Control group patients will follow the usual surgical waiting list protocol (Estimated 1,5-2 months). Baseline and preoperative ultrasonography will also be performed in these patients, in which it will be verified that there are no significant changes in vascular mapping (punctures sites, hematomas, etc.) and the indication of AVF performed in the initial visit will be confirmed. Dynamometry, bicipital and tricipital skinfolds measurement, brachial diameter, analytical parameters of nutrition and muscle mass and bioimpedanciometry will be performed both at the onset visit and at the preoperative visit. The only difference with PIE group is the 4 weeks follow-up ultrasound that will not be performed in control group.