Is a thyroid ultrasound recommended for patients with thyroiditis?

Thyroid Ultrasound for Thyroiditis

Thyroid ultrasound should be ordered selectively for thyroiditis—it is indicated when there is a palpable nodule, atypical presentation, concern for coexisting malignancy, or need to characterize morphology, but it is not routinely necessary for straightforward cases diagnosed by clinical presentation and thyroid function tests. 1

Initial Diagnostic Approach

The evaluation of thyroiditis should begin with thyroid function tests, particularly TSH measurement, before considering any imaging. 1 This laboratory-first approach is critical because:

• TSH results guide the appropriate imaging pathway and prevent unnecessary testing 1
• Most thyroiditis cases can be diagnosed clinically with laboratory confirmation alone 2
• Imaging does not help differentiate among causes of hypothyroidism in adults 2

When Ultrasound IS Indicated for Thyroiditis

Proceed with thyroid ultrasound in the following specific scenarios:

• Palpable thyroid nodule requiring characterization for malignancy risk 1
• Atypical clinical presentation where the diagnosis is uncertain 1
• Concern for coexisting thyroid malignancy, particularly in Hashimoto's thyroiditis where there is increased cancer risk 3
• Obstructive symptoms such as dyspnea, orthopnea, dysphagia, or dysphonia suggesting goiter 1
• Suspected substernal extension with respiratory compromise (though CT/MRI may be needed) 1

Specific Thyroiditis Subtypes Where Ultrasound Adds Value

Hashimoto's Thyroiditis:

• Ultrasound demonstrates diffuse hypoechogenicity in approximately 18-20% of patients with autoimmune thyroiditis 4
• This hypoechoic pattern predicts hypothyroidism development—63.6% of patients with reduced echogenicity had or developed hypothyroidism versus 0% with normal echogenicity over 18 months 4
• Ultrasound helps identify nodules requiring fine-needle aspiration, as malignancy occurs in hypoechoic masses and US-guided FNA has 100% sensitivity for detecting cancer 3

Subacute Granulomatous Thyroiditis:

• Characteristic findings include ill-defined hypoechoic lesions without discrete round/oval shape and absence of hypervascularity 5
• Ultrasound confirms diagnosis when combined with painful neck swelling and/or fever 5

When Ultrasound Is NOT Indicated

Do not order ultrasound for:

• Routine hypothyroidism workup in adults—imaging does not differentiate causes and all show decreased radioiodine uptake 2
• Straightforward clinical thyroiditis diagnosed by symptoms and TSH/antibody testing alone 1
• Screening purposes without specific clinical indication 2

Common Pitfalls to Avoid

• Ordering radionuclide scanning instead of ultrasound in euthyroid patients wastes resources and provides low diagnostic value 1
• Failing to check TSH before imaging leads to unnecessary testing and potential radiation exposure 1
• Using ultrasound alone to diagnose thyroiditis without correlating with thyroid function tests and clinical presentation 1
• Assuming normal ultrasound excludes autoimmune thyroiditis—focal thyroiditis can occur with normal echogenicity 4

Algorithmic Decision Framework

1. Start with TSH and thyroid antibodies (TPOAb, thyroglobulin antibodies)
2. If palpable nodule present → Order ultrasound to characterize and guide FNA if needed
3. If obstructive symptoms present → Order ultrasound to assess goiter size and substernal extension
4. If atypical presentation or diagnostic uncertainty → Order ultrasound for morphological evaluation
5. If straightforward clinical thyroiditis with appropriate labs → Ultrasound not needed; treat based on clinical diagnosis

Role of Doppler Ultrasound

Doppler ultrasound can differentiate overactive thyroid (increased blood flow in Graves disease) from destructive thyroiditis (decreased blood flow), with sensitivity 95% and specificity 90%. 2 However, radionuclide uptake study remains preferred as it directly measures thyroid activity rather than inferring from blood flow. 2