Guideline Recommendations for Imaging Evaluation of an Enlarged Thyroid Gland (Goiter)

1. Preferred Initial Imaging Modality

The American College of Radiology recommends thyroid ultrasound as the investigation of choice for evaluating an enlarged thyroid gland. 1
Ultrasound is the preferred first‑line imaging technique because it confirms that a neck mass originates from the thyroid gland. 1
Ultrasound characterizes the size and morphology of the goiter, providing essential anatomic detail. 2
When the goiter is nodular, ultrasound evaluates suspicious nodule features to guide further management. 3

Substernal extension – CT of the neck is indicated because it is superior to ultrasound for assessing mediastinal involvement. 1, 4
Deep retropharyngeal extension – CT is recommended to delineate extension into the retropharyngeal space. 2
Obstructive symptoms – CT quantifies tracheal compression when patients present with airway‑related complaints. 5
Surgical planning – CT is advised to map a compressive goiter before operative intervention. 6
CT is preferred over MRI for goiter assessment because it is less susceptible to respiratory motion artifact. 1
Iodinated contrast is unnecessary for routine goiter CT unless an infiltrative neoplasm is suspected. 5

Serum TSH should be obtained before imaging; a subnormal TSH (suggesting thyrotoxicosis) warrants consideration of radionuclide uptake and scan. 7
In euthyroid patients with goiter, imaging proceeds directly to ultrasound without additional functional testing. 2

Radionuclide uptake and scan has a limited role but may be useful when the goiter is associated with thyrotoxicosis. 7, 8
The scan confirms that the entire enlarged gland consists of thyroid tissue. 5
In multinodular goiter, radionuclide results should be compared with ultrasound to identify hypofunctioning or isofunctioning nodules that may require biopsy. 7
Iodine‑123 is preferred over Iodine‑131 for thyroid imaging because of superior image quality. 1

MRI – Not a first‑line option; it is more expensive and prone to respiratory motion artifact. 1, 6
FDG‑PET/CT – Not recommended as an initial imaging study for goiter. 2, 8
Routine CT or MRI is unnecessary at initial work‑up or during follow‑up unless specific indications (e.g., substernal extension, surgical planning) are present. 6

Do not bypass ultrasound and proceed directly to CT, even when substernal extension is suspected; ultrasound should always be performed first. 2
Do not order radionuclide scanning in euthyroid patients with a simple goiter, as it adds no diagnostic value. 3
Do not use iodinated contrast for routine goiter CT; reserve contrast only for cases where an infiltrative neoplasm is suspected. 5

In patients with hyperthyroidism and a clinically evident goiter where Graves’ disease is not clearly diagnosed, the American College of Endocrinology and the American Association of Clinical Endocrinologists recommend performing radioactive iodine uptake (RAIU) and scintigraphy to clarify the underlying cause. 9
When thyroid nodularity is suspected or identified on examination or ultrasound, the same guideline advises adding a thyroid scan to assess the functional status of the nodules. 9

For individuals with diffuse thyroid enlargement and no nodules, a diffuse uptake pattern on RAIU is consistent with Graves’ disease and directs standard hyperthyroidism treatment (antithyroid drugs, radioactive iodine, or surgery). 9
Nodules that are non‑functioning on scintigraphy or that display suspicious sonographic features should be managed according to the thyroid nodule guidelines used for euthyroid patients, including consideration of fine‑needle aspiration. 10
Nodules ≥ 1 cm with suspicious ultrasound characteristics should undergo fine‑needle aspiration before radioactive iodine therapy is selected, to exclude malignancy. 10

The 2011 ATA/AACTE guideline estimates the prevalence of thyroid cancer in toxic multinodular goiter at up to 9 %, which is comparable to the 10.6 % prevalence reported in nontoxic multinodular goiter, highlighting the importance of thorough nodule evaluation. 10