You can’t live without a liver. Spleen? Sure. Only one kidney? You bet. But the liver? Nope. It serves myriad functions, which cannot be substituted by another organ. For both pets and humans, liver care is essential.
The liver is the largest internal organ in a mammal’s body, sitting on top of the intestines and directly below the diaphragm and the lungs. As food travels through the intestines, nutrients are absorbed by intestinal cells and essentially dumped into the blood flowing through the intestinal walls. All of this blood eventually collects in the intestinal blood vessels and funnels into the liver via the portal vein. The liver then processes all of this blood before the blood returns to the heart. So whatever you or your pet eats or drinks in some way flows to the liver.
All of these nutrients and molecules from the intestines are processed by the liver. Many toxic chemicals and compounds are broken down into less toxic or non-toxic substances, which the body then eliminates in either the bile or urine. This is where alcohol is processed and removed from the body via several enzymes: first alcohol dehydrogenase then aldehyde dehydrogenase. This process also deactivates / processes other chemicals, too. And many other enzymes deal with myriad chemicals and medication, too, rendering them either active, or deactive, depending upon the substance. There is only so much capacity in the liver to do these functions, so for you humans, don’t drink too much!
Many of the substances coming from the intestines need to be processed into other substances. One is sugars. While the body can use glucose directly, the liver also stores sugars in the form of a molecule called glycogen. When exercising and in need of energy, the liver mobilizes this glycogen, providing sugars for energy. Fats are also processed into usable materials. The liver breaks them down and can even reassemble new fats. It also takes up cholesterol and makes different compounds from cholesterol, including bile and bile salts. In order for the intestines to break down and absorb fats in the first place, they need to be processed, and this is done by bile, which is released from the liver, stored in the gall bladder (a sac located under the liver) and secreted into the small intestine. Once the bile salts do their job, they are resorbed by the intestines and reprocessed by the liver via a process called enterohepatic recycling.
Cats are prone to developing fatty liver disease when the liver is processing too much fat. This is seen in cases where an overweight cat stops eating, or is eating less than required, and fat is mobilized for energy. Too much fat can cause liver dysfunction and may even lead to death. Treatment requires supportive care and restoring proper nutritional intake.
Bilirubin, a byproduct of recycling red blood cells, is also processed by the liver. Bilirubin is a good indicator of liver function – unless there is an underlying disease causing rapid destruction of red blood cells, the only other main reason for elevated bilirubin is decreased clearance by the liver. In animals the first sign of liver disease may be jaundice, where the gums, whites of the eyes, and skin take on a yellow/orange tinge. This is from a bilirubin build-up. Jaundice in any animal should be considered an emergency in need of an immediate diagnostic work-up.
The liver is the main manufacturer of the blood protein albumin, which maintains oncotic blood pressure. Without albumin, fluids leak out of the blood vessels, causing swelling of tissues. It also produces blood clotting facers, which are essential to stop bleeding. Myriad other substances are also manufactured b liver tissues.
Liver disease can cause a failure of any of the above processes. In people with cirrhosis of the liver, they don’t produce enough albumin, can have clotting disorders, poorly digest food ingredients, may have problems regulating their blood sugar. Both dogs and people can have bile tract problems, leading to gall bladder problems, including formation of stones in the gall bladder and even deadly infections.
Many diseases can cause liver problems in animals. Leptospirosis, a bacterial infection found here in DC, can damage liver cells, leading to liver failure. Cancer of the liver is sadly common. And in some cases, slugging bile can cause severe liver disease. Leptospirosis is seen in unvaccinated dogs, with the first signs usually being lethargy, vomiting, and overall not feeling well. Treatment is with supportive care and antibiotics, but frequently this disease is fatal.
When veterinarians are concerned about liver disease, the first test performed is a chemistry, looking at liver values and bilirubin. X-rays may also be indicated. Further examination may require an ultrasound of the abdomen and liver, which enables the clinician to see the lobes of the liver, the gall bladder and associated structures. In certain cases a needle aspirate can be obtained, especially when a cancerous process is suspected. In dogs hemangiosarcoma, adenocarcinoma, and lymphoma are amongst the most common liver tumor types.
In many cases, there will be mild elevations in liver markers noted on routine chemistries and no apparent reason for these abnormalities. Many times the pet will be placed on a liver support supplement such as SAMe, which helps improve blood flow through the liver, restoring normal liver values and function. Careful monitoring is instituted to monitor for any changes.
When there are elevations in liver markers, it is important to attempt to ascertain the cause of the elevations. Prompt intervention can help prevent further damage to the liver, especially in treatable disease. Given time and love, the liver has an amazing ability to regenerate itself. But it is most important to be kind to your liver in the first place: you can’t live without it.
Dan Teich, DVM, is the Medical Director at District Veterinary Hospital. Learn more at www.districtvet.com