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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com canine PiTuiTary dePendenT HyPeradrenocorTicism series Peer reviewed 42 and imaging modalities are available to diagnose HAC and distinguish between the various causes of hypercortisolism. No single test is perfect and, if the initial screening test is negative and high clinical suspicion of HAC exists, additional tests should be performed. Endocrine evaluation of patients with HAC and nonadrenal illness can be diffcult, and it is important to eliminate or manage the concurrent illness before undertaking adrenal function tests. ACTH = adrenocorticotropic hormone; ADH = adrenal dependent hyperadrenocorticism; AT = adrenocortical tumor; cACTH = canine ACTH; CT = computed tomography; HAC = hyperadrenocorticism; HDDS = high-dose dexamethasone suppression; LDDS = low-dose dexamethasone suppression; MRI = magnetic resonance imaging; PA = pituitary adenoma; PDH = pituitary dependent hyperadrenocorticism; UCCR = urine cortisol to creatinine ratio References 1. Behrend EN, Kooistra HS, Nelson R, et al. Diagnosis of spontaneous canine hyperadrenocorticism: 2012 ACVIM consensus statement (small animal). J Vet Intern Med 2013; 27:1292-1304. 2. Feldman EC, Feldman MS, Nelson RW. Use of low and high-dose dexamethasone tests for distinguishing pituitary dependent from adrenal tumor hyperadrenocorticism in dogs. JAVMA 1996; 9:772-775. 3. Feldman EC. Comparison of ACTH response and dexamethasone suppression as screening tests in canine hyperadrenocorticism. JAVMA 1981; 182:506-510. 4. Meijer JC, de Bruijne JJ, Rijnberk A, Croughs RJM. Biochemical characterization of pituitary-dependent hyperadrenocorticism in the dog. J Endocrinol 1978; 77:111-118. 5. Meijer JC, Lubberink AAME, Rijnberk A, Croughs JM. Adrenocortical function tests in dogs with hyperfunctioning adrenocortical tumors. J Endocrinol 1979; 80:315-319. 6. Mack RE, Feldman EC. Comparison of two low-dose dexamethasone suppression protocols as screening and discrimination tests in dogs with hyperadrenocorticism. JAVMA 1990; 197:1603-1606. 7. May ER, Frank LA, Hnilica KA, Lane IF. Effects of a mock ultrasonographic procedure on cortisol concentrations during low-dose dexamethasone suppression testing in clinically normal adult dogs. Am J Vet Res 2004; 65:267-270. 8. Rijnberk A, van Wees A, Mol JA. Assessment of two tests for the diagnosis of canine hyperadrenocorticism. Vet Rec 1988; 122:178-180. 9. van Liew CH, Greco DS, Salman MD. Comparison of results of adrenocorticotropic hormone stimulation and low-dose dexamethasone suppression test with necropsy fndings in dogs: 81 cases (1985-1995). JAVMA 1997; 211:322-325. D Av ID BRUYETTE David Bruyette, DVM, Diplomate ACVIM, is the medical director at VCA West Los Angeles Animal Hospital and President and CEO of Veterinary Diagnostic Investigation and Consultation. He was an assistant professor and head of internal medicine at Kansas State University and director of its Analytical Chemistry Laboratory. Dr. Bruyette received his DVM from University of Missouri and completed an internship at Purdue University and residency in internal medicine at University of California–Davis. He then became a staff internist at West Los Angeles Veterinary Medical Group and member of the Department of Comparative Medicine at Stanford University. FIGURE 5. Axial (A) and sagittal (B) T1 post contrast MRI images from a dog with PDH prior to surgery. Note the pituitary (arrows). A B FIGURE 6. Axial (A) and sagittal (B) T1 post contrast MRI images from dog in Figure 5 after surgery. B A