Soft tissue surgery (endocrine) Flashcards
where are the thyroid glands found?
paired glands that sit laterally to the trachea (rings 5-8)
what structures sit near the right thyroid gland that we need to be aware of when performing surgery?
carotid sheath and recurrent laryngeal nerve
what structures sit near the left thyroid gland that we need to be aware of when performing surgery?
oesophagus and recurrent laryngeal nerve
should we be able to feel normal thyroid glands?
no - suggests abnormality
what supplies blood to the thyroid glands?
cranial/caudal thyroid arteries
what veins drain the thyroid glands?
cranial/caudal thyroid veins
where can ectopic thyroid tissue be found?
along trachea, thoracic inlet, mediastinum, descending aorta
where does the external pair of parathyroid glands sit?
near cranial pole of thyroid gland
where does the internal pair of parathyroid glands sit?
embedded within the caudal pole of each thyroid gland
is feline hyperthyroidism usually unilateral or bilateral?
bilateral
what are the functions of thyroid hormone?
increase metabolic rate
increase catabolism of fat/muscle
increase body temperature
increase sympathetic drive
acts of emetic centre and cardiac muscle
what are the clinical signs of hyerparathyroidism?
weight loss and polyphagia
behavioural change - restless/aggression
PUPD
vomiting and diarrhoea
cardiac signs (murmur, tachycardia)
what are the classical finding on biochemistry of cats with hyperparathyroidism?
increased liver enzymes
decreased creatinine
decreased potassium
increased phosphate
what is the diagnostic test used for hyperparathyroidism?
total T4 (increased)
what are the possible treatment options for hyperparathyroidism?
medical - antithyroid drugs, radioiodine
surgical - thyroidectomy
what are the two anti-thyroid medications available?
carbimazole
methimazole
how do anti-thyroid medications work?
block thyroid hormone synthesis by blocking oxidation of iodide in the thyroid gland
how many treatments of radioactive iodine is needed for hyperparathyroidism?
one is usually curative
what are the disadvantages of radioactive iodine for treating hyperparathyroidism?
requires 2 week hospitalisation
specialist procedure (few centres do it)
what are the advantages of radioactive iodine for treating hyperparathyroidism?
curative and minimal side effects
minimal cat/owner compliance needed
targets ectopic thyroid tissue
what must be done before thyroidectomy?
get cat in euthyroid state by using anti-thyroid drugs
control cardiac murmur/tachycardia if present
treat hypertension
ensure cat in normokalaemic
how are patients positioned for thyroidectomy?
dorsal recumbency (thoraci limbs pulled caudally)
what are the steps of the cervical approach for thyroidectomy?
incision from larynx to manubrium
sternohyoid and sternothyroid muscles bluntly separated to reveal trachea
paratracheal fascia bluntly dissected to expose thyroid
what is the appearance of normal thyroid glands?
pale tan and flat
what is the appearance of thyroid glands with thyroid adenomatous hyperplasia?
brown/red and plump
what are the advantages of a bilateral thyroidectomy?
single surgery and cheaper
what is the main disadvantage of bilateral thyroidectomy?
risk of hypoparathyroidism
what is a staged thyroidectomy?
largest gland removed and then second removed 4 weeks later
what are the two types of thyroidectomy?
modified intracapsular (external parathyroid gland preserved)
modified extracapsular
what is the modified intracapsular thyroidectomy?
incise into thyroid capsule and bluntly direct it out, then cut most of the capsular tissue away leaving the external parathyroid gland
what is the modified extracapsular thyroidectomy?
make an incision around the external parathyroid to preserve it and then remove the thyroid within its capsule
what are the main complications of thyroidectomy?
haemorrhage
laryngeal paralysis
horners syndrome
hypothyroidism
hypoparathyroidism
recurrence
why is iatrogenic hypoparathyroidism commonly seen after thyroidectomy?
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
what are the most common canine thyroid gland tumours?
carcinoma
why is cross-matching prior to thyroidectomy highly recommended?
large risk of severe haemorrhage
should the parathyroid be preserved in canine thyroidectomy of a mass?
no - risk of leaving neoplastic cells
