Prognostic factors for outcome after transsphenoidal hypophysectomy in dogs with pituitary-dependent hyperadrenocorticism

Abstract

Object The aim of this study was to determine prognostic factors for outcome after transsphenoidal hypophysectomy in dogs with pituitary-dependent hyperadrenocorticism (PDH). Methods One veterinary neurosurgeon performed transsphenoidal hypophysectomies in 181 dogs with PDH over a 12-year period. Survival analysis was performed with the Kaplan–Meier method. Prognostic factors were analyzed with the univariate Cox proportional hazard analysis followed by stepwise multivariate analysis. The log-rank test was used to assess disease-free fractions in three groups categorized according to early postoperative urinary corticoid/creatinine (C/C) ratios. Results Multivariate analysis revealed that old age, large pituitary size, and high preoperative concentrations of plasma adrenocorticotropic hormone were associated with an increased risk of PDH-related death. In addition, large pituitary size, thick sphenoid bone, high C/C ratio, and high concentration of plasma α-melanocyte–stimulating hormone (α-MSH) before surgery were associated with an increased risk of disease recurrence in the dogs that went into remission after hypophysectomy. Disease-free fractions were significantly higher in dogs with postoperative urinary C/C ratios in the lower normal range (< 5 × 10−6) than in dogs with postoperative C/C ratios in the upper normal range (5–10 × 10−6). Conclusions The results of this study indicate that pituitary size, sphenoid bone thickness, plasma α-MSH concentration, and preoperative level of urinary cortisol excretion are predictors of long-term remission after transsphenoidal hypophysectomy for PDH in dogs. Urinary C/C ratios measured 6 to 10 weeks after surgery can be used as a guide for predicting the risk of tumor recurrence.