Fact File

Dogs or cats can bleed or bruise if there is a problem with their blood clotting function.

This can be obvious from the outside, with bruising of the skin, nosebleeds, or blood in the urine noted, for example. However, sometimes animals can bleed internally, into their chest or abdominal space, into their joints or brain, or into their gut (when blood might be seen in vomit or faeces, or the faeces may be dark or black in colour).

It is firstly important to find out if there is a local problem causing the bleeding, for example if a tumour is present or if the dog or cat has suffered from trauma. The simplest way to do this is through discussion with the animal’s owner, a careful physical examination, blood tests and then sometimes diagnostic imaging such as radiography (x-rays), ultrasound or a CT scan.

If the clinician does decide a blood clotting problem is present, then further tests are likely to be necessary. Most blood clotting problems are due to either a problem with platelets (small cell fragments that start the blood clotting process) or clotting factors (substances in the blood which stabilise the initial blood clot formed by the platelets). Sometimes there can be problems with breaking down blood clots too quickly, but this is rare.

Different cures for different causes

There are many possible causes of problems with blood clotting. There are many inherited clotting problems described in dogs and cats such as haemophilia, but these are very rare. The most common bleeding problems we see at the RVC are:

  • Immune-mediated thrombocytopenia. This is a disease where the dog or cat’s immune system destroys their own platelets. These patients are treated with immunosuppressive drugs and red blood cell transfusions.
  • Rodenticide intoxication. Many rat poisons work by stopping blood clotting and they have the same effect on dogs and cats as they do on rats. Dogs particularly can find these poisons tasty. We can treat these animals with vitamin K and sometimes plasma and red blood cell transfusions. 
  • Angiostrongylus vasorum (lung worm) infection. Lung worm can cause problems with blood clotting, and we don’t completely understand why although the RVC has on-going research in this area which may help us find more effective treatments. Affected dogs are treated with anti-parasite drugs and plasma transfusions.

The importance of donors

Plasma and red blood cell transfusions can be very useful to treat many patients with clotting problems. We are always keen to hear from owners who think their pet might be a suitable blood donor. Please look at our website here and let us know if your cat or dog could be a life saving hero!

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