Congenital pituitary cyst resulting in adipsic central diabetes insipidus and secondary hypernatremia in a cat.

case summaryA 9-month-old intact female domestic mediumhair cat presented with a 5-month history of obtundation, lethargy, hypernatremia (181 mmol/l; reference interval [RI] 151-158 mmol/l), hyperchloremia (142 mmol/l; RI 117-126 mmol/l), azotemia (blood urea nitrogen 51 mg/dl; RI 18-33 mg/dl), creatinine 3.0 mg/dl (RI 1.1-2.2 mg/dl), hyperphosphatemia (8.3 mg/dl; RI 3.2-6.3 mg/dl) and total hypercalcemia (11.4 mg/dl; RI 9-10.9 mg/dl), with concurrent polyuria with adipsia. Neurologic evaluation revealed proprioceptive deficits, and this finding paired with a history of focal seizure-like activity despite improving sodium concentrations suggested a cerebrothalamic lesion. For this reason, and historical and biochemical findings consistent with adipsic diabetes insipidus (DI), MRI of the brain was performed, which revealed a lesion of the hypophyseal fossa consistent with a pituitary cyst. Given the patient's age and the timeline of clinical signs, a congenital pituitary cyst was strongly suspected. The patient was managed initially with intravenous fluids to correct the hypernatremia, then managed for more than 4 years with topical ocular desmopressin acetate administration and free water administered through a feeding tube. This cat's clinical diagnosis included a congenital pituitary cyst with subsequent central DI and primary adipsia. RELEVANCE AND NOVEL INFORMATION: The clinical presentations of primary adipsia or central DI are both rare in cats. This is the first report to describe these conditions occurring in a cat owing to a congenital pituitary cyst and describes successful long-term management of this condition.