Endocrine Surgery

Question 1

What are different endocrine surgeries?

Answer 1

• Feline thyroidectomy
• Canine thyroidectomy
• Canine parathyroidectomy
• Adrenalectomy

Question 2

Which thyroid gland is more cranial?

Answer 2

Right

Question 3

what are nearby structure of the thyroid gland?

Answer 3

• Right = carotid sheath, recurrent laryngeal nerve
• Left = Oesophagus, Recurrent laryngeal nerve
• Parathyroid glands

Question 4

What is blood + nerve supply of the thyroid glands?

Answer 4

• Blood supply = cranial thyroid artery (common carotid)
• caudal thyroid artery (brachiocephalic artery)
• Innervation = Thyroid nerve - branch of cranial laryngeal nerve (vagus)

Question 5

Where is it common to get ectopic thyroid tissue?

Answer 5

• Along the trachea
• Thoracic inlet
• Mediastinum
• Thoracic descending aorta

Question 6

Function of thyroid hormone?

Answer 6

• 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

Question 7

CS of hyperthyroidisim?

Answer 7

• 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%):

Question 8

Dx of hyperthyroidism?

Answer 8

• Haematology
• Serum biochemistry - increase liver enzymes + phosphate, decreased creatinine + K+
• Increase total T4
• Scintigraphy

Question 9

Tx of hyperthyroidism?

Answer 9

• Medical =
• iodine restricted diet
• anti-thyroid drugs (carbimazole)
• radioiodine (iodine-131)
• Surgical = thyroidectomy

Question 10

What is pre-op management of thyroidectomy? Cat

Answer 10

• 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

Question 11

What is surgical approach to thyroidectomy? Cat

Answer 11

• 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

Question 12

How do you distinguish thyroid + parathyroid gland?

Answer 12

• Normal thyroid = pale tan + flat
• Thyroid adenomatous hyperplasia = brown + plump
• Parathyroid gland = smaller + paler (look like fat)

Question 13

What are advantages / disadvantages of bilateral thyroidectomy?

Answer 13

• Advantages = Single anaesthetic episode, ££
• Disadvantage = Greater risk hypoparathyroidism

Question 14

What are advantages / disadvantages of staged bilateral thyroidectomy?

Answer 14

• Largest gland removed, other gland removed up to 6mo later - Typically 3-4 weeks
• Advantage = Lesser risk hypoparathyroidism
• Disadvantages = Two anaesthetic episodes, ££££

Question 15

What are different surgical techniques to thyroidectomy?

Answer 15

1. Intracapsular Technique
   - Incision into thyroid capsule = blunt dissection of parenchyma
   - External parathyroid preserved
   - High recurrence rate
2. Extracapsular Technique
   - Thyroid removed within its capsule along with parathyroid
   - High rate hypoparathyroidism in bilateral disease
   - Low recurrence rate
3. Modified Intracapsular Technique
4. Modified Extracapsular Technique

Question 16

What is parathyroid Autotransplantation?

Answer 16

• If external parathyroid is removed / blood supply disrupted
• Dissected parathyroid into pocket in the sternohyoid m + sternothyroid m
• Takes 7-21 days to function

Question 17

What are thyroidectomy complications?

Answer 17

• Haemorrhage
• Dyspnoea
• Laryngeal paralysis
• Horner’s syndrome
• Hypothyroidism
• Hypoparathyroidism
• Recurrence

Question 18

What is iatrogenic hypoparathyroidism? What should be done?

Answer 18

• 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

Question 19

What are nature of canine thyroid tumours?

Answer 19

• Carcinomas
• High metastatic rate
• Non-functional
• Old larger breed dogs

Question 20

How are canine thyroid tumours diagnosed?

Answer 20

• Imaging - US, CT
• Cytology
• DO NOT Biopsy - risk of severe haemorrhage

Question 21

What is pre op management of thyroidectomy in dogs w thyroid tumours?

Answer 21

• No need euthyroid state
• Tx of severe tachycardia, arrythmias + hypertension
• Coagulation panel
• Blood typing + cross-matching

Question 22

What are complications of canine thyroidectomy?

Answer 22

• Haemorrhage
• hypothyroidism
• hypoparathyroidism
• laryngeal paralysis
• megaoesophagus
• aspiration pneumonia

Question 23

What is the mean survival time of thyroid tumours?

Answer 23

• Mobile tumours = 3 years
• Invasive tumours = 6-12months

Question 24

What is seen with primary hyperparathyroidism?

Answer 24

• Excessive production of PTH = hypercalcaemia
• other glands atrophy due to negative feedback
• CS =
• Fibrous osteodystrophy
• PUPD
• Urolithiasis and UTI = Stranguria, pollakiuria, haematuria

Question 25

How is primary hyperparathyroidism diagnosed?
Tx?

Answer 25

• Serum biochemistry = increased ionised calcium, normal renal values, normal to high PTH, Decreased PTH-rp
• Ultrasonography
• Tx = Parathyroidectomy

Question 26

What is post op management of parathyroidectomy

Answer 26

• Monitor Ca conc daily for 5-7days
• Keep calm
• Treat if hypocalcaemia

Question 27

What are different adrenal tumours?

Answer 27

• Non-functional
• Cortisol secretin tumours = adenoma, adenocarcinoma
• result in hyperadrenocorticism (cushings)
• Catecholamine-secreting tumours = Phaeochromocytoma = severe paroxysmal hypertension + tachycardia

Question 28

Dx of adrenal tumours?

Answer 28

• Haematology and biochemistry
• Urinalysis +/- urine metanephrine
• LDDST (low dose dexamethasone test)
• Imaging = Ultrasound, CT - Can be found incidentally

Question 29

What is pre-op management of adrenelectomy?

Answer 29

• 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

Question 30

What are complications of adrenelectomy?

Answer 30

• Haemorrhage
• Pulmonary thromboembolism
• Hypoadrenocorticism
• Wound complications
  Mortality rates =
• 13-60% - adrenocortical tumours
• 9-47% - phaeochromocytoma