Any type of blood clot requires immediate treatment to give the cat the best chance to recover. Be aware, however, that most cats who "throw" a blood clot will experience another one a few months later.

Excessive blood clotting can be caused by a wide number of conditions and is often the result of some type of heart disease. The most common type of blood clot is called a saddle thrombus. This type of blood clot is seen almost exclusively in cats and is usually an indicator of serious heart disease. A cat suffering from this type of blood clot may have trouble moving its legs and will experience agonizing pain.

A blood clot can form inside the heart or a blood vessel (a thrombus) and may travel through the bloodstream (embolism). If all or part of a clot is dislodged from its point of origin and travels through the bloodstream, it may become lodged in a new location (thromboembolism). The most common blockage point is located in the lower abdomen where the aorta branches out to supply blood to both hind legs. This area is known as the saddle. A clot often comes to rest at this point, blocking circulation. Common symptoms are listed as follows:

Although cats are not the only animal to suffer from excessive blood clots, they are the most prone to the condition. Certain breeds such as Abyssinians, Ragdolls and Birmans are more likely to develop blood clots than other breeds. Middle-aged male cats are also at increased risk and are twice as likely to develop an aortic thromboembolism as females. 

The most common result of blood clots in cats is the development of a saddle thrombus. The technical term for the condition is feline aortic thromboembolism (FATE). FATE affects as many as 25 percent of all cats with the common feline heart condition hypertrophic cardiomyopathy. In some instances, FATE is the first and the only sign of heart disease. Other heart diseases that can cause excessive blood clotting include restrictive cardiomyopathy and dilated cardiomyopathy. 

Hypertrophic cardiomyopathy, restrictive cardiomyopathy and dilated cardiomyopathy all cause structural changes in the heart. These changes weaken the heart muscle and make it unable to properly pump blood. Stagnant blood in the heart can lead to the formation of blood clots. The clots will eventually dislodge and enter the bloodstream. If the clot is large enough, it will form the classic saddle thrombus. Smaller fragments may find their way to the brain, intestines or kidneys.

Other causes of excessive blood clotting in cats include hyperthyroidism and lung cancer.

The diagnosis of a blood clot in cats is based on what the veterinarian notices at the examination. Lab work and diagnostic imaging may be necessary to confirm the diagnosis in order to detect any underlying heart disease and to rule out other potential conditions. The complete diagnostic workup can include:

Your veterinarian may ask you when the cat first started showing symptoms of discomfort to help make the correct diagnosis.

A blood clot can have serious consequences if not handled promptly. A cat with an acute case of FATE will be required to remain in the animal hospital for at least 48 hours before going home. In some, cases, even with the best of care, a cat must be humanely euthanized.

Strong painkillers are administered to help the cat relax. The pain alone could send them into heart failure and eventual death.

Fluid therapy is critical to prevent dehydration and treat circulatory shock. In heart disease patients, however, it must performed with care.

Once a cat has suffered a blood clot, it is likely to experience another one. Taking anti-clot medication can help prevent the formation of another clot. Although aspirin has been the traditional drug used to treat the condition, the human anti-clot drug Plavix is now being considered for use with cats. 

As with any serious medical condition, it is critical that you keep all follow-up appointments for your pet. Your veterinarian will probably recommend strict cage rest for your cat for a certain period of time. Depending on the severity of the blood clot, this can range from several days to a couple weeks. Nursing care may be required until the cat regains function of its hind legs. 

Recovery for a cat affected by a blood clot depends on the severity of the obstruction and the integrity of the heart. Cats who only suffered a mild blockage with minor paralysis may experience a complete recovery if given the correct treatment.