Thrombocytopenia in Dogs

Clumped platelets among red blood cells under a microscope.
Platelets are smaller than red blood cells and play an important role in clotting.

 Getty Images/Ed Reschke

In This Article

Thrombocytopenia is fairly common in dogs. It occurs when their platelet count is low. This causes issues with clotting and can mean there is a serious underlying disease that will need treatment.

What Is Thrombocytopenia in Dogs?

Thrombocytopenia occurs when a dog has a low number of platelets in its blood. Platelets are important for clotting, so if your dog does not have enough of them in their body it is at risk of sudden bleeding or bruising. In dogs, it is usually seen as a symptom of an underlying disease and is rarely seen in cats.

The number of platelets can drop below 30,000/μL of blood, or even sometimes 10,000/μL, in a dog with thrombocytopenia. These are extremely low numbers considering dogs normally have about 200,000/μL.

Symptoms of Thrombocytopenia in Dogs

  • Spontaneous bleeding or hemorrhage
  • Skin bruising
  • Gum bruising
  • Blood in feces
  • Nose bleeds
  • Black stool
  • Blood in urine

Since thrombocytopenia affects a dog's blood clotting abilities, spontaneous bleeding and hemorrhage can occur. This may happen if a dog gets a small wound or even without any trauma.

Nose bleeds may also suddenly occur and blood can even be seen in the stool and urine of a dog with thrombocytopenia. Black stool is an indication that the blood has been digested, but red blood may also be seen.

Finally, large bruises called ecchymoses along with small bruising called petechiae can occur on the gums and skin of a dog with thrombocytopenia. All of these symptoms are due to having low platelets.

Causes of Thrombocytopenia in Dogs

Thrombocytopenia can be caused by a number of diseases or issues in a dog:

  • Drug and vaccine reactions: Some medications such as chemotherapeutics, azathioprine, and estrogen have a side effect of causing thrombocytopenia. Occasionally, vaccines for distemper and hepatitis have also reportedly caused a decrease in platelets, but these levels do not typically drop low enough to cause spontaneous bleeding.
  • Infections: Several tick-borne diseases, including Ehrlichia and Anaplasma
  • Bone marrow diseases: Leukemia and other diseases affecting the bone marrow of a dog
  • Cancer: Lymphoma, carcinomas, sarcomas, and other cancers can cause platelets to be destroyed and result in thrombocytopenia.
  • Vasculitis: Platelets can be destroyed rapidly in dogs with vasculitis, a disease of the blood vessels, resulting in thrombocytopenia.
  • Disseminated intravascular coagulation (DIC): This serious disease creates blood clots within a dog's body and therefore uses up the platelets that are available.
  • Genetics: Specific dog breeds such as Cavalier King Charles Spaniels and Greyhounds are known to develop thrombocytopenia. Often times, these findings are not concerning in these breeds if the dog is otherwise healthy.
  • Enlarged spleen: Splenomegaly can result in thrombocytopenia since the spleen stores a large number of platelets in it.
  • Rodenticide poisoning: If a dog accidentally eats some rodent poison that is designed to cause internal bleeding, thrombocytopenia may be seen alongside hemorrhage.
  • Idiopathic: A common cause of thrombocytopenia is referred to as being idiopathic or immune-mediated. This is because no one understands why the body suddenly stops producing adequate platelets.

Diagnosing Thrombocytopenia in Dogs

In order to diagnose a dog with thrombocytopenia, a veterinarian will perform a complete blood count. This will tell them how many platelets the dog has and whether or not it is an adequate amount. If a dog has a low number of platelets, thrombocytopenia is diagnosed. Other tests may be performed to discover the cause of the thrombocytopenia.

Treatment for Thrombocytopenia in Dogs

The treatment and prognosis for thrombocytopenia will depend on the cause. Medications to treat illnesses and infections, discontinuation of agents causing thrombocytopenia, surgery to remove an enlarged spleen or cancer, controlling of bleeding, and even on rare occasion, platelet transfusions may be necessary for treatment.

How to Prevent Thrombocytopenia in Dogs

Often times there is no way to prevent thrombocytopenia from occurring in dogs since it is most commonly immune-mediated or caused by various diseases that are difficult, if not impossible, to prevent.

Dogs with known thrombocytopenia issues should not be used in breeding programmes, rodenticides should always be kept out of reach of pets, and tick-control is recommended. Immune support with various supplements may be helpful in keeping a dog healthy overall, but there is no guarantee that a dog won't develop a condition that causes thrombocytopenia.

Article Sources
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  1. Huang AA, Moore GE, Scott-Moncrieff JC. Idiopathic immune-mediated thrombocytopenia and recent vaccination in dogs. J Vet Intern Med. 2012;26(1):142-148. doi:10.1111/j.1939-1676.2011.00850.x