Hemoglobinuria and Myoglobinuria in Cats
Hemoglobin serves to carry oxygen to the tissues, and also carries the pigment that causes the blood to appear red. The destruction of blood cells within the blood vessels frees hemoglobin into the blood plasma (the yellowish colored liquid matter of the blood), where it binds with haptoglobin, a blood plasma protein which functions for the purpose of binding with free hemoglobin in order to prevent loss of iron. However, when all of the haptoglobin is used up, hemoglobin spills over into the blood, binding reversibly to blood proteins, and changing the color of the plasma from a faint yellow to pink. The unbound hemoglobin is then cleared through the kidneys.
Myoglobin serves the same purpose as hemoglobin but is particular to the muscles, and is differentiated by the amount of oxygen and carbon monoxide it delivers to the tissues (more, and less, respectively). Muscle damage releases myoglobin into the blood plasma, but it does not bind to serum proteins. Consequently, plasma color does not change, and the myoglobin is quickly cleared from the blood by the liver and kidneys.
If there is too much hemoglobin and myoglobin in the blood plasma, these proteins will no longer be reabsorbed in the kidneys, and will instead spill over into the urine.
Not only can hemoglobin and myoglobin damage the kidneys, but their presence in the blood indicates low oxygen-carrying capacity, which can result in liver damage, serious illness, and shock, all of which serve to further decrease the amount of oxygen available through the muscles and blood. In addition, the destruction of red blood cells inside the blood vessels, along with severe muscle damage, can bring about disseminated intravascular coagulopathy (DIC), an often fatal blood clotting disease.
Symptoms and Types
- Increased heart rate
- Lack of energy, lethargy
- Pale white or purple tinged gums
- Yellow skin and/or yellow whites of eyes (jaundice)
- Tenderness and bruising
- Blood in the urine (urine is pink or red-colored)
Some of the possible causes for hemoglobinuria and myoglobinuria are listed here.
- Injury and trauma (heat stroke, extreme exercise, electric shock)
- Infectious agents (parasites of the blood)
- Low blood phosphate
- Genetic diseases
- Immune-mediated hemolytic anemia
- Acute muscle inflammation
- Crush injury
- Extreme exercise
- Prolonged spasms/seizures
- Toxins, drugs, and food reactions:
- Menadione (used as a vitamin K supplement)
- Methylene blue
- Acetaminophen (pain reliever)
- Snake venom
Your veterinarian will perform a thorough physical exam on your cat, taking into account the background history of symptoms and possible incidents that might have precipitated this condition. You will need to give a thorough history of your cat's health and recent activities. A complete blood chemical profile will be conducted. This will include a complete blood count, and a test to measure for toxic levels of copper and zinc concentrations. Your doctor will also probably take a blood smear to look for irregularities of the red blood cells, and may also use the ammonium sulfate test to detect hemoglobin or myoglobin presence in the blood.
A urinalysis to look for bilirubin in the urine is another test that will be necessary for pinpointing the exact cause of the condition. Bilirubin is a red-yellow bile pigment that comes from the degradation of the red pigment (heme) in hemoglobin; too much bilirubin cannot be processed by the liver and will spill over into the urine. Excess bilirubin in the blood is also the cause of yellowing of the skin and eyes.
Radiographs and ultrasounds are useful for visualizing the liver in case of copper-associated liver disease, or to reveal swallowed coins or cage bolts/nuts – both common sources of zinc or copper poisoning.