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Thromboembolism, a Blood Clot in a Dog’s Legs

 

A blood clot in a dog’s legs is not a common event, especially when compared to the incidence of blood clots affecting humans. In humans, blood clots often result from conditions such as deep vein thrombosis (DVT) and atherosclerosis, both conditions that are quite uncommon in dogs. On top of that, blood clots in humans are often precipitated by risk factors such as the use of oral contraceptives and smoking which, of course, are not risk factors present in dogs. However, there are cases where a blood clot in a dog’s legs may form, albeit rare, and as in people, the consequences can be disastrous if left untreated.

Formation of Blood Clots in Dogs  

Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine

Thrombosis occurs when clotting of the blood in a part of the circulatory system takes place. A blood clot, also known as a thrombus, is basically an aggregation of platelets (special cells found in the blood with the purpose of forming a clot) and fibrin (an insoluble protein formed from fibrinogen and meant to form a fibrous mesh that impedes the flow of blood).

Thrombus, or blood clots, may form in the left side of the heart or in the arterial system and may lodge at the site of thrombus formation or at a distant site. When a thrombus causes a blockage, the condition is medically referred to as thromboembolism.

In dogs, there are several predisposing conditions that may cause thromboembolism. These conditions include cancer, heart disease, immune-mediated hemolytic anemia (IMHA), disseminated intravascular coagulation (DIC), blood transfusions, Cushing’s disease, hypothyroidism, history of recent surgery, dehydration, shock, systemic infection (sepsis), protein-losing nephropathy, etc.




Symptoms of blood clots in dogs may vary based on several factors such as location, whether the blockage is partial or complete, over all blood supply and organ reserve. While blood clots may lodge in a dog’s legs, a likely more common place for a blood clot to lodge is in the vessels of the lungs, triggering acute respiratory distress.

A Blood Clot in a Dog’s Legs

Joelmills, Wikipedia CC BY-SA 3.0

A blood clot in a dog’s legs may occur as a result of a serious heart issue. When the dog’s heart fails to pump well, the blood can pool and clot within the chamber and then the blood clot travels until it reaches a small blood vessel that it can no longer pass through.

A blood clot in a dog’s legs takes place when a clot travels out of the heart and then reaches the junction of the aorta and the smaller iliac arteries. This area is called “distal aorta” and any blockages of the aorta are known as “aortic thromboembolism. ” Once here, the blood clot gets lodged and may block blood flow to the dog’s back legs (saddle thrombosis). This type of clot takes place more commonly in cats rather than dogs.

When a clot blocks blood flow to a dog’s legs,  the lack of blood flow causes the tissues and muscles to starve and die from lack of nutrition. This muscle death is quite painful. The dog may develop cold legs and cold paws and the vet may have a hard time finding a pulse in the femoral arteries of the rear legs. The skin on the paws may appear blue in color rather than pink. The muscles may appear swollen.

Affected dogs may also show loss of sensation (scuffing the paws on the ground), unsteady gait, stumbling, rear legs giving out and a reluctance to walk.  The dog may also manifest breathing problems. Occasionally, only one leg is affected.

Although blood clots most commonly affect the rear legs, sometimes blood clot may form as well in a dog’s front legs. In this case, the symptoms are less pronounced and usually only one front leg is affected.




Loss of blood flow to a dog’s leg is considered an emergency because should the leg go too long without blood supply, there are risks of losing the leg, points out veterinarian Dr. Christine M.

Did you know? The aorta is the largest artery in your dog’s body. It’s responsible for distributing oxygen-rich blood to your dog’s legs, kidneys, intestines, and brain.

“When animals have heart conditions, they are at an increased risk for blood clots. If they form a clot large enough, it can cause what we refer to as a saddle thrombus and block blood supply to the hind limbs. However, this is more common in cats than dogs.”~Dr. Maggie, veterinarian

At the Vet’s Office

The vet will inquire about the dog’s medical history, the symptoms noted and will conduct a physical examination. The vet will look at the gums,  listen to the heart with a stethoscope (for a murmur or irregular heartbeat) and will palpate the legs.

Blood work and a urine test may be carried out. A chest  x-ray may reveal any abnormal enlargement of the heart and presence of fluid around the dog’s lungs.  Heart disease should be ruled out by echocardiogram (ultrasound of the heart.) An MRI may be also helpful and may help rule out   herniated disks which put pressure on a dog’s spine and can cause paralysis of the back legs causing similar symptoms of a blood clot.

If a blood clot is suspected, the dog is quickly hospitalized to prevent complete heart failure and reduce the dog’s level of pain and stress.

For complicated cases, a visit to a veterinarian specializing in internal medicine may be needed. Many vets have a great background in treating many conditions, but a lot of times a specialist is needed to determine the cause and proper treatment of certain conditions when they are not typical to the normal vets’ practice.

Treatment of a blood clot in a dog’s legs requires addressing the underlying condition and addressing the blood clot itself. A blood thinner such as aspirin, given under the guidance of the vet, can help prevent future clots, considering that aspirin lowers the tendency of platelets to form clots.

Other drugs used to treat blood clots in dogs include the anticoagulant drugs fragmin, warfarin or heparin. This latter is a drug widely used for humans dealing with blood clots. Steroids may also be prescribed for the purpose of reducing inflammation. Pain killers are often delivered. Despite these treatment options, generally dogs suffering from blood clots have a high rate of recurrence and serious underlying medical conditions and therefore the prognosis may not be good.

Sadly, while in humans surgery is common to remove blood clots, in veterinary medicine this is not an option because the equipment needed is prohibitively expensive and it is quite a delicate procedure.


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