The body has a delicate balancing job to keep blood fluid enough to flow through tiny capillaries, but still provide clots to stop hemorrhages when needed.
This trick is pulled off by the interaction of chemicals called coagulation factors. These work in a domino-like way: Factor A activates factor B, which activates factor C and so on. But if 1 factor is deficient, like a missing domino, the process is interrupted.
In practical terms, this means blood doesn’t clot.
Coagulation deficiencies in cats and dogs are usually an inherited problem handed down from a parent. The problem is usually detected early in life when the pet has a minor cut that bleeds out of all proportion to the injury. Some animals are mildly affected, while others have a serious deficiency that could endanger their lives.
It doesn’t take much for a dog with a clotting factor deficiency to bleed. It can be something minor — like a toenail clip — that starts the bleeding, but it just won’t stop.
Sometimes the problem goes undetected until the pet has surgery, such as for neutering when the pet bleeds uncontrollably with the first incision.
Some pets have subtle signs of a problem, such as blood spots on their gums, regular nosebleeds or bleeding from the gums. Other signs present in a far more dramatic way, such as when pets collapse after a knock or a blow from massive internal bleeding.
Clotting factors are genetically coded for, and inherited coagulation deficiencies are passed down along family lines.
Many disorders (e.g., hemophilia) are carried on the X chromosome, and therefore males are more commonly affected because they have only one X chromosome (XY) whereas females are more often carriers (XX).
The 2 most common coagulation factor deficiencies:
- Hemophilia — well recognized in the German Shepherd, Airedale, Cocker Spaniel and English Springer Spaniel (and other breeds)
- Von Willebrand disease (vWd) — runs in certain lines of the doberman, standard poodle, Shetland sheepdog and German wire-haired pointer, among others
In vWd, the factor that’s missing helps platelets stick to the wall of a damaged blood vessel and also to themselves — a bit like trying to build a wall without mortar in a flowing river.
If a young animal bleeds unexpectedly, then a suspicion of coagulation factor deficiency should be raised, although other problems causing excessive bleeding must also be ruled out.
- The first step is to run a blood profile to assess the amount of blood loss, count the number of platelets and see if red blood cells are being actively damaged or not.
- It is also necessary to check for conditions, such as lungworm, that may cause clotting problems.
- In addition, a sample is sent to an outside lab for a coagulation panel that looks for the presence of all the factors.
- Genetics tests can also be done for specific conditions such as vWd and hemophilia.
A pet with a serious bleed may need a blood transfusion or possibly a plasma transfusion to provide clotting factors. First-aid measures, such as applying pressure to the bleed to try to stop it, are important.
If a dog or cat has a clotting problem, prevent them from playing roughly to decrease the chances of minor injury.
It is not practical or possible to supplement animals with specific clotting factors. Prevention is largely about stopping these disorders from being passed on to the next generation and not breeding from affected animals.
- “Bleeding disorders in dogs: Inherited disorders.” Johnstone. In Practice, 24: 2–10.
- “Inherited coagulation factors.” Fogh & Fogh. Vet Clin North Am Small Anim Pract, 18(1): 231–244.
- “Diagnosis of bleeding disorders.” Johnstone. Vet Clin North Am: 21–34.
This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Jan. 1, 2016.