Page 132 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 10
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Surgery of the thyroid and

parathyroid glands

Davina Anderson

Introduction Anatomy and function

The thyroid and parathyroid glands are a significant Thyroid glands
cause of disease in both the dog and the cat. They are
intimately related to each other anatomically but the The thyroid glands are paired ductless glands situated
physiological consequences of disease or surgical lateral and slightly ventral to the trachea (Figure 10.1). Their
removal are vastly different. The thyroid gland produces size and position varies with species and breed, but they
thyroxine, which is involved in metabolic homeostasis; are usually found between the fifth and eighth tracheal
parathyroid hormone (PTH) is pivotal for calcium homeo- rings. Dorsal to the right thyroid gland are the common
stasis. Both glands can be affected by neoplastic pro- carotid artery, internal jugular vein, tracheal duct and
cesses that may result in excess secretion of active vagosympathetic nerve trunk. The recurrent laryngeal
hormone. Equally, both glands may cease to produce nerve passes dorsally close to the right thyroid lobe. The
hormones as a result of either iatrogenic damage after left thyroid gland is usually further caudal and adjacent to
surgery or primary inflammatory or autoimmune con- the oesophagus, so that it is not in contact with the carotid
ditions. The BSAVA Manual of Canine and Feline sheath. The caudal laryngeal nerve passes dorsally. In the
Endo crinology deals with medical aspects of gland dis- dog and cat, accessory (ectopic) thyroid tissue is common
orders; this chapter only covers those conditions that and can be found anywhere along the midline cervical or
require surgery. thoracic structures. The cranial thyroid artery arises from

Anatomy of
10.1 the thyroid
and parathyroid glands.

Caudal laryngeal nerve
Cranial thyroid artery
Recurrent laryngeal nerve Left cranial thyroid artery
Left common carotid artery

Left external
Right thyroid gland parathyroid gland
Left thyroid gland

Oesophagus
Right vagosympathetic trunk
Left caudal thyroid artery
Right common carotid artery

Sternohyoid/thyroid muscles

BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, second edition. Edited by Daniel J. Brockman, David E. Holt and Gert ter Haar. ©BSAVA 2018 123

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