Blood Clots in Dogs

Blood clots can form when platelets and plasma proteins in the blood thicken and clump together. When these clots get stuck in the vessels, they can cut off the flow of blood to essential parts of the body, such as the brain, lungs or heart. If your dog develops the symptoms of a blood clot, it is crucial to get veterinary care as soon as possible. This is a potentially life-threatening condition which can progress rapidly, and timely care greatly improves your dog’s chances of survival.

When blood clots form and lodge in the blood vessels, they can cut off the flow of blood to essential parts of the body, such as the brain, lungs, or heart.

The symptoms of a blood clot will vary greatly depending on where the clot is located:

Brain

• Drunken gait
• Head pressing
• Head tilting
• Loss of coordination
• Loss of eye reflexes
• Loss of facial reflexes
• Seizures
• Tremors
• Weakness 

Gastrointestinal 

• Bloody urine
• Diarrhea
• Severe abdominal pain
• Vomiting

Heart

• Anxiety
• Difficulty breathing
• Hind leg weakness
• Leg pain
• Pale or blue pads or nail beds
• Paralysis
• Vomiting

Legs

• Cold limb or limbs
• Lameness
• Pain in limbs

Lungs

• Difficulty breathing 
• Fatigue
• Inability to sleep
• Increased respiration 
• Pale gums

Types 

Blood clots can occur anywhere in the body but are more common in some areas than others:

• Brain - If the blood clot develops in the brain, it can lead to stroke and neurological symptoms that come on suddenly.
• Heart - Blood clots often travel through the heart, but only occasionally lodge there; when they do, they can cause the animal to pass out suddenly
• Lungs - Clots that occur in the lungs can be extremely painful and cause difficulty breathing
• Legs - When blood clots form in the legs your dog may lose the ability to use that limb, and it may feel cold to the touch. Paw pads may turn a blue colour.
• Gastrointestinal tract - Clots in the digestive tract may appear similar to other gastrointestinal disturbances; vomiting and diarrhea may occur as well as abdominal pain

Blood clots can form when platelets and plasma proteins thicken. This can happen for a variety of reasons, including:

• Aneurysm
• Cancer
• Cushing’s disease
• Damaged vessels
• Diabetes
• Heartworm
• High cholesterol
• High blood pressure
• Immune-mediated hemolytic anemia
• Inflamed pancreas
• Injury
• Kidney disease
• Long term corticosteroid use
• Parasite infection
• Reduced blood flow
• Underactive thyroid

Tests to determine a definitive diagnosis will often start with imaging tests to confirm the presence of a blood clot and indicate exactly where it is located. These imaging tests will vary depending on the suspected location of the clot. The brain would be imaged using either an MRI or CT scan, and a CT scan could also be used for clots located in the lungs. Clots that are lodged in the legs or heart, or near the kidneys and liver will most likely be examined by ultrasound. Your veterinarian may even include a coagulation test known as a thromboelastography, which can tell the technician if your pet’s blood is more or less likely to clot. Once the blood clot is confirmed, the source of the clot will then be evaluated. Blood tests such as a biochemistry analysis and complete blood count can help to detect many diseases and disorders that can lead to blood clots forming.

Initial therapy is either directed at removing the obstruction to the blood vessel, without creating new obstructions or supportive therapies if it is deemed safer to let the body clear the clot on its own. The clot-dissolving medication Streptokinase, which was designed for use in humans, is quite effective for canine patients as well. In some cases, the return of blood flow can cause dangerous levels of potassium, lactates, and acids to invade the patient's body. This syndrome is called reperfusion injury and is more common in cats than in dogs, and occurs most often with clots in the abdominal aorta. Surgical removal of the clot may also be an option for removing the blood clot, depending on where exactly it is located. They may choose to remove the clot by making an incision directly into the vessel, however, bleeding risks can be increased with this type of surgery.

Some situations allow for a specialized catheter to be threaded into the vessel to pull the clot out manually. Once the clot is removed or if your veterinarian deems it safer to let the body dissolve the clot, treatment will be focused on preventing new clots from forming. Anti-inflammatory and anti-coagulant medications like low-dose aspirin and heparin will be given, and your dog will be closely monitored until the danger from the clot has passed.

Blood clots can be dangerous when they occur, and many canines succumb rather quickly. The prognosis for dogs with blood clots that reach the veterinary clinic will depend on where the blood clot is located and how quickly treatment is begun. Keeping the recovering patient in a calm, quiet environment will help encourage healing, as will having appropriate food and water within their reach.  Some patients respond better to treatments than others, and recovery can also be affected by how quickly any underlying causes are diagnosed and addressed. Specialized feeding and care instructions may be given by your veterinarian to facilitate healing, and it is essential that you follow your veterinarian’s instructions regarding aftercare, as it can be unique to your dog.