title: Intra-Parenchymal Renal Resistive Index Variation (IRRIV) Describes Renal Functional Reserve (RFR): Pilot Study in Healthy Volunteers.
abstract: An increase of glomerular filtration rate after protein load represents renal functional reserve (RFR) and is due to afferent arteriolar vasodilation. Lack of RFR may be a risk factor for acute kidney injury (AKI), but is cumbersome to measure. We sought to develop a non-invasive, bedside method that would indirectly measure RFR. Mechanical abdominal pressure, through compression of renal vessels, decreases blood flow and activates the auto-regulatory mechanism which can be measured by a fall in renal resistive index (RRI). The study aims at elucidating the relationship between intra-parenchymal renal resistive index variation (IRRIV) during abdominal pressure and RFR. In healthy volunteers, pressure was applied by a weight on the abdomen (fluid-bag 10% of subject's body weight) while RFR was measured through a protein loading test. We recorded RRI in an interlobular artery after application of pressure using ultrasound. The maximum percentage reduction of RRI from baseline was compared in the same subject to RFR. We enrolled 14 male and 16 female subjects (mean age 38 ± 14 years). Mean creatinine clearance was 106.2 ± 16.4 ml/min/1.73 m(2). RFR ranged between -1.9 and 59.7 with a mean value of 28.9 ± 13.1 ml/min/1.73 m(2). Mean baseline RRI was 0.61 ± 0.05, compared to 0.49 ± 0.06 during abdominal pressure; IRRIV was 19.6 ± 6.7%, ranging between 3.1% and 29.2%. Pearson's coefficient between RFR and IRRIV was 74.16% (p < 0.001). Our data show the correlation between IRRIV and RFR. Our results can lead to the development of a "stress test" for a rapid screen of RFR to establish renal susceptibility to different exposures and the consequent risk for AKI.
authors.affiliation: Institute of Life Sciences, Sant'Anna School of Advanced StudiesPisa, Italy; Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research InstituteVicenza, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Samoni
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Nalesso
authors.affiliation: Institute of Life Sciences, Sant'Anna School of Advanced StudiesPisa, Italy; Department of Clinical and Experimental Medicine, University of PisaPisa, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Meola
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Villa
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: De Cal
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: De Rosa
authors.affiliation: Institute of Life Sciences, Sant'Anna School of Advanced StudiesPisa, Italy; Department of Clinical and Experimental Medicine, University of PisaPisa, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Petrucci
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Brendolan
authors.affiliation: Division of Nephrology, Center for Immunity, Inflammation and Regenerative Medicine, University of Virginia Health System Charlottesville, VA, USA.
authors.forename: Mitchell H
authors.initials: MH
authors.lastname: Rosner
authors.affiliation: Department of Nephrology, Dialysis and Transplantation, San Bortolo Hospital and International Renal Research Institute Vicenza, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Ronco
keywords: color doppler; healthy volunteers; intra-parenchymal renal resistive index variation (IRRIV); protein loading test; renal blood flow; renal functional reserve (RFR); renal hemodynamics; renal resistive index (RRI)