Soft tissue surgery (endocrine)

Question 1

where are the thyroid glands found?

Answer 1

paired glands that sit laterally to the trachea (rings 5-8)

Question 2

what structures sit near the right thyroid gland that we need to be aware of when performing surgery?

Answer 2

carotid sheath and recurrent laryngeal nerve

Question 3

what structures sit near the left thyroid gland that we need to be aware of when performing surgery?

Answer 3

oesophagus and recurrent laryngeal nerve

Question 4

should we be able to feel normal thyroid glands?

Answer 4

no - suggests abnormality

Question 5

what supplies blood to the thyroid glands?

Answer 5

cranial/caudal thyroid arteries

Question 6

what veins drain the thyroid glands?

Answer 6

cranial/caudal thyroid veins

Question 7

where can ectopic thyroid tissue be found?

Answer 7

along trachea, thoracic inlet, mediastinum, descending aorta

Question 8

where does the external pair of parathyroid glands sit?

Answer 8

near cranial pole of thyroid gland

Question 9

where does the internal pair of parathyroid glands sit?

Answer 9

embedded within the caudal pole of each thyroid gland

Question 10

is feline hyperthyroidism usually unilateral or bilateral?

Answer 10

bilateral

Question 11

what are the functions of thyroid hormone?

Answer 11

increase metabolic rate
increase catabolism of fat/muscle
increase body temperature
increase sympathetic drive
acts of emetic centre and cardiac muscle

Question 12

what are the clinical signs of hyerparathyroidism?

Answer 12

weight loss and polyphagia
behavioural change - restless/aggression
PUPD
vomiting and diarrhoea
cardiac signs (murmur, tachycardia)

Question 13

what are the classical finding on biochemistry of cats with hyperparathyroidism?

Answer 13

increased liver enzymes
decreased creatinine
decreased potassium
increased phosphate

Question 14

what is the diagnostic test used for hyperparathyroidism?

Answer 14

total T4 (increased)

Question 15

what are the possible treatment options for hyperparathyroidism?

Answer 15

medical - antithyroid drugs, radioiodine
surgical - thyroidectomy

Question 16

what are the two anti-thyroid medications available?

Answer 16

carbimazole
methimazole

Question 17

how do anti-thyroid medications work?

Answer 17

block thyroid hormone synthesis by blocking oxidation of iodide in the thyroid gland

Question 18

how many treatments of radioactive iodine is needed for hyperparathyroidism?

Answer 18

one is usually curative

Question 19

what are the disadvantages of radioactive iodine for treating hyperparathyroidism?

Answer 19

requires 2 week hospitalisation
specialist procedure (few centres do it)

Question 20

what are the advantages of radioactive iodine for treating hyperparathyroidism?

Answer 20

curative and minimal side effects
minimal cat/owner compliance needed
targets ectopic thyroid tissue

Question 21

what must be done before thyroidectomy?

Answer 21

get cat in euthyroid state by using anti-thyroid drugs
control cardiac murmur/tachycardia if present
treat hypertension
ensure cat in normokalaemic

Question 22

how are patients positioned for thyroidectomy?

Answer 22

dorsal recumbency (thoraci limbs pulled caudally)

Question 23

what are the steps of the cervical approach for thyroidectomy?

Answer 23

incision from larynx to manubrium
sternohyoid and sternothyroid muscles bluntly separated to reveal trachea
paratracheal fascia bluntly dissected to expose thyroid

Question 24

what is the appearance of normal thyroid glands?

Answer 24

pale tan and flat

Question 25

what is the appearance of thyroid glands with thyroid adenomatous hyperplasia?

Answer 25

brown/red and plump

Question 26

what are the advantages of a bilateral thyroidectomy?

Answer 26

single surgery and cheaper

Question 27

what is the main disadvantage of bilateral thyroidectomy?

Answer 27

risk of hypoparathyroidism

Question 28

what is a staged thyroidectomy?

Answer 28

largest gland removed and then second removed 4 weeks later

Question 29

what are the two types of thyroidectomy?

Answer 29

modified intracapsular (external parathyroid gland preserved) modified extracapsular

Question 30

what is the modified intracapsular thyroidectomy?

Answer 30

incise into thyroid capsule and bluntly direct it out, then cut most of the capsular tissue away leaving the external parathyroid gland

Question 31

what is the modified extracapsular thyroidectomy?

Answer 31

make an incision around the external parathyroid to preserve it and then remove the thyroid within its capsule

Question 32

what are the main complications of thyroidectomy?

Answer 32

haemorrhage laryngeal paralysis horners syndrome hypothyroidism hypoparathyroidism recurrence

Question 33

why is iatrogenic hypoparathyroidism commonly seen after thyroidectomy?

Answer 33

very likely to remove at least one of the parathyroid glands so the other take a bit of time to undergo hyperplasia its usually very mild

Question 34

what are the most common canine thyroid gland tumours?

Answer 34

carcinoma

Question 35

why is cross-matching prior to thyroidectomy highly recommended?

Answer 35

large risk of severe haemorrhage

Question 36

should the parathyroid be preserved in canine thyroidectomy of a mass?

Answer 36

no - risk of leaving neoplastic cells