Fig. 2. Power Doppler ultrasound (US)-guided sialography (51/F) for diagnosing sialodochitis of the left parotid gland. A. On preoperative US images, there are no observable pathologic changes in the parotid gland. B. The position of the catheter in the main duct is confirmed by a linear hyperechoic signal with posterior enhancement (arrow). C. During fluid injection, an increase in blood flow is observed at the tip of the universal cannula. D. As the contrast agent entered, parotid gland duct dilatation, periductal vasodilation, and increased blood flow are observed.