It is uncertain whether patients with renal vascular disease will have renal or mortality benefits from re-establishing renal blood flow with renal revascularization procedures. Patients will be assessed for the standard nephrology research outcomes of progression to doubling of creatinine, need for dialysis, and death, as well as other cardiovascular outcomes. The investigators will also establish whether the use of a new inexpensive, simple and available ultrasound test, the renal resistance index (RRI), can identify patients with renal vascular disease who will not benefit from renal revascularization procedures.