Is a thyroid ultrasound indicated for Hashimoto's (Hashimoto's thyroiditis)?

Thyroid Ultrasound for Hashimoto's Thyroiditis

Thyroid ultrasound is NOT routinely indicated for the diagnosis or management of Hashimoto's thyroiditis in adults, as imaging does not help differentiate among causes of hypothyroidism and does not change clinical management. 1

When Ultrasound Is NOT Needed

The American College of Radiology explicitly states that there is no role for ultrasound imaging in the workup of hypothyroidism in adults, including Hashimoto's thyroiditis. 1 The key reasoning includes:

• Imaging for thyroid morphology does not help differentiate among causes of hypothyroidism 1
• All causes of hypothyroidism will have decreased radioiodine uptake, making functional imaging equally unhelpful 1
• The diagnosis of Hashimoto's thyroiditis is made clinically with laboratory confirmation (elevated TSH, positive anti-thyroid peroxidase antibodies, anti-thyroglobulin antibodies) 2
• Treatment is thyroid hormone replacement regardless of imaging findings 1

When Ultrasound IS Indicated in Hashimoto's Patients

Despite the general recommendation against routine imaging, ultrasound becomes appropriate in specific clinical scenarios:

Presence of Thyroid Nodules

• When a palpable thyroid nodule is detected on physical examination 2
• When there is concern for coexisting thyroid malignancy 2
• Hashimoto's thyroiditis patients can develop thyroid nodules that require evaluation for malignancy, with studies showing 28.7-31.5% of operated nodules in HT patients being malignant 3, 4

Suspicious Clinical Features

• Atypical presentation of thyroiditis 2
• Rapidly enlarging thyroid mass (concern for lymphoma, which can develop in HT) 3
• Compressive symptoms such as dyspnea, orthopnea, dysphagia, or dysphonia suggesting goiter with substernal extension 2

Ultrasound Characteristics When Performed

When ultrasound is indicated in Hashimoto's patients with nodules, specific features help risk-stratify:

Benign-Appearing Features in HT Nodules

• Hyperechoic or isoechoic nodules are usually benign 3
• Regular margins are seen in 75% of focal HT nodules 5
• Central vascularity pattern is common in benign HT nodules (85.7%) 5

Malignancy-Suspicious Features

• Hypoechogenicity (though less common in focal HT than in malignant nodules: 29.6% vs 42.3%) 5
• Microcalcifications (significantly less common in focal HT at 3.6% vs 44.4% in malignancy) 5
• Marked hypoechogenicity, irregular margins, or cervical lymphadenopathy strongly suggest malignancy over focal HT 5
• Solid composition, hypoechogenicity, and microcalcifications are the most predictive sonographic features for malignancy in HT patients 4

Role of Fine-Needle Aspiration

• Ultrasound-guided FNA is superior to palpation-guided FNA in HT patients, with 100% sensitivity for detecting malignancy versus missed diagnoses with palpation alone 3
• US-guided FNA helps differentiate focal HT from lymphoma, pseudotumor, and carcinoma, which can be sonographically indistinguishable 3
• FNA showed 90% sensitivity and 61.5% specificity for preoperative diagnosis in HT patients with nodules 4

Critical Pitfalls to Avoid

• Do not order routine ultrasound for straightforward Hashimoto's thyroiditis diagnosed by clinical presentation and thyroid function tests 2
• Do not use radionuclide scanning for hypothyroidism evaluation—it provides no diagnostic value 1
• Do not assume all nodules in HT patients are benign inflammatory changes—malignancy rates are significant (28.7-31.5% in surgical series) 4
• Be aware that elastography has limited value in detecting thyroid cancer in HT patients with severe hypoechoic thyroid tissue 6