Progression of diabetic nephropathy: value of intrarenal resistive index (RI)

We used duplex Doppler analysis to determine whether the intrarenal RI can be used as a predictor in patients with diabetic nephropathy. Intrarenal resistive index (RI) values were obtained from intraparenchimal arteries of both kidneys, either the arcuate or interlobar arteries. Clinical parameters and renal function were also evaluated at baseline and after three and six months. Forty patients with diabetic nephropathy were divided into two groups based on their intrarenal RI values: group 1 had values of >or=70 and group 2 had values <70. Progression of renal function (delta creatinine clearance, delta CCr) was estimated by linear regression of the slope of decline of CCr plotted against time. At baseline, sixteen patients (40%) had an intrarenal RI value >or=70. Eight patients (50%) of them had a decline in renal function after six months. In comparison, among patients with intrarenal RI values <70 (n=24), only 2 had a decline in renal function. In multivariate regression analysis, proteinuria, lower baseline CCr and RI were independent predictors of declining renal function. An intrarenal RI value of >or=70 identifies diabetic patients at risk of progressive renal disease. The RI of interlobar arteries seems to be a dependable marker of intrarenal changes and can be used as a non-invasive, easily available parameter of the evolution in patients with advanced clinical diabetic nephropathy.