Complete Surgical Removal of a Very Enlarged Pituitary Corticotroph Adenoma in a Dog

A 13 yr old castrated male vizsla was referred to the authors' institute because of polyuria, polydipsia, polyphagia, and weight loss. Pituitary-dependent hypercortisolism (PDH) was diagnosed by hormone testing and adrenal and pituitary imaging. Computed tomography (CT) revealed a pituitary mass measuring 21 mm in width. Medical therapy was initiated with trilostane. Despite adequate control of the hypercortisolemia, the polyuria and polydipsia persisted and the dog developed neurologic signs due to the pituitary mass effect. Pituitary transsphenoidal debulking surgery was performed and immunocytochemistry confirmed a corticotroph adenoma. The dog survived for 13 mo after surgery. Postmortem examination revealed an empty fossa without pituitary remnants and the presence of a malignant pheochromocytoma in the right adrenal gland. This case report demonstrates, for the first time, that a large pituitary adenoma in the dog may be treated successfully by pituitary surgery.