jaundice is defined as yellowish pigmentation of the skin, urine, serum and organs by accumulation of the pigment called bilirubin at the blood or tissue level. It is a symptom, which is common in multiple diseases, so if our cat shows an abnormal coloration at some point in its body, our veterinarian will have to perform several tests to establish a differential diagnosis.
If your cat suffers from this disorder and you want to know a little more about its origin, in the next article on our site we will detail the most common causes of jaundice in cats.
What is bilirubin?
Bilirubin is a product that forms after the breakdown of erythrocytes (red blood cells), when they reach the end of their life (which lasts about 100 days). In the spleen and bone marrow, these red blood cells are destroyed, and from the pigment that gave them their color, hemoglobin, another yellow one, bilirubin, is formed.
It is a complex process in which hemoglobin is first transformed into biliverdin, which in turn is transformed into fat-soluble bilurribuna, and is released into the circulation, through which it travels together with a protein until it reaches the liver.
In the liver, the body's great purifier, it is transformed into conjugated bilirubin and it is stored in the gallbladderEvery time the gallbladder empties into the small intestine, a portion of bilirubin comes out with the rest of the bile components and, after the action of certain bacteria, is finally transformed into the normal pigments that we see every day, although we do not let us know: stercobilin (colors stool) and urobilinogen (colors urine).
Why does jaundice appear in cats?
At this point we can already realize that the liver is the key. Jaundice appears when the body is unable to correctly excrete bilirubin and other biliary components, although the place where the failure occurs is difficult to find in First instance.
To simplify this complex topic, we could talk about:
- Hepatic jaundice (when the cause is in the liver).
- Posthepatic jaundice (the liver does its job, but there is a failure in storage and transport).
- Non-hepatic jaundice (when the problem has nothing to do with the liver, nor with the storage and excretion of the pigment)
Symptoms of jaundice in cats
As we indicated at the beginning of the article, jaundice itself is already a symptom that indicates that the feline is suffering from a he alth problem. Likewise, the most obvious sign of this disorder is the yellowish color of the skin, being more evident in the mouth, ears and, in general, the areas with less fur of the feline.
Hepatic jaundice
In hepatic jaundice we observe that something is wrong at the liver level, since it cannot fulfill its mission and it is not able to release the bilirubinthat arrives. Under normal conditions, liver cells (hepatocytes) excrete this pigment into the bile canaliculi that run through the cell network, and from there it will pass into the gallbladder. But when the cells are affected by some pathology, or there is such an inflammation that it is not possible to pass the bilirubin to the framework of the bile channels, an intrahepatic cholestasis
What causes can cause liver jaundice in cats?
Any pathology that directly affects the liver can produce this accumulation of bilirubin. In cats we have the following:
- Hepatic lipidosis: feline fatty liver can appear as a consequence of prolonged fasting in felines with a lot of fat, which is mobilized without order towards the liver in an attempt to get nutrients and eventually invade it, as well as for many other reasons. But sometimes it is never known what causes its appearance, and we must call it idiopathic hepatic lipidosis.
- Neoplasm: Especially in older patients, primary neoplasms are a common cause of liver failure. They are called primary because they originate in the liver, without external factors, unlike the secondary ones.
- Feline hepatitis: hepatocytes can be destroyed by substances that the cat accidentally ingests, and that can lead to hepatitis.
- Biliary cirrhosis: Fibrosis of the bile canaliculi causes an inability to fulfill its mission and evacuate bilirubin to the gallbladder.
- Alterations at birth vascular level.
Sometimes we have alterations that can cause secondary liver failure, that is, produced by pathologies that, as a collateral effect, give rise to liver problems. We can find livers affected by neoplasms secondary to feline leukemia and also alterations or liver damage due to a feline infectious peritonitis infection, toxoplasmosis, or due to a diabetes mellitus. As a consequence of any of these problems, we will see a clear jaundice in the cat.
Posthepatic jaundice
The cause of the bilirubin buildup is outside the liver, when the pigment has already passed through the hepatocytes for processing. For example, a mechanical obstruction of the extrahepatic bile duct, the one that drains bile into the dudodenum. This obstruction can be caused by:
- A pancreatitis, inflammation of the pancreas.
- A neoplasm in the duodenum or pancreas, which compresses the area by proximity and makes it impossible to excrete the contents of the gallbladder.
- A break after a trauma to the bile duct, which prevents bile from being evacuated into the intestine (run over, blow, fall from a window…).
In cases of a total interruption of the flow of bile (rupture of the bile duct) you can see the yellowish color in mucous membranes or skin and, however, notice the faeces without color, since the pigment that gives them color, does not reach the intestine (stercobilin).
Non-hepatic jaundice
This type of jaundice in cats occurs when the problem is an excess production of bilirubin, so that the liver is not able to to release the extra amount of pigment, despite the fact that nothing is damaged in it, nor in the transport to the duodenum. It occurs, for example, in hemolysis (ruptured red blood cells), which may be due to factors such as:
- Toxic: for example, paracetamol, naphthalene or onions are substances that break down he althy red blood cells, causing anemia and an overload for the system in charge of destroying the remains of those blood cells.
- Viral or bacterial infections, such as haemobartonellosis. Antigens will be deposited on the surface of the red blood cells, and the immune system will see them as a target to target and destroy. Other times external help is not needed, and the immune system itself has a fault and begins to destroy its own erythrocytes for no reason.
- Hyperthyroidism: The mechanism by which jaundice occurs in cats with hyperthyroidism is not well understood, but it may be an increase in breakdown of red blood cells.
How do I know what is causing my cat's jaundice?
The laboratory and diagnostic imaging tests will be essential, along with a detailed clinical history that our veterinarian will prepare from the information that we facilitate. Although it may seem irrelevant to us, every detail must be communicated, for example, does our cat often play with hair ties?
The blood count and biochemistry, as well as determining the hematocrit and total protein, are the beginning of a battery of complementary tests.
In cats with jaundice, it is easiest to find the elevated liver enzymes, but it does not tell us if the cause is hepatobiliary disease primary or secondary. Sometimes, an excessive increase of one of them with respect to the rest can guide us, but an ultrasound and radiological study should always be carried out (masses, obstructions of the duodenum, fat infiltration… can be detected). Even before this, history and basic examination can allow the veterinarian to find nodules in the thyroid, fluid in the abdomen (ascites), and learn of possible exposure to hepatotoxic drugs.
Jaundice, therefore, must be understood as a symptom shared by hundreds of alterations of all kinds, so finding out its origin without a complete anamnesis, examination and performance of laboratory and diagnostic imaging tests in many cases (and even biopsies in others), it is impossible.
