A blood clot, or thrombus, may form at any location in a dog's body. Clots may develop as a result of a partially blocked artery. In some cases, dogs may have an underlying condition that causes excessive clotting. These might include an inflamed pancreas, cancer, parasite infection or an underactive thyroid.
Clots may break loose and become lodged in another location in the body. The specific symptoms of a blood clot vary depending on where the clot is lodged. Blood clots may be fatal in dogs. If your dog displays any signs or symptoms of a blood clot, seek immediate veterinary care.
Clots in the Lungs
If a blood clot lodges in an artery of your dog's lungs, it prevents oxygenated blood from getting to the lungs. This condition is called pulmonary thromboembolism. Symptoms include sudden difficulty breathing, increased respiratory rate, pale or blue gums, fatigue and the inability to sleep. Dogs also may cough and spit up blood.
Pulmonary thromboembolism is usually fatal. In some cases, the pet can recover with rest and oxygen therapy to allow your vet to treat the underlying cause of the blood clot. Common causes include cancer, heart disease, Cushing's disease and blood bacterial infections. Clots often recur if the underlying cause is not fully resolved.
Clots in the Heart
Symptoms of a blood clot in the heart, or aortic thromboembolism, include vomiting, paralysis, leg pain, abnormal gait, difficulty breathing, anxiety and pale or blue pads or nail beds. Untreated, these clots can lead to complete heart failure.
Clots in the Brain
Blood clots in the brain cause a vascular accident or stroke. Symptoms vary depending on where in the brain the clot is lodged.
Clots in the telencephalon, or cerebral cortex, cause a loss of reflexes in the eye, loss of feeling in the nose, weakness and seizures. You also may see a behavior called head pressing, when your dog will press his head against the wall or another object for no explainable reason.
Crossed eyes, back and forth eye movements, loss of eye reflexes and head tilting are symptoms of a blood clot in the thalamus. Clots in the cerebellum cause a drunken gait, tremors, rigidness in the neck and body, twisting the head up or back and loss of eye reflexes. Symptoms of a blood clot in the brain stem include weakness in the legs, pain in the head and neck, altered consciousness and loss of facial reflexes.
Dogs with underlying causes such as Cushing's disease or chronic kidney failure have a decreased chance of survival.
Other Blood Clots
If the clot is blocking blood flow to organs in the genital or urinary systems, your dog may have blood in his urine. Vomiting and inability to control bowel movements or urination are signs of a blood clot affecting abdominal organs.