Resistive index predicts renal prognosis in chronic kidney disease: results of a 4-year follow-up

Abstract

While the clinical validity of Doppler ultrasonography in chronic kidney disease (CKD) is still controversial, we have shown in a 2-year follow-up study that the resistive index (RI) could estimate renal prognosis in CKD. The purpose of the present study is to determine whether RI could predict long-term renal prognosis in CKD. We performed a 4-year follow-up study with an observational cohort of 281 CKD patients (GFR 51 ± 31 ml/min/1.73 m(2), age 54 ± 17 years). The patients were examined by Doppler ultrasonography for RI [(peak-systolic velocity--end-diastolic velocity)/peak-systolic velocity] to be calculated. Glomerular filtration rate (GFR) was estimated with the revised Japanese equation. Worsening renal function was defined as a decrease in GFR of at least 20 ml/min/1.73 m(2) or the need for long-term dialysis therapy until the end of the 4-year follow-up. Among the 281 CKD patients, 89 patients presented with worsening renal function during the 4-year follow-up. When we divided the patients into two groups by RI value of 0.70, Kaplan-Meier analysis showed that the event-free rates of worsening renal function at 48 months were 0.86 and 0.37 in patients with RI ≤ 0.70 and RI > 0.70, respectively (log-rank test, p < 0.001). Cox proportional-hazard analysis identified overt proteinuria (≥ 1.0 g/g creatinine), high RI (>0.70), low GFR (<50 ml/min/1.73 m(2)) and high systolic blood pressure (≥ 140 mmHg) as independent predictors of worsening renal function. This study demonstrated that high RI as well as proteinuria, low GFR, and hypertension were independent risk factors for the progression of CKD in the 4-year follow-up.