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31 MAY/JUNE 2017 ■ TVPJOURNAL.COM CONTINUING EDUCATION of dogs younger than 1 year having ALP activity >150 U/L. 6 Bone ALP may also be elevated in patients with osteomyelitis or osteosarcoma. Dogs with hyperadrenocorticism and those receiving glucocorticoids can be expected to have increased ALP activity due to the glucocorticoid-induced isoenzyme. Conditions that can cause an increase in ALP activity include those listed in Table 1 . The highest activities of ALP have been reported with conditions such as cholestasis, steroid hepatopathy, chronic hepatitis, and hepatic necrosis. 7 This lack of tissue specificity can make increases in activity of ALP hard to interpret. The half-life of ALP is approximately 70 hours in dogs and 6 hours in cats. 3 In cats, which lack the glucocorticoid-induced isoenzyme with a TABLE 1 Causes of Increased Liver Enzyme Activity ALT/AST ALP ENDOGENOUS CAUSES Metabolic/endocrine Hepatic lipidosis (cats), diabetes mellitus, hyperthyroidism (cats), hypothyroidism (dogs), hyperadrenocorticism Hepatic lipidosis (cats), diabetes mellitus, hyperadrenocorticism, hypothyroidism (dogs) Hypoxic Hepatic congestion, thrombosis, anemia, sepsis, seizures Neoplastic Lymphoma, metastatic neoplasia (eg, mast cell tumor), hepatocellular carcinoma Bile duct carcinoma, pancreatic carcinoma, lymphoma Inflammatory Acute/chronic hepatitis, cholangitis, cholangiohepatitis, cholecystitis, pancreatitis, enteritis Acute/chronic hepatitis, cholangitis, cholangiohepatitis, cholecystitis, pancreatitis, enteritis Infectious Leptospirosis, histoplasmosis, feline infectious peritonitis, schistosomiasis, ascending bacterial infections, toxoplasmosis Can cause increases in ALP activity, but they are less consistent and not as marked as those of ALT Other • Steroid hepatopathy (caused by endogenous or exogenous glucocorticoids) • Benign nodular hyperplasia • Muscle injury (AST > ALT): myositis, muscular dystrophy, trauma • Hemolysis • Extrahepatic bile duct obstruction: gallbladder, mucocele, pancreatic neoplasia, choledocholithiasis • Benign nodular hyperplasia • Increased osteoblastic activity: osteosarcoma, fracture repair, rickets, hyperparathyroidism • Benign familial hyperphosphatemia (Siberian huskies) • Vacuolar hepatopathy • Growth (young dogs) EXOGENOUS CAUSES Medications Tetracyclines, carprofen, phenobarbital, azathioprine, antifungal medications (ketoconazole/itraconazole), trimethoprim–sulfadiazine, lomustine, amiodarone, diazepam (cats), griseofulvin, zonisamide Corticosteroids (dogs), phenobarbital, primidone Toxins Cycads, xylitol, zinc, aflatoxin, amanita mushroom, blue-green algae, heavy metals, carbon tetrachloride Can cause increases in ALP activity, but they are less consistent and not as marked as those of ALT Trauma Yes