Dennis

‘Dennis’, a 45kg, 8 year old, male neutered Boxer dog presented with a 3 week history of polyuria and polydipsia, with unusual behavioural changes. Clinical examination was unremarkable and haematology/biochemistry including dynamic bile acids were within normal ranges. Urinalysis demonstrated minimally concentrated urine (USG: 1.019) but was otherwise unremarkable with negative urine culture.

Primary differential diagnoses included endocrine disease, infectious disease and neoplasia.

Several typical clinical and laboratory signs of hyperadrenocorticism were not present - the size of the dog meant that a comprehensive abdominal ultrasound would be challenging and may not be definitive. We decided to perform CT imaging of the brain, thorax and abdomen.

CT identified a pituitary mass lesion that was most likely neoplastic. Bilaterally enlarged adrenal glands were also detected. The main differential was that of a functional pituitary tumour: likely a macroadenoma with secondary pituitary-dependant hyperadrenocorticism. A low-dose dexamethasone test was performed, confirming pituitary-dependent Cushings disease and the PUPD resolved on trilostane medication.

The owner was warned that given the presence of a suspected macroadenoma, neurological signs and/or progression of the behavioural changes may occur. Radiation therapy and hypophysectomy were discussed as additional management options.

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