Subacute thyroiditis is also called subacute granulomatous thyroiditis or non-infectious thyroiditis. Clinical manifestations include low-grade fever, anterior cervical pain, enlarged thyroid gland, and accelerated blood sedimentation. The typical features of ultrasound are hypoechoicity, marked tenderness, and increased thickness. Hypoechoic changes are mainly limited hyperechoic, ultrasound can see one or more uneven hyperechoic areas in one or both thyroid glands, with blurred edges, patchy shape, and irregular pattern, and in a few cases, there will be a large area of diffuse hyperechoic area. The blood flow signal is slightly increased compared with the surrounding thyroid parenchyma and is unevenly distributed, with no obvious vascular encircling or hemodynamic signs, and the arterial flow rate is essentially normal.