Determinants of renal flow reserve in adult patients with and without renal artery stenosis.

Renal flow reserve (RFR) is a hemodynamic measure of renal microvascular function and may help identify patients with renal artery stenosis (RAS) who could benefit from revascularization. Reference ranges and clinical correlates of RFR in patients with and without RAS remain unknown. We analyzed intra-arterial renal flow velocity measurements from 76 participants with and without RAS, all with eGFR ≥30 mL/min/1.73m. Each underwent baseline and dopamine-induced hyperemic flow assessments using an intrarenal bolus of 30 μg/kg. RFR was defined as the ratio of mean hyperemic to baseline flow. Group differences were assessed using descriptive statistics and linear regression models adjusting for potential confounders. Median RFR was similar between participants with RAS (1.73, IQR 1.31-2.11) and those without (1.88, IQR 1.60-2.47). Lower RFR was associated with lower eGFR (p = 0.027). Higher RFR values were observed in participants using beta-blockers (p = 0.010), independent of age, sex, eGFR, and blood pressure. RFR was negatively associated with eGFR and positively with beta-blocker use. No associations were found with age, sex, hypertension, diabetes, or presence of RAS. The link with beta-blockers may be caused by interactions with the systemic and renal dopaminergic system.