What is the arterial and venous supply to the thyroid gland?

Arterial supply Superior and inferior thyroid arteries on both sides. The superior thyroid artery is a branch of the external carotid and the inferior thyroid artery is a branch of the thyrocervical trunk, which in turn is a branch of the subclavian artery. At times the single thyroid ima artery, which is a direct branch of the brachiocephalic trunk, may be present in the midline.

Venous supply This is via the superior, middle and inferior thyroid veins on both sides. The former two drain into the internal jugular veins whereas the inferior thyroid veins drain into the brachiocephalic veins.

What specific pre-operative measures are taken prior to a thyroidectomy for thyrotoxicosis?

• Patients must be made euthyroid

• Vocal cord assessment using indirect laryngoscopy

• Biochemical analysis of calcium metabolism pre-operatively

• β-blockers may also be considered in an unstable patient

• In large retro-sternal goitres a CT scan is performed to assess tracheal deviation and the extent of retro-sternal extension

• Iodine for 2 weeks pre-operatively can reduce the vascularity of the gland

What different types of thyroidectomy do you know?

• Hemithyroidectomy (lobectomy or isthmusectomy)

• Total thyroidectomy (subtotal, near total or total)

What is a subtotal thyroidectomy?

Subtotal thyroidectomy refers to the excision of the entire gland but leaving about 4 g of thyroid tissue on each side. It is thought that this will reduce the risk of damage to the recurrent laryngeal nerves as well as protecting the parathyroids. There is also enough thyroid tissue left behind to avoid post-operative thyroid hormone replacement.