Tumors of the Endocrine System

Question 1

Most clinically important pituitary tumor in the dog?

What does it do?

Answer 1

corticotroph adenoma

produces chronically excessive amounts of adrenocorticotrophic hormone (ACTH) and is associated with clinical signs of hypercortisolism

Question 2

In the cat, the most clinically significant pituitary tumor is?

What does it do?

Answer 2

growth hormone (GH)–secreting somatotroph adenoma

causes hypersomatotropism and acromegaly

Question 3

What is the age for HAC in dogs?

What is the cause in cats?

Answer 3

Middle age to older

excessive blood levels of glucocorticoids

Question 4

What is the most common form of HAC in dogs?

What % of cases are these?

Answer 4

Pituitary-dependent hypercortisolism (PDH)

80-85%

Question 5

What does PDH do?

Answer 5

autonomous synthesis and secretion of ACTH from a pituitary tumor

bilateral adrenal cortical hyperplasia and hypercortisolemia. The pituitary tumor is relatively insensitive to negative feedback by cortisol, and a loss of hypothalamic control over ACTH release occurs because corticotropin- releasing hormone (CRH) secretion is suppressed by the chronic hypercortisolemia

Question 6

Pituitary tumors that secrete ACTH are derived from what cell type?

What % arise from what part of the pituitary? What controls it?

The remainder arise from what part of pituitary? What controls it?

Answer 6

Pituitary corticotroph cell

70% to 80% arise from the pars distalis under the control of CRH

pars intermedia=20-30% - under dopaminergic and serotoninergic control

Question 7

Difference between micro- and macrotumors?

Answer 7

microtumors are less than 1 cm in diameter, and macrotumors are 1 cm or larger in diameter

Question 8

How common are pituitary ACAs?

Answer 8

Uncommon

In a study of 33 dogs with pituitary tumors that underwent necropsy evaluation after brain imaging, 61% had a pituitary adenoma, 33% had an invasive adenoma, and 6% had an adenocarcinoma.

Question 9

Age of dogs with PDH?

Gender predilection?

Breed predisposition?

Answer 9

9 years

female dogs are slightly overrepresented

dachshunds, terrier breeds, German shepherd dogs, and poodle

Question 10

What do the adrenal look like with PDH?

Answer 10

adrenals of patients with PDH are often bilaterally enlarged with increased thickness; they typically maintain a normal shape and are homogeneous in echogenicity

Question 11

In a study of 13 dogs that underwent MRI evaluation of the brain at the time of diagnosis of PDH and before medical therapy was instituted, eight of the dogs had a visible pituitary mass and none of the dogs had clinical signs of neurologic disease.

§ Four of the dogs showed enlargement of the pituitary tumor on MRI 1 year later, and a pituitary tumor also was detected in two dogs that did not have a visible mass on the initial MRI.

§ Two of the 13 dogs had developed neurologic signs at the time of the 1-year follow-up MRI.

Question 12

In a study evaluating diagnostic imaging findings in 157 dogs with PDH with and without neurologic signs, central nervous system (CNS)–specific signs such as circling, seizures, and ataxia were neither sensitive nor specific for predicting the presence of a pituitary macrotumor.

o Signs such as lethargy, mental dullness, and decreased appetite were highly specific for detection of a pituitary macrotumor but not highly sensitive.

Question 13

What % of dogs with PDH dont have a visible tumor on CT or MRI?

What % develop neurologic signs and when?

Answer 13

40-50% and unlikely to develop neurologic signs

15-25%, 6 to 18 months

Question 14

If a pituitary mass is detected but is less than 8 mm in diameter what is the recommendation?

For masses greater than 8 mm in diameter?

Answer 14

medical therapy and repeat imaging in 12–18 months

RT is recommended

Question 15

Measurement of ____ precursor concentrations could help in the selection of patients for brain imaging because it has been shown that pro-opiomelanocortin/pro-ACTH levels in plasma are correlated with pituitary tumor size in dogs with PDH.

Plasma cortisol concentrations at baseline and 4 or 8 hours after administration of a low dose of dexamethasone do not appear to correlate with the development of neurologic signs.

Answer 15

plasma ACTH

Question 16

2 common medical treatment for PDH?

How does mitotane work?

Answer 16

trilostane and mitotane

Mitotane (o,p′-DDD, Lysodren) is a potent adrenocorticolytic agent that is cytotoxic to the adrenal cortex, particularly the zona fasciculata and zona reticularis

Question 17

Canine pituitary tumors express what receptors in comparison to humans?

What is pasireotide?

Answer 17

Somatostatin receptor subtype 2 (SST2), in contrast to human tumors, which express predominantly subtype 5 (SST5)

somatostatin receptor analog that binds to receptors of the subtypes SST1, SST2, SS, and SST5

In a small study of 20 dogs with PDH, pasireotide therapy produced improvements in plasma ACTH concentrations, urine cortisol:creatinine ratios, tumor size, and clinical signs in most dogs, although three dogs developed diabetes mellitus.45

§ In a more recent study, pasireotide therapy was combined with trilostane therapy (eight dogs) or mitotane therapy (one dog) in nine dogs with PDH resulting from a macroadenoma. No adverse effects were noted, and tumor volume decreased in six of the nine dogs, but it increased in three of the nine.46 Unfortunately pasireotide is extremely expensive,

Question 18

Hoe does selegilene work?

Answer 18

acts by inhibiting degradation of dopamine, thereby potentially inhibiting ACTH secretion from the inter- mediate lobe of the pituitary gland

Additional disadvantages are documented poor efficacy, expense, and inability to monitor response with ACTH stimulation testing

Question 19

What is cebergoline?

Answer 19

Dopamine D2 receptor agonist that also acts to reduce pituitary ACTH secretion by increasing dopaminergic tone

In the only published study of cabergoline use in dogs with PDH, 17 of 40 dogs showed a favorable clinical response.

§ Decreases in ACTH concentrations, urine cortisol:creatinine ratios, and pituitary tumor size also were reported.

Question 20

What is bromocriptine?

Answer 20

dopamine agonist and also acts to reduce plasma ACTH concentrations

Because of adverse effects and lack of demonstrated efficacy, it is not recommended for treatment of canine PDH

Question 21

Cyproheptadine arose from the hypothesis that excessive ACTH secretion could result from excessive serotoninergic stimulation of the pituitary gland. This drug has been shown to be ineffective in clinical cases.50

• Retinoic acid also has been used in the management of canine PDH. This medication may inhibit pituitary tumor development, reduce ACTH production, and inhibit cell proliferation. One study showed promise in terms of a decrease in the size of pituitary tumors and subjective improvement in clinical signs.

Question 22

Treatment of choice for humans with PDH?

How do you determine if pituitary gland is enlarged?

Answer 22

Hypophysectomy

Evaluating the pituitary height:brain area (P:B) ratio; a P:B ratio >0.31 is consistent with pituitary enlargement

Question 23

Transsphenoidal hypophysectomy first was reported in a large cohort of dogs in 1998.

o In that study the 1- and 2-year estimated survival rates were 84% and 80%, respectively.

o Forty-three dogs went into remission, and recurrence of HAC was reported in five dogs.

Question 24

The same group since has published the largest cohort of dogs with PDH treated with transsphenoidal hypophysectomy to date, reporting the outcomes in 306 dogs.

o In that study 91% of the dogs survived the 4-week perioperative period.

o The median survival time (MST) was 781 days, and the median disease-free interval (DFI) was 951 days.

o The recurrence rate was 27%, and recurrence of HAC was diagnosed a median of 555 days from surgery.

o When the pituitary gland size was evaluated using the P:B ratio, dogs with larger tumors had a shorter survival time (ST) and an increased risk of recurrence.

o Postoperative ACTH and cortisol concentrations may give some indication of the risk of residual disease. However, this should be evaluated in light of the tumor size, baseline ACTH levels, and individual patient

Question 25

In a prospective study of 150 dogs treated with transsphenoidal hypophysectomy for

o PDH, the 1-, 2-, 3-, and 4-year estimated survival rates were 84%, 76%, 72%, and 68%, respectively.

o Twelve dogs died postoperatively, and 127 went into remission, of which 32 later experienced a recurrence of disease.

o Complications included central diabetes insipidus in 53% of dogs under- going remission and incomplete hypophysectomy in nine dogs.

o The overall success rate of transsphenoidal hypophysectomy was determined to be 65% in this study.54 Reported complications of transsphenoidal hypophysectomy include hemorrhage, electro- lyte imbalance, postoperative neurologic deficits, decreased tear production, thromboembolic disease, recurrence of PDH, and perioperative death.

o However, the overall outcome of this procedure is favorable, resulting in rapid resolution of disease and a long period of remission or complete resolution in patients that survive the perioperative period.53,56

• In this case series of 26 dogs with PDH, the overall mortality associated with the surgery was 19%; however, the five deaths occurred in the first 10 dogs treated, with no mortality in the subsequent 16 dogs.

Question 26

Dow and colleagues treated six dogs with functional pituitary macrotumors; the dogs were given 40 Gy in 10 equal fractions.

o The MST was 743 days; neurologic signs resolved in all the dogs; and ACTH levels remained high for at least 1 year after therapy.

Question 27

1 year after therapy.6

o Cobalt 60 RT was used to treat six dogs with PDH caused by a pituitary tumor that was detectable on MRI; tumor size was significantly reduced in all cases, but clinical signs of PDH were adequately controlled only in one dog.

§ The effects of megavoltage irradiation on pitu- itary tumors was evaluated in 24 dogs with neurologic signs; 10 dogs experienced complete remission of neurologic signs, and another 10 dogs achieved partial remission; 4 dogs died, either during radiation therapy or shortly thereafter.

§ As in previous studies a correlation was noted between relative tumor size and the severity of neurologic signs in dogs with pituitary tumors. A correlation between tumor size and remission of neurologic signs also was noted after pituitary irradiation, which suggests that early treatment of these tumors should improve the prognosis, although control of ACTH secretion was unlikely.

Question 28

A retrospective study of RT for the treatment of pituitary masses demonstrated significantly improved STs and control of neurologic signs in 19 dogs that received RT compared to 27 untreated control dogs with pituitary masses.

o The mean ST in the treated group was 1405 days, compared to 551 days in the nonirradiated group.

o The 1-, 2-, and 3-year estimated survival rates were 93%, 87%, and 55% for the irradiated dogs and 45%, 32%, and 25% for the nonirradiated dogs, respectively.

Question 29

Treated dogs with smaller tumors lived longer than those with larger tumors; again, this suggests that early diagnosis and treatment of pituitary tumors are beneficial.

• Five of 14 dogs with PDH in this study were reported to show resolution of clinical signs of HAC, together with at least one normal ACTH stimulation test result after completion of RT.5
• A recent nonrandomized observational study compared two coarse fractionated radiation protocols for canine pituitary macrotumors and found that dogs treated with 10 fractions of 3.8 Gy/fraction on a Monday/ Wednesday/Friday protocol had a longer ST than dogs treated once weekly to a total dose of 38 Gy.

Question 30

___% of cases of HAC in the cat are the result of pituitary disease

Most of these cats will have a ____ that secretes ____

Answer 30

80-85%

pituitary adenoma, excessive ACTH

Question 32

Feline HAC is commonly associated with _____?

Clinical signs?

What is noted on labwork in comparison to dogs?

Answer 32

insulin-resistant diabetes mellitus

polyuria, polydipsia, polyphagia, and weight loss

Dogs have elevated ALP; Cats may have increased alanine aminotransferase activity, hypercholesterolemia, azotemia, and a minimally concentrated urine

Question 33

Transsphenoidal hypophysectomy was described in seven cats with PDH.

o Two of the cats died within 4 weeks of surgery from unrelated causes, and the remaining five cats experienced remission of their disease.

o Two additional cats died several months after surgery, and one cat experienced a relapse of PDH 19 months after treatment, likely associated with pituitary remnants after surgery.

Question 34

Feline acromegaly is a disease of ____ cats that results from chronic excessive ___ secretion, usually from a functional somatotroph ____ of the ____ of the pituitary gland

Answer 34

older, GH, adenoma, pars distalis

Question 35

Feline acromegaly

In an early study of 184 diabetic cats, 59 had markedly increased serum insulin–like growth factor-1 (IGF-1) concentrations, and acromegaly was confirmed in 17 of 18 cats that were examined by CT, MRI, or necropsy.86

• The same group subsequently published the results of screening for acromegaly in a much larger group of 1221 diabetic cats.

o They found that 319 (26.1%) of the cats had serum insulin-like growth factor 1 (IGF-1) concentrations consistent with acromegaly; 63 of these cats underwent pituitary imaging, and the presence of a pituitary lesion was confirmed in 94% of this group.

Question 36

A study of diabetic cats in Europe recently found that 36 of 202 (17.8%) cats evaluated had serum IGF-1 concentrations consistent with acromegaly.

• Study of 184 cats, the IGF-1 assays were performed on blood samples submitted to a labora- tory at a referral institution for measurement of serum fructosamine, which is a test that may be more likely to be performed in cats with diabetes that is difficult to regulate.
• The prevalence of acromegaly in the average or typical diabetic cat is likely in the range of 10% to 15%, but the prevalence in cats that are difficult to regulate is probably closer to 30%

Question 37

Feline acromegaly is more common in ___ cats?

Breed predilection?

Age?

Answer 37

male

None

Middle age to older

Question 38

What causes insulin resistance in feline acromegaly?

Physical changes observed?

Answer 38

Insulin resistance is due to a GH-induced postreceptor defect in the action of insulin on target cells.

These changes may include enlarged feet, broadening of the face, protrusion of the mandible (Fig. 26.2), increased spacing between the teeth, and abdominal enlargement.

Question 39

Are neurologic signs common with feline acromegaly?

Answer 39

Neurologic signs associated with the pituitary tumor generally appear to be uncommon but may be underrecognized or underreported. Lethargy, mental dullness, or impaired vision may occur but often can be subtle.

Question 40

Feline acromegaly is the result of ____ from a pituitary gland tumor, and ____ have been reported in several cats with acromegaly.

o Unfortunately, a feline GH assay currently is not reliably available in the United States. The physical changes in patients with acromegaly are due to the anabolic effects of GH, which are mediated by peripher- ally synthesized IGF-1. This hormone is produced in the liver and other tissues, and serum concentrations of IGF-1 increase in the presence of chronically increased GH production. Because GH secretion may be pulsatile, even in some acromegalics, and because it has a short half-life, an increased serum IGF-1 level has been suggested to be a more sensitive test for acromegaly because it may reflect GH levels over the preceding 24 hours.

Answer 40

excessive GH secretion, increased serum GH concentrations

Question 41

One study confirmed that IGF-1 measurement is a useful screening test for feline acromegaly, with a sensitivity and specificity of 84% and 92%, respectively.90 No difference in serum IGF-1 concentrations was seen among well-controlled diabetic cats, poorly controlled diabetic cats, and healthy cats.90

o The highest IGF-1 noted in a diabetic cat was 153 nM, with a normal reference range of 12 to 92 nM; thus some overlap exists between the IGF-1 values found in acromegalic cats and those found in poorly regulated diabetic cats.

§ This author’s experience (KL) is that IGF-1 levels in cats with acromegaly usually are at least twice the value of the high end of this reference range, at least by the time the cats are investigated for causes of insulin resistance.

§ In Europe, the serum IGF-1 concentration typically is expressed in ng/mL, with a positive predictive value of 95% for an IGF-1 >1000 ng/mL

Question 42

MRI likely is more sensitive than CT,99 but both imaging modalities may reveal a normal pituitary in a cat with acromegaly if the size of the mass is below the limit of detection

o In a case-control study of CT findings, 68 acromegalic diabetic cats were compared to 36 control cats. Cats with acromegaly had significantly thicker bones, skin, and subcutaneous tissues, and narrower nasopharynges compared to the control cats.

o Additional imaging findings supportive of acromegaly include echo- cardiographic changes as noted previously, enlarged kidneys and adrenal glands, and evidence of pancreatic changes on abdominal ultrasound examination.

Question 43

The largest reported case series of cats undergoing hypophysectomy focused on anesthetic management and complications in 37 cats with acromegaly103; the same group reported the outcome of surgical hypophysectomy in 21 diabetic cats in abstract form.104 These two publications provide relatively little detail but in summary:

o 3 of 21 cats died postoperatively; all 18 surviving cats experienced a reduction in serum IGF-1 concentrations; and 14 of these cats achieved diabetic remission.

Question 44

RT is the treatment for feline acromegaly that has been most widely reported in the veterinary literature.a

o Conventional fractionated RT protocols range from five fractions given weekly to as many as 20 fractions given over a period of 4 weeks.

§ Improved diabetic control is one potential outcome of RT therapy, although IGF-1 concentrations do not appear to correlate with this improved control.

Question 45

SRT for feline acromegaly

§ A recent study documented the outcome of SRT, delivered in 3 or 4 doses, for the treatment of acromegaly in 53 cats.

§ The overall MST was 1072 days, with no association noted between tumor size or serum IGF-1 concentration and survival.

§ Causes of death included neurologic disease, heart disease, kidney disease, and unrelated diseases.

§ Seven of 50 cats in which serum T4 concentrations were monitored developed hypothyroidism months to years after SRT.

§ Diabetic regulation was followed in 41 of the 53 cats, and 39 experienced a reduction in insulin dose, with 13 (32%) cats going into diabetic remission.

Question 46

Somatostatin analogs, also termed somatostatin receptor ligands (SRLs), bind to _____, suppressing the release of ___ from the pituitary gland.

These medications are available as long- or short-acting preparations, and the response to SRLs is assessed by measurement of IGF-1 and GH levels and tumor size, and evaluation of clinical signs.

Answer 46

somatostatin receptors, GH

Question 47

Octreotide

§ Otreotidehas been evaluated in a small number of cats with acromegaly. In five cats short-acting octreotide was used for up to 4 weeks with no apparent improvement in GH levels.

§ However, another study showed that GH levels were significantly reduced for up to 120 minutes postinjection in five cats with acromegaly that received a single dose of octreotide.

§ These studies used the short-acting form of octreotide and were performed over a very short time without assessment of the clinical response.

Question 48

Pasireotride

§ Both short- and long-acting pasireotide have been studied in acromegalic cats, with encouraging results.

§ Treated cats experienced improved insulin sensitivity, and serum IGF-1 concentrations were reduced. Diarrhea was a common side effect, and the expense of this medication is a significant impediment for most cat owners.

Question 49

For many cats with acromegaly, insulin therapy is the only treatment available or acceptable to the owner. In general these patients should receive the amount of insulin necessary to control their diabetes, although adequate blood glucose regulation can be difficult to achieve in many cases.

• The short-term prognosis for cats diagnosed with acromegaly generally is fair to good, but the long-term prognosis is poor without specific therapy.83 Patients may succumb to cardiac or renal failure, neurologic dis- ease, or complications of poorly regulated diabetes mellitus. In one early case series the MST was 20.5 months

Question 50

Functional cortisol-secreting tumors of the adrenal cortex are responsible for ___ of canine and feline cases of naturally occurring HAC, with PDH accounting for ____

Answer 50

15% to 20%, 80% to 85%.

Question 51

Functional adrenocortical tumors in dogs and cats also can secrete one or more sex hormones, including?

Answer 51

androstenedione, progesterone, 17-hydroxyprogesterone, testosterone, and estradiol

Question 52

The presence of ____ suggests an adrenal tumor, but this finding is not highly specific, and it cannot be used to differentiate between benign and malignant masses.

Answer 52

mineralization,

Question 53

Adrenal gland neoplasia

Ultrasonography has been reported to be ____% sensitive and approximately __% specific for the detection of adrenal tumor invasion into the caudal vena cava.

Answer 53

80% to 100. 90

Question 54

Contrast-enhanced CT has been shown to provide accurate preoperative evaluation of canine adrenal masses with___% sensitivity and __% specificity for the detection of vascular invasion by adrenal tumors.

Answer 54

92%, 100%

Question 55

Canine Adrenocortical Tumors

Adenomas typically are___; tumors larger than___ are more likely to be carcinomas.

Answer 55

smaller, 2 cm

On histopathologic examination, adenocarcinomas appear more likely to exhibit a trabecular growth pattern, peripheral fibrosis, capsular invasion, necrosis, and/or hemorrhage.138 They are less likely to exhibit cytoplasmic vacuolization, extramedullary hematopoiesis, or fibrin thrombi.

Question 56

Approximately __% of adrenocortical carcinomas invade into the phrenicoabdominal vein with extension into the renal vein and/ or caudal vena cava.

Metastasis was identified in approximately __% of dogs with adrenocortical carcinomas.

Dogs with PDH and dogs with ADH are ____ in age, but almost __% of dogs with ADH weigh ___ compared to approximately __% of dogs with PDH.

Answer 56

20%

50%

similar, 50%, >20kg, 25%

Question 57

Sensitivity of the ACTH stimulation test for the diagnosis of ADH is only approximately __%.

An ultrasound study of dogs with equivocal adrenal asymmetry suggested that a maxi- mal dorsoventral thickness of the smaller gland of less than 5.00 mm was consistent with a diagnosis of ADH.

Answer 57

60%

Question 58

____ is the treatment of choice for dogs with ADH.

o In one series of 144 dogs undergoing surgical removal of a functional adrenocortical tumor, the prognosis was described as excellent for patients that survived 4 weeks postoperatively, and the average life expectancy was 3 years.

o Nine of 144 dogs were euthanized at the time of surgery, and 29 dogs died during surgery or immediately postoperatively.

o MSTs of 230 to 778 days have been reported for dogs undergoing adrenalectomy for adrenal carcinomas, compared to an MST of 688 days for dogs with adenomas.11

Answer 58

Surgical adrenalectomy

Question 59

SRT has been reported in a small number of dogs with adreno- cortical tumors with vascular invasion.

o In the nine dogs evaluated, of which six dogs had nonsecretory tumors, the MST was 1030 days, tumor size was reduced, and no dogs experienced severe radiotoxicity..

Question 60

____ therapy for ADH should be used when surgery is not a good option for the patient or client, or they may be used before adrenalectomy in patients that are significantly debilitated by HAC.

Answer 60

Mitotane or trilostane

Question 61

Treatment with mitotane as an alternative to surgical adrenalectomy uses the drug as a true cytotoxic agent. Detailed protocols are readily

§ This treatment can be effective; a mean ST of 16.4 months was reported in a series of 32 dogs, and dogs without evidence of metastatic disease appeared to have a better response to mitotane therapy.

§ Trilostane is not a cytotoxic drug, but it has been used successfully to manage patients with ADH, a small number of dogs with metastatic disease.

Question 62

In a retrospective study comparing trilostane and mitotane in dogs with ADH, the MSTs for dogs treated with trilostane and mitotane were 353 days and 102 days, respectively.

§ These STs were not significantly different; however, this study did further confirm that STs are significantly reduced with metastatic disease.

Question 63

The MSTs in a more recent study were 15.6 months and 14 months for dogs with ADH treated with mitotane or trilostane, respectively; thus either medication is a reasonable option for ADH if surgery is not feasible.

Question 64

Aldosterone-secreting adrenocortical tumors have rarely been reported in dogs. Clinical findings include lethargy, anorexia, polyuria/polydipsia, hypokalemia, metabolic alkalosis, and hypertension. The diagnosis is confirmed by ruling out other causes of hypokalemia, together with finding a markedly increased plasma aldosterone concentration.

Question 65

Hyperadrenocorticism in cats is ___, and only ___% of cases are due to a functional adrenocortical tumor.

Answer 65

rare, 15-20%

Question 66

A recent case series documented the clinical findings in 33 cats with adrenal neoplasia that had a histopathologic diagnosis.

o Thirty of the 33 cats were diagnosed with a cortical tumor, and only three had a pheochromocytoma. Of the 25 cats that underwent adrenal function tests, 19 cats were diagnosed with a functional tumor, and of these 16 cats had hyperaldosteronism, one had hypercortisolemia, one had high estradiol, and one had hypersecretion of multiple hormones.

o Increasing evidence indicates that primary hyperaldosteronism (also termed primary aldosteronism or Conn’s syndrome) has been an underrecognized condition in cats. In fact, it has been suggested to be the most common adrenocortical disorder in this species.

o Plasma aldosterone can be measured in cats, and normal or increased plasma concentrations in the face of hypokalemia would be regarded as inappropriate. However, definitive diagnosis using aldosterone levels is difficult without measurement of the plasma renin activity and calculation of an aldosterone:renin ratio.159

o The oral fludrocortisone suppression test had been shown to be useful in the diagnosis of feline hyperaldosteronism.

o Most cats with hyperaldosteronism have an adrenal adenoma or carcinoma.

o Bilateral adenomas have been reported, and some cats have adrenal hyperplasia.

Question 67

Feline Adrenocortical Tumor

____ is the treatment of choice for cats with unilateral disease, and good outcomes have been reported both for adenomas and for carcinomas, in addition to tumors associated with vena cava thrombosis

Medical management with potassium supplementation, antihypertensive drugs, and the aldosterone antagonist spironolactone can give reasonable STs in patients that are not surgical candidates.

Answer 67

Adrenalectomy

Question 68

Chromaffin cells are part of the ____ and are present in the ____ and other locations throughout the body.

Answer 68

sympathetic nervous system, adrenal medulla

Question 69

Neoplastic chromaffin cells in the adrenal medulla give rise to ______, which are tumors that predominantly secrete _____

Answer 69

pheochromocytomas, catecholamines

Question 70

Pheochromocytomas are ___ in dogs and rare in cats

Answer 70

uncommon, rare

Question 71

With pheochromocytoma, metastasis is reported in up to ___% of affected dogs

• invasion by the tumor has been reported in as many as ___% of cases.

o This finding is not specific for pheochromocytoma because vascular invasion can also occur with adrenocortical tumors.

Answer 71

40%, 82%

Question 72

_____is sensitive and specific for detecting vascular invasion by adrenal tumors.

• Unfortunately no ultrasound or CT findings can distinguish definitively between pheochromocytoma and other adrenal

Answer 72

Ultrasound

Question 73

Immunohistochemical staining for ____ can distinguish pheochromocytomas from adrenocortical tumors on tissue obtained at surgery or necropsy.

Answer 73

chromogranin-A

Question 74

The best differentiation between pheochromocytoma and other diseases appears to be provided by measurement of ____, either in ______

Answer 74

normetanephrine, urine or plasma.

Question 75

____ is the only definitive treatment for pheochromocytoma.

o Chemotherapy and RT have not been evaluated in dogs with pheochromocytoma.

o Radiotherapy using 131I-metaiodobenzylguanidine was reported in one dog.

o The prognosis for dogs with pheochromocytoma depends on ___, the presence of ____, and ____. An MST of ___ days has been reported after surgical treatment of pheochromocytoma.

o Dogs without metastatic disease that survive the perioperative period appear to have a good prognosis pheochromocytoma.

Answer 75

Surgery

tumor size, metastases, local invasion

374

Question 76

Patients with ADH also may be medically managed with ___ before surgery to mitigate ___ and potentially reduce the risk of ____ that can result from their prothrombotic state.

Answer 76

trilostane or mitotane, metabolic derangements, thromboembolic disease

Question 77

Pretreatment with ___ has been recommended before surgery, because ____ was shown in one study to improve the ST significantly in dogs undergoing adrenalectomy.

Answer 77

α-blockade, phenoxybenzamine

Question 78

The perioperative mortality rate for adrenalectomy ranges from ___%.

Answer 78

15% to 37

Question 79

Compared with dogs, significantly fewer accounts are available of adrenalectomy in cats.

o In one series of 33 cats with adrenal neo- plasia, 26 cats underwent adrenalectomy and 20 (77%) survived for at least 2 weeks postoperatively.

§ The MST for cats undergoing surgery was 50 weeks. Complications included pancreatitis, lethargy and anorexia, and significant hemorrhage.

§ Three of the cats developed postoperative hypoadrenocorticism.

o In a series of 10 cats undergoing unilateral adrenalectomy for management of aldosterone-secreting tumors, eight cats survived to discharge

§ overall MST was 1297 days, with none of the cats requiring further medical therapy.

Question 80

Laparoscopic adrenalectomy for unilateral adrenal tumors also has been described in cats, but 4 of the 11 reported cases required con- version to laparotomy.

o Ten of the 11 cats survived to discharge, and the MST was 803 days.

Question 81

Incidental Adrenal Masses

• In a published study of dogs undergoing abdominal ultrasound examination, 4% were found to have an incidental adrenal gland lesion, with affected dogs being older than a control population with no adrenal lesions.

o Twenty of these dogs underwent surgery or necropsy; six were determined to have malignant tumors, all of which had a maxi- mum dimension greater than 20 mm.

• In another study of 20 dogs with non–cortisol-secreting adrenal tumors that did not undergo surgery,

o MST was 17.8

• In a series of 270 dogs undergoing abdominal CT for reasons unrelated to adrenal disease, 25 (9.3%) had adrenal gland masses; as with the ultrasound findings, these incidental masses were more likely in older dogs.
• Adrenalectomy should be considered for masses that are functional, locally invasive, or larger than 2.5 cm in maximum dimension. Masses smaller than 2 cm with no evidence of hormonal activity should be monitored with regular imaging.
• A suggested protocol is to repeat the sonogram monthly for 3 months after the initial study and then less frequently if no significant change is noted, with further intervals determined by the appearance of the mass and the clinical status of the patient. However, the growth of these masses is not necessarily predictable or uniform over time.