Feline Medicine Q&A 04

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A water deprivation test followed by an ADH response test has been performed in a cat with clinical signs and initial assessment consistent with diabetes insipidus. The water deprivation test was stopped after 8 hours as the cat was noted to be clinically dehydrated. Results are shown graphically. Following ADH administration the USG increased to 1.020.

Question	Answer		Article
What is the diagnosis?	The absence of change in USG following water deprivation is consistent with diabetes insipidus. The response to ADH is diagnostic of central diabetes insipidus.		Link to Article
What are the treatment options?	The treatment options include: As long as constant access to water is ensured so that the cat does not become dehydrated, and the owner is happy to live with a very polydipsic and polyuric cat, treatment is not mandatory. The owner should be informed of the risk of rapid, life-threatening dehydration which can occur if access to water is restricted or illness (e.g. vomiting or diarrhoea) occurs. Treatment with desmopressin, a synthetic analogue of ADH. Desmopressin is available as oral, parenteral, and intranasal preparations licensed for human use. A starting dose of 1–5 μg per cat once to twice a day is recommended; in general higher doses are required when oral dosing is used (e.g. 50 μg per cat twice daily). The intranasal preparation can be administered by the conjunctival route and comprises 100 μg/ml (one drop corresponds to 1.5–4 μg). The dose is modified to produce remission of clinical signs. In some cases, severe polydipsia is not completely controlled by desmopressin alone and non-hormonal treatment may be added to the regime. Chlorpropamide (40 mg/day) potentiates the renal tubular effects of ADH and can help to stabilize cats with central or partial central diabetes insipidus. It should be used with some caution in view of the fact that in humans it is a potent hypoglycaemic. Thiazide diuretics can also be used in this situation and have a paradoxical effect to reduce polyuria.		Link to Article
What is the prognosis?	The prognosis depends on the cause of the disease but is good with congenital and idiopathic central diabetes insipidus, as long as the cat has free access to water. Central diabetes insipidus has been reported following CNS trauma and may improve/resolve with time. Where central diabetes insipidus is associated with neoplasia, the prognosis is dependent on the rate of progression of the tumour.		Link to Article