>>Ok, just looked it up, its called von Willebrand's Disease. How common is it?
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It's common enough that a basic test is indicated before a surgery. For that matter, we should do a general blood screening for the basics (liver values, kidney values, white counts, red blood cell count, etc.) on dogs before they go under general anesthesia, unless one has been done recently. It gives baseline values to compare to later in life for healthy dogs, and it saves the lives of dogs who have medical problems that did not otherwise show up.
I have a relative with a 12-year-old dog who would not have seen his first birthday except for a pre-operative blood check prior to scheduled neutering surgery. He has a severe kidney defect that has turned out to be controllable with diet. At the time of the blood test, his values were so bad, they were surprised he wasn't in a coma. The surgery was cancelled, and he's still intact. That blood test definitely saved his life.
Blood testing for our dogs is a bargain.
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Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47