Page 893 - Small Animal Internal Medicine, 6th Edition

CHAPTER 50 Disorders of the Adrenal Gland 865

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A B

FIG 50.9
Ultrasound images of the adrenal glands in a 10-year-old female spayed Bichon Frise
presented for acute onset of vomiting. (A) An unexpected mass involving the right adrenal
gland, measuring 1.4 cm in maximum diameter, was identified (arrows). (B) The left
adrenal gland was normal in size and shape (arrows); the maximum diameter was
0.6 cm. The normal-size left adrenal gland suggests that the right adrenal mass is a
pheochromocytoma or is nonfunctional. Results of routine blood work and of tests for
hyperadrenocorticism were normal.

A B

FIG 50.10
Ultrasound images of the adrenal glands (arrows) in an 11-year-old female spayed Shih
Tzu. The right adrenal gland (A) measured 1.8 cm in maximum diameter and had a
nodular echogenic pattern. In contrast, the left adrenal gland (B) had a large nodule
located in each pole of the gland; each measured approximately 1.4 cm in maximum
diameter. Tests of the pituitary-adrenocortical axis were diagnostic for pituitary-dependent
hyperadrenocorticism; this finding, in conjunction with the findings on ultrasound, suggests
macronodular hyperplasia of the adrenal glands.

diagnostic testing for hyperadrenocorticism, and results of ACTH concentration is evaluated when abdominal ultra-
an abdominal ultrasound may include valuable information sound suggests an adrenal mass but results of the LDDS test
regarding probable location of the lesion. Tests to establish are inconclusive or suggest PDH, and when an adrenal mass
the diagnosis of hyperadrenocorticism include the urine is identified with contralateral adrenomegaly.
cortisol/creatinine ratio (UCCR), the ACTH stimulation Baseline serum cortisol measurement, by itself, provides
test, the low-dose dexamethasone suppression (LDDS) test, no diagnostic value in diagnosing hyperadrenocorticism. We
and the oral dexamethasone suppression test (Table 50.2). use the ACTH stimulation test to establish the diagnosis of
Discriminatory tests are used to identify the cause (i.e., PDH hypoadrenocorticism, to identify iatrogenic hyperadreno-
versus ATH) in dogs with confirmed hyperadrenocorticism corticism, and to monitor trilostane and mitotane treatment.
and include the LDDS test, the high-dose dexamethasone We do not routinely use the ACTH stimulation test to diag-
suppression (HDDS) test, and baseline endogenous ACTH nose hyperadrenocorticism because of problems with sensi-
concentration. Tests that we commonly use to establish the tivity and specificity. We never establish the diagnosis of
diagnosis of hyperadrenocorticism are UCCR in conjunc- hyperadrenocorticism solely on the basis of results of an
tion with the LDDS test, and tests that we commonly use to ACTH stimulation test.
identify the cause (i.e., PDH versus ATH) include the LDDS Indicators for performing diagnostic tests for hyperadre-
test and abdominal ultrasound. The HDDS test can be used nocorticism recommended by the 2012 American College of
if abdominal ultrasound is not available. An endogenous Veterinary Internal Medicine (ACVIM) consensus statement