An Introduction to Anemia
The word anemia means lack of blood. And of course, without enough blood to carry oxygen and nutrients around the body, your pet will, at the very least, feel weak, lousy, and disoriented.
You or your vet will suspect and/or confirm that your pet has anemia because:
1. the mucus membranes are pale
2. the patient is weak
3. the patient is breathing extra hard...trying to supply the
oxygen that the tissues are demanding
4. when your vet blanches out the gums with his or her finger, it
too long for the pink color to return. (this is known as
cutaneous refill time CRT)
5. when blood is drawn...perhaps for something unrelated...your
vet or vet tech will notice that the blood is too "thin"
6. laboratory confirmation by doing a red blood cell count and
pack cell volume (PCV note: this test is also known as an
Note: some of the above symptoms can be pretty subtle and there's a lot of normal variation of mucus membrane color from one pet to another. It takes a sharp professional (veterinarian) to pick up anemia in the early stages of the disease.
The details of anemia can be quite complicated, but the 3 basic causes are pretty straight forward:
1. Loss of blood from trauma, Intestinal tract ulceration,
donation, surgery, or parasites
2. Lack of blood because the bone marrow isn't producing blood
cells normally...there are a bunch of potential reasons
including radiation, cancer, and hormone imbalances
3. Lack of blood because the spleen or immune system is
destroying blood cells at an excessive rate for some reason
Some discussion about the above listed causes of anemia:
Loss of blood from trauma. The cause of the anemia can be pretty obvious if your pet has been shot or hit by a car or so forth.
What may not be obvious, though, if there isn't an external wound, is whether your pet has pale mucous membranes and is weak due to just shock ... or massive internal bleeding in addition. It can be hard to tell.
In both cases, an important part of the treatment involves giving IV fluids and/or a transfusion. But if massive internal bleeding is suspected, your vet will have to make the dangerous (and expensive) decision whether or not to do emergency exploratory surgery in hopes of finding the internal wound and stopping the blood loss.
Doing such surgery is very high risk when the patient is already weak from shock, but it may also be the only hope of saving a life. On the other hand, sometimes a good pressure bandage, medications, replacement fluids, and a little luck is good enough and a safer choice. You simply have to trust your vet's experience and decision.
Loss of blood from intestinal tract ulceration:
Intestinal and stomach ulcers aren't too common in veterinary medicine compared with American Human medicine. Perhaps being a pet is less stressful than being an American Human. Maybe the difference is diet related.
At any rate, when pets bleed enough from the GI tract to cause anemia, it's usually associated with parasites. (In humans, the most common parasite is an organism called heliobacter.) In pets, the most common parasites that cause anemia are hook and whip worms, either of which causes lots of micro ulcerations along the intestines.
Other causes of ulceration include heliobacter organisms, less common parasites, bowel cancer, food allergies, foreign bodies, the eating of inappropriate stuff like plastic toys, nails, caustic chemicals etc, and other inflammatory diseases of the bowel.
Loss of blood from hook or whip worms:
Parasites in the bowel cause micro ulcerations that bleed and I mention this in the above section about ulcers, but whip and hook worm disease is so common, I want to make some additional comments about this cause of anemia. Your pets are exposed to hook and whip worm larvae quite frequently whenever they walk out of doors. And most puppies are born with worms or infested through nursing.
Most pets don't become visibly sick, though, because:
1. their immune system is robust from good diet etc, and this
keeps parasite survival to a minimum
2. they have good owners that regularly deworm their pets,
thereby keeping parasite levels to a minimum. This is
important through out the pet's life, but especially for pups
they have owners that use the dewormers that their vets
recommend. this has nothing to do with greedy vets...it's
because the worms keep getting resistant to various products
and your vet keeps up with which products are working best.
3. they have good owners that pay attention to their pet's stool
now and then, and allow their vet to do fecal checks.
Note: for those of you protecting your dogs and cats with heartworm preventives, you are also helping to protect your pets from many (but not 100%) intestinal worms.
Other worms such as the common round worm and tape worms might cause enough GI inflammation to cause bleeding, but in general, the worms mostly likely to cause anemia are hook and whip worms. Both are microscopic and bore a little hole into the intestinal lining that lets them suck blood. They secrete a chemical in their saliva that keeps the blood from clotting. That's great for the worm, but when they finish eating they leave a bloody hole that doesn't clot well.
Well look, these holes are microscopic and no big deal ... unless there are hundreds of them. If lack of deworming etc allows the worms to multiply to high numbers, then eventually there will be enough little microscopic bleeding ulcers to cause significant inflammation and bleeding which in turn will lead to a weak, run down, anemic patient and possible death.
In addition to the blood loss and inflammation, those microscopic holes allow gut organisms (poop) to gain access into the blood stream and that can cause a whole slew of other problems (endo-toxic shock).
I went off on this tangent to re-enforce the importance of having your pets checked regularly by a vet, having stools or fecal samples done periodically, and taking the time, expense, and trouble of keeping your pet healthy to include regular deworming!
Loss of blood from blood donation or surgery
Well now, these are controlled situations and not much needs to be said. Your vet will be aware and ready to handle any potential problems that might occur. Recovery is usually rapid.
If you didn't know that dogs and cats donated blood, you might find it interesting that many vet clinics have a clinic mascot who donates blood when needed. Commercial, synthetic blood replacement products are now available, but they're quite expensive.
Lack of blood because the bone marrow isn't producing blood cells normally...there are a bunch of potential reasons including radiation, cancer, and hormone imbalances
Normally, blood is constantly being produced in the bone marrow. Red blood cells stay functional and healthy for approximately 3 weeks, and are then recycled through the spleen.
But all kinds of things can go wrong. The production of blood is a very dynamic system involving hormones or factors produced by the liver and kidney. The immune system is also involved, and anything involving the immune system can be complicated and confusing. And the bone marrow is sensitive to disease, radiation, cancer, sex hormones, and various drugs.
I'll try to return to this subject soon and try to make sense of it all for you, but in the meantime, trust your vet to explain what's going on in your pet's situation.
To find out what's going on in your pet's situation, your vet will need to do at least some of the following:
1. blood work that will shed light on the type of anemia and whether or not there are associated diseases going on such as liver disease, kidney disease, clotting diseases, Cushing disease, Addison's disease, diabetes, etc.
2. a bone marrow biopsy is a fairly invasive and expensive test, but
it tells us a lot. Whether or not your vet recommends this will
depend on the severity of the case.
3. radiographs are nice for picking up clues regarding the general
health of the bones and for detecting bone cancer
4. ultra sound is useful for detecting an enlarged spleen
5. repeat blood tests to see whether our treatment is working
Lack of blood because the spleen or immune system is
destroying blood cells at an excessive rate for some reason
more info as soon as I can