Feline Hepatic Lipidosis, colloquially known as Fatty Liver Disease, is a condition cat owners need to be aware of, especially when a cat is diagnosed with it or when it's a potential complication during another health issue. Often, this condition stealthily emerges as the cat, once overweight, rapidly sheds pounds. Owners, unaware of the danger, may initially celebrate the apparent weight loss. However, by the time the cat ceases eating and becomes visibly ill, the disease is already well underway, demanding aggressive intervention for a successful reversal. The silver lining is that there's hope for recovery if timely action is taken, as long as the disease hasn't advanced too far.
Red Flag: Unexplained Weight Loss in Cats
Sudden, unexplained weight loss in cats should always raise concern. It's crucial to have your cat evaluated by a veterinarian before they become severely ill.
Typically, cats affected by Fatty Liver Disease are middle-aged and have undergone significant weight loss, at least 25% of their original body weight. They exhibit poor appetite and may also experience gastrointestinal distress (such as vomiting, diarrhea, or constipation), with 38% displaying these symptoms. Weaker cats might also have imbalances in electrolytes or suffer from vitamin deficiencies due to liver disease.
Fatty Liver's Diagnostic Challenges
Feline Hepatic Lipidosis often presents a bleeding tendency, making liver biopsies a risky endeavor. In such cases, it's generally safer to perform a needle aspirate rather than a biopsy, as it poses fewer risks. A characteristic aspirate revealing fat infiltration is typically sufficient for diagnosis, especially when combined with ultrasound findings that suggest the entire liver has a fatty texture.
Spotting a Cat in Liver Failure
A cat in the throes of liver failure presents unmistakable signs. It may appear jaundiced, exhibiting yellowing of the eyes, though this symptom often goes unnoticed by pet owners. Additionally, a blood test may reveal elevated bilirubin levels, a yellow pigment usually regulated by the liver. Alternatively, an icteric cat's urine may assume a bright orange or brown hue due to accumulated bilirubin.
If bilirubin levels aren't elevated, liver disease may still be detected through blood tests, particularly the elevation of alkaline phosphatase (ALP), an enzyme that should not be elevated in cats under normal circumstances. An elevated ALP is a strong indicator of liver disease and may necessitate follow-up testing, such as a bile acids liver function test. Other liver enzymes commonly monitored are alanine aminotransferase (ALT) and aspartate aminotransferase (AST). While these enzymes can increase relatively easily and are less specific to liver evaluation than ALP, a significant increase might still warrant further liver assessments. In cases of hepatic lipidosis, the elevation in ALP is often quite pronounced.
Liver Disease vs. Liver Failure: Unpacking the Difference
Distinguishing between tests that assess liver damage (such as enzymes) and those that measure liver function (like bile acids) is crucial. Enzymes like ALT and AST are normally contained within liver cells, so their presence in the bloodstream indicates liver cell death. Liver damage can occur without a significant drop in overall liver function.
Liver function tests, on the other hand, gauge how well the liver is performing a specific task, often processing a biochemical substance in a detectable manner. This helps determine whether the liver requires support and if a biopsy is necessary for diagnosis. Tissue sampling, either through biopsy or needle aspirate, is essential for a definitive diagnosis of liver disease. Without tissue samples, it's challenging to pinpoint the specific type of liver disease, hampering tailored treatment.
Diagnosis Sequence for Fatty Liver Disease
Diagnosing Fatty Liver Disease often follows a typical sequence:
- The cat shows evident signs of illness and visits the veterinarian.
- The cat may exhibit jaundice, a common symptom in 70% of cats with lipidosis.
- Routine blood tests reveal significant ALP elevations.
- Bile acids tests confirm liver disease, particularly when bilirubin levels are elevated.
- Ultrasound indicates liver involvement.
- Needle aspirate or biopsy confirms hepatic lipidosis.
Understanding the Mechanism of Fatty Liver Disease
The development of a fatty liver can occur within as little as two weeks when a cat experiences a drastic reduction in food intake, typically around 50-75 percent. Fatty Liver Disease's roots are deeply embedded in the feline evolutionary past. Cats evolved as carnivorous predators, consuming multiple small meals throughout the day, which suited their physiology and metabolism. Their bodies adapted to thrive on a carnivorous diet and maintain lean body conditions, never anticipating extensive fat stores.
However, modern domesticated cats live a far different lifestyle. They often have ample opportunities to become overweight. While this might not pose an immediate threat, should a cat fall ill, stop eating, or become lost, a significant problem emerges. Fat stores are mobilized, and the feline liver, unaccustomed to processing large amounts of mobilized fat, becomes infiltrated with fat deposits, ultimately failing. This process is further complicated by cats' unique dietary protein requirements; protein malnutrition sets in rapidly when cats cease eating.
The Cat's Appetite and the Slippery Slope
Fatty Liver Disease rarely occurs spontaneously. It typically follows an underlying cause that initiated reduced food intake. If you're fortunate, this underlying cause has been resolved (for example, if the cat was lost and is now found). However, it's essential to recognize that in over 90% of cases, a second underlying condition is present, one that may carry a less favorable prognosis.
Cornell University's study of 157 cats with lipidosis unveiled the primary conditions associated with this disease:
- 28% had inflammatory bowel disease.
- 20% had a secondary type of liver disease, typically cholangiohepatitis.
- 14% had cancer.
- 11% had pancreatitis.
- 5% experienced social stressors (new cat, new home, conflicts with other pets or humans).
- 4% faced various respiratory conditions.
- 2% were diabetic.
A potentially helpful lab test for identifying underlying causes is the GGT (gamma-glutamyl transpeptidase) level. While it's generally not elevated in lipidosis, it may rise in the presence of other liver diseases or pancreatitis.
Treatment: A Multi-Pronged Approach
The cornerstone of Fatty Liver Disease treatment involves aggressive nutritional support. A high-protein, low-carbohydrate diet is crucial, with protein accounting for ideally 35-45% of the diet's metabolizable energy. Most feline recovery formulas meet this requirement, as do diets designed for managing feline diabetes. Your veterinarian will select an appropriate food based on your cat's specific needs and nutritional composition.
Administering Nutritional Support
When it comes to feeding cats with Fatty Liver Disease, several methods can be employed:
- Nasogastric Tube: A feeding tube is passed through the nose, down the esophagus, and securely sewn in place to deliver a liquid diet. While it doesn't require anesthesia, it does demand careful handling to prevent displacement. An Elizabethan collar is often necessary to protect the tube. Moreover, due to its small diameter, only liquid diets are suitable for this type of tube.
- Esophagostomy/Pharyngostomy Tubes: These tubes are easily placed with short-acting anesthesia, positioned to exit the side of the neck, and secured in place. They don't typically require an Elizabethan collar for protection and can accommodate slurry or blenderized diets.
- Stomach Tube/PEG Tube: Placed under anesthesia, these tubes protrude from the side of the body, connecting directly to the stomach to deliver blenderized food. While more invasive, they don't necessitate an Elizabethan collar, either.
Feeding Guidelines for Success
- Determine the daily food requirement.
- On the first day, provide only 1/3 - 1/2 of the day's calorie requirement.
- On the second day, offer around 2/3 of the full calorie requirement.
- Assisted feeding should continue for four to six weeks.
- Clear the feeding tube with warm water before and after use.
- Warm the food to a comfortable temperature, avoiding cold meals to prevent vomiting.
- Administer food slowly to avoid rapid stomach distention, which can induce vomiting.
- Consult your veterinarian before administering medication through the feeding tube, as certain medications may clog the tube or be incompatible with specific tube types.
General Liver Support
Several therapeutic treatments offer supportive care for the liver:
- Ursodiol: Assists bile flow and prevents the absorption of toxic bile products from the intestine.
- SAMe: An antioxidant that supports liver function.
- L-Carnitine: A supplement aiding fat transport.
- Taurine: This amino acid helps bind specific toxic bile acids for removal. It's often deficient in cats with poor appetites and is typically supplemented for a short duration.
- Antibiotics: Keep harmful bacteria in check within the intestine.
- Vitamin B-12 (Cobalamin): Often depleted in cases of chronic intestinal disease. Supplementation is recommended, even without blood level testing.
- Vitamin K: Necessary for cats with hepatic lipidosis due to abnormal blood clotting ability.
Refeeding Injury and Its Management
When a starved cat starts eating again, it can undergo severe metabolic changes in the first few days. The pancreas releases insulin to store calories, which can lead to a drop in potassium levels, causing weakness, urinary retention, heart muscle depression, and more. This is why gradual refeeding is crucial to avoid refeeding injury. It's essential to start with half or less of the required calories and gradually increase the intake over a few days.
Key Takeaway: Nutritional Support is the Key to Recovery
Survival and recovery from Fatty Liver Disease reach approximately 90% with proper nutritional support. Reluctance or hesitation regarding feeding tubes should be cast aside, as there's no room for uncertainty when dealing with this disease.
One critical lesson to remember is that Fatty Liver Disease rarely occurs without an underlying cause that must be addressed alongside the condition itself. Early detection and intervention, coupled with dedicated nutritional support, provide the best chances for your cat's successful recovery.
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