BACKGROUND:
Nowadays, duplex ultrasonography is used both for screening and for preoperative assessment of carotid arteries and has in many institutions completely replaced carotid angiography for the latter purpose. The study aimed to identify resistivity index abnormalities in common carotid arteries in patients with occluded or severely stenosed internal carotid artery.

METHODS:
16 patients with severe (>70%) internal carotid artery stenosis or occlusion were studied by Duplex ultrasonography for a period of 12 months.

FINDINGS:
The mean age was 73.37±7.67 years. Resistivity index in common carotid artery was 0.85±0.03 on stenotic side compared with 0.74±0.04 on contralateral side (p<0.05). There was no side deference regarding flow velocities.

CONCLUSION:
In patients with occluded or severly stenosed internal carotid artery, compensatory vasodilatation occurs in same side in cerebral vessels and this is too significant to result in decrease of resistivity index on the contralateral common carotid artery.

KEY WORDS:
Duplex ultrasonography, resistivity index, peak systolic velocity