Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

352 •DOG OWNER’S HOME VETERINARY HANDBOOK
Red blood cell production can be depressed by certain drugs. Estrogen is an
important cause of bone marrow depression. This includes estrogens given for
medical purposes as well as those produced by testicular and ovarian tumors.
Other drugs that depress the bone marrow include chemotherapy agents,
chloramphenicol, butazolidin, thiacetarsamide, quinidine, and trimethoprimsulfadiazine.
Primary and metastatic cancer can invade the bone marrow and crowd out
normal cells, also depressing red blood cell production.
The diagnosis of inadequate red cell production is made by bone marrow
biopsy.
Treatment: Treatment is directed toward eliminating the cause of the
bone marrow deficiency. The dog should be screened for kidney and liver disease.
Iron deficiency anemia warrants stool examination and a further medical
workup. Estrogen-producing tumors of the ovary or testicle should be
sought and treated. Many drug-related causes of bone marrow depression
reverse when the drug is stopped.
Erythropoietin is a substance that stimulates red blood cell production. It is
normally manufactured by the kidneys and, to a much lesser extent, by the
liver. Recombinant erythropoietin can be helpful in dogs if the bone marrow
is capable of responding. Human erythropoietin has been used for the most
part, but the dog eventually develops antibodies against it. A new canine
recombinant version will be available soon.
CLOTTING DISORDERS
Clotting disorders are caused by an absence of one of the coagulation factors
needed to complete the clotting sequence. Severe deficiencies are associated
with spontaneous bleeding. Blood in the urine or stools may be associated
with a spontaneous bleeding disorder.
Von Willebrand’s Disease
Von Willebrand’s disease (vWD) is the most common inherited bleeding disorder
in dogs. It has been described in more than 50 breeds. Both males and
females can transmit and express the genetic trait. The disease is inherited as
an autosomal dominant gene with variable expression. That is, the severity of
the bleeding is related to the degree to which the gene is expressed.
The bleeding is caused by a deficiency of a plasma protein called the von
Willebrand factor, which is critical for normal platelet function in the early
stages of clotting.
In most cases the bleeding in vWD is mild or inapparent, and lessens with
age. Severe problems include prolonged nosebleeds, bleeding beneath the
skin and into the muscles, and blood in the stool and urine. There is often a