Sonographic features of focal Hashimoto's thyroiditis.

Objective: To evaluate the diagnostic values of gray-scale and color Doppler ultrasound in the diagnosis of focal Hashimoto's thyroiditis (FHT).
Methods: The gray-scale and colour Doppler ultrasound data of 120 patients with histopathologically confirmed FHT were retrospectively studied. The background of thyroid parenchyma was subjectively evaluated as absence or presence of diffuse Hashimoto's thyroiditis. The vascular types of thyroid nodules were determined as follows: hypovascularity, marked internal flow, marked peripheral flow, and focal thyroid inferno.
Results: Among all 120 nodules, 71 (59.2%) were located in normal thyroid parenchyma, 49 (40.8%) in the background of diffuse Hashimoto's thyroiditis. In the normal thyroid background, hypoechoic nodules accounted for 85.9% (61/71), and only 14.1% (10/71)nodules were isoechoic or hyperechoic. However, in the background of diffuse Hashimoto's thyroiditis, 40.8% were hypoechoic and 59.2% were isoechoic or hyperechoic. The difference was statistically significant (P<0.001). In terms of the vascular types, the hypovascularity, marked internal flow, marked peripheral flow, and focal thyroid inferno accounted for 45 %, 25.9%, 20.8%, and 8.3%, respectively.
Conclusion: The "focal inferno" is a relative specific color Doppler feature of FHT.