The liver is the body's largest internal organ and performs over 500 functions — metabolism, detoxification, protein production, bile secretion, vitamin storage, and immune function. Because of its massive reserve capacity, liver disease often progresses silently until 70-80% of function is lost. Elevated liver enzymes on routine blood work are frequently the first indication of a problem — but elevated enzymes alone don't tell you the diagnosis.
Understanding Liver Enzymes
| Enzyme | What It Indicates | Common Causes of Elevation |
|---|---|---|
| ALT (Alanine aminotransferase) | Liver CELL DAMAGE (leakage enzyme) | Hepatitis, toxins, medications, hypoxia, infection |
| ALP (Alkaline phosphatase) | CHOLESTASIS (bile flow problems) OR induction | Cushing's, steroids, bile duct obstruction, nodular hyperplasia (benign), bone growth in puppies |
| GGT | Bile duct disease, cholestasis | Bile duct obstruction, pancreatitis, liver tumors |
| Bilirubin | Bile pigment (elevated = jaundice) | Liver failure, bile duct obstruction, red blood cell destruction |
| Albumin | Liver FUNCTION (production capacity) | Low = liver failure, GI loss, kidney loss. This is a function test, not a damage test. |
Common Liver Diseases
- Chronic hepatitis: Inflammatory liver disease. Copper-associated hepatitis common in Dobermans, Bedlington Terriers, Labrador Retrievers, Cocker Spaniels.
- Portosystemic shunt (PSS): Congenital abnormal blood vessel bypassing the liver. Seen in small breeds (Yorkshire Terrier, Maltese, Shih Tzu). Symptoms: small size, seizures, behavioral changes, urinary crystals.
- Nodular hyperplasia: Benign lumps common in older dogs. Often found incidentally on ultrasound. No treatment needed but must be differentiated from tumors.
- Hepatic lipidosis: Fat accumulation in liver. Usually secondary to diabetes, Cushing's, or obesity.
- Liver tumors: Hepatocellular carcinoma (primary liver cancer), metastatic cancer from other organs.
- Toxic hepatopathy: Drug-induced (NSAIDs, phenobarbital, azole antifungals), xylitol poisoning, blue-green algae, Sago palm.
Diagnosis
- Blood work (liver enzymes, bile acids, albumin, bilirubin, coagulation)
- Abdominal ultrasound (size, architecture, masses, blood flow)
- Bile acids test (liver function assessment)
- Liver biopsy (definitive diagnosis for chronic hepatitis — determines type and severity)
Treatment
- Depends entirely on the specific disease. "Liver disease" is not a single condition.
- Chronic hepatitis: Immunosuppressives (prednisolone, azathioprine), copper chelation (penicillamine) if copper-associated, hepatoprotectants (SAMe, ursodiol, milk thistle)
- Portosystemic shunt: Surgical correction or medical management (lactulose, low-protein diet, antibiotics)
- Toxic hepatopathy: Remove the toxin, supportive care, hepatoprotectants
- Hepatic diet: Hill's l/d, Royal Canin Hepatic — modified protein, added antioxidants
Hepatoprotective Supplements
- SAMe (S-adenosylmethionine): Antioxidant, supports glutathione production. Most evidence-based liver supplement. Brand: Denamarin.
- Milk thistle (silymarin): Antioxidant, anti-inflammatory. Modest evidence supporting liver protection.
- Ursodiol (ursodeoxycholic acid): Prescription bile acid that protects liver cells and improves bile flow.
- Vitamin E: Antioxidant support. Useful in copper-associated hepatitis.
Frequently Asked Questions
My dog has elevated liver enzymes. How worried should I be?
Mildly elevated enzymes (1.5-3x normal) on an otherwise healthy dog may represent: medication effects, recent anesthesia, muscle damage (CK can cross-react), or benign nodular hyperplasia in older dogs. Significantly elevated enzymes (>5x normal) or any elevation with clinical signs (vomiting, jaundice, appetite loss) warrants further investigation. Context matters enormously.
