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Abstract-The progression of renal disease depends on various clinical parameters such as hypertension and proteinuria.We recently showed that an increased renal resistance index measured by duplex ultrasound is associated with a poor prognosis in patients with renal artery stenosis. We now prospectively tested the hypothesis that a high renal resistance index (Ն80) predicts progression of renal disease in patients without renal artery stenosis. In 162 patients newly diagnosed with renal disease, the resistance index (1-[enddiastolic velocity/maximum systolic velocity]*100) was measured in segmental arteries of both kidneys. Creatinine clearance was measured at baseline, at 3, 6, and 12 months, and then at yearly intervals thereafter (mean follow-up 3Ϯ1.4 years). The combined endpoint was a decrease of creatinine clearance by Ն50%, end-stage renal disease with replacement therapy, or death. Twenty-five patients (15%) had a renal resistance index value Ն80 at baseline. Nineteen (76%) had a decline in renal function; 16 (64%) progressed to dialysis, and 6 (24%) died. In comparison, in patients with renal resistance index values Ͻ80, 13 (9%) had a decline in renal function, only 7 (5%) became dialysis-dependent, and 2 (1%) died (PϽ0.001). In a multivariate regression analysis, only proteinuria and resistance index were independent predictors of declining renal function. A renal resistance index value of Ն80 reliably identifies patients at risk for progressive renal disease.

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To study the effect of prolonged recumbency on plasma vasopressin and renin activity, eight women (23-34 yr) were subjected to 17 days of absolute bed rest. The +3 Gz tolerance of the subjects was tested before and after 14 days of bed rest. From day 2 and through day 17 of bed rest, plasma arginine vasopressin (AVP) levels were reduced 33%. Plasma renin activity (PRA) increased 91% (P less than 0.05) above ambulatory control values from days 10 through 15 of bed rest. When compared to precentrifuge values, exposure to +3 Gz prior to bed rest provoked a 20-fold rise (P less than 0.05) in mean plasma AVP but resulted in only a slight increase in PRA. After bed rest, acceleration increased plasma AVP 7-fold (P less than 0.02); however, the magnitude of this increase was less than the post +3Gz value obtained prior to bed rest. After bed rest, no significant rise was noted in PRA following +3 Gz. This study demonstrates that prolonged bed rest leads to a significant rise in the PRA of female subjects, while exposure to +Gz acceleration provokes a marked rise in plasma AVP.

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