Thyroid anatomy, scan technique, and pathology Flashcards
What is the normal volume of a thyroid in males and females?
Males - 12-18cc
Females - 10-15cc
What part of a lesion and what piece of anatomy are you using to define the echogenicity of a nodule?
The solid portion compared to the thyroid parenchyma (hyperechoic) or the strap muscles (hypoechoic)
What hormones does the thyroid produce?
T3, T4, and calcitonin
What is produced as a precursor for the production of T3 and T4?
Thyroglobin
Where does the oesophagus sit in relation to the thyroid?
Posterior to left lobe
What are some US signs of glandular enlargement, aside from measurements?
Bulging of the anterior surface of both lobes and lateral extension of lobes over the CCA’s
What are three congenital abnormalities of the thyroid (+ brief description)?
Pyramidal lobe (persistant distal portion of the thyroglossal duct arising from isthmus)
Tubercle of Zuckerkandl (extension of normal thyroid tissue from posterior aspect of rt/lt lobe inferomedially)
Ectopic thyroid (check base of tongue for potential thyroid remnant - lingual thyroid)
What is a thyroglossal duct cyst?
Cyst which arises from a failure of the thyroglossal duct to shrink.
Where are thyroglossal duct cysts usually located?
Infrahyoid
What is thyroid hyperplasia and why does it occur?
Enlargement of the thyroid from anything that lowers intrathyroidal iodine levels.
What are colloid nodules?
Benign hyperplastic nodules made of thyroid tissue.
What are the US appearances of colloid nodules?
Isoechoic
Can be hyperechoic due to interfaces between cells and colloid
What are some benign features of thyroid nodules?
Hypoechoic halo - usually from peripheral vessel or oedema
Anechoic (cystic) areas from degenerative change
Bright echogenic foci with comet-tail artifact
Thin intracystic septations
What are the US appearances of multi-nodular goitre?
Multiple discrete nodules separated by normal tissue
Enlarged gland throughout
No normal tissue
What are the US appearances of benign follicular adenoma?
Difficult to distinguish from hyperplastic nodules
Often have hypoechoic halo from fibrous capsule and vessels
Spoke-wheel vessel arrangement
What are the US appearances of an intraparathyroid adenoma?
Round/oval well-circumscribed, hypoechoic, solid lesion
Hypervascular with marginal vessels
What are the US appearances of ectopic thymus?
Well-defined, irregular lesion in/immediately caudal to thyroid
Dot-dash pattern
What are the US appearances of papillary thyroid cancer?
Punctate echogenic foci (infarction of papillae tips)
Microcalcs
Hypoechoic solid tumour
What are the US features of anaplastic thyroid cancer?
Large, ill-defined mass
Heterogenous echogenicity
Calcs
Invasion into soft tissues
What does primary thyroid lymphoma look similar to?
Hashimotos thyroiditis
What are the most sinister features of a thyroid nodule?
Solid
Hypoechoic
Taller than wide
Lobulated, irregular, or extrathyroidal extension
Peripheral rim calcs or PEF
What is Grave’s disease?
Hyperfunction of the thyroid
What are the US appearances of Grave’s disease?
Enlarged thyroid (may be more heterogenous than with diffuse goitre)
Hypoechoic
Hypervascularity
What are the different types of thyroiditis?
Autoimmune (Hashimoto’s)
Acute (bacterial infection - rare)
Chronic (fibrosing form)
Post-partum
