Vasopressin Response to Osmotic Stimulation in 18 Young Dogs with Polyuria and Polydipsia

Abstract

Common disorders of water homeostasis leading to polyuria include a variety of endocrine, metabolic, and renal disturbances. After exclusion of most of these conditions, the diagnostic dilemma of differentiating between central diabetes insipidus, primary polydipsia, and nephrogenic diabetes insipidus may remain. Here, we report on 18 young dogs with polyuria that had been present in most cases since the dogs were puppies. The conditions were categorized according to the plasma vasopressin (VP) response to hypertonicity. The VP response to osmotic stimulation was tested by IV infusion of 20% NaCl for 2 hours. The VP response in all dogs was abnormal. Three categories could be distinguished: an exaggerated response (n = 3), a subnormal response (n = 4), and a nonlinear response with high plasma VP concentrations unrelated to increases in plasma osmolality (n = 11). The VP response to hypertonicity did not consistently distinguish among different clinical entities. In the 9 dogs with variations in urine osmolality compatible with primary polydipsia, exaggerated, subnormal, and nonlinear responses were observed. Examination of the present data questions the generally accepted notion that VP measurements during hypertonic saline infusion are the "gold standard" for the diagnostic interpretation of causes of polydipsia and polyuria. Studies of the peripheral reflection in plasma of the pulsatile VP release in healthy and polyuric individuals, with and without osmotic provocation, should be performed.

Transient distal renal tubular acidosis with nephrogenic diabetes insipidus after general anaesthesia in a dog

“…A water deprivation test is usually performed to diagnose DI, but this test should be performed on well-hydrated dogs under careful medical supervision and should not be performed if the dog is considered to be at risk (Etish et al, 2014;van Vonderen et al, 2004).…”

“…A water deprivation test is usually performed to diagnose DI, but this test should be performed on well‐hydrated dogs under careful medical supervision and should not be performed if the dog is considered to be at risk (Etish et al., 2014 ; van Vonderen et al., 2004 ). The present case was 7% dehydrated, exceeding the dehydration level of 5% required for the water deprivation test (Feldman et al., 1996 ).…”

Desmopressin acetate-induced water intoxication in a dog with psychogenic polydipsia

“…After exclusion of causes for acquired nephrogenic DI, the differentiation between central DI, primary nephrogenic DI and psychogenic PD is based on results of the MWDT, response to DDAVP trial therapy and measurement of plasma osmolality 1. Measurement of plasma vasopressin concentrations under osmotic stimulation has been called into question, as findings were inconsistent and could not distinguish between different disorders 17. Although the MWDT is considered the best differentiating tool, it is time-consuming, expensive and unpleasant for the patient.…”