Renal Oxygenation and Perfusion Responses to Handgrip ExerciseinPatients with Chronic Kidney Disease: A Pilot MRI Study

Introduction: Chronic Kidney Disease (CKD) is characterized by sympathetic nervous system overactivation at rest and during exercise that contributes to cardiovascular risk and progression of kidney disease. Sympathetic overactivation in CKD may induce renal vasoconstriction and renal perfusion deficits, thereby contributing to progression of kidney disease. While resting renal perfusion has been widely studied, renal hemodynamic responses to sympatho-excitatory stress remain poorly understood in CKD patients. This pilot feasibility study evaluated the use of comprehensive MR imaging techniques to test the hypothesis that patients with CKD have exaggerated reductions in renal oxygenation and blood flow during sympatho-excitation induced via handgrip exercise compared to non-CKD controls. METHOD: Patients with CKD stage III-IV and non-CKD controls underwent 3T-MRI scanning (Siemens Prisma), while performing two 3-minute handgrip exercises at 30% maximal grip strength using an MRI-compatible digital dynamometer. Blood Oxygen Level-Dependent (BOLD) MR images, obtained during breath-holding, measured renal tissue oxygenation, at rest and every minute during handgrip. Arterial Spin Labeling (ASL) MR images, obtained during free-breathing, assessed renal perfusion at rest and the final exercise minute. Renal tissue oxygenation (T2*) and renal blood flow (RBF) were extracted from manually traced cortical regions of interest (ROIs). Results: Four patients with CKD (70 ± 4 yr, 1 male, eGFR: 48 ± 13 mL/min/1.73 m 2 ) and four non-CKD (59 ± 3 yr, 3 males, eGFR: 97.3 ± 6.8 mL/min/1.73 m 2 ) were included for analysis. The mean T2* was similar at rest between CKD and controls (35.7 ± 8.6 vs 39.3 ± 4.6 ms, P = 0.504), with no significant changes during exercise in either group. Mean RBF was lower in patients with CKD both at rest (190 ± 54 vs. 350 ± 80 mL/100g/min, P = 0.019) and during exercise (219 ± 78 vs. 375 ± 77 mL/100g/min, P = 0. 030) compared to controls, with no significant exercise-induced changes in either group. Conclusion: This pilot study demonstrated the feasibility of MRI-based renal stress test to measure renal oxygenation and perfusion at rest and during exercise. In our preliminary data, patients with CKD exhibited persistently reduced renal perfusion, suggesting microvascular dysfunction, but renal oxygenation remained comparable to controls. Future studies with larger cohorts should explore medullary perfusion and time-resolved perfusion dynamics to further characterize CKD-related renal hemodynamic dysregulation. NIH R01HL135183; NIH R61AT10457; VA Merit I01CX001065; K01DK137620-01A1 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.