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Year 4 Small Animal Studies > Soft Tissue Surgery: Endocrine Surgery > Flashcards

Soft Tissue Surgery: Endocrine Surgery Flashcards

1
Q

Describe the position of the thyroid glands in cats

What are some important nearby structures?

A
  • Paired- one left, one right in dogs may communicate ventrally
  • Lateral/ventral to trachea 5-8 rings
  • right- tracheal rings 1-5
  • left- tracheal rings 3-8

Nearby structures
* Right- carotid sheath, recurrent laryngeal nerve
* Left- oesophagus, recurrent laryngeal nerve
* Parathyroid glands

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2
Q
  1. What is the cranial border of the larynx
  2. What is in the carotid sheath
  3. What does the recurrent laryngeal nerve supply?
A
  1. Cricoid cartilage
  2. Common carotid artery, internal jugular, vasosympathetic trunk
  3. Innervates most intrinsic muscles of the larynx
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3
Q
  1. What is the blood supply of the thyroid glands?
  2. What is the venous drainage of the thyroid?
  3. What is the innervation of the thyroid gland?
A
  1. Cranial thyroid artery- common carotid branch, Caudal thyroid artery- brachiocephalic artery (absent in most cats)
  2. Cranial thyroid vein, Caudal thyroid vein
  3. Innervation- thyroid nerve
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4
Q

Where is ectopic thyroid tissue commonly found?

A
  • Along the trachea
  • Thoracic inlet
  • Mediastinum
  • Thoracic descending aorta
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5
Q

Where are the parathyroid glands found?

A

Two pairs- location varies
* External- near the cranial pole of each thyroid gland
* Internal- embedded within the caudal pole of each thyroid gland

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6
Q

What are the functions of thyroid?
What are the clinical signs of hyperthroidism?

A

Functions
* 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

Clinical signs
* Weight loss despite polyphagia
* Behavioural changes- hyperactivity
* PUPD
* GI signs- vomiting/diarrhoea
* Respiratory signs

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7
Q

What are common clinical exam findings of hyperthyroid cases?

A
  • Poor BCS
  • May be restless and/or vocal
  • Thin/roughened hair coat
  • Cardiac disease- tachycardia, gallop rhythm, murmurs
  • Hypertension
  • Palpable, mobile cervical mass
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8
Q

How can hyperthyroid disease be diagnosed?

A
  • Haemtology- no specific findings
  • Serum biochem- increased liver enzymes, decreased creatinine, decreased K+, increased phosphate
  • Increased total T4
  • Scintigraphy
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9
Q

What are the advantages and diadvantges of anti-thyroid medications?

A

Advantages
* Readily available
* Reversible in the event of side effects
* Initially cheaper

Disadvantages
* More expensive in the long term
* Side effects
* Patient and owner compliance

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10
Q

What are the advantages and disadvantages of radioactive iodine?

A

Advantages
* Curative
* Minimal side effects
* Cheaper long term
* Minimal cat/owner compliance

Disadvantages
* requires hospitalisation for 4-14 days
* High initial exposure
* Specialist procedure

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11
Q

How is a thyroidectomy preoperatively managed?

A
  • Euthyroid state- antithyroid drugs 6-12 weeks
  • Check for unmasking significant renal disease
  • Cardiac assessment if persistent tachycardia/murmur- B-blocker
  • Treat hypertension
  • Ensure normokalaemia
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12
Q
  1. What are the considerations for thyroidectomy?
  2. What position is best?
  3. Describe the surgical approach?
A
  1. Delicate surgery, careful homeostasis, preserve parathyroid
  2. Dorsal recumbancy- towel under neck, thoracic limbs pulled and secured
  3. Incision from larync to manubrium, sternohyoid and sternohyoid mm bluntly separated to reveal trachea, paratracheal fascia bluntly dissected to expose thyroid glands
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13
Q

How is the parathyroid identified?
Why does care need to be taken?

A

Normal thyroids- pale tan and flat
Parathyroid- typically paler then thyroid tissue

Parathyroid must be differentiated from fat deposits on the thyroid capsule
PT glands have a fine blood vessel that bifurcates and surround the gland

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14
Q

Whats the advantages/disadvantages of bilateral/staged bilateral thyroidectomy?

A

Bilateral
* Adv- single anaesthetic episode
* Dis- greater risk hypoparathyroidism

Stages bilateral- largest gland removed, second upto 6 months later
* Adv- less risk of hypoparathyroidism
* Dis- two anaesthetics

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15
Q

What are the four surgical techniques for thyroidectomy?

A
  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, low recurrence rate
  3. Modified intracapsular
  4. Modified extracapsular

Modified technique preferred

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16
Q
  1. Describe the modified intracapsular technique?
  2. Describe the modified extracapsular technique
A
  1. Initially same approach as for intracapsular technique- incise capsule and blunt dissect gland parenchyma free. Most of remaining capsule then excised- small cuff of capsule left around the external parathyroid
  2. Incision of the capsule around the external parathyroid- preserving its blood supply. Remainder of the capsule and thyroid gland dissected free
17
Q

When is a parathyroid autotransplantation indicated?
Describe the process

A

Performed when external parathyroid is inadvertently removed or blood supply disrupted

  • Small pocket made in the sternohyoid or sternohyoid m
  • Dissected parathyroid gland inserted into this pocket which is sutured closed
  • Vital to avoid concurrent transplant of thyroid cells
  • Takes 7-21 days for transplant to begin functioning- acute hypocalcaemia not prevented
18
Q

What are the potential complications of thyroidectomy?

A
  • Haemorrhage
  • Dyspnoea
  • Laryngeal paralysis
  • Horner’s syndrome- vagosympathetic trunk damage/inflammation
  • Hypothyroidism
  • Hypoparathyroidism
  • Recurrence
19
Q
  1. What does iatrogenic hypoparathyroisism cause?
  2. How is it treated?
A
  1. Mild transient disease in serum calcium- restlessness, face twitching, tetany, weakness, anorexia, panting, seizures
  2. Acute, clinical hypocalcaemia- slow IV calcium gluconate- monitor ECG
    Subclinical hypocalcaemia- oral vitamin D and calcium- 3 weeks
19
Q
  1. What does iatrogenic hypoparathyroisism cause?
  2. How is it treated?
A
  1. Mild transient disease in serum calcium- restlessness, face twitching, tetany, weakness, anorexia, panting, seizures
  2. Acute, clinical hypocalcaemia- slow IV calcium gluconate- monitor ECG
    Subclinical hypocalcaemia- oral vitamin D and calcium- 3 weeks
20
Q

How are canine thyroid tumours diagnosed?

A

Ultrasound- origin, invasivness and vascularity
CT- invasiveness, vascularity, staging
Cytology- confirm thyroid origin
Biopsy contraindicated- high risk of severe haemorrhage

21
Q

What is the preoperative managment for thyroidecotmy in dogs?

A
  • Euthyroid state- not necessary like in cats
  • Treatment of severe tachcardia, arrythmias and hypertension
  • Coagulation panel
  • Blood typing and cross-matching
22
Q
  1. How are canine thyroids removed?
  2. What are the complications?
  3. What is the mean survival time?
A
  1. Mobile tumours most amenable, invasive highly vascular- similar to feline thyroidectomy
  2. Haemorrhage, hypothyroidism, hypoparathyroidism, laryngeal paralysis, megaoesohpagus, aspiration pneumonia
  3. Mobile tumours- 3 years, Invasive tumours- 6-12 months
22
Q
  1. How are canine thyroids removed?
  2. What are the complications?
  3. What is the mean survival time?
A
  1. Mobile tumours most amenable, invasive highly vascular- similar to feline thyroidectomy
  2. Haemorrhage, hypothyroidism, hypoparathyroidism, laryngeal paralysis, megaoesohpagus, aspiration pneumonia
  3. Mobile tumours- 3 years, Invasive tumours- 6-12 months
23
Q

What are the clinical signs of primary hyperparathyroidism?

A

Fibrous oestodystrophy
PUPD
Urolithiasis and UTI- stanguria, pollakuria, haematuria

24
Q

How is primary hyperparathyroidism diagnosed?

A

Serum biochemistry
* Increased ionised calcium
* Normal renal values
* Normal to increased PTH
* Decreased PTH-rp

Ultrasonography

25
Q

How is a parathyroid removed from a dog?

A
  • Same positioning and approach as for thyroidectomy
  • Identifying abnormal glands can be difficult- slightly enlarged and firm, external parathyroid glands visually assessed, internal parathyroid usually palpable
  • External parathyroidectomy- sharp incision between parathyroid and thyroid capsules, partial thyroidectomy if incomplete excision
  • Internal parathyroid ectomy- partial thyroidectomy- remove the caudal pole of the thyroid containing the affected gland
25
Q

How is a parathyroid removed from a dog?

A
  • Same positioning and approach as for thyroidectomy
  • Identifying abnormal glands can be difficult- slightly enlarged and firm, external parathyroid glands visually assessed, internal parathyroid usually palpable
  • External parathyroidectomy- sharp incision between parathyroid and thyroid capsules, partial thyroidectomy if incomplete excision
  • Internal parathyroid ectomy- partial thyroidectomy- remove the caudal pole of the thyroid containing the affected gland
26
Q

How is parathyroidectomy post operatively managed in dogs?

A
  • Monitor Ca concentration for 5-7 days
  • Keep calm- cats indoors for 14 days
  • Treatment of hypocalcaemia as previously described
  • Recurrence rate
27
Q
  1. Where are the adrenal glands located?
  2. Describe the inner composition of adrenal glands?
A

Located medial to cranial poles of each kidney
* Left- adjacent to the aorta
* Right- adhered to the caudal vena cava

Outer cortex and internal medulla
Cortex- zona glomerulus (aldosterone), zona fasiculata (glucocorticoids), reticularis (sex hormones)
Medulla- catecholamines- adrenaline

28
Q

What is the difference btween an adenoma or phaeochromocytoma with adrenal tumours?

How are they diagnosed?

A

Adenoma- cortisol-secreting tumours
Phaeochromocytoma- catecholamine-secreting tumours

Diagnosis
* Haematology and biochemistry
* Urinalysis ± urine metanephrine
* LDDST
* Imaging: ultrasound, CT

29
Q

What are hyperadrenocorticism clinical signs?

A
  • PUPD
  • PP
  • Panting
  • Abdominal enlargment
  • Alopecia
  • Muscle weakness
  • Lethargy
30
Q

What is the preoperative managment for adrenalectomy?

A

Cortisol-secreting tumours:
* Trilostane for 3-4 weeks- reduce immunosupression, hypertension, hypercoagulability, pancreatitis, wound healing complications

Phaechromocytomas
* alpha blocker- 2-3 weeks- limit inoperative hypertension
* B-blocker may also be required- limit persistent tachycardia

Very difficult anaesthetics

31
Q

Describe the process of an adrenalectomy?

A
  • Ventral midline coeliotomy
  • Exposure of the right adrenal gland is more complicated- left- colonic manouvre
    Right- transection of hepatorenal ligament, retraction of the right lateral and caudal hepatic lobes cranially
  • Incise peritoneum at lateral aspect of the gland- avoiding aorta, vena cava and renal vasculature
  • Gland meticulously dissected free
    While minimizing manipulation as much possible, more difficult for invasive masses, concurrent unilateral nephrectomy may be required
32
Q

What are the potential complications of adrenalectomy?

A
  • Haemorrhage
  • Pulmonary thromboembolism
  • Hypoadrenocorticism
  • Wound complications

Year 4 Small Animal Studies (97 decks)

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