When to Get a Thyroid Ultrasound
Thyroid ultrasound is recommended for evaluation of palpable thyroid nodules, abnormal thyroid function tests with suspected structural thyroid disease, or for surveillance of known thyroid cancer. 1
Indications for Thyroid Ultrasound
Nodule Evaluation
- Palpable thyroid nodules - Ultrasound should be performed for all palpable thyroid nodules 1
- Nodules causing clinical symptoms such as compression or cosmetic concerns 2
- Nodules with maximal diameter ≥2cm 2
- Autonomously functioning thyroid nodules 2
Cancer Surveillance
- Post-thyroidectomy surveillance - Perform within 6-12 months after surgery for all patients with differentiated thyroid cancer 2
- Ongoing surveillance in patients with history of thyroid cancer based on risk stratification:
High-Risk Populations
- History of childhood head/neck irradiation 1
- Family history of thyroid cancer 1
- Rising thyroglobulin or thyroglobulin antibodies in patients with history of thyroid cancer 2
Ultrasound Features Requiring Further Evaluation
Suspicious ultrasound features that warrant fine-needle aspiration biopsy (FNAB) include:
- Hypoechogenicity
- Microcalcifications
- Irregular or microlobulated borders
- Solid composition
- Absence of peripheral halo
- Increased intranodular vascularity 1, 3
Risk Stratification Based on Nodule Size
| Nodule Size | Management |
|---|---|
| <1.0 cm | Monitor with ultrasound if no suspicious characteristics [1] |
| 1.0-1.4 cm | Consider FNAB if suspicious characteristics present [1] |
| ≥1.5 cm | FNAB recommended [1] |
Limitations and Pitfalls
- Clinical palpation alone is unreliable - approximately 50% of palpable "solitary" nodules are actually part of multinodular glands when examined with ultrasound 4
- Palpation is only reliable for nodules ≥1 cm in diameter 4
- Small, impalpable thyroid nodules (<1 cm) without suspicious features generally do not require further evaluation 4
- Avoid assuming benign nature without proper evaluation of suspicious nodules 1
Follow-up Recommendations
For benign nodules requiring monitoring:
- Initial follow-up at 1 month
- Subsequent follow-ups at 3,6, and 12 months during the first year
- Annual follow-up thereafter 1
For thyroid cancer surveillance:
- First post-operative ultrasound at 6-12 months 2
- Further imaging depends on risk stratification and thyroglobulin levels 2
Thyroid ultrasound is a highly sensitive imaging modality that plays a crucial role in the evaluation of thyroid pathology and should be used judiciously based on clinical presentation and risk factors.