Background: 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.
Methods: 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.
Results: 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.
Conclusions: 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.