Psychogenic polydipsia

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Psychogenic polydipsia is a central nervous disorder of dogs characterized by polydipsia (≥ 100 ml/kg/day).

Affected dogs often compulsively search for water and have clinically measurable hyponatremia.

In humans, this is often associated with psychiatric disorders and patients present with intracranial hypertension, lethargy, seizures and in severe cases, death[1].

In dogs, clinical symptoms are usually absent in association with polydipsia, apart from polyuria, as they rarely exceed their renal excretory capacity of 200ml/kg/day.

A history of head injury may be present, alluding to central nervous damage, particularly the thalamus and adenohypophysis.

Diagnosis is one of exclusion, with blood tests and a modified water deprivation test used to eliminate other differential diagnoses, particularly central diabetes insipidus[2].

Other causes of polydipsia which should be exclude in a differential diagnosis include:

Blood tests, with examination of hematology, biochemistry and thyroxine levels, together with urinalysis and bacterial culture, will help to exclude other causes.

Ultrasonography is recommended to exclude renal lymphoma, renal dysplasia, polycystic kidney disease, etc.

A trial therapy desmopressin acetate should be undertaken to rule out central diabetes insipidus or nephrogenic diabetes insipidus.

Administration of 0.2 mg desmopressin tablet orally every 8 hours or 1 to 4 drops of nasal spray should cause a decrease in polydipsia if central diabetes insipidus is the cause, with minimal improvement with nephrogenic diabetes insipidus and psychogenic polydipsia.

References

  1. Soupart A & Decaux G (1996) Therapeutic recommendations for management of severe hyponatremia: Current concepts on pathogenesis and prevention of neurologic complications. Clin Nephrol 46:149–69
  2. Olenick CL et al (1999) Congenital renal dysplasia and psychogenic polydipsia in a Bernese mountain dog. Can Vet J 40(6):425-426
  3. Grünbaum EG & Moritz A (1991) The diagnosis of nephrogenic diabetes insipidus in the dog. Tierarztl Prax 19(5):539-544
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