Endocrine Flashcards
what is the general structure of the thyroid?
paired bilobed gland - right and left glands
where does the thyroid gland typically lie?
caudal to the larynx, between 5th and 8th tracheal rings
where is the thyroid in relation to the trachea?
ventrolateral to the trachea
right gland slightly more cranial than left
why is the thyroid at risk of haemorrhage during surgery?
very well vascularised
why is it important to be aware of iatrogenic damage during surgery on the thyroid?
there are numerous neurological structures in the area which require careful identification during surgery
where can ectopic thyroid tissue be found?
lying in the midline from the tongue to the abdomen
why is is possible to have ectopic thyroid tissue?
as a result of the path the thyroid tissue undergoes during embryonic development
why do we place oesophagostomy tubes on the lhs of the neck?
the oesophagus sits more on the lhs of the neck, in contact with the left thyroid gland
what is a functional thyroid condition?
one which produces thyroid hormones
how can we categorise surgical conditions of the thyroid?
functional vs non-functional
benign vs malignant neoplasia
when benign conditions can affect the thyroid gland?
adenoma
adenomatous hyperplasia
cysts
what malignancies can affect the thyroid gland?
carcinoma
adenocarcinoma
what type of benign thyroid masses affect dogs?
typically small and non-functional - rarely diagnosed
what type of benign thyroid masses affect cats?
typically functional and cause hyperthyroidism
what is the most common type of thyroid mass in cats?
95% of all cases are benign adenoma/adenomatous hyperplasia
are malignant thyroid masses in dogs typically functional?
no - mostly non-functional, do not cause hyperthyroidism and are instead presented due to the mass itself
are thyroid masses often malignant in cats?
no - typically functional, benign masses
do thyroid cysts occur commonly?
no - rare
what are the main pre-operative considerations for thyroidectomy?
body condition score
likelihood of metastasis
cardiovascular effects
renal effects
ocular effects
co-morbidities - typically older animals
degree of medical stabilisation achieved
what are the pre-op cardiovascular considerations for thyroidectomy?
tachycardia
hypertension
what are the pre-op renal considerations for thyroidectomy?
pre-renal azotemia
what are the pre-op ocular considerations for thyroidectomy?
retinal detachment secondary to hypertension
what are the pre-op c-morbidity considerations for thyroidectomy?
CVS, renal, increased GA risk, cachexia, arthritis
what is the benefit of medical stabilisation before thyroidectomy?
improvement of asa status
what is involved in medical stabilisation of hyperthyroidism?
decrease HR with anti-thyroid meds
treat hypertension and stabilise rhythm with atenolol
support renal function - diet, supplements, fluids
try to increase body weight
what are the pre-operative considerations for thyroidectomy in dogs?
BCS - may be reduced due to effects of cancer
metastasis?
co-morbidities present as usually older animals
do dogs require medical stabilisation before thyroidectomy?
not usually needed, usually non-functional so far sew systemic effects
how wide should the clip be for thyroidectomy?
from level of jaw to thoracic inlet lengthways
wide clip - to jugular grooves widthways
what position should the patient be in for thyroidectomy?
dorsal recumbency with sandbag under neck to elevate, keep neck straight
why is it better to do unilateral thyroidectomy if possible?
risk of bilateral surgery much higher
how might the parathyroid gland(s) be salvaged during thyroidectomy?
sometimes reimplantation of the parathyroid tissue into the surgical site will allow for neovascularisation
what is the risk of reimplanting the parathyroid tissue?
risks seeding tumour
what are the surgical options for thyroidectomy?
several techniques for vet to choose from
need to consider whether unilateral/bilateral, esp in regards to removal of parathyroid glands
what are the complications of thyroidectomy which are unrelated to surgical technique?
GA risks - ASA status
unmask CRF if cat and/or a functional mass
hypothyroidism
what are the complications of thyroidectomy which are related to surgical technique and skill?
haemorrhage
seroma formation
laryngeal paralysis
horners syndrome
hypocalcaemia
recurrence of tumour
which thyroidectomy surgeries are at higher risk of haemorrhage?
possible with all, but particularly with canine invasive masses
how can haemorrhage be avoided during thyroidectomy?
careful surgical technique
what affects likelihood of seroma formation after thyroidectomy?
related to size of mass
how can we avoid seroma formation after thyroidectomy?
careful surgical technique
how can horners syndrome develop as a result of thyroidectomy?
damage to sympathetic trunk (rare)
what are the signs of horners syndrome after thyroidectomy?
anisocoria
third eyelid partially across
how can we avoid post-op hypocalcaemia from iatrogenic hypoparathyroidism?
protect the parathyroids by good choice of technique and careful surgical technique
staged procedure - remove one side only (whichever is larger)
consider pre-emptive peri-operative support e.g. pre-op vit D and post-op calcium (both oral)
when is recurrence of a thyroid mass more common?
presence of ectopic tissue
use of an intracapsular technique
with malignant neoplasia
what is important to consider when weighing up medical or surgical management for thyroid masses?
age of patient - will surgery be cheaper than life-long medication if patient is younger
how many parathyroid glands are there in total?
4
name all the parathyroid glands
left extracapsular (cranial)
right extracapsular
left intracapsular (caudal)
right intracapsular
what is the overall role of the parathyroid glands?
increase blood calcium
how are the parathyroid glands arranged?
in 2 sets of pairs
what are the options for medical treatment of primary hyperparathyroidism?
ethanol injection
heat ablation
what is the surgical treatment option for primary hyperparathyroidism?
parathyroidectomy
what is the most important post-op concern after parathyroidectomy?
monitoring for hypocalcaemia
which species more commonly develops primary hyperparathyroidism?
most commonly seen in dogs
what is the prognosis post-op for primary hyperparathyroidism?
usually benign, functional adenoma (95%)
what are the pre-op considerations for parathyroidectomy?
systemic effects of hyperparathyroidism
co-morbidities unrelated to hyperparathyroidism
medical stabilisation
complications
what systemic effects might we see in pre-op parathyroidectomy patients?
hypercalcaemia affects renal function
what might be involved in pre-op medical stabilisation of parathyroidectomy patients?
diuresis with high levels of IVFT to ‘dilute’ the calcium (?)
support renal function, care not to overhydrate
how wide should the clip be for parathyroidectomy?
level of jaw to thoracic inlet
jugular grooves widthways
what approach is used for parathyroidectomy?
ventral midline - px in dorsal recumbency
when might the associated thyroid be removed during parathyroidectomy?
if intracapsular/caudal parathyroid
are multiple glands removed during thyroidectomy?
almost always going to be removing one of four rather than multiples
what complications might occur during thyroidectomy which are unrelated to surgical technique?
complications dur to ASA status
post-op hypothyroidism possible
what complications might occur during thyroidectomy which are related to surgical technique?
haemorrhage
seroma formation
laryngeal paralysis
horners syndrome
hypoparathyroidism
which types of parathyroid masses are more likely to haemorrhage?
possible with all, but particularly with canine invasive masses
how can haemorrhage be avoided during parathyroidectomy?
careful surgical technique
how can laryngeal paralysis be caused by parathyroidectomy?
if damage to recurrent laryngeal nerves
how can laryngeal paralysis be avoided during parathyroidectomy?
careful surgical technique
how might horners syndrome be triggered during parathyroidectomy?
damage to sympathetic trunk (rare)
why can post-op hypocalcaemia occur after parathyroidectomy?
3 remaining parathyroid glands function is suppressed by the functional mass - delay for these to recover function
what should be involved in post-op care after parathyroidectomy?
IVFT - according to clinical appearance and losses
analgesia - avoid NSAIDs
monitor for complications - renal function (BP), calcium
why should NSAIDs be avoided after thyroidectomy?
protect renal function
what is the prognosis for recovery after parathyroidectomy?
usually good
hypocalcaemia can be transiet (days) or take weeks/months to recover
what is the endocrinological result/risk of unilateral thyroidectomy?
removes 1 of 2 thyroids
removes 1 of 2 caudal parathyroids (cranials left in place but may be damaged)
low risk hypocalcaemia and hypothyroidism
what is the endocrinological result/risk of bilateral thyroidectomy?
removes 2 of 2 thyroids
removes 2 of 2 caudal parathyroids (cranials left in place but may be damaged)
higher risk hypocalcaemia
hypothyroidism
what is the endocrinological result/risk of unilateral parathyroidectomy?
removes 1 of 2 thyroids
removes 1 of 2 caudal parathyroids (cranials left but may be damaged/already suppressed)
highest risk hypocalcaemia
low risk hypothyroidism
when do initial signs of iatrogenic hypoparathyroidism usually occur?
within 2-3 days post-op
what are the initial signs of iatrogenic hypoparathyroidism?
inappetence
weakness/lethargy
ptyalism
pawing at face
what are the more advanced signs of iatrogenic hypoparathyroidism?
tremors
tetany
seizures, coma and death
why can it sometimes be difficult to recognise iatrogenic hypoparathyroidism?
can be difficult to differentiate between true hypoparathyroidism and normal GA/post-op effects
how can vitamin D supplementation help with post-parathyroidectomy hypocalcaemia?
increases calcium absorption from the GI tract and reduces loss through kidneys
how should we monitor post-parathyroidectomy calcium?
various protocols recommended for when 1st test and how often should be checked
what should we be testing when monitoring for hypocalcaemia post-parathyroidectomy?
ionised calcium rather than total calcium - bedside ideally
what is the best outcome for post-parathyroidectomy hypocalcaemia?
try to allow the normal and homeostatic processes to sort themselves out without interference
what is the backup plan for post-parathyroidectomy hypocalcaemia?
when blood calcium (ionised) drops and clinical signs appear, start treatment
why is post-op hypocalcaemia tricky to manage?
the remaining parathyroids function is likely to have been suppressed - may require decreased calcium (just below normal) in order for glands to re-activate
what are the hypocalcaemia treatment options?
vitamin D
oral calcium
IV calcium
how should vitamin D be given for hypocalcaemia?
orally, 24 hours before surgery (takes 24-48hrs to have an effect)
why is vitamin D beneficial for hypocalcaemia?
‘wakes up’ the systems ready for the drop in calcium
what is given for oral calcium supplementation?
elemental calcium in divided doses for the owner to give at home
what is given for IV calcium treatment?
10% calcium gluconate
when/how should IV calcium be given for hypocalcaemia?
given slowly over 10-20 mins
give if clinical signs
give if levels very low with/without clinical signs
why should IV calcium only be given if clinical signs present/levels very low?
over-treatment with IV calcium during hospitalisation will slow the recovery of the remaining parathyroid tissue
why should patients receiving calcium treatment be monitored with ECG?
can severely affect heart function - monitor for arrhythmia and bradycardia
what method should be followed for IV calcium administration?
initial bolus, followed by CRI
what type of fluids should be avoided in patients receiving calcium supplementation IV?
fluids containing bicarbonate, lactate or phosphate
why should fluids containing bicarbonate, lactate or phosphate be avoided in patients receiving IV calcium supplementation?
will precipitate calcium
why should calcium not be given subcut?
can cause skin sloughs
describe the orientation of the pancreas
right limb runs next to duodenum
left limb sits next to spleen
body is close to important structures (pancreatic ducts, common bile duct)
how can the pancreas of a cat differ to the dog?
sometimes have a second ‘accessory’ duct
what types of condition can affect the pancreas?
endocrine disease
exocrine disease
pancreatitis
pancreatic abscessation
pancreatic cysts
which conditions of the pancreas can be treated surgically?
endocrine - insulinoma
exocrine - exocrine pancreatic neoplasia
pancreatic abscessation
pancreatic cysts
how serious is exocrine pancreatic neoplasia?
highly aggressive
why doe pancreatic abscesses often occur?
often secondary to pancreatitis
what type of tumour is an insulinoma?
malignant carcinoma
where to insulinomas often metastasise to?
lymph nodes and liver
what are the clinical signs of insulinoma?
lethargy
tremors and seizures
collapse
peripheral neuropathy due to hypoglycaemia
very low hypoglycaemia (<2mmol/l) in an upright dog
how is insulinoma diagnosed?
blood work (insulin/glucose ratio)
imaging
what is involved in pre-op insulinoma management?
feeding regime - q4-6hrs, diabetic food, careful pre-op starving
exercise - gentle, regular
manage hypoglycaemia - good feeding and exercise, educate O on signs
why should we have care with IV glucose administration in patients with insulinoma?
can push glucose even lower with exogenous glucose admin - encourages insulin production
how can we manage a hypoglycaemic crisis?
oral - anything sugary
one-off IV - 0.5-1ml/kg 50% dextrose
glucose infusion - start with 2.5% solution, monitor blood glucose and titrate ASAP if needed
what is involved in glucose management during partial pancreatectomy for insulinoma?
5% dextrose infusion during surgery with glucose monitoring every 30 mins
what are the surgical considerations during partial pancreatectomy?
gentle technique - reduce risk of pancreatitis
small nodule - can be difficult to find
check liver - may have secondary mets
what is the result of a partial pancreactectomy?
removes sources of insulin, provided remove all insulinoma tissue
what different factors need to be considered post-op for insulinoma?
feeding and exercise regime
management of hypoglycaemia
drugs
complications
prognosis after surgery
what might be involved in feeding and exercise management after partial pancreatectomy?
feeding as pre-op initially, may require feeding tube
exercise as pre-op initially
why is it important to monitor glucose post-op for insulinoma?
micro-metastasis can result in persistent hypoglycaemia post-op - look for normalisation
what drugs might be given post-op for insulinoma?
IVFT
analgesia
steroids - helps raise glucose level
octreotide
chemo (strepozocin) - for residual tumour and mets
what complications should we monitor for post-op insulinoma?
persistence of hypoglycaemia
transient hyperglycaemia
pancreatitis
can develop diabetes mellitus
what is the prognosis for insulinoma?
depends on staging -
stage 1 - can survive more than 2 years
stage 3 - can get 6 months with surgery
what gives a better prognosis for insulinoma?
generally accepted that surgery gives a better prognosis than medical management alone
where are the adrenal glands located?
close to kidneys and major blood vessels (CVC, renal vessels)
what is the internal anatomy of the adrenal glands?
outer cortex
inner medulla
what is produced by the adrenal cortex?
androgens
mineralocorticoids
glucocorticoids
what is produced by the adrenal medulla?
catecholamines (e.g adrenaline)
what type of masses typically affect the adrenal cortex?
adenoma/adenocarcinoma
what type of masses typically affect the adrenal medulla?
pheochromocytoma
what are the surgical conditions of the adrenal glands?
adrenal masses - benign/malignant, primary or secondary tumours (renal)
secondary - pituitary-dependent hyperadrenocorticism and secondary adrenal gland hyperplasia/hypertrophy
what is the treatment option for pituitary-dependent hyperadrenocorticism?
hypophysectomy
what are the main clinical signs of adrenal gland disease?
none (incidentaloma)
functional changes
haemoabdomen
why is it important to know if an adrenal mass is functional?
patient with functional mass likely to have more complex medical needs for pre-op stabilisation and/or might not mean surgery is best treatment option
what conditions can result from overproduction from the adrenal cortex?
conns syndrome (mineralocorticoids e.g. aldosterone) - seen in cats
cushings (glucocorticoids e.g. cortisol)
masculinising syndrome (androgens e.g. testosterone)
what conditions results from overproduction from the adrenal medulla?
pheochromocytoma (catecholamines e.g. epinephrine/norepinephrine) –> intermittent hypertension
why can adrenal gland disease result in haemoabdomen?
some adrenal masses will present with spontaneous bleeding, causing retroperitoneal swelling or haemoabdomen
what can classify the severity of adrenal gland neoplasia?
aggression
what type of tumour does a benign enlargement of the adrenal glands tend to be?
typically adenomas
what type of tumour does a malignant enlargement of the adrenal glands tend to be?
typically adenocarcinoma
how aggressive are pheochromocytomas of the adrenal glands?
can be benign or malignant
why are malignant adrenal tumours at higher risk of haemorrhage?
can have a tumour thrombus where the tumour invades the vena cava
what are the pre-op considerations for adrenalectomy?
ASA status - systemic effects of mass, co-morbidities
medical stabilisation to improve ASA status
unilateral vs bilateral surgery
what systemic effects do we need to consider pre-op for adrenalectomy?
conns syndrome can cause hypokalaemia
cushings syndrome likely treated with endogenous steroid = poor surgical candidate
phaeochromocytoma –> excess adrenaline/noradrenaline = unstable patient
what might be involved in pre-op stabilisation before adrenalectomy?
manage hypokalaemia with supplementation
stabilise cushings with medication e.g. trilostane
phaeo - stabilise with medication (e.g. phenoxybenzamine for 2-3 weeks pre-op)
what is phenoxybenzamine?
alpha adrenergic blocker - can help manage phaeochromocytoma
what is important to prepare before bilateral adrenalectomy?
have blood ready - haemorrhage a significant risk
why does adrenalectomy surgery have a high mortality rate (15-20%)?
very challenging anaesthesia, surgery and aftercare
some will die from blood loss on table and some will develop post-op thromboembolism
short and long post-op periods very challenging
how does functionality of the tumour affect peri-operative adrenalectomy management?
patients with functional tumours have more complex needs peri-operatively than non-functional to ensure fit for surgery
what is important to monitor intra-op for adrenalectomy?
CVS function - ECG for arrhythmias, blood pressure
electrolytes
what are the possible intra-op complications during adrenalectomy?
tumour rupture
haemorrhage
tachycardia/arrhythmias
hyper/hypotension
may need supplementation of gluco- and mineralocorticoids during surgery (dexamethasone, sodium, potassium)
what are the possible post-op complications after adrenalectomy?
electrolyte abnormalities
hyper/hypotension
adrenal insufficiency requiring supplementation
delayed healing
pulmonary thromboembolism
SIRS/sepsis
how can post-op adrenal insufficiency be managed after adrenalectomy?
requires supplementation (like an iatrogenic addisons) - mineralocorticoids and glucocorticoids
