Increases in alkaline phosphatase (ALP) are most commonly associated with the liver, but there are numerous other sources of increases. Hours after ingestion of colostrum, neonatal puppies/kittens have very high levels of ALP. Young dogs and cats are also likely to have high levels of the bone isoform of ALP. Bone disease, endocrine disease, neoplasia, and other disorders can also cause increases of ALP. A phenomenon known as enzyme induction occurs when certain drugs, such as topical, ophthalmic, and otic glucocorticoids as well as anticonvulsants, are given. Dogs with increased cortisol levels due to hyperadrenocorticism will also have elevated ALP levels. Although ALP is used primarily as an indicator of hepatobiliary disease, these other sources for elevation should be considered.

COMMENTARY: This article, available for free at www.vetclinpathjournal.org, is an in-depth review of ALP and a good reminder that not all elevations in ALP are due to liver disease. More research on the various isoenzymes may have other diagnostic potentials.

Alkaline phosphatase: Beyond the liver. Frenanez NJ, Kidney BA. VET CLIN PATHOL 36:223-233, 2007.