The Relationship Between IRRIV and RFR Under Normal Conditions: External Validation

Normal subjects display a significant capacity to increase in baseline GFR under physiological needs (e.g. pregnancy) or pathological states (e.g. solitary kidney). This capacity is known as renal functional reserve (RFR), and it is calculated as the difference between the measured maximum GFR achieved through a renal stress test and the baseline GFR measured in rest conditions.In clinical practice, the most common renal stress test is performed as a standardized protein loading test. In a pilot study, the investigators demonstrated a significant correlation between RFR and the intra-parenchymal renal resistive index variation (IRRIV) during an echo renal stress test in a cohort of healthy volunteers. IRRIV test has proven to be rapid, safe, bedside and easy to perform and it might represent a preliminary test in screening patients' RFR. For this purpose, externally validation of IRRIV test is performed in a validation cohort of healthy subjects.