Figure 2. (a) The left common carotid artery (CCA) demonstrates normal flow throughout systole and diastole. (b) The single vessel beyond the carotid bulb shows prominent diastolic flow; not a typical feature of the external carotid artery (ECA). (c) A longitudinal colour Doppler ultrasound demonstrates a branching artery (arrow) which correctly identifies the single artery as the ECA.