Color duplex sonography of occlusion of the common carotid artery with reversed flow in the extracranial internal carotid artery

In a small percentage of cases with an occluded common carotid artery (CCA), the patency of the arteries beyond the carotid bulb is preserved. Color duplex sonography is useful for assessing blood flow in these vessels. We present a case of retrograde flow in an internal carotid artery (ICA) with an occluded ipsilateral CCA identified using color duplex sonography in a 70-year-old man with diabetes and known atherosclerotic disease. Color duplex sonography revealed that the right CCA was totally occluded near its origin and that flow was re-established at the bulb. Flow in the right ICA was directed cephalad, with a low-frequency, damped waveform; flow in the right external carotid artery (ECA) was bidirectional, with increased reversed diastolic flow. Extensive atherosclerotic lesions were also found in the left side. Endarterectomy of the left carotid bifurcation was performed. Follow-up color duplex sonography 3 months later revealed a small increase of stenosis in the left CCA and mild stenosis in the left ICA. The right CCA remained occluded, but reversed flow with a high-resistance flow pattern was seen in the ipsilateral ICA that supplied the ECA, which had cephalad-directed flow.