Blood Clots in Cats: Symptoms, Treatment and Prevention

Blood clots in cats, medically known as thrombi, occur when blood flow in an artery or vein is restricted or the blood vessel lining is damaged, leading to clot formation that partially or fully blocks blood vessels. This can happen in the heart, especially if the left atrium is enlarged—a common complication of heart disease in cats.

One of the most serious forms of this condition is Feline Arterial Thromboembolism (FATE), where clots formed in the heart break loose and travel through the bloodstream. These clots commonly lodge at the branching point of the aorta near the hind legs, called a saddle thrombus, which causes sudden blockage of blood flow to the rear limbs. This results in sudden paralysis, intense pain, and other distressing symptoms that require immediate veterinary attention.

Causes of Blood Clots in Cats

In cats, the primary cause of dangerous blood clots such as FATE is heart disease, particularly cardiomyopathy that leads to an enlarged left atrium. Damage or changes in the heart muscle can cause abnormalities in blood flow, encouraging clots to form. Other less common causes include hyperthyroidism, cancer, or protein loss in the body.

When clots form within the heart, they may break away and be propelled through the high-pressure aorta until they lodge in narrower vessels where blood flow to limbs or organs is blocked.

Recognising Symptoms

The most notable symptoms occur when a saddle thrombus blocks blood flow at the aortic bifurcation, which supplies the legs with oxygenated blood. Signs include:

• Sudden limping, lameness, or paralysis of one or both hind legs
• Severe pain causing vocalisation or collapse
• Cold, pale, or bluish colouring of footpads or nail beds
• Firm or stiff muscles in affected limbs
• Difficulty breathing or increased respiration
• Vomiting and loss of appetite
• Lethargy and anxiety

Cold extremities and the colour change in the paw are hallmark signs of oxygen deprivation and should prompt urgent veterinary contact.

Diagnosis and Veterinary Care

Diagnosing a blood clot in cats involves a thorough veterinary examination including medical history, blood and urine tests, and blood pressure measurement. Advanced imaging such as X-rays or ultrasound may be used to assess heart condition and locate clots.

Because blood clots like saddle thrombus cause acute, severe symptoms, quick diagnosis and treatment are critical to provide pain relief and support organ function.

Treatment Options

Saddle thrombus is a veterinary emergency. Treatment usually requires hospitalisation where your cat will receive:

• Pain relief and sometimes oxygen therapy
• Heat therapy to dilate blood vessels in the affected limb
• Intravenous fluids to support organs and manage shock
• Anticoagulant medication to thin blood and dissolve clots

In some cases, surgery may be necessary to remove the clot or amputate a severely affected limb. Recovery depends on the severity and overall health of the cat.

Prognosis and Long-Term Care

Blood clots caused by heart disease have a guarded to poor prognosis due to severity and risk of recurrence. However, milder cases may respond to ongoing medication and management.

Amputation, although intimidating, can allow young, healthy cats to live a good quality of life. Regular veterinary check-ups and heart medication are often advised to manage underlying conditions and reduce future risk.

Prevention and Responsible Ownership

It is challenging to predict which cats will develop blood clots, but knowing your cat’s breed, health history, and signs of heart disease can help. Annual veterinary health checks are essential to detect early heart abnormalities. If signs such as a heart murmur emerge, preventative care including medication might be started.

Responsible cat ownership means staying vigilant for changes in mobility or behaviour and seeking immediate veterinary care if symptoms of thromboembolism appear.