A senior dog has a persistent isolated high ALP. What is a reasonable interpretation?

• A. Could be a benign age-related isoenzyme, drug effect, or liver/biliary disease; pursue hepatic workup if clinically indicated.
• B. It definitively indicates kidney disease.
• C. It is normal in all cases.
• D. It indicates a bone fracture.

Answer: (A)

Alkaline phosphatase comes from two main sources in dogs: the liver (bile ducts) and bone. In a senior dog, a persistent, isolated elevation in ALP is not diagnostic of one specific disease; it reflects several possible causes. It could be a benign age-related or drug-induced increase from a liver or bone isoenzyme, or it could indicate liver or biliary tract disease. Because ALP is non-specific, you interpret it within the whole clinical context and pursue hepatic workup if there are signs or the elevation persists—including further liver tests, bile acids, imaging, and other diagnostics as indicated. It is not a marker of kidney disease, it is not normal in all cases, and it does not point to a bone fracture by itself.