Oxygen is vital for living organisms. No animal can survive without oxygen. Oxygen is carried in the blood through hemoglobin — an iron containing oxygen transport protein in red blood cells of all vertebrates. Hemoglobin carries oxygen to the tissues as well as pigment that make the blood appear red. Hemoglobinuria is a condition characterized by presence of hemoglobin in the urine.
Hemoglobin is freed with the destruction of red blood cells within blood vessels. This free hemoglobin binds with haptoglobin in the blood serum. Haptoglobin is another protein in blood serum that serves to bind with free hemoglobin, consequently removing it from blood stream and preventing iron loss. If too much free hemoglobin is present and all the haptoglobin has been used up, this excessive free hemoglobin spills over into the blood where it binds reversibly with blood proteins and changes the color of plasma from faint yellow to pink. This unbound hemoglobin is then cleared through kidneys. Too much hemoglobin in blood plasma results in inability of the kidneys to reabsorb this protein and hemoglobin spills over into the urine.
Myoglobin is also a protein and serves the same purpose as hemoglobin — to carry oxygen — but it is specific to the muscles. Myoglobin carries and stores oxygen to the muscles. Myoglobin is released into the blood plasma due to an injury to the muscle. This myoglobin does not bind with serum protein and is cleared through liver and kidneys. Too much of myoglobin in the blood plasma results in spilling over of this protein into the urine. This condition is called Myoglobinuria.
Therefore, Hemoglobinuria is a symptom where a large amount of hemoglobin protein is found in the urine of dogs, whereas myoglobinuria is a symptom where a large amount of myoglobin protein is found in the urine of dogs.
Excessive amounts of free hemoglobin and myoglobin in the blood signifies low oxygen carrying capacity of the blood which can result in damage to the liver, serious illness or shock. All these conditions further decrease oxygen available to the body through blood and muscles. Furthermore, severe muscle damage and destruction of red blood cells inside the blood vessels can trigger a potentially fatal blood clotting disorder known as disseminated intravascular coagulopathy (DIC) — formation of small blood clots insides blood vessels throughout the body.
A dog with hemoglobinuria will show signs such as
Blood in the urine (urine is pink or red-colored)
Increased heart rate (tachycardia)
Pale appearance (jaundice)
Fatigue and lethargy
Pale white or purple tinged gums
The symptoms related to Myoglobinuria are: