Renal hemodynamics across the adult lifespan: Relevance of flow pulsatility to chronic kidney disease

Background: Elevated renal flow pulsatility may contribute to the pathogenesis of chronic kidney disease (CKD). The purpose of this study was to investigate the associations among age, renal flow pulsatility, and CKD biomarkers in non-CKD adults and CKD patients. Methods: Non-CKD adults (n = 415) and CKD patients (n = 136) aged between 22 and 83 years underwent the renal blood flow measurement using duplex ultrasonography. Pulsatility index (PI) and resistive index (RI) were calculated to assess renal flow pulsatility. The CKD biomarkers such as urinary liver-type fatty acid-binding protein (L-FABP) and serum fibroblast growth factor 23 (FGF23) were measured from each participant. Aortic hemodynamic parameters were measured by applanation tonometry. Results: In non-CKD adults, advancing age was associated with elevations of renal PI and RI which slowly increased during middle-aged (PI: β = 0.14, RI: β = 0.17) and accelerated in older adults (PI: β = 0.34, RI: β = 0.33). In CKD patients, age-related increases in renal PI and RI were observed only in the middle age group (PI: β = 0.23, RI: β = 0.26). Multivariate analysis demonstrated that renal PI and RI were independently associated with CKD biomarkers, including urinary L-FABP and serum FGF23, and aortic pulse pressure. Conclusions: Advancing age is associated with a progressive elevation of renal flow pulsatility which manifests during middle age and accelerates in later life. Moreover, elevated renal flow pulsatility is associated with the presence of CKD in each age group and also with biomarker levels that reflect CKD progression.