Detection of transplant renal artery stenosis: determining normal velocities at the renal artery anastomosis

Purpose: Renal artery anastomosis peak systolic velocity (RAA PSV) exceeding 250 cm/s and a ratio of the renal artery to the adjacent external iliac artery (RAA:EIA) exceeding 1.8 historically suggest significant transplant renal artery stenosis (TRAS). However, the range of RAA PSV in transplants without TRAS has not been established. Methods: A retrospective review of renal transplants at a single institution over 5 years was performed identifying patients without graft dysfunction, failure, or refractory hypertension. RAA PSV obtained during interval postoperative sonograms was recorded. Results: Of 1141 patients, 844 met the inclusion criteria. Mean RAA PSV for 377 patients evaluated within 2 days of transplant measured 195 cm/s; RAA PSV exceeded 250 cm/s in 97 patients (26%). Mean RAA PSV for 820 patients evaluated 1-month post-transplant measured 206 cm/s; RAA PSV exceeded 250 cm/s in 224 patients (27%). Mean RAA PSV for 785 patients evaluated 4-month post-transplant measured 203 cm/s; RAA PSV exceeded 250 cm/s in 201 patients (26%). Mean RAA PSV for 766 patients evaluated 1-year post-transplant measured 189 cm/s; RAA PSV exceeded 250 cm/s in 141 patients (18%). At each of the given time points, 24%–34% of normal patients had RAA-to-EIA ratios greater than 1.8. Conclusion: Approximately, 26% of patients without TRAS have RAA PSV > 250 cm/s in the first 9 months, and 18% do at 1 year. Similar findings also occurred with regards to the RAA-to-EIA ratio threshold of 1.8. In isolation, a PSV over 250 cm/s or 1.8 ratio threshold for suspicion of TRAS will lead to a large number of false-positive assessments.