The ins and outs of polyuria and polydipsia in veterinary practice

There are many terms used to describe abnormalities in urine production. Here we set out to provide a concise reference for the most common ones you'll encounter in veterinary practice.
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Apr 01, 2014


GETTY IMAGES/AMANDA ROHDE
Recently a colleague asked us if we could direct her to a reference source for normal and abnormal drinking and urine volumes for cats and dogs. Although this information is available, it is scattered in different textbooks and journal articles. The primary objective of this article is to provide this information in one concise location.

What is polydipsia?

Polydipsia is defined as increased thirst or greater-than-normal water consumption. Daily maintenance water requirements for dogs may be calculated from this formula:
140 x (body weight in kg)0.75

Daily water requirements for cats may be calculated from this formula:
80 x (body weight in kg)0.75

Normal water consumption usually will not exceed approximately 90 ml/kg/day in dogs or 45 ml/kg/day in cats. If water consumption is greater than 90 ml/kg/day in dogs or 45 ml/kg/day in cats, the animal is considered to have polydipsia.

What is a normal volume of urine?

Normal urine volume is influenced by several variables. It has been estimated that healthy adult dogs in a normal environment will produce approximately 20 to 40 ml/kg of urine every 24 hours (1 to 2 ml/kg/hour). In one study, healthy adult cats produced an average of 28 ml/kg of urine every 24 hours.

Newborn puppies have a comparatively limited ability to concentrate or dilute urine in response to changes in extracellular fluid volume. Puppies and kittens are predisposed to rapid dehydration as a result of their higher water requirements, their comparatively greater insensible water losses and their decreased ability to maximally concentrate urine.