Central Diabetes Insipidus in a Cat

Background: Diabetes insipidus is a rare disease in cats with few reports in the scientific literature. It has two major forms: Central Diabetes Insipidus (CDI); characterized by decreased secretion of antidiuretic hormone (ADH), and Nephrogenic Diabetes Insipidus (NDI); characterized by decreased ability to concentrate urine because of resistance to ADH. The diagnosis is based on excluding diseases with polydipsia/polyuria, the water deprivation test and response to desmopressin. This case report describes Central Diabetes Insipidus in a domestic cat, as well as its response to desmopressin administered intranasally. Case: A 2-year old, male cat of non-defined breed and castrated was seen due to a history of polyuria and polydipsia (PU/PD) that arose after allegedly ingesting thorns that got stuck to its body while going out of the house. Physical examination revealed an active well-fed animal with mild dehydration and persistent paradoxical ischuria. The complementary tests performed: abdominal ultrasound, blood test, urinalysis, serum urea, creatinine, glucose, cortisol, total T4, Total T3 and vasopressin, were within the reference values, except for urinary density and T4 that were below the standard. Based on the laboratory results, conditions compatible with PU and PD symptoms were excluded; however, despite normal vasopressin levels, diabetes insipidus was not ruled out, given the prevailing clinical manifestations. The water deprivation test was dispensed to the patient in the face of dehydration accompanied by hyposthenuria, keeping the patient dehydrated despite polydipsia and water availability. This was followed by the response to desmopressin given intranasally, where gradual increase of urinary density and consistent reduction in urinary volume over time were observed. The findings confirmed the Central Diabetes Insipidus diagnosis. The home therapy treatment consisted of intranasal administration of 10 mu g desmopressin of continuous use, every 24 h. Discussion: ADH or vasopressin is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and released by the posterior lobe of the pituitary gland. Its main role is to maintain water homeostasis in the body. This hormone secretion is regulated by the osmolarity of body fluids, volume and pressure of the vascular system. The animals with central diabetes insipidus condition display failing ADH secretion, resulting in water intake generally superior to 100 mL/kg/day (Normal: 40-70 mL/kg/day) and the clinical symptoms, PU and PD, weight loss and dehydration, the latter when deprived of water intake. The cat in the study displayed acute symptoms. However, the lack of neurologic symptoms commonly observed in animals with diabetes insipidus caused by either trauma or brain neoplasms, and physical examination findings that could explain the origin of the disease, raised doubts about the triggering event. Therefore, it is believed that in the reported case the nature of the disease is idiopathic. The diagnosis was reached by excluding major diseases with the same symptoms, PU and PD, plus by the water deprivation test and response to intranasal administration of desmopressin. Given the normal level of DHA serum recorded, its measurement was not an efficient diagnosis method for DIC. The use of intranasal desmopressin was a good administration route for the species given the absence of discomfort, good applicability and the excellent clinical response observed, thus constituting an excellent therapeutic method for continuous use in cats.