Canine Hypoadrenocorticism and Other Adrenal Issues (Rolph)

Question 1

Define hypoadrenocorticism.

Answer 1

Deficiency of glucocorticoids and/or mineralocorticoids.

Question 2

What are the functions of the adrenal glands?

Answer 2

• Aldosterone secretion (influenced by K+ and AngIII [and Na, ACTH]) - Glucocorticoid secretion (ACTH)

Question 3

What are the causes of hypoadrenocorticism?

Answer 3

Results from:

• Adrenal cortex destruction (primary hypoadrenocorticism)
• Deficiency in ACTH production (secondary hypoadrenocorticism)

Question 4

What are the causes of primary hypoadrenocorticism?

Answer 4

Destruction of adrenal cortex

• Idiopathic
• Immune-mediated
• Infiltrative disease (i.e. lymphoma, amyloidosis, granulomatous disease)
• Hemorrhagic infarction
• Iatrogenic destruction

Question 5

What is primary hypoadrenocorticism?

Answer 5

When ≥ 90% of the gland is destroyed

• Lack of mineralocorticoid
• Glucocorticoid deficiency

Question 6

What occurs if only the zona fasiculata is affected?

Answer 6

Atypical hypoadrenocorticism

Question 7

What is secondary hypoadrenocorticism?

Answer 7

Decreased ACTH production

• Most frequently associated w/ drug administration (i.e. corticosteroids or progestogens)
• Underlying hypothalamic-pituitary disorder (tumor, trauma, congenital defect)
• Mineralocorticoid production unaffected (electrolytes normal)

Question 8

What is the signalment for hypoadrenocorticism?

Answer 8

• Any age dog (reported from 4wks to 16 yrs; avg. 4-5 yrs.)
• Female predisposition (some breeds, i.e. Portuguese Water Dogs, Bearded Collie, Standard Poodle, have equal M:F)
• Any breed affected (most common: Great Dane, Poodle, WHWT, Rottweiler, Soft-coated Wheten Terrier, SpSp, Bassett, Nova Scotia duck tolling retriever)

Question 9

What are the pathogonomic signs of hypoadrenocorticism?

Answer 9

**NO PATHOGONOMIC CS**

• Waxing/waning/vague disease affecting multiple body systems
• Often have prolonged ‘problems’
• Usually chronic condition but can have acute presention (especially after ‘stressful’ event)

Question 10

What are some clinical signs of hypoadrenocorticism?

Answer 10

• Poor appetite/anorexia
• Lethargy/depression
• Vomiting/regurgitation
• Weight loss
• Weakness
• Dehydration
• Bradycardia (in a collapsed or dog in shock, should raise suspicion of hyperkalemia)

Question 11

What are some laboratory findings of hypoadrenocorticism?

Answer 11

• Hyperkalemia, hyponatremia, hypochloremia = most consistent
• Sodium:Potassium ratio < 21:1 (sometimes 20:1)
  
  • Sensitive for primary hypoadrenocorticism but not specific
• Mild, normocytic, normochromic non-regenerative anemia
• Lack stress leukogram
• Azotemia
• Hyperphosphatemia (decreased GFR)
• Elevated iCa
• Hypoglycemia, hypoalbuminemia
• Mild/moderate increased in ALT, AST
• USG: typically < 1.030 (sodium loss → medullary washout)

Question 12

What’s a laboratory finding in dogs with atypical hypoadrenocorticism?

Answer 12

Typically have normal Na:K

Question 13

What may show on diagnostic imaging for hypoadrenocorticism?

Answer 13

• Radiography: possible signs of hypovolemia
• Ultrasound: decreased adrenal gland size

Question 14

Other tests and results for hypoadrenocorticism?

Answer 14

• Blood pressure may be low
• ECG: normal → hyperkalemia

Question 15

How do you diagnose hypoadrenocorticism?

Answer 15

• Low basal cortisol (> 50 units RULES OUT hypoadrenocorticism)
  
  • Not diagnostic but a rule-out
• ACTH stimulation test (show adrenals aren’t producing; flat line low)

Question 16

How do you treat hypoadrenocorticism?

Answer 16

• Aggressive IVF
• Address hyperkalemia/dysrhythmias
• Glucocorticoid replacement (IV dexamethasone; prenisolone)
• Mineralocorticoid replacement (fludrocortisone acetate or DOCP IM)

Question 17

How long does it take for a patient to typically respond to hypoadrenocorticism treatment?

Answer 17

1-2 days

Question 18

What’s the prognosis of hypoadrenocorticism?

Answer 18

Excellent (possible MST of 4.7 years)

Question 19

What is a phaechromocytoma?

Answer 19

Uncommon neuroectodermal tumor coming from chromaffin cells within the adrenal medulla

• If extra-adrenal chromaffin cells involved → paraganglioma

Question 20

What is the signalment of a phaeochromocytoma?

Answer 20

• Rare in dogs and cats
• No breed or gender predisposition (except cats: all were DSH)
• Dog mean age: 10.5 years (1-26 years)
• Cat age: 7-18 years

Question 21

What are some clinical signs of a phaeochromocytoma?

Answer 21

May be intermittent signs, non-specific

• Hypertension
• Hind limb edema
• Acute blindness
• Lethargy
• Adipsia
• PU/PD
• Seizures
• Weight loss

Question 22

What does a physical exam of a patient with a phaeochromocytoma look like?

Answer 22

Normal in many

• Increased bronchovesicular or alveolar sounds (pulmonary hypertension → congestion, edema)
• Tachypneic on auscultation
• Abdominal mass (25% dogs, 33% cats)
• Hyperemic mucous membranes
• Hind limb edema (caudal vena cava invasion)

Question 23

How do you diagnose a pheochromocytoma?

Answer 23

• BP (may have intermittent hypertension)
• Unremarkable bloodwork, biochemistry, urinalysis
• May find mass on CT, U/S, or abdominal rads (but doesn’t determine if functional mass)
• Measure plasma/urinary metabolites (normetanephrine, metanephrine, vanillymandelic acid all from norepinephrine and epinephrine)

Question 24

What is treatment for a pheochromocytoma?

Answer 24

• Phenoxybenzamine (hypertension control)
• Surgical removal

Question 25

What’s the prognosis in dogs with a pheochromocytoma?

Answer 25

50% malignant

• If not metastasized: survival post-op 18 mos.-2 years
• If benign and surgery successful, can live normal life

Question 26

What’s the prognosis in cats with a pheochromocytoma?

Answer 26

Highly variable