Thromboembolism

A thromboembolism is a medical emergency – and one that can literally become life-threatening within minutes. What happens? A blood clot (thrombus) blocks an artery or vein and thus cuts off blood flow to organs or tissues. The insidious thing: The thrombus initially forms somewhere in the vascular system, then detaches and travels through the bloodstream – until it gets stuck at a narrow point. The consequences range from organ damage and paralysis to death.

What is a thromboembolism?

A blood clot forms in an artery or vein, detaches from its origin, and is carried away by the blood flow. If it then gets stuck at a narrow point, blood flow is interrupted – with partly dramatic consequences. The heart, lungs, brain, or legs can be affected. Depending on where the clot gets stuck, the clinical picture looks completely different.

Causes of thromboembolism in dogs

Several factors can contribute to a thrombus forming and then detaching:

Heart diseases:

• Dogs with heart valve insufficiency, cardiomyopathy, or atrial fibrillation are more likely to develop thromboses – the impaired blood circulation noticeably promotes clotting.
• Thrombi that form in the heart can detach and be carried to other body regions.

Coagulation disorders:

• Inherited or acquired coagulation disorders drive the risk of excessive blood clotting up significantly.
• Diseases such as Cushing’s syndrome or kidney failure alter the blood composition so that clotting is triggered more easily.

Cancer:

• Tumours – especially those in blood vessels or bone marrow – considerably increase the blood’s tendency to clot.

Injuries and surgery:

• Trauma or surgical procedures can damage blood vessels and increase the risk of thrombus formation. This applies particularly after major operations on the heart or blood vessels.

Prolonged immobility:

• Inactive dogs – for example after injuries or during severe phases of illness – are more susceptible. The slowed blood flow noticeably favours the formation of clots.

Symptoms of thromboembolism in dogs

Which symptoms occur depends on where the clot blocks blood flow. Almost always, they come suddenly – this is an important warning signal:

1. Sudden paralysis: If the clot blocks an artery to the hind legs, it can lead to abrupt paralysis – experts speak of a saddle thromboembolism. The dog literally cannot stand up anymore from one second to the next.
2. Pain: Severe pain in the affected area is often accompanied by restlessness, panting, or loud whining.
3. Cold limbs: With thromboembolisms in the hind legs, the affected extremities feel noticeably colder than the rest – after all, blood flow is interrupted.
4. Weakness or collapse: A pulmonary embolism manifests through breathing difficulties; the dog becomes extremely weak and may collapse. Bluish mucous membranes due to oxygen deficiency are a serious sign.
5. Breathing difficulties: A clot in the pulmonary arteries leads to shortness of breath, coughing, rapid breathing – and sometimes a bluish discolouration of the tongue or mucous membranes.
6. Neurological deficits: If brain arteries are affected, the dog shows stroke-like signs: sudden disorientation, balance problems, seizures or unconsciousness.

Diagnosis of thromboembolism in dogs

Investigation requires a thorough veterinary examination – and usually several steps:

1. Clinical examination: The vet palpates and observes the dog for pain, paralysis, weakness and shortness of breath. Skin temperature of the limbs and blood circulation are specifically checked.
2. Ultrasound: A Doppler ultrasound makes blood flow in the affected vessels visible and can directly detect clots in the hind leg arteries or in the heart.
3. X-ray: If a pulmonary embolism is suspected, an X-ray of the chest provides important clues about damage to the lungs and heart.
4. Blood tests: Coagulation tests – including the measurement of D-dimer – indicate abnormal blood clotting. At the same time, underlying conditions such as Cushing’s syndrome, infections or kidney problems can be narrowed down.
5. Echocardiogram: In cases of heart disease, an echocardiogram (heart ultrasound) is performed to assess heart function and possible thrombi in heart valves or heart chambers.

Treatment of thromboembolism in dogs

The aim of therapy is to dissolve or remove the clot, restore blood flow and prevent new thrombi. The earlier action is taken, the better:

1. Anticoagulants (blood thinners): Medications such as heparin or warfarin slow the formation of further clots and stabilise existing thrombi – the body can then gradually break them down itself.
2. Thrombolytic therapy: Active substances such as alteplase or streptokinase actively dissolve the blood clot. Due to the increased risk of bleeding, they are only used in selected cases.
3. Pain management: Painkillers – opioids or NSAIDs – alleviate the dog’s suffering and improve its well-being during treatment.
4. Oxygen therapy: In cases of pulmonary embolism or significant breathing difficulties, oxygen is administered to ensure tissue supply and alleviate shortness of breath.
5. Surgical interventions: In severe cases – particularly with clots in main arteries or heart vessels – surgical removal of the thrombus may become necessary.
6. Treatment of the underlying condition: If a heart disease, a tumour or a coagulation disorder is the cause, it must be treated in parallel – otherwise the next clot is imminent.

Prognosis

To be honest: The prognosis depends heavily on where the clot is located and how quickly action is taken. Thromboembolisms in the lungs or brain are potentially life-threatening – every hour counts here. With saddle thromboembolisms involving hind leg blockage, the outlook is often cautious because permanent tissue damage to the limbs can occur. However, one thing always applies: Early diagnosis and consistent therapy significantly reduce the risk of lasting damage.

Prevention of thromboembolisms in dogs

Prevention is difficult – but not impossible. The key lies in the consistent treatment of underlying conditions:

1. Regular veterinary check-ups: Dogs with known heart diseases or coagulation disorders should remain under close monitoring.
2. Medicinal prevention: For dogs at high risk, the vet may prescribe anticoagulants prophylactically.
3. Movement and early mobilisation: After operations or injuries, it is important to get dogs moving again as early as possible – even light activity promotes blood flow and noticeably reduces the risk of clotting.