Urinalysis - Ketones
Introduction
Ketone bodies include acetone, beta-oxybutyric acid (hydroxybutyrate) and acetoacetic acid. They are formed in the liver if the body is deficient in carbohydrates and in case of increased lipid decomposition (i.e. when the process of lipolysis is more pronounced than the process of lipogenesis). The increased concentration of fatty acids leads to the formation of high amounts of acetoacetyl-CoA, from which acetoacetic acid is formed. The acetoacetic acid is influenced by hydroxybutyrate dehydrogenase, producing beta-oxybutyric acid. This is a reversible process, as differentiated from the irreversible process of acetoacetic acid conversion into acetone.
The occurrence of ketone bodies in the blood and urine is known as ketonemia and ketonuria, respectively. The accumulation of ketone bodies leads to acidosis, which may result in ketone coma or death. Acetone is mostly eliminated by the lungs, and via kidneys along with acetoacetic acid. The amount of acetoacetic acid is about 10 times greater than the amount of excreted acetone. A urine containing a considerable amount of acetone has a fruit-like odor, while acetoacetic acid and beta-oxybutyric acid are odorless substances. Ketonuria may be a sequel of diabetes, starvation, low-carbohydrate diet, elevated body temperature, etc.
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