Hepatic Lipidosis

What is Feline Hepatic Lipidosis (FHL), and what pathognomonic hallmarks define it?

• Common metabolic hepatobiliary disease in cats.

• Categorized by excessive accumulation of triglycerides in 80% of hepatocytes and an increase in total liver weight.

Differentiate between Primary and Secondary Feline Hepatic Lipidosis.

• Primary FHL (5% of cases): Occurs in a previously healthy cat due to absolute environmental lack of food, unpalatable diet, or forced starvation.

• Secondary FHL (95% of cases): Triggered by anorexia/hyporexia secondary to underlying medical conditions such as Pancreatitis, Inflammatory Bowel Disease (IBD)/GI disease, Cholangitis/Hepatic disease, Diabetes Mellitus/DKA, Chronic Kidney Disease (CKD), or Neoplasia (e.g., Lymphoma).

What duration of anorexia triggers Feline Hepatic Lipidosis?

• Typically 2 to 14 days of persistent anorexia or severe hyporexia.

Explain the hormonal cascade triggered by prolonged negative energy balance in cats.

• Decreased food intake leads to decreased circulating insulin and insulin resistance.

• Surging levels of catabolic/counter-regulatory hormones: Glucagon, Growth Hormone (GH), Cortisol, and Catecholamines (Epinephrine).

• These hormones upregulate Hormone-Sensitive Lipase (HSL) in visceral adipose tissue, driving massive lipolysis.

• Non-Esterified Fatty Acids (NEFA) are released from adipose tissue into portal circulation and flooded directly into the liver.

Why are obligate carnivores uniquely susceptible to hepatic lipid accumulation during starvation?

Cats have unique requirements for essential fatty acids, amino acids, and vitamins. During prolonged anorexia, key nutritional deficiencies impair:

• Very Low-Density Lipoprotein (VLDL) Assembly & Excretion: Hepatocytes cannot package accumulated triglycerides into VLDLs for export into circulation.

• Mitochondrial beta-Oxidation: Inability to break down fatty acids into Acetyl-CoA for energy.

What is the physiological role of L-Carnitine in hepatic lipid metabolism?

L-Carnitine regulates the transport of long-chain fatty acids across the mitochondrial membrane into the mitochondrial matrix for beta-oxidation. Relative or absolute L-carnitine deficiency impairs fatty acid breakdown, worsening triglyceride storage inside hepatocytes.

How does intracellular lipid accumulation cause liver injury and cholestasis?

Severe hepatocyte swelling (steatosis) causes physical distension and compression of adjacent bile canaliculi. This leads to intrahepatic cholestasis, accumulation of toxic intrahepatic bile acids, secondary parenchymal hepatocyte damage, and rapid decline in liver function.

What is the classic signalment and risk factors for Feline Hepatic Lipidosis?

• Age: Primarily middle-aged cats (mean age- 7 years), though any age can be affected.

• Breed/Sex: No true sex or breed predilection.

• Body Condition: A history of obesity followed by sudden, rapid weight loss is a major predisposing factor.

What are the primary historical and physical exam findings in cats with Hepatic Lipidosis?

Severe hyporexia/anorexia, marked weight loss, icterus/jaundice (sclera, mucous membranes, pinnae), dehydration, vomiting, nausea, ptyalism (hypersalivation), diarrhea or constipation, and decreased mentation/lethargy.

What is the classic serum chemistry liver enzyme pattern in Feline Hepatic Lipidosis?

ALP>ALT (marked elevation in Alkaline Phosphatase with comparatively mild-to-moderate elevation in Alanine Aminotransferase) accompanied by severe Hyperbilirubinemia.

Which critical electrolyte derangements occur in Feline Hepatic Lipidosis, and why are they dangerous?

• Hypokalemia: Worsens or precipitates Hepatic Encephalopathy and causes muscular weakness.

• Hypophosphatemia: Risks severe refeeding syndrome and erythrocyte hemolysis.

• Hypomagnesemia: Causes refractory hypokalemia and cardiac instability.

What other specific laboratory findings are seen on Chemistry, CBC, UA, and Coagulation panels?

• Chemistry: Hyperglycemia (due to stress/counter-regulatory hormones/insulin resistance) OR Hypoglycemia (end-stage liver failure); elevated $\beta$-hydroxybutyrate (BHBA ketones); variable pseudofunction changes (decreased BUN, albumin).

• CBC: Non-regenerative anemia, inflammatory leukogram, Heinz body formation.

• Urinalysis: Bilirubinuria (always abnormal in cats).

• Coagulation Profile: Prolonged PT/aPTT due to liver dysfunction and impaired Vitamin K absorption (cholestasis).

Why are Serum Bile Acids CONTRAINDICATED in evaluating suspected Hepatic Lipidosis?

Because cats with hepatic lipidosis are already clinically icteric with elevated total bilirubin. Bile acids will predictably be severely elevated and offer no diagnostic utility.

What are the characteristic findings on Abdominal Ultrasonography for hepatic lipidosis?

The liver is diffusely enlarged (hepatomegaly) with rounded borders and is diffusely hyperechoic compared to falciform fat and renal cortex.

What is the diagnostic hallmark of Hepatic Lipidosis on Fine-Needle Aspirate (FNA) Cytology?

Severe hepatocellular steatosis (vacuolation), featuring microvesicular or macrovesicular lipid droplets distending the cytoplasm of hepatocytes.

What are the pros and cons of FNA Cytology vs. Histopathology for diagnosing FHL?

• FNA Cytology:

  • Pros: Safe, minimally invasive, requires minimal or no sedation, rapidly confirms presumptive diagnosis.

  • Cons: May miss underlying primary diseases (e.g., small cell lymphoma, cholangitis, pancreatitis); shows only 51% agreement with histopathology.

• Histopathology (Biopsy):

  • Pros: Definitive diagnosis (>80% hepatocytes affected) and identifies underlying inflammatory/neoplastic conditions.

  • Cons: Requires general anesthesia; high risk of bleeding due to coagulopathies; risk of vagovagal collapse.

What are the two core phases of managing Feline Hepatic Lipidosis?

• Phase 1: Initial Stabilization (Correcting hypoperfusion, dehydration, electrolytes, and coagulopathies).

• Phase 2: Nutritional Support (Enteral tube feeding—the definitive cure).

Outline the step-by-step initial stabilization protocol prior to feeding.

• Fluid Therapy: Rehydrate and correct hypoperfusion using balanced crystalloids.

• Electrolyte Supplementation: Aggressively supplement Potassium (K), Phosphorus (P), and Magnesium (Mg) before initiating feeding to prevent fatal Refeeding Syndrome.

• Coagulopathy Management: Administer Vitamin K1 subcutaneous injections; administer fresh frozen plasma if actively bleeding.

• Anemia: Administer packed red blood cells (pRBCs) if severe anemia/Heinz body hemolysis is present.

• Hepatic Encephalopathy: Administer Lactulose, anti-seizure drugs (if seizing), and anti-nausea/anti-emetic medications (e.g., Maropitant, Ondansetron).

Why must treatment address both Primary and Secondary disease simultaneously?

Over 95% of cases are secondary. Even if hepatic lipidosis is successfully managed with enteral nutrition, the cat will relapse or fail to recover unless the underlying trigger (e.g., pancreatitis, cholangitis, IBD, lymphoma) is identified and treated concurrently.