Magnetic resonance imaging of the brain in dogs with recently diagnosed but untreated pituitary-dependent hyperadrenocorticism

Elizabeth H. Bertoy From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Edward C. Feldman From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Richard W. Nelson From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Cynthia A. Duesberg From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Philip H. Kass From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Michael H. Reid From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Arthur B. Dublin From the Veterinary Medical Teaching Hospital (Bertoy, Duesberg), the Departments of Medicine (Feldman, Nelson) and Epidemiology and Preventive Medicine (Kass), School of Veterinary Medicine, University of California, Davis, CA 95616, and Diagnostic Radiologic Imaging, Sacramento, CA 95825 (Reid, Dublin).

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Summary

Magnetic resonance imaging was used to determine the prevalence of visible pituitary masses in 21 dogs with recently diagnosed and untreated pituitary-dependent hyperadrenocorticism. All dogs had clinical signs and routine database values (CBC, serum biochemical panel, and urinalysis) consistent with a diagnosis of hyperadrenocorticism, and none had clinical signs suggestive of an intracranial mass. Each dog had plasma cortisol concentrations after adrenocorticotropic hormone administration or low-dose dexamethasone administration consistent with hyperadrenocorticism. Pituitary-dependent hyperadrenocorticism was confirmed by the finding of 2 equal-size adrenal glands on abdominal ultrasonography and by results of plasma endogenous adrenocorticotropic hormone concentration and high-dose dexamethasone suppression testing. Sagittal and transverse Tl-weighted magnetic resonance images of the brain were obtained before and after IV administration of gadopentenate dimeglumine.

Eleven dogs had visible masses, ranging in size from 4 to 12 mm at greatest vertical height. Mean age and body weight of dogs with a visible pituitary mass was not significantly different from dogs without a visible mass. There was no significant difference in endocrine test results when comparing dogs with a visible pituitary mass to dogs without. The prevalence of visible pituitary masses in dogs with pituitary-dependent hyperadrenocorticism was greater than suggested by the prevalence of clinical neurologic signs.

Summary

Magnetic resonance imaging was used to determine the prevalence of visible pituitary masses in 21 dogs with recently diagnosed and untreated pituitary-dependent hyperadrenocorticism. All dogs had clinical signs and routine database values (CBC, serum biochemical panel, and urinalysis) consistent with a diagnosis of hyperadrenocorticism, and none had clinical signs suggestive of an intracranial mass. Each dog had plasma cortisol concentrations after adrenocorticotropic hormone administration or low-dose dexamethasone administration consistent with hyperadrenocorticism. Pituitary-dependent hyperadrenocorticism was confirmed by the finding of 2 equal-size adrenal glands on abdominal ultrasonography and by results of plasma endogenous adrenocorticotropic hormone concentration and high-dose dexamethasone suppression testing. Sagittal and transverse Tl-weighted magnetic resonance images of the brain were obtained before and after IV administration of gadopentenate dimeglumine.

Eleven dogs had visible masses, ranging in size from 4 to 12 mm at greatest vertical height. Mean age and body weight of dogs with a visible pituitary mass was not significantly different from dogs without a visible mass. There was no significant difference in endocrine test results when comparing dogs with a visible pituitary mass to dogs without. The prevalence of visible pituitary masses in dogs with pituitary-dependent hyperadrenocorticism was greater than suggested by the prevalence of clinical neurologic signs.

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