Why Is My Dog's Bleeding Time Increased ?

Why Is My Cat's Bleeding Time Increased ?

To see what normal blood and urine values are for your pet, go here

For an explanation of causes of most abnormal blood and urine tests go here

To see how tests are often grouped, go here

Ron Hines DVM PhD

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Bleeding Time

Buccal Mucosal Bleeding Time (BMBT) or Toenail Bleeding Time

This simple in-office screening test allows your veterinarian to measure how well your dog or cat ’s blood clots (hemostasis) after an injury or incision. That depends on how well its blood platelets and the complicated clotting mechanism are functioning. Your veterinarians might be motivated to run this test if your pet is anemic, bleeding without an explainable cause or because extensive surgery is contemplated.

For a wound of any sort to stop bleeding, a plug (of adhering, sticky blood platelets) must form in the blood vessels supplying it. To perform the test, a prick is made in the inner surface of your dog’s lip and a stop watch is used to measure the period of time it takes before the flow of blood from the wound to cease. Similar tests could be performed on cats - but rarely are; I generally check their clotting speed on glass.

The chief problems with the bleeding time test are restrain of the pet during the procedure and variations in the results due to differing techniques and oral vascularity (the pet's capillary bed).

Some have used the BMBT as an initial screening test on Doberman Pincer dogs for a genetic blood clotting defect called von Willebrand disease, although more sophisticated tests need to be run when results are positive or suspicious (the latest Ettinger's Expert Consult, 7e, finds no correlation between vWD levels and BMBT bleeding time).

A similar test times how long a toenail that has been sheared to the quick, continues to bleed (Cuticle Bleeding Time CBT aka Toenail Bleeding Time TBT). It is painful and I do not suggest it.

Your dog or cat’s bleeding time can be extended when it has received NSAIDs (such as aspirin, Rimadyl, Deramaxx, Previcox, etc.) - particularly if the pet already has other health issues that delay its blood coagulation or if it has genetic bleeding tendencies (such as mild von Wilibrand disease [vWD]).

Bleeding time is sometimes increased in disseminated intra vascular coagulation (DIC, a shock-like condition) problems, but not consistently.

Bleeding time it can also increased in liver failure due to reduced clotting factor production. (ref) and in a specialized form of liver disease, portosystemic shunts. (ref)

A similar situation can occur in pets that are uremic (azotemic) due to advanced kidney disease and occasionally in pets with congestive heart disease ...(ref) as well.

Blood clotting can also be delayed in dogs infected with Leishmania , Ehrlichia or Anaplasma (wikipedia is wrong, it also occurs in dogs) or in cats that are carriers of FLV or FIV.

Diseases that involve the bone marrow (myeloproliferative disorders) can also be responsible as will any other illness that causes low thrombocyte (platelet) numbers.

Some uncommon inherited disorders can cause extended bleeding times. They include defective blood platelets occasionally seen in otterhounds and Great Pyrenees dogs (Glanzmann's thrombasthenia) and platelet defects in spitz, basset hounds and American cocker spaniels.  Inherited Chediak-Higashi syndrome, when it affects Persian cats with a smoke-blue hair coat, can also responsible for increased bleeding time.

Emergency blood substitutes (dextran70) can also caused delayed blood clotting as can also happen when large amounts of IV fluids are give (clotting factors are diluted). (ref)

Accidental consumption of certain rodent poisons (such as those containing diphacinone) also increase bleeding time.

Complementary tests :

Blood clotting panel , Liver Function Panel , liver biopsy

.................... DxMe