TRANSSPHENOIDAL HYPOPHYSECTOMY IN BEAGLE DOGS - EVALUATION OF A MICROSURGICAL TECHNIQUE

Objective-Assessment of a microsurgical technique for transsphenoidal hypophysectomy in dogs. Study Design-Prospective study using physical examination, pituitary function testing, computed tomography (CT), and histological examination at autopsy. Animals or Sample Population-Eig ht laboratory beagle dogs. Methods-Pituitary function was assessed bef ore and at 10 weeks after hypophysectomy by combined administration of four releasing hormones (anterior pituitary), administration of halop eridol (pars intermedia), and infusion of hypertonic saline (posterior pituitary). Results-CT imaging enabled accurate preoperative localiza tion of the pituitary. Appropriate positioning and surgical technique facilitated exposure of the pituitary and its extraction without hemor rhage. Postoperative recovery was generally uncomplicated. None of the eight dogs had somatotropic. gonadotropic, lactotropic, melanotropic, or posterior pituitary responses to stimulation at 10 weeks after hyp ophysectomy. Four dogs (ACTH nonresponders) also had no corticotropic response and four (ACTH responders) bad small but significant response s in the combined anterior pituitary function test. Adrenocortical atr ophy was more pronounced in the ACTH nonresponders than in the respond ers. No residual pituitary tissue was found along the ventral hypothal amic diencephalon but nests of pituitary cells were found embedded in fibrous tissue in the sella turcica. Conclusions-The surgical techniqu e proved to be safe and effective. Microscopic nests of pituitary cell s in the sella turcica may be responsible for residual corticotropic r esponse to hypophysiotropic stimulation after hypophysectomy.Clinical Relevance-The surgical technique may be used in the treatment of dogs with pituitary-dependent hyperadrenocorticism. The corticotropic respo nse is the most sensitive criterion in assessing completeness of hypop hysectomy in dogs. (C) Copyright 1997 by The American College of Veter inary Surgeons.