by Barry B. Burtis D.V.M.
Black, white, tri-colour, gray, sable, champagne, tortoiseshell, seal-point, ginger and many more, both singly and as combinations, are the colours they come in. Yes, you can find a cat in just about any colour you prefer. However, if you are a cat lover there is one colour of cat you do not want to have and that colour is yellow. I want to explain why a yellow cat is not good.
I should be more specific and say that there are particular places where yellow is bad. The sclera is the white area of the eyeball. The mucus membranes are the tissues that line various body cavities that are exposed to the external environment and internal organs. In several places, mucus membranes are continuous with the skin - at the nostrils, lips, ears, genital area and the anus. If you notice any hint of the colour yellow in the sclera, the mucus membranes or the skin of your cat, you need to contact your veterinarian immediately.
When the nice, bright white sclera or the healthy pink colour of the mouth and gums and skin of a cat becomes yellow we say it has jaundice. Icterus, probably more commonly used in medical jargon, is a synonymous term for jaundice. Jaundice is not a specific disease rather it is a condition caused by a process in the body that may be caused by various disorders.
Hemoglobin is the oxygen carrying part of red blood cells that circulate throughout the body. When red blood cells die, the hemoglobin is broken down into heme and globins. Bilirubin is a yellow breakdown product of heme. If a problem occurs somewhere in the chain of events that occurs in cat's body that helps it get rid of this breakdown product, bilirubin will accumulate, first in the blood and then in other body tissues. The body parts mentioned earlier are the tissues where this abnormal buildup of bilirubin and the resultant yellow colour is usually first noticed.
When veterinarians find a cat that is jaundiced there are several diseases that will be considered as most likely causes of the problem in this species. If something causes a massive death of red blood cells, the cat's ability to handle the large amount of bilirubin release may be overwhelmed and lead to jaundice. Cats are susceptible to several of these illnesses that affect the blood system. Infection with the feline leukemia virus or Haemobartonella, a blood parasite, can cause the death of large numbers red blood cells. Also, although less common in cats than dogs, certain immune-mediated diseases can lead to red blood cell destruction.
At other times, bilirubin will accumulate in a cat's body when there is failure of the organ primarily involved in processing bilirubin - the liver. In most animal species that are susceptible to jaundice, it is liver problems that are most commonly involved in causing the problem. This is true for cats as well.
In the liver bilirubin is processed, moved to the gall bladder and excreted in bile. It turns out that cats are deficient in one of the enzymes that assist in this processing. Therefore they are made more susceptible to some causes of jaundice.
Hepatitis, cholangiohepatitis (inflammation of the gall bladder system, as well as the liver), feline infectious peritonitis, toxoplasmosis and lymphoma are some of the more common liver diseases that affect cats and can cause jaundice.
Finally there can be problems outside the liver that affect the processing of bilirubin and hence cause jaundice. Pancreatitis, cancer, liver parasites and rupture of the gall bladder are examples of such disorders.
Laboratory blood and urine tests, imaging with x-rays and/or ultrasound and very often biopsies of the liver are usually necessary to determine the exact cause of jaundice in a cat. Treatment will depend on the cause of the problem. Next time I want to discuss the most common cause of jaundice in cats and the measures recommended its treatment.