An ultrasound is a radiological investigation that uses sound waves to generate an image of your thyroid gland. The ultrasound examination may provide information on the size of your thyroid, the presence and size of one or more nodules, and whether a nodule is solid, or contains fluid (cystic). Many nodules may be partly solid, and partly filled with fluid. Ultrasound assessments may also suggest the presence of calcification, and may detect one or more lymph nodes in the neck adjacent to the thyroid. The ultrasound exam is painless, and may take from 15-45', depending on the complexity of the exam, the local anatomy of the patient, and the skill of the ultrasonographer. Frequently, a biopsy may be carried out under ultrasound guidance.
An ultrasound examination does not provide sufficient information to determine whether a nodule is benign or malignant. Features that may sometimes be associated with thyroid cancers, such as calcifications and prominent lymph nodes, may also be seen in the presence of benign thyroid disease.
Serial ultrasound examinations may be useful for determining whether one or more thyroid nodules have changed (increased or decreased) in size over various time periods.
Given the sensitivity of ultrasounds, it is quite common for additional small nodules to be detected, several mm in size, that were not detected during physical examination of the thyroid. These very small nodules are not usually of major clinical significance.
Are there features on ultrasound that increase the suspicion that a nodule may represent a thyroid cancer?
Although not diagnostic, a number of studies suggest that fine calcifications within a nodule increase the risk of thyroid cancer in that nodule. See Role of intrathyroidal calcifications detected on ultrasound as a marker of malignancy. Laryngoscope. 2004 Oct;114(10):1753-7.