Primary polydipsia in a cat.

Case summary: In cats, polyuria (PU) and polydipsia (PD) are defined as a urine specific gravity (USG) consistently <1.035 and water consumption >100 ml/kg/day. A 2-year-old castrated male domestic shorthair cat with PU/PD was brought to our hospital. Diagnostic tests for PU/PD included physical examination, blood analyses (complete blood count, serum chemistry profile, electrolytes, ionised calcium, symmetric dimethylarginine and thyroxine concentration), thoracic radiography, abdominal ultrasound examination, urinalysis, urine cortisol:creatinine ratio, urine protein:creatinine ratio and urine culture. A modified water deprivation test resulted in a USG >1.036 and cranial MRI did not identify any abnormalities. Therefore, the cat was administered desmopressin, which failed to decrease water consumption or increase the USG above the untreated level; thus, primary PD was confirmed.

Relevance and novel information: This rare case of feline primary PD is the first reported that did not identify evidence of structural pathology of the pituitary gland.