Role of ultrasound in the assessment of nodular thyroid disease

The role for ultrasound (US) in the assessment of nodular thyroid disease has increased in recent years. This expanded role has been highlighted in recent consensus guidelines on the management of nodular thyroid disease. In this review, we address the potential roles for US in assessing thyroid nodules and review these recent guidelines. In particular, we review the evidence that US characteristics of thyroid nodules can predict the risk of malignancy. A predominantly solid nodule, hypoechogenicity, microcalcification, macrocalcification, ill-defined margins, intranodular vascularity, and taller-than-wide shape have all been associated with increased risk of malignancy, but no single US characteristic is sufficiently sensitive or specific to exclude or diagnose malignancy by itself. However, the use of combinations of US characteristics to stratify nodules into high and low risk for malignancy appears a promising strategy. Unselected nodules without any suspicious US features have a low risk of malignancy (<2%), whereas malignancy rates are much higher in nodules with at least two suspicious features. Recent guidelines endorse this approach of using combinations of US features to guide nodule selection for fine needle aspiration.