The ins and outs of polyuria and polydipsia in veterinary practice
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:
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.