Pathologic Thrombosis in Dogs

In dogs, as well as other mammals, blood clotting is a natural process that can stop excessive blood loss and help to heal wounds. Sometimes, however, a thrombosis or blood clot can form in an artery where it restricts blood flow and prevents oxygen from reaching the surrounding tissue.

Part of the blood clot may break off and be carried through the circulatory system, called an embolus. This can be very dangerous if the embolus becomes lodged near a vital organ. Normal blood is balanced between proteins and substances which aid clotting and other elements which decrease coagulation and prevent thrombosis formation. Some conditions can imbalance blood levels and lead to excessive clotting called pathologic thrombosis. If the dog is treated for the underlying condition before a blood clot forms, there will be a much better outlook for recovery.

Some underlying conditions can imbalance levels of proteins and other substances in the blood, increasing its viscosity and tendency to form clots. These conditions make it much more likely for a dog to develop a life-threatening thrombosis or blood clot. Excessive blood clotting, or pathologic thrombosis as it is defined by veterinarians, can lead to blocked arteries and numerous other complications.

Some conditions progress slowly and may begin as only a mild illness. Symptoms to look for and discuss with your veterinarian include:

• Difficulty maintaining normal exercise level
• Loss of weight or general ill health
• Wheezing or heavy breathing
• Purplish tinge to the skin
• Coughing sometimes with blood
• Nosebleed
• Fainting
• Swollen abdomen
• Excessive thirst
• Changes in appetite
• Fever
• Yellowish, jaundiced appearance

Once a blood clot has formed, symptom are very serious and you should seek emergency treatment immediately.

• Suspect a blood clot in the lungs if your dog has:
• Sudden difficulty breathing
• Coughing up blood or bloody mucus
• Elevated respiratory rate
• Blood clots in the heart can cause a variety of symptoms:
• Heart murmur
• Pain or symptoms of a heart attack
• Fluid accumulation in the abdomen
• Fever, lethargy, and lameness
• Elevated respiratory rate
• Clots which block blood flow to the urinary system, genitals or abdomen can cause:
• Bloody urine
• Abdominal pain
• Vomiting
• Inability to control bowels or bladder

Types

Most clots are made up of coagulated blood. In some instances, they can also contain pus or bacteria making them a source of infection as well as circulatory blockage. Occasionally fat and foreign material can also end up in the blood stream.

Clots can restrict blood flow to many vital organs in the body.

• A pulmonary embolism or thrombosis effects the tiny capillaries of the lungs.
• A clot in the brain can lead to a stroke.
• Clots can lead to heart failure as well as infection of the heart lining.

There are a number of conditions which have been shown to contribute to thrombosis risk in dogs.

• High cholesterol
• Increased adrenaline levels
• Kidney disease
• Diabetes
• Underactive thyroid
• Inflammation of the pancreas

Some long-term diseases will lead to blood clots if they are left untreated.

• Infective Endocarditis - bacterial infection of the heart lining which leads to pneumonia and clots in the lungs.
• Heartworm Disease - parasite infection of the heart which creates clots in the lungs.
• Immune-Mediated Hemolytic Anemia - a condition in which immune antibodies attack and destroy red-blood cells increasing the likely hood of clot formation. It can be caused by cancer tumors, infection or drugs.
• Cushing’s disease - a hormone imbalance caused by a tumor on the pituitary gland or by developing a tolerance to certain drugs. Blood clots can develop if left untreated.
• Aneurysm - enlarged blood vessel in the brain which may rupture and cause a blood clot.
• Ehlers Danlos Syndrome - very rare skin defect present at birth which causes bruising and blood clots.

If your dog has severe symptoms which may indicate a blood clot, treat it has an emergency and get immediate help. The best way to avoid blood clots is to diagnose and treat underlying conditions that create pathologic thrombosis. Discuss any unusual symptoms or deterioration in health with your dog’s veterinarian. Depending on the symptoms tests, can be performed to determine if your dog’s problems are related to a disease that causes excessive blood clotting.

Blood tests can check for diabetes, high cholesterol, and other imbalances. X-rays can check for heartworm, fluid around the heart from infection, tumors or blood clots in the lungs. A CT scan can determine if your dog has an aneurism. There is a specific test for Cushing’s disease if it seems likely your dog has that condition. The veterinarian may need to run a number of tests before finding the cause of your dog’s illness. If the condition is caused by a tumor, further tests will need to determine whether the tumor is malignant or benign before deciding on a treatment plan.

It’s important to pay close attention to your dog’s health in order to accurately diagnose conditions which cause excessive blood clotting before they become a serious problem. Take note of changes in eating and drinking, exercise level, weight loss or behaviors that seems out of the ordinary and discuss everything with the veterinarian.

There can be a number of treatments based on your dog’s diagnosis. Most underlying conditions are treatable with medication. Even if the underlying condition is not treatable, anti-coagulant medication can make the danger of thrombosis formation less. Sometimes blood transfusions are required to bring blood to a healthier level.

After blood clots have formed, they are also treated with anti-coagulation drugs and any infection or inflammation is controlled with medication. The animal may need an IV or oxygen to stabilize the situation. Depending on the placement, clots can sometimes be broken up with treatment. The dog will most likely need to stay in a veterinary hospital for monitoring.

Heartworm treatment involves several injections of an arsenical compound to kill the parasites and can be dangerous if your dog is not in good health to begin with. Your dog will need to be monitored closely after treatment as the dead heartworms can cause problems in the lungs for quite some time.

Cushing’s disease that is not caused by a malignant tumor usually is managed by medication rather than surgery. Some types with moderate symptoms may not need treatment.

Dogs with infective endocarditis often need to be treated for congestive heart failure. Significant doses of antibiotics can usually kill the bacteria, but the dog will probably need long term heart medication.

Surgery may be required if your dog’s problems are due to a malignant tumor. Depending on the placement of the tumor, the risk factor will need to be evaluated by a veterinarian.

Excessive blood clotting is a serious condition. If your dog survives, he will probably need long term medication. Medications can sometimes involve side effects. Discuss all medications with your veterinarian and evaluate the benefits versus the negative consequences.

Some dogs may recover from diseases which cause pathologic thrombosis if they are treated early. Others can lead fulfilling with the condition managed by medication and monitoring. In some cases, your dog may need to follow a special diet or exercise plan. Pay close attention to the instructions from the vet and be consistent with administering medication doses.