Small Animal Dermatology, 3rd edition

CHAPTER 26 HYPERADRENOCORTICISM, CANINE 397

DIAGNOSTICS

 Hemogram: eosinopenia, lymphopenia, neutrophilic leukocytosis, erythrocytosis,

thrombocytosis.

 Serum chemistry: elevated alkaline phosphatase in over 80% of cases, mild increase

in ALT, hypercholesterolemia, hypertriglyceridemia; 5–10% of dogs may have hyper-

glycemia (diabetes), decreased blood urea nitrogen (BUN) concentration; thyroid val-

ues may be low.

 Urinalysis: may reveal decreased specific gravity (<1.018), proteinuria secondary

to glomerulopathy/glomerular sclerosis, hematuria, pyuria, or increased numbers of

bacteria in urine.

 Urine cortisol-creatinine ratio (UCCR): highly sensitive test; not specific (nonadrenal

diseases may cause an elevated UCCR).

 Abdominal radiographs: may show hepatomegaly; approximately 50% of adrenal

tumors will be mineralized and visible on radiographs.

 Thoracic cavity radiographs: may show bronchial calcification or metastasis from an

adrenal adenocarcinoma; osteopenia may also be identified.

 Ultrasonography/CT/MRI: useful for differentiating PDH from ADH and for staging

ADH.

 CT and MRI: often useful for demonstrating macroadenomas.

 Pathology (PDH): gross examination reveals normal-sized pituitary to pituitary

macroadenoma and bilateral adrenocortical enlargement; microscopic – evaluation

for pituitary corticotroph hyperplasia or adenoma of pars distalis or pars intermedia

and adrenocortical hyperplasia.

 Pathology (ADH): gross examination reveals variable-sized adrenal mass, atrophy of

contralateral gland (rarely, bilateral tumors), and metastasis in some patients with

adrenal carcinoma; microscopic – evaluation for adrenocortical adenoma or carci-

noma.

Screening Tests

 Screening tests for HAC: ACTH stimulation test, LDDST, and UCCR.

 ACTH stimulation test:
Used to diagnose HAC: cannot distinguish between PDH and ADH
ACTH stimulation test assesses adrenocortical reserve
Best test for monitoring response to adrenolytic therapy or adrenal enzyme

blockers

ACTH stimulation test: PDH cases; sensitivity 80–83%, specificity 59–93%

Inferior (due to low sensitivity) as a screening test for spontaneous HAC to low-

dose dexamethasone suppression test (LDDST)

ACTH stimulation test often performed as a first step because of a shorter time

to complete the test (1–2 hours versus 8 hours for LDDST)

Postpone testing if the patient has a concurrent serious illness to minimize false-

positive test results