Anemia is a defined as a
deficiency of red blood cells (erythrocytes) in the circulatory system. Adult
are anemic when the concentration of red cells in whole blood is less than 37
percent by volume. The normal range is 39 to 60 percent. Red cells are produced
by the bone marrow and have an average life span of 110 to 120 days. Old red
cells are trapped by the spleen and removed from the circulation. The iron they
contain is recycled to make new erythrocytes.
The purpose of red blood cells is to carry oxygen. Thus, the symptoms of
anemia are caused by insufficient oxygen in the organs and muscles. Signs
include lack of appetite, lethargy, and weakness. The mucous membranes of the
and tongue become pale pink to white. In dogs with severe anemia, the pulse and
respiratory rate are rapid, and the dog may collapse with exertion. A heart
murmur may be heard.
Anemia can be caused by blood loss, hemolysis, or inadequate red blood cell
In adult dogs the most common causes of blood loss are trauma, slow
gastrointestinal bleeding associated with stomach and duodenal ulcers, parasites, and tumors in the gastrointestinal tract.
Chronic blood loss also occurs through the urinary system. Hookworms and fleas are common causes of chronic blood loss in
Treatment: Treatment must be directed toward the cause of the anemia.
Gastrointestinal bleeding can be detected by checking the stools for
microscopic traces of blood. Urinalysis will pick up traces of blood in the urine
that may not be visible to the naked eye. Other tests can also be used to
determine the cause of the occult (microscopic) bleeding.
Hemolysis is an acceleration in the normal process of red blood cell
breakdown. Red blood cells break down to form bile and hemoglobin. With severe
hemolysis, these breakdown products accumulate in the body. Accordingly, in a
dog experiencing an acute hemolytic crisis you would expect to see jaundice and
hemoglobinuria (passing dark-brown urine that contains hemoglobin). In
addition, the dog appears weak and pale and has a rapid pulse. The spleen,
liver, and lymph nodes may be enlarged.
Causes of hemolysis include immune-mediated hemolytic anemia, congenital
hemolytic anemia, infectious diseases (such as canine babesiosis and leptospirosis), drug reactions
to medications such as acetaminophen, and poisonous snake
bites. A number of bacteria produce toxins that destroy red blood cells, so
hemolysis can also occur with severe infections.