Concurrent pituitary and adrenocortical lesions on computed tomography imaging in dogs with spontaneous hypercortisolism

BACKGROUND: Spontaneous hypercortisolism or Cushing's syndrome in dogs is either pituitary or adrenal dependent, but concurrent pituitary and adrenal hypercortisolism also has been reported. OBJECTIVE: To determine how often concurrent pituitary and adrenal lesions are present in dogs with spontaneous hypercortisolism. ANIMALS: Two hundred one client‐owned dogs with spontaneous hypercortisolism. METHODS: Retrospective study. Pre‐ and post‐contrast computed tomography (CT) scans of the pituitary and adrenal glands were performed in dogs with confirmed hypercortisolism. RESULTS: In dogs with dexamethasone‐suppressible hypercortisolism (122/201), 78 dogs (64%) had an enlarged pituitary gland (median pituitary height/brain area [P/B], 0.43 × 10(−2) mm(−1); range, 0.32‐1.21 × 10(−2) mm(−1)). Two of these 78 dogs had concurrent adrenal lesions. In the remaining dogs (44/122; 36%), the pituitary gland was not enlarged. In the dexamethasone‐resistant group (79/201), the pituitary gland was enlarged in 47 dogs (59%; median P/B, 0.57 × 10(−2); range, 0.32‐1.50 × 10(−2) mm(−1)). Eight of these 47 dogs (17%) had concurrent adrenal lesions. In the remaining 32 dexamethasone‐resistant dogs (41%), the pituitary gland was not enlarged. Among them, 27 dogs had adrenal lesions and suppressed ACTH concentrations consistent with adrenal‐dependent hypercortisolism and 5 dogs were diagnosed with pituitary‐dependent hypercortisolism. CONCLUSIONS AND CLINICAL IMPORTANCE: Concurrent pituitary and adrenal lesions were present in 5% of all dogs with hypercortisolism and in 10% of the dexamethasone‐resistant dogs. Diagnostic imaging of both pituitary and adrenal glands should be included in the diagnostic evaluation of every dog with spontaneous hypercortisolism to obtain information needed for estimation of prognosis and choosing the optimal treatment.