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CFT II > Exam 3 - Adrenal Masses > Flashcards

Exam 3 - Adrenal Masses Flashcards

1
Q

what is the general feedback loop occurring in pituitary-dependent hyperadrenocorticism?

A

the anterior pituitary gland, usually due to a tumor, releases large amounts of stimulating hormone (ACTH)

this causes the target organs, the adrenal glands, to produce large amounts of cortisol

the large amount of cortisol released starts a negative feedback loop with the hypothalamus, so very small amounts, if any, of releasing hormone is produced

however, the anterior pituitary continues to release large amounts of ACTH which results in the large production & release of cortisol in the body which is why we see clinical signs

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2
Q

what does ACTH target?

A

the cortex of the adrenal glands - produces cortisol/corticosteroids

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3
Q

what are the 3 parts that make up the adrenal cortex?

A
  1. zona glomerulosa - top layer & produces aldosterone
  2. zona fasciculata - middle layer & produces cortisol
  3. zona reticularis - deepest layer & produces androgens
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4
Q

what are the 3 general ways in which we see hyperadrenocorticism in companion animals?

A
  1. most common is pituitary dependent - secondary level problem, ACTH-producing tumor of anterior pituitary
  2. primary level - functional adrenal cortical tumor
  3. iatrogenic cause due to steroid administration
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5
Q

what does the medulla of the adrenal glands make?

A

catecholamines

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6
Q

what are the classic signs of hyperadrenocorticism?

A

polyuria, polydipsia, polyphagia, skin changes, alopecia, pot belly appearance

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7
Q

what dog breed may be predisposed for adrenal cortical tumors?

A

german shepherds

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8
Q

what is the distribution seen of pituitary-dependent hyperadrenocorticism & primary adrenal disease?

A

~80% are pituitary-dependent

the rest are cortical tumors

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9
Q

what is the most reliable test for diagnosing a cortical tumor causing hyperadrenocorticism?

A

low dose dexamethasone suppression test - tumor isn’t impacted by the dexamethasone, so it will continue producing cortisol

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10
Q

what results on a low dose dexamethasone suppression test supports a cortical adrenal tumor? is it conclusive?

A

failure to suppress at 4-hr & 8-hr - cortisol never drops/is suppressed

not conclusive - many dogs with pituitary-dependent hyperadrenocorticism have the same pattern

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11
Q

what is the idea behind how a low dose dexamethasone suppression test works?

A

pre-injection cortisol is taken

the patient is given a dose of dexamethasone, an exogenous steroid, which in a healthy animal, should start a negative feedback loop signaling the hypothalamus & anterior pituitary to stop producing releasing/stimulating hormones - so you would expect cortisol results to drop significantly (low at 4 & 8 hours)

in a patient with hyperadrenocorticism due to a cortical tumor, cortisol would never drop and may increase a small amount

in a patient with pituitary-dependent hyperadrenocorticism, can either be low at 4 hours & increase at 8, or stay increased similarly to a cortical tumor causing hyperadrenocorticism

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12
Q

why is an ACTH stimulation test not useful for diagnosing a patient with a cortical tumor causing hyperadrenocorticism?

A

unreliable in a dog with a cortical tumor because the tumor may or may not express receptors that would respond to ACTH

may get a robust (cushingoid) response, may be normal, or may just be a flat line

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13
Q

what is the idea behind how a ACTH stimulation test works?

A

this test measures the ability of the adrenal cortex to secret endogenous cortisol in response to exogenous ACTH where samples are collected before administration and after at 1 hour to evaluate cortisol concentration

baseline normal is 1-4 ug/dL & normal dogs/cats will have a 2-3 fold increase in cortisol

pituitary-dependent hyperadrenocorticism dogs will have cortisol concentrations greater than 20 ug/dL

test works on the principle of stimulation of the pituitary-adrenal axis & is used to help determine the enlargement of adrenal glands

adrenal glands that are enlarged due to chronic stimulation from ACTH or that are neoplastic but functional, will show an exaggerated response to exogenous ACTH

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14
Q

why is abdominal ultrasound indicated in a dog with hyperadrenocorticism?

A

need to identify the location, size, & invasiveness of the mass as well as look for metastasis

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15
Q

what are the advantages & disadvantages of using CT for diagnosing a dog with hyperadrenocorticism due to a cortical tumor?

A

ct is superior in a tumor with vascular invasion

requires deep sedation/anesthesia

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16
Q

why take abdominal radiographs in a dog with hyperadrenocorticism due to a cortical tumor?

A

50% of tumors are calcified - may be able to see it on rads

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17
Q

what would you expect for results of an endogenous ACTH test in a dog with hyperadrenocorticism due to a cortical tumor? what are the problems with this test? when would you pick this test?

A

low results - high amounts of cortisol from the adrenal glands start the negative feedback loop

have to be careful with the sample - hormone needs to be handled very very carefully

great way to differentiate between pituitary dependent hyperadrenocorticism & a cortical adrenal tumor causing hyperadrenocorticism

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18
Q

why not use a high dose dexamethasone suppression test for diagnosing a dog with hyperadrenocorticism due to a cortical tumor?

A

an adrenal tumor will not be suppressed!!!!!!! you’re just giving a wildly high dose of dex

not very specific - dogs with pituitary-dependent don’t suppress it either

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19
Q

why use an inhibin test for diagnosing a dog with hyperadrenocorticism due to a cortical tumor? how does it work?

A

used to differentiate between a pheochromocytoma & cortical tumor

glycoprotein from gonadal & adrenal tissues that is increased in dogs with hyperadrenocorticism for any reason & also increased in dogs with non-functional cortical tumors

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20
Q

an adrenalectomy is ideal for what?

A

early malignant or benign functional adrenal tumors

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21
Q

T/F: you can’t tell benign from malignant on adrenal tumors until removal

A

true

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22
Q

how is an adrenalectomy patient prepped? what does post-op care look like? what are the risks associated with this treatment?

A

careful pre-op planning!!!!!! patient put on trilostane for 2-4 weeks

deal with acute hypocortisolemia post-op

taper prednisone over a few weeks while other gland regains function & use ACTH stimulation test to evaluate status of the remaining gland

risks/disadvantages - very expensive, risky, & requires a referral hospital

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23
Q

what is the most common functional cortical tumor in cats? what age of cats are affected?

A

cortical tumor releasing aldosterone - conn’s syndrome

cats >10 years old

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24
Q

what medical management can be utilized for treating a dog with hyperadrenocorticism due to a cortical tumor?

A

trilostane - can effectively control signs, treat like a dog with pituitary-dependent hyperadrenocorticism, good option for $$$ case or a poor surgical candidate

mitotane - less effective than trilostane but may slow tumor down

+/- clopidogrel

25
Q

what clinical findings are associated with hypokalemia with conn’s syndrome in cats?

A

life threatening hypokalemia - weakness/floppy, cervical ventroflexion, plantigrade stance, polydipsia, polyuria

26
Q

what are your rule outs for hypokalemia in a cat?

A

inappropriate fluid therapy

diuretic administration

gi tract loss

renal tubular dysfunction

diabetes mellitus

toxicity

27
Q

what clinical findings are associated with hypertension with conn’s syndrome in cats?

A

blindness

anisocoria

hyphema

mydriasis

28
Q

what clin path findings are seen in cats with conn’s syndrome?

A

hypokalemia - fluctuates & worse if not eating, <3 mEq/L is an emergency

+/- hypernatremia - usually normal, but total body Na+ is increased

hypophosphatemia

metabolic alkalosis - H+ is pumped out & Na+ is reclaimed in the distal nephron

increased CK & AST - often dramatic

29
Q

what clinical signs may be seen in a cat with conn’s syndrome that indicate other adrenal hormone excess?

A

cushingoid signs

aggression

30
Q

how is conn’s syndrome diagnosed in cats?

A

baseline aldosterone - single high value may be diagnostic

plasma renin activity & aldosterone:renin ratio - gold standard in people but not available in vet med

urine aldosterone:creatinine ratio - not perfect but looks useful

fludrocortisone suppression test

imaging - ultrasound or CT

31
Q

how is a fludrocortisone suppression test used for diagnosing a cat with conn’s syndrome?

A

similar concept to LDDST - fludrocortisone is like aldosterone, so, it should suppress the RAAS system in a normal animal

failure to suppress aldosterone indicates autonomous production

32
Q

why is hypokalemia so bad in a cat with conn’s syndrome?

A

it will cause cardiac issues & the cat will stop breathing

must address this first - NO FLUIDS

33
Q

how is hypokalemia treated in a cat with conn’s syndrome?

A

calculate their k max - 0.5 mEq/kg/hr

dilute 1:9 in D5W for peripheral use - will slough the vein otherwise because it is very caustic!!!!

infuse for 4-6 hours & then recheck

also give oral potassium - okay to do concurrently alongside IV infusion

34
Q

why give spironolactone to a cat with conn’s syndrome? what do you do with the oral potassium supplementation when you give this?

A

it is an aldosterone antagonist

back down on the oral potassium when you start

35
Q

how is hypertension treated in a cat with conn’s syndrome?

A

ideal to confirm diagnosis prior - then can give spironolactone

+/- amlodipine

36
Q

what is the ideal treatment for a cat with conn’s syndrome?

A

surgery!!!! may need fludrocortisone

contralateral gland atrophy - wean off over a few weeks

37
Q

what are functional medullary tumors called?

A

pheochromocytomas

38
Q

what hormones do pheochromocytomas release?

A

epinephrine & norepinephrine

39
Q

what animals do we commonly see pheochromocytomas in?

A

middle aged to older dogs - loose association with hyperadrenocorticism in dogs (especially pituitary-dependent)

40
Q

pheochromocytomas sound benign but are locally aggressive - how?

A

these tumors invade vessels, kidneys, etc

41
Q

T/F: pheochromocytomas are common incidental adrenal masses in dogs

A

true

42
Q

what clinical signs are seen in dogs with pheochromocytomas?

A

can be episodic/subtle - often no signs noted by the owner

cardiac arrhythmias - tachycardia

hypertension - blindness & stroke

blanching

anxiety & panic attacks

43
Q

how are pheochromocytomas diagnosed?

A

imaging - ultrasound or ct, with ct providing better vascular information

urine metanephrines

44
Q

how are urine metaephrines used for diagnosing pheochromocytomas?

A

they are breakdown products of catecholamines that are released continuously & are pretty reliable

45
Q

how are dogs with pheochromocytomas treated for hypertension?

A

alpha adrenergic blockers are routinely used +/- amlodipine

46
Q

what treatment is typically used for pheochromocytomas?

A

pre-treat the patient with phenoxybenzamine even if not hypertensive - seems to improve peri-operative outcomes

adrenalectomy

47
Q

T/F: adrenal masses are noted in about ~5% of older dogs with most being harmless, non-functional, benign tumors

A

true

48
Q

what characteristics of an adrenal tumor should make you pay attention upon imaging?

A

any mass that is > 2 cm

any mass with vascular invasion

49
Q

how do you determine functionality of an adrenal tumor?

A

check patient’s BP & ECG

review physical exam, history, & labwork for signs of hyperadrenocorticism

consider running a LDDST if suspicious for pituitary-dependent hyperadrenocorticism

measure urine metanephrines - rule out pheochromocytomas

50
Q

T/F: benign/malignant aspects of adrenal tumors are not related to functionality of the tumor

A

true

51
Q

what is an example of a functional adrenal medullary tumor?

A

pheochromocytoma - releases catecholamines

52
Q

T/F: the adrenal glands are a common site for metastatic disease

A

true

53
Q

what is the most common functional adrenal cortical tumor in the dog?

A

adrenal cortical tumor releasing cortisol

54
Q

why do we pre-treat a dog with trilostane prior to an adrenalectomy for a cortical tumor?

A

it improves healing

reduces risk of clotting & infection

may help wake up the contralateral gland

55
Q

why do you prepare for hypocortisolemia after an adrenalectomy in a dog with a cortical tumor?

A

other gland is likely atrophied!!!

need to support the patient

56
Q

when would you use clopidogrel for a dog with a cortical adrenal tumor?

A

useful if vascular invasion is noted

may reduce risk of thromboembolic complications

57
Q

if you have a non-functional adrenal tumor that is <2 cm, what do you recommend?

A

repeat imaging in 3 months

58
Q

if you have a non-functional adrenal tumor that is >2 cm, what do you recommend?

A

recommend removal - high likelihood of malignancy

CFT II (28 decks)

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