Renal Doppler ultrasound: comparison of measurements sampled in different anatomical locations

Purpose Renal Doppler ultrasound can be used to predict acute kidney injury and assess venous congestion. There is no consensus on which renal vessels should be used for Doppler sampling. This study compares renal Doppler ultrasound measurements obtained in renal hilar and interlobar arteries and veins in patients recovering from open-heart surgery. Methods This secondary analysis included data from 99 patients who underwent cardiac surgery. Doppler ultrasound was performed on both hilar and interlobar vessels in each kidney and renal venous flow pattern, renal venous stasis index (RVSI), and renal arterial resistive index (RI) were assessed. Results For renal venous flow pattern Kappa was 84% for hilar vs interlobar measurements, 63% for hilar measurements on either side, and 77% for interlobar measurements on either side. When comparing RVSI the biases ranged from 0.2–4.8%, limits of agreement were consistently wide, and percentage error ranged from 96–133%. The comparisons of RI showed biases from 0.1–0.4% with limits of agreement consistently narrow. Percentage error ranged from 9.9–12.3% Conclusions In a population of postoperative open-heart cardiac surgery patients, comparable results can be expected when sampling renal venous flow pattern from hilar and interlobar veins. Overall low bias but also low precision can be expected when sampling RVSI in hilar and interlobar veins on either side. In regard to RI, low bias and high precision can be expected when sampling from hilar and interlobar arteries on either side.