Image courtesy of Dr. Teri Ann Oursler

Owners of cats that have been diagnosed with fatty liver disease or for whom fatty liver is being considered can use some information. 

Briefly, lipidosis (the medical name for "fatty liver") is a cause or contributing cause of liver failure when a cat that was once overweight loses weight too quickly. Often, the owner is not aware that this is dangerous and is pleased to see an obese cat trimming down. By the time the cat actually stops eating and is clearly sick, the disease is well underway and will require more aggressive support to try and reverse it. The positive news is that there is a good recovery rate for this condition, provided it has not progressed too far.

The average cat with lipidosis is middle-aged, was at one time obese but has lost at least 25% of its original body weight, has a poor appetite, and may have an obvious upset stomach (38% will have vomiting, diarrhea, or constipation). Cats that are especially weak may also have electrolyte imbalances or vitamin deficiencies from their liver disease.

In lipidosis, there is frequently a bleeding tendency that can make obtaining a biopsy sample somewhat risky. If ultrasound is suggestive of lipidosis, it is generally safer to take a needle aspirate rather than a biopsy sample, which is a bigger bite of tissue. An aspirate showing fat infiltration is usually diagnostic, especially when ultrasound shows the entire liver has a fatty texture.

A Cat in Liver Failure

The cat in liver failure is jaundiced (meaning their flesh is developing a yellow tinge), frequently nauseated, will not eat, and generally is an obviously ill animal.  The jaundice (clinically termed icterus) is often not noticed by pet owners but can be seen by carefully examining the whites of the eyes for a yellowish color. Sometimes, the yellow is not evident to the naked eye, but the trouble is picked up as a blood test elevation in bilirubin, a yellow pigment normally kept in check by the liver. Alternatively, an icteric cat's urine will look bright orange or even brown as bilirubin builds up.

If the bilirubin is not elevated, liver disease may be picked up as an elevation in a blood test enzyme called alkaline phosphatase (ALP). This enzyme should never be elevated in cats under any normal circumstances, though there are several forms of this enzyme, and an elevation does not necessarily indicate liver disease. An ALP elevation suggests liver disease and, if there is no obvious alternative explanation for ALP increase, it requires follow-up testing such as a “bile acids” liver function test and/or imaging of the liver, such as an ultrasound.

Other liver enzymes commonly monitored on routine blood panels are alanine aminotransferase (ALT) and aspartate aminotransferase (AST). These enzymes may increase relatively easily and are not as important in liver evaluation as ALP elevations, but a substantial increase may also warrant follow-up liver testing. In the event of hepatic lipidosis, also called fatty liver, the elevation in ALP is often dramatic.

Liver Disease Vs. Liver Failure

It is important to distinguish tests of liver damage (like enzymes) versus tests of liver function (like bile acids). The enzymes ALT and AST are normally held inside liver cells; when their presence is detected free in the bloodstream, this is an indicator of liver cell death. A liver can have damage without any decrease in overall liver overall function.

A liver function test is different. Here, the liver is actually asked to do something (generally process a biochemical in a detectable way). In this way, we can see if the liver actually needs support and whether or not we have a good chance of getting a diagnosis through a biopsy. Tissue sampling, such as a biopsy or a needle aspirate, is crucial to diagnosing liver disease. Without a tissue sample, all we can tell is whether or not the liver is in failure, and specific therapy for a specific type of liver disease is not possible (though general support of the failing liver may still be possible.)

A typical pathway for diagnosis of this condition would be:

• The cat is obviously sick and seen by the vet.
• The cat may show the yellow pigment changes typical of liver disease (70% of cats with lipidosis have jaundice).
• Routine blood tests show marked ALP elevations.
• Bile acids are elevated (testing bile acids is not necessary if bilirubin is elevated).
• Ultrasound shows a disease process involving the liver in its entirety.
• A needle aspirate or tissue biopsy shows hepatic lipidosis.

Fatty Liver (Hepatic Lipidosis)

The so-called fatty liver is one of the most common causes of liver failure in cats and it stems from the cat's natural history. Cats evolved as predators of small birds and rodents, eating multiple small meals throughout the day. Their physiology is geared towards a completely carnivorous diet and with the assumption that cats would live lean and never have the opportunity to develop extensive fat stores.

Of course, this all changed when cats became domesticated. The modern housecat has every opportunity to become overweight, and while this may not be of disastrous consequence on a day to day basis, should the cat get sick and stop eating or get accidentally lost or confined where food is unavailable, a significant problem erupts. 

The fat stores mobilize. Normally, in starvation, fat is moved from the body's storage depots to the liver for processing into lipoproteins, but the feline liver has not evolved to handle huge amounts of mobilized fat. The liver becomes infiltrated with fat and fails. Complicating matters is the high dietary protein requirement unique to cats; protein malnutrition develops very fast when cats do not eat.

Why Would a Cat Stop Eating in the First Place?

Initially, there is an underlying cause of the decrease in eating that leads cats down the slippery slope to lipidosis. If you’re lucky, the underlying cause has resolved (such as the cat was lost/starved and has now been found). It is important to keep in mind that even though lipidosis usually carries a fair prognosis, in more than 90% of cases, there is a second condition that requires attention, one with a prognosis that might not be so fair. 

Cornell University looked at 157 cats with lipidosis and looked at what conditions were primary. Here is a summary of what they found:

• 28% had inflammatory bowel disease
• 20% had a second type of liver disease (usually cholangiohepatitis)
• 14% had cancer
• 11% had pancreatitis
• 5% had social problems (new cat, new home, threatening other pet or person at home)
• 4% had some kind of respiratory disease
• 2% were diabetic

A lab test that might be helpful in determining the underlying cause is the GGT (gamma-glutamyl transpeptidase) level. It is usually not elevated in lipidosis but would be elevated if there is an underlying additional liver disease or in the event of pancreatitis.

Treatment

The cornerstone of treatment for lipidosis involves aggressive nutritional support. The diet for a cat with lipidosis should be high protein/low carbohydrate. Ideally, 35-45% of the diet's metabolizable energy should be protein to reverse the metabolic state of the disease. Most feline recovery formulas will meet this requirement, as will diets made to manage feline diabetes. Your veterinarian will select an appropriate food based on how the food will be delivered to your cat as well as its nutritional composition. If this is done carefully, the recovery rate approaches 90%.

Generally, by the time a cat has gotten into trouble with hepatic lipidosis, most owners have already tried tempting them with assorted favorite foods and gotten no results. At the point where lipidosis has developed, your cat should not be given a choice about eating; there are several methods of providing food.

Nasogastric Tube

A feeding tube can be passed through the nose, down the esophagus, and sewn into place to allow feeding of a liquid diet. Placing this kind of tube does not require anesthesia, and the tube is relatively easy to use. Some problems are associated with this type of feeding tube. For example, the tube can be dislodged by an errant paw, necessitating replacement; an Elizabethan collar is necessary to protect the feeding tube. Furthermore, only liquid diets can be given through the tube due to its small diameter. The tube can also be pushed backward after a vomiting attempt so that it opens towards the mouth instead of the stomach. All of these problems make the N-G tube the least popular of all the feeding tubes when it comes to long-term use; however, often this form of feeding is used for the first few days as this is when bleeding risk is highest and the patient is least stable for anesthesia. One of the other tubes can be placed when the patient is more stable.

Esophagostomy or Pharyngostomy Tube

The esophagostomy or pharyngostomy tube is easily placed with short-acting anesthesia and sewn in place, creating a feeding tube that exits the side of the neck. A bandage or padded collar is placed to hold the tube in position and keep it from catching on things, though the tube is comfortable enough that an Elizabethan collar (plastic cone collar) is not necessary. The cat can be mobile with comfort, and the diet can be slurried or blenderized as the tube is larger than the nasogastric feeding tube. The tube must stay in place for at least two weeks but can stay in place for many months if necessary. The tube does not interfere with eating normally when the cat recovers food interest. 

Stomach Tube/PEG Tube

A gastrostomy tube is placed under anesthesia and protrudes from the side of the body. The tube connects directly to the stomach and similarly allows for blenderized food to be delivered. Placement is a bit more invasive than esophagostomy and requires specific equipment but is another way to feed a sick cat. A bandage covers the tube and the cat is generally comfortable; an Elizabethan collar is not necessary.

The diet for a cat with lipidosis should be high protein/low carbohydrate. Ideally, 35-45% of the diet's metabolizable energy should be protein to reverse the metabolic state of the disease. Most feline recovery formulas will meet this requirement, as will diets made for managing feline diabetes. Your veterinarian will select an appropriate food based on how the food will be delivered to the cat as well as its nutritional composition.

Assisted Feeding

This method is generally discouraged as it can be so distasteful for the cat and can create food aversion where the cat no longer wishes to eat normally, even after recovery, because of bad association with the necessary manipulations. Talk to your veterinarian if you have any questions. 

Rules for Overall Nutritional Support 

• Know how much of the food should be fed per day
• The first day, only 1/3 - 1/2 of the day's calorie requirement should be provided.
• The second day only 2/3 or so of the full calorie requirement should be provided.
• Assisted feeding should be expected to continue for four to six weeks.
• Feeding tubes should be cleared with warm water before use and cleared again with water afterward.
• Food must be warmed to a comfortable temperature. Food straight from the refrigerator can induce vomiting.
• Food should be given fairly slowly. Rapid distention of the stomach can induce vomiting.
• Before giving medication through the feeding tube, please visit with your veterinarian as some medications can clog the tube and some medications are incompatible with some types of feeding tubes. If you end up giving medication through the tube, it is all the more important to clear the tube with 6 cc of tepid water.
• If a feeding tube plugs or blocks, flushing with warm water usually will unplug the tube.

General Liver Support

There are several general therapeutic treatments that are supportive to the liver that might be used.

• Ursodiol - assists bile flow and helps prevent absorption of toxic bile products from the intestinal tract.
• SAMe - this antioxidant has shown promise in supporting liver function.
• L-Carnitine - a supplement helpful in transporting fats.
• Taurine - this amino acid helps bind certain types of toxic bile acids for their removal from the body. It is usually deficient in cats that have not been eating properly and short-term (7-10 days) supplementation is a good idea for cats with lipidosis.
• Antibiotics - keep the harmful numbers of overgrowing bacteria in check within the intestine.
• Vitamin B-12 (cobalamine) - this vitamin readily depletes in chronic intestinal disease. Ideally, a blood level of this vitamin would be checked before therapy, but often, because it is inexpensive and safe to use, a course of injections or oral supplementation is included in therapy. As a general rule, cats with lipidosis are deficient in all the B vitamins, and a general supplement at twice the usual dose is a good idea.
• Vitamin K - most cats with hepatic lipidosis have abnormal blood clotting ability due to the inability of the liver to recycle vitamin K-dependent blood clotting factors.

A low red blood cell count is a common complication of lipidosis and may be caused by Vitamin K-related bleeding/clotting issues, inadequate blood phosphorus leading to red blood cell rupture, or precipitation of abnormal hemoglobin within the red blood cell (Heinz body anemia). There is approximately a one in four chance that a lipidosis cat will need some kind of blood transfusion before leaving the hospital.

Refeeding Injury

When a patient has been in a starvation state for a while and then begins to eat, some serious metabolic problems may occur in the first few days as the metabolism changes. When food is eaten, the pancreas releases insulin in an attempt to store the calories. Unfortunately, insulin also drives circulating potassium inside cells, and cats with hepatic lipidosis are often depleted of potassium to start. This sudden drop in potassium can make a cat quite weak (causing a drooping neck, listlessness, urine retention/inability to urinate normally, heart muscle depression, and more). Insulin will drive phosphate into cells similarly, leaving the bloodstream depleted. Red blood cells will not have enough phosphate to maintain their own structure; they burst, causing severe anemia.

If the blood phosphate level drops below 2.2 mg/dl, an IV supplement will be needed. After the phosphate level starts to rise, an oral supplement of phosphate is given (usually lactose-free cow's milk works well). Expect your cat to be monitored in the hospital for the first three days following initiation of nutritional support, and possibly longer.

Refeeding injuries can be usually avoided by starting with half (or less) of the required amount of calories and gradually working up to the full nutritional requirement over a few days. Having a low blood potassium level at the time of lipidosis diagnosis is associated with an increased chance of death.

Many people are reluctant to place or work with feeding tubes and want to try feeding their cat at home. There is no room for tentative treatment when it comes to this disease.

Cats that show a 50% drop in their total bilirubin level within 7 - 10 days are statistically likely to survive.

Keep in mind that hepatic lipidosis generally does not spontaneously happen. If there is an underlying cause, it must also be addressed.