Combined Two-Dimensional Ultrasound Doppler Technique

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Abstract
A combination of a real time phased array sector scanner and a range-gated 16-channel pulsed Doppler system was used for the evaluation of renal artery flow patterns in 25 echogenic subjects. Eight of these had renal artery stenosis, 5 an increased peripheral resistance in the kidney, and 12 showed normal renal flow patterns with consistent forward flow during the entire heart cycle. In normals, the ratio of end systolic (S2) versus early peak systolic (S1) velocity was 0.52 ± 0.11 (range 0.37–0.84). In the patients with renal artery stenosis S2/S1 ranged from 0 to 0.30. Five of the 8 patients with renal artery stenosis could be evaluated before and after percutaneous transluminal dilatation (PTA). After successful PTA (diameter reduction < 50% and pressure gradient < 20 mm Hg) S2/S1 returned to normal. The patients with increased peripheral resistance due to an angiographically proven small kidney exhibited a variety of flow patterns with S2/S1 ranging from 0 to 0.29, similar to the ones with renal artery stenosis. The results suggest that the noninvasive determination of the ratio S2/S1 with the aid of ultrasound Doppler measurements permits a differentiation between normal and abnormal flow patterns and can be applied for the follow-up of patients after PTA. In utilizing the described method, neither the angle between the Doppler beam and the vessel axis, nor the vessel diameter must be evaluated.

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