Endocrine Surgery Flashcards
What are different endocrine surgeries?
- Feline thyroidectomy
- Canine thyroidectomy
- Canine parathyroidectomy
- Adrenalectomy
Which thyroid gland is more cranial?
Right
what are nearby structure of the thyroid gland?
- Right = carotid sheath, recurrent laryngeal nerve
- Left = Oesophagus, Recurrent laryngeal nerve
- Parathyroid glands
What is blood + nerve supply of the thyroid glands?
- Blood supply = cranial thyroid artery (common carotid)
- caudal thyroid artery (brachiocephalic artery)
- Innervation = Thyroid nerve - branch of cranial laryngeal nerve (vagus)
Where is it common to get ectopic thyroid tissue?
- Along the trachea
- Thoracic inlet
- Mediastinum
- Thoracic descending aorta
Function of thyroid hormone?
- Increase metabolic rate
- Increase catabolism of fat and muscle
- Increase body temperature
- Increase sympathetic drive
- Direct action on emetic centre and cardiac muscle
- Some impact on every tissue/organ in the body
CS of hyperthyroidisim?
- Weight loss despite polyphagia
- Behavioural changes
- Hyperactivity/restlessness/aggression/vocalization/over-
grooming - PU/PD
- Gastrointestinal signs (vomiting / diarrhoea)
- Respiratory signs, tremors, seizures, ventroflexion of the neck: (less common)
- Apathetic hyperthyroidism (<10%):
Dx of hyperthyroidism?
- Haematology
- Serum biochemistry - increase liver enzymes + phosphate, decreased creatinine + K+
- Increase total T4
- Scintigraphy
Tx of hyperthyroidism?
- Medical =
- iodine restricted diet
- anti-thyroid drugs (carbimazole)
- radioiodine (iodine-131)
- Surgical = thyroidectomy
What is pre-op management of thyroidectomy? Cat
- Aim for euthyroid state (anti-thyroid drugs 6-12wks)
1. GA safety
2. Check for unmasking of significant renal disease - Cardiac assessment if persistent tachycardia/murmur
- Treat hypertension
- Ensure normokalaemia
What is surgical approach to thyroidectomy? Cat
- Positioning = dorsal recumbency
- Ventral midline cervical approach
- incise from larynx to manubrium
- blunt dissection of sternohyoid + sternothyroid m. to reveal trachea
- blunt dissection of paratracheal facia to expose thyroid glands
How do you distinguish thyroid + parathyroid gland?
- Normal thyroid = pale tan + flat
- Thyroid adenomatous hyperplasia = brown + plump
- Parathyroid gland = smaller + paler (look like fat)
What are advantages / disadvantages of bilateral thyroidectomy?
- Advantages = Single anaesthetic episode, ££
- Disadvantage = Greater risk hypoparathyroidism
What are advantages / disadvantages of staged bilateral thyroidectomy?
- Largest gland removed, other gland removed up to 6mo later - Typically 3-4 weeks
- Advantage = Lesser risk hypoparathyroidism
- Disadvantages = Two anaesthetic episodes, ££££
What are different surgical techniques to thyroidectomy?
- Intracapsular Technique
- Incision into thyroid capsule = blunt dissection of parenchyma
- External parathyroid preserved
- High recurrence rate - Extracapsular Technique
- Thyroid removed within its capsule along with parathyroid
- High rate hypoparathyroidism in bilateral disease
- Low recurrence rate - Modified Intracapsular Technique
- Modified Extracapsular Technique
What is parathyroid Autotransplantation?
- If external parathyroid is removed / blood supply disrupted
- Dissected parathyroid into pocket in the sternohyoid m + sternothyroid m
- Takes 7-21 days to function
What are thyroidectomy complications?
- Haemorrhage
- Dyspnoea
- Laryngeal paralysis
- Horner’s syndrome
- Hypothyroidism
- Hypoparathyroidism
- Recurrence
What is iatrogenic hypoparathyroidism? What should be done?
- If parathyroid tissue removed - decrease in serum calcium
- CS = hypocalcaemia = restlessness, muscle twitching, weakness, anorexia, panting
- Tx = IV calcium gluconate + monitor ECG whilst giving
- Oral vitamin D + calcium
What are nature of canine thyroid tumours?
- Carcinomas
- High metastatic rate
- Non-functional
- Old larger breed dogs
How are canine thyroid tumours diagnosed?
- Imaging - US, CT
- Cytology
- DO NOT Biopsy - risk of severe haemorrhage
What is pre op management of thyroidectomy in dogs w thyroid tumours?
- No need euthyroid state
- Tx of severe tachycardia, arrythmias + hypertension
- Coagulation panel
- Blood typing + cross-matching
What are complications of canine thyroidectomy?
- Haemorrhage
- hypothyroidism
- hypoparathyroidism
- laryngeal paralysis
- megaoesophagus
- aspiration pneumonia
What is the mean survival time of thyroid tumours?
- Mobile tumours = 3 years
- Invasive tumours = 6-12months
What is seen with primary hyperparathyroidism?
- Excessive production of PTH = hypercalcaemia
- other glands atrophy due to negative feedback
- CS =
- Fibrous osteodystrophy
- PUPD
- Urolithiasis and UTI = Stranguria, pollakiuria, haematuria
How is primary hyperparathyroidism diagnosed?
Tx?
- Serum biochemistry = increased ionised calcium, normal renal values, normal to high PTH, Decreased PTH-rp
- Ultrasonography
- Tx = Parathyroidectomy
What is post op management of parathyroidectomy
- Monitor Ca conc daily for 5-7days
- Keep calm
- Treat if hypocalcaemia
What are different adrenal tumours?
- Non-functional
- Cortisol secretin tumours = adenoma, adenocarcinoma
- result in hyperadrenocorticism (cushings)
- Catecholamine-secreting tumours = Phaeochromocytoma = severe paroxysmal hypertension + tachycardia
Dx of adrenal tumours?
- Haematology and biochemistry
- Urinalysis +/- urine metanephrine
- LDDST (low dose dexamethasone test)
- Imaging = Ultrasound, CT - Can be found incidentally
What is pre-op management of adrenelectomy?
- If cortisol secreting tumour = treat cushings first
= Trilostane for 3-4wks =
-Reduce immunosuppression, hypertension,
hypercoagulability, pancreatitis and wound healing
complications - Management of hypertension if persistent (ACEI)
- Phaeochromocytomas =
- α-blocker (phenoxybenzamine) for 2-3 weeks
- Limit intraoperative hypertension
- Β-blocker (propranolol/atenolol) may also be required
- Limit persistent tachycardia
What are complications of adrenelectomy?
- Haemorrhage
- Pulmonary thromboembolism
- Hypoadrenocorticism
- Wound complications
Mortality rates = - 13-60% - adrenocortical tumours
- 9-47% - phaeochromocytoma
