The proteins, straches, and fats that we eat are broken down into amino acids, sugars, carbohydrates, and fatty acids by our digestive system and are transported to the liver by the portal veinous system. There's a great illustration pictured above.
The liver is like a factory that recieves all sorts of raw materials and then uses these raw materials to make things the body needs. Here's a list:
It uses the carbohydrates to make glucose and other sugars that the body needs for energy.
It regulates the amounts of sugars, protein, and fat that enter the blood stream
The spleen recycles red blood cells and one of the waste products from this process is bilirubin, a by-product of hemoglobin. The liver removes this waste product from the blood and uses this molecule to make bile which it stores in the gallbladder. Bile, in turn, is released into the upper intestines and aids in the breakdown and absorption of fats.
Amino acids are the critical molecular building blocks for making albumin and globulins and hundreds of specialized proteins needed by our body. We get these amino acids from digesting plant and animal proteins. One of the major waste products from digesting proteins is ammonia. The liver removes the ammonia from the portal vein and uses the nitrogen in the manufacturing of proteins. The waste products from this process are urea and creatinine which have to be excreted through the kidneys.
The liver also stores some nutrients, such as vitamin A, iron, and other minerals.
It produces cholesterol and plays a major role in fat storage for future energy use by the body.
It produces clotting factors, chemicals needed to help blood clot.
It breaks down, or metabolizes alcohol that comes from fermenting digesta in our colons... or ingested on purpose on Saturday nights.
It breaks down, or metabolizes poisons, venoms, and toxins that we are exposed to.
The liver is the organ that metabolizes most of the medications we use. This is why veterinarians (and physicians) routinely monitor liver enzymes when potent medications are being given.
The liver is awesome, but it is contantly being bombarded with waste products, environmental toxins, internal toxins, bacteria and virus' that get past the front lines of our immune system, ammonias, aldehydes, lipids, and excess sugar. A lot can go wrong and the liver is vulnerable to infection, inflammation, parasites, auto-immune attacks, vascular problems, kidney problems, and cancer. And sometimes it is simply overwhelmed by all the junk we eat, drink, and inhale.
Here's a list of the liver diseases we commonly encounter in practice:
Jaundice or Icterus
Liver disease due to Feline Infectious Peritonitis (FIP)
Cancer of the Liver
Infectious Liver Disease (Hepatitis)
Parasitic Liver Disease
Cirrhosis (associated with alcohol poisoning in humans but seen in pets too due to other causes)
Enlarged Liver (hepatomegaly)
Gall Bladder Problems
What To Expect When You Go To The Vet
Most people won't realize that their pet has liver disease when they take their pet to the vet...they'll just know that their pet is sick or has been losing weight, or has a very poor hair coat. Unless the patient has yellow gums, eyes, ear flaps, and urine (jaundice), we usually can't tell if a patient has liver disease without the aid of some blood tests.
If your pet is sick enough to go to the vet... there's a pretty good chance that the liver is either the cause of the problem or is affected significantly. And if your pet is being treated for any major problem in the body, there's a good chance the liver will be affected by either the disease itself or the medications used to treat the disease.
And the easiest and least expensive way to check is to run some blood tests.
These tests are now routine in most veterinary practices and very important in monitoring your pet's health. I discuss each of these screening tests in the column to your left.
Other diagnostic tools that are more expensive but somewhat to very helpful are:
Radiographs: when it comes to the liver, radiographs are actually not all that helpful other than to see if the liver is much smaller (chronic liver disease) or much larger (acute liver disease) than usual. We can also see gallbladder stones on plain radiographs. But remember that everything is connected and what radiographs give us is the big picture; is the heart enlarged? are the lungs diseased or cancerous? are there kidney or bladder stones? are the kidneys normal in size and shape? are there bowel obstructions or severe gas? What part of the liver is abnormal? The radiographs often help guide us as to where to look with the ultrasound which views things in more detail but only in a very small area compared to radiographs.
Ultrasound: we can see a lot more detail with an ultrasound to include the identifications of liver abscess', cancers, bile duct obstructions, liver shunts, and blood flow into the liver. A lot of practices are getting and learning to use ultrasounds now that this technology has been so greatly improved and more affordable.
Cardiology Heart disease in Cats, Cardiac Hypertrophy, Valvular disease, Cardiac Insufficiency, Congestive Heart Failure, Heartworm Disease, and a little history about the milestones in treating heart disease
Cats: general information page and directory of diseases and problems specific to cats including vaccine recommendations, leukemia, feline viral infections, feline upper respiratory disease and cats that just aren't feeling well.
The largest vein in the body is the vena cava which is returning oxygen depleted blood back to the heart. Because it passes through the liver it is squeezed or pinched off like a hose if the liver swells from infection or other disease. The second largest vein in the body, indicated by the big green arrow is the hepatic portal vein. It carries all the nutrients, medications, toxins, hormones, and waste products from the intestines, the pancreas, and the spleen to the liver for processing.
ALT screen: This inexpensive test can be done in the clinic. ALT are the initials of an enzyme (alanine aminotransferase) that is normal INSIDE liver cells. If there is excessive levels of ALT detected free in the blood, this tells us that a higher than usual amount of liver cells are under pressure, inflamed, and under going cell death. When liver cells die and rupture, ALT is released. A certain percentage of liver cells die and are regenerated all the time, but excessive cell death indicates disease.
There are several other liver enzyme tests available and they are often run together in what we call a liver panel... but ALT is the most common and useful clinical test because it is a sensitive test that warns us that the liver is acutely... and hopefully temporarily... inflamed. This helps us monitor the use of potent medications; we know to back off if the ALT gets too high.
ALK Phos or ALP screen: This is another liver enzyme test that is commonly done in the clinic and is almost too sensitive in that it becomes elevated a little with both very minor liver disease and serious, chronic liver disease. It can even rise a little with indigestion. So we have to be a little cautious in interpreting mild to moderate elevations of this enzymes. But if the elevation is high, this is a good indication of severe liver disease, bone disease, cancer, and most often; gall bladder obstruction.
GGT (Gamma-glutamyl transferase) is another enzyme that is often included on liver panel tests. It rises with mild-severe liver inflammation so it's not very helpful in determining how bad the liver inflammation is. But it's useful is the ALK PHOS is high, because both ALK PHOS and GGT will be highly elevated in gall bladder obstruction but only the ALK PHOS is likely to be elevated with bone disease. High GGT is also a flag for alcohol consumption in humans and an indicator of possible congestive heart failure. GGT is also useful for monitoring barbituate levels for those patients getting phenobarbital for seizure control.
Bile Acids: Bile is made in the liver, stored in the gall bladder, and leaked out into the upper gastro-intestinal tract whenever the stomach squeezes digesta from the stomach into the upper intestines. Bile is needed to digest fats. But the bile is then transported back to the liver where it is supposed to be recycled. But if the liver is not functioning well ... or the bile ducts are clogged up, the bile acids will not removed from the blood efficiently and their levels will rise.
An elevated fasting level of bile acids, due to impaired hepatic clearance, is a sensitive indicator of liver disease. Following meals, serum bile acid levels have been shown to increase only slightly in normal pets, but markedly in patients with various liver diseases, including cirrhosis, hepatitis, blockages of the bile ducts (cholestasis), and blockages of the portal vein (portal-vein thrombosis).
Very high levels of bile acids (also called bile salts) indicate the probable cause might be a liver shunt where blood from the intestines bypasses the liver. This is somewhat common in certain breeds and I discuss liver shunts on another page.
Bilirubin is a waste product of the spleen that is processed by the liver and used in the production of bile. If the bilirubin levels are high, this indicates either bile duct obstruction or diseases... often cancer... of the spleen. So you can see how we use these test results together... If the ALK PHOS and GGT and Bilirubin are elevated, then we know the gall bladder or bile ducts are the problem. If just the Bilirubin is elevated, then we know that the spleen is likely to be the culprit.
Albumin and Total Protein: Only the liver makes albumin... the smallest but most numerous protein molecule in the blood. Most of the protein floating around free in the blood stream is albumin, so low levels of albumin would indicate that the liver is not functioning well. Unfortunately this test isn't very sensitive and not too helpful in diagnosing liver disease. It's kind of like a politician's smile.... But a rising albumin or total protein level is helpful in telling us that the liver is getting better.
Biopsy: nothing tends to give a more definitive diagnosis than a biopsy but this involves inserting a very long needle deep into the body under sedation, local or general anesthesia. An ultrasound is often used to guide the needle into the right spot.
Cat Scans and MRI: these technologies are often superior but just not available in typical veterinary clinics (yet). They are, however, available at specialty clinics. Which brings up referral for pets with liver disease. We will discuss this option in just a moment.
We don't have many treatment options specifically for liver disease. But here's what we do have:
Antibiotics: curative IF the problem is due to bacterial infection which is pretty common. They also prevent secondary infections
Steroids: used in chronic hepatitis to decrease inflammation and scarring. Also just to make the patient feel better. But we have to be cautious; steroids can actually cause liver disease or make things worse.
Digestive aids: sucralfate, cimetidine, probiotics, and pancreatic enzyme supplements are often helpful in pets with poor liver function
Furosemide or other diuretics: when the liver swells, it squeezes the vena cava which is the very large vein returning blood to the heart. When the vena cava is squished, blood pressure in the vein rises to the point where fluid leaks out into the abdomen. This extra fluid in the abdomen puts pressure on the diaphragm which makes breathing difficult. Sometimes diuretics are needed to get rid of this excess fluid.
Zinc acetate or Penicillamine: one of the jobs of the liver is to bind and excrete copper which is a waste product of hemoglobin production. If the liver is sick, then copper levels can become toxic. These two medications are used to reduce copper levels.
Anti nausea medications: when the liver is sick, the patient is often nauseated to some degree and related to this, not eating. Anti nausea medications help with this.
Fluid and electrolyte therapy is critical in many cases.
Special diets high in albumin and low in copper are made for dogs and cats and is an important part of the treatment in chronic liver disease.
A daily vitamin and mineral supplement is often advised for pets with liver disease to help prevent deficiencies. If copper storage disease is diagnosed, this supplement should not contain any copper.
Supplemental vitamin K may be necessary to help control bleeding disorders, since a diseased liver produces and stores less of this vitamin which is necessary for the liver to produce clotting factors.
S-Adenosylmethionine or "Sam-E"
This is a fairly new medication being used by veterinarians to help support the liver in it's role as a detoxifier for the body.
If toxins or drug metabolites build up in the blood...and they do as a normal part of cellular life in addition to the external poisons that most people think of when I say "toxins"...they can cause damage to the organs, make you feel sick, and start the cascade of chemical and cellular events leading to death. So the liver's role in filtering these endo and exo toxins by changing them into a form that can be eliminated through the bowels or urine is enormously important.
The liver's # 1 way of detoxifying is by making a potent antioxidan called glutathione. It makes glutathione from S-Adenosylmethionine which comes from the amino acid methionine which in turn comes from various foods in our diet.
Whenever the liver is sick, diseased, or not functioning well, the production of glutathione levels go down and the body starts to get into trouble from the build up of toxins.
Giving supplemental S-Adenosylmethionine (SamE) has been very helpful in treating liver patients. Denosyl SD4 was the original brand name product containing SamE but there are several generic neutroceuticals available now. They are often combined with milk thistle which is an herbal treatment that I'm pretty sure has legitimate benefits for liver patients.
S-Adenosylmethionine and has been proven to greatly increase the levels of glutathione in the body of pets even when the liver is diseased. In addition, this powerful anti-oxidant protects liver cells from cell death and may be useful in cell regeneration and healing.
The problem with SamE tablets is that they are expensive, large in size, and have to be swallowed whole. They are enteric coated to prevent digestion in the stomach because stomach acids inactivate the SamE molecule.
Prescription diets made just for cats and dogs with liver disease can make a big difference