 The assessment of GFR by 51Cr-EDTA will be performed in a subgroup of 15 patients from each arm of the study in a parallel manner before and after the intervention using the 51Cr-EDTA intravenous single injection technique at a dose of 150μCi with blood samples taken at 2, 3 and 4 hours later. Samples will be centrifuged and 2 ml of plasma will be pipetted in duplicate for gamma counter counting. An exponential equation evaluates the plasma decay of 51 Cr-EDTA, providing the value of GFR . 