Duplex sonographic registration of age and diabetes-related loss of renal vasodilatory response to nitroglycerine

Background. Nitroglycerine effects dilatation of the vas afferens in the kidney by its active metabolite nitric oxide (NO). In diabetic nephropathy, NO appears to cause hyperfiltration and proteinuria. The aim of this study was to investigate the potential of duplex Doppler ultrasonography in recording changes in resistive indices following nitroglycerine and whether the extent of changes in diabetic nephropathy is reduced as a result of the arteriolar dilatation mediated by NO. Methods. Fifty-three subjects made up three groups: group 1, 12 young healthy volunteers (5 male, 7 female, 28+/-6 years); group 2, 21 older healthy volunteers (7 male, 14 female, 62+/-8 years); group 3, 20 patients (13 male, 7 female, 56+/-18 years) with mild diabetic nephropathy. The resistive index (RI) was measured in the interlobar arteries before, and 1, 3 and 5 min after administration of 0.8 mg sublingual nitroglycerine. Results. The initial RI of 0.592 decreased in group 1 by 10.8% (P<0.01) after nitroglycerine, in group 2 the initial figure of 0.631 decreased by 5.9% (P<0.01), and in group 3 the initial figure of 0.669 decreased by 3.4% (P<0.01). Initial RI values differed significantly between groups 1 and 3 (P<0.01) and groups 1 and 2 (P<0.01), as did values between all healthy volunteers (groups 1 and 2, n=33) and patients with nephropathy (P<0.005). The extent of Delta RI differed significantly between groups 1 and 3 (P<0.01), 1 and 2 (P<0.02), and between all volunteers and group 3 (P<0.003). In groups 1 and 2 the initial RI was dependent on age (P<0.03), in group 3 on age and creatinine clearance (P<0.02 and P<0.05 respectively). Delta RI correlated with age in the healthy subjects (P<0.01) and with duration of diabetes in diabetic nephropathy (P<0.03). Conclusions. Haemodynamic changes in renal perfusion caused by nitroglycerine can be detected using duplex ultrasonography. In healthy subjects, Delta RI declines with increasing age. In diabetic nephropathy patients, the response to nitroglycerine is reduced. The increased initial RI in such patients suggests fixed arteriolar damage.