Urine Ketones

The ketone pad on the multi-reagent dip stick detects mainly acetoacetic acid and acetone (to a far lesser extent); β-hydroxybutyrate is not detected. The ketones react with sodium nitroprusside which forms a purple color change.

The table below illustrates how results from the dipstick (Multistix) correlates to those from the Criterion, the machine used to "read" the dipstick at Cornell University.

Ketonuria indicates deranged energy metabolism such that fat is used instead of glucose. This usually occurs in states of negative energy balance, where energy intake does not meet demands. Fat metabolism can result in production of the ketone bodies in amounts greater than can be metabolized by peripheral tissue; filtration into urine in excess of tubular reabsorption then results in ketonuria. Some specific causes include:

• Unregulated diabetes mellitus in dogs and cats
• Pregnancy toxemia in sheep, camelids
• Bovine ketosis
  (For more information on pregnancy toxemia and bovine ketosis, refer to the Glucose, BHB and NEFA sections of the Clinical Chemistry module.)
• Starvation or malnutrition, especially in immature animals

Because the color change on the dipstick can be quite subtle, positive reactions are confirmed with the Acetest. This comes in tablet form and contains lactulose to enhance the color change. The reaction with the Acetest is much more apparent than on the dipstick pad.