhythm abnormalities (arrhythmias) can also be detected through an ECG.

Additional diagnostic procedures may include pulmonary angiography, which involves injecting a radiocontrasting agent into the dog’s lung arteries to enhance visibility on X-rays, and spiral computed tomography (CT), a three-dimensional X-ray imaging method used for non-selective angiography.


For dogs suffering from PTE, hospitalization is necessary, primarily to administer oxygen therapy. If the dog isn’t getting sufficient oxygen to its heart, lungs, or brain, the vet may advise confinement in a caged setting, typically because of hypoxemia or syncope. Nonetheless, the veterinarian will address the root cause of the condition once a definitive diagnosis has been determined.

Living and Management

Regrettably, this illness typically leads to fatality. Without addressing the underlying cause, pets often experience a recurrence of PTE.

Your vet will arrange weekly check-ups with your dog to monitor its blood clotting times since anticoagulant medications can induce bleeding disorders at the opposite end of the spectrum. While the new low-molecular-weight heparin anticoagulants are safer, they also come at a higher cost.

Close monitoring of your pet and regular communication with your veterinarian will generally suffice, especially considering your dog may require anticoagulant treatment for several months.

Approved physical activity or other forms of therapy may enhance blood circulation. Your veterinarian will advise you on suitable activities tailored to your pet’s specific needs. The objective is to prevent future PTE occurrences in immobile dogs with severe conditions.

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