Spontaneous hypercortisolism or Cushing's syndrome in dogs is due to a pituitary tumour (PT) or an adrenocortical tumour (AT), but concurrent PT and AT have also been reported. The objective of this retrospective study was to analyse the clinical and computed tomographic (CT) imaging data of a large group of dogs diagnosed with spontaneous hypercortisolism to report for concurrent PT and AT.

The clinical records of 202 dogs with spontaneous hypercortisolism, referred to the authors' institution, were reviewed. Diagnosis was based on physical and biochemical changes suggestive of hypercortisolism and confirmed by endocrine function tests. Endocrine tests revealing dexamethasone resistance in combination with an endogenous plasma ACTH concentration <40 ng/ml was interpreted as functional AT. In all dogs, pre- and postcontrast CT of both the pituitary gland and the adrenal glands was performed. A pituitary/brain (P/B) ratio >0.31 was interpreted as enlarged, consistent with a PT. Heterogeneous adrenal structure, asymmetric shape, and adrenal width >15 mm were consistent with an AT. Adrenal expansion into blood vessels greatly supported the diagnosis of an AT.

In dogs with suppressible hypercortisolism (122/202), 78 dogs (64%) showed an enlarged pituitary gland (median P/B ratio 0.43, range 0.32–1.21) on CT. Two of these 78 dogs were diagnosed with a concurrent AT. In the remaining dogs with suppressible hypercortisolism (44/122; 36%) a pituitary microadenoma (median P/B ratio 0.27, range 0.07–0.31) was diagnosed.

In the non-suppressible group (80/202), 47 of the 80 dogs (59%) had an enlarged pituitary gland (median P/B ratio 0.57, range 0.35–1.50) and in 8 of the 80 dogs (10%) a concurrent AT was present. In the remaining 33 dogs (41%) from this group, the pituitary gland was not enlarged (median P/B ratio 0.23, range 0.09–0.30). Among them, a pituitary microadenoma was diagnosed in 6 dogs. In the other 27 dogs, ATs (2 bilateral, 25 unilateral) were diagnosed and confirmed by a plasma ACTH concentration <40 ng/ml in all cases and by histopathology in 21/27 cases.

We conclude that concurrent adrenal and pituitary lesions are present mainly in dogs with non-suppressible hypercortisolism. Results of this study show that CT evaluation of both the pituitary and the adrenal glands should always be included in the diagnostic work-up of dogs with hypercortisolism to provide optimal treatment and prognosis.

Disclosures

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