Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: An embolism happens when a blood clot or other material blocks a blood vessel. In dogs, the most important types are pulmonary thromboembolism (a clot in the lungs, causing sudden breathing difficulty), aortic thromboembolism (a clot affecting blood flow to the back legs), and fibrocartilaginous embolism (a piece of disc material blocking blood flow to the spinal cord, causing sudden weakness). Clots in dogs usually happen alongside another disease, such as immune-mediated anemia, Cushing’s disease, protein-losing kidney or gut disease, or cancer. All are emergencies.
Pulmonary thromboembolism (lung clot)
Signs
- Sudden difficulty breathing or fast breathing
- Blue or gray gums
- Weakness or collapse
- Coughing, sometimes with blood
Risk factors
- Immune-mediated hemolytic anemia (IMHA)
- Cushing’s disease or high-dose steroids
- Protein-losing kidney or intestinal disease
- Cancer, sepsis, or pancreatitis
- Heartworm disease
Aortic thromboembolism
Less common in dogs than cats. Signs are often gradual: back-leg lameness or weakness, cool back legs, and pain, sometimes worse with exercise. It’s often linked to protein-losing kidney disease or other clotting risks.
Fibrocartilaginous embolism (FCE)
- Sudden weakness or paralysis, often in one leg or on one side, frequently during exercise
- Brief pain at onset, then usually not painful
- Signs typically don’t worsen after the first 24 hours
- More common in large and giant breeds, and Miniature Schnauzers
Many dogs with FCE improve significantly with rehabilitation over weeks to months.
Diagnosis
- Bloodwork, clotting tests, and urine protein testing
- Chest X-rays and heart ultrasound
- Ultrasound of blood vessels, or CT angiography
- MRI for suspected FCE
Treatment
- Oxygen and supportive care in the hospital
- Anticoagulant or antiplatelet drugs, such as heparin, clopidogrel, rivaroxaban, or apixaban
- Treating the underlying disease
- For FCE: supportive care and physical rehabilitation. Blood thinners aren’t used.
Veterinary consensus guidelines recommend preventive clot medication for dogs with high-risk conditions like IMHA and protein-losing nephropathy.
What to avoid
- Human blood thinners or aspirin without your vet’s direction.
- Waiting if your dog has sudden breathing trouble or sudden weakness.
Frequently asked questions
Can dogs recover from a blood clot?
Some do, especially with treatment of the underlying cause. Lung clots can be life-threatening.
Is FCE the same as a stroke?
It’s often called a spinal stroke, since it blocks blood flow to part of the spinal cord.
Sources
- Goggs R, et al. Consensus on the Rational Use of Antithrombotics in Veterinary Critical Care (CURATIVE). J Vet Emerg Crit Care. 2019
- Merck Veterinary Manual: Thromboembolic disease in dogs
- De Risio L, Platt SR. Fibrocartilaginous embolic myelopathy in small animals. Vet Clin North Am Small Anim Pract. 2010
- Merck Veterinary Manual: Immune-mediated hemolytic anemia
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.