Functional Kidney Stress Testing with Multiparametric Magnetic Resonance Imaging and Oral Protein Loading.

BACKGROUND: This prospective feasibility study evaluated a noninvasive kidney stress test using multiparametric MRI combined with an oral protein challenge to assess the renal blood flow response during renal functional reserve activation in healthy adults. METHODS: Seventeen healthy participants underwent baseline and postprandial MRI at 30-60, 60-90, and 90-120 minutes following oral ingestion of animal protein (0.7 g/kg). MRI measurements included renal blood flow, T2* mapping, kidney volume, and cortical thickness. A subset of participants underwent a plant-based protein control experiment and test-retest studies at short- and long-term intervals. Changes from baseline were assessed using paired statistical tests, and reproducibility was evaluated using intraclass correlation coefficients. RESULTS: After ingestion of animal protein ingestion there was a significant increase in renal blood flow at all postprandial time points (mean change: +11 ± 6%, p < 0.001), with an early response observed within 30-60 minutes. Cortical T2* showed a modest increase (+5 ± 9%, p = 0.03), whereas the other parameters remained unchanged. No significant changes were observed following plant-based protein ingestion. Test-retest analysis demonstrated good reproducibility of the renal blood flow response to acute stress (ICC = 0.81). CONCLUSIONS: Multiparametric MRI combined with oral protein loading provides a feasible, noninvasive approach to assess renal functional reserve. The renal blood flow response is robust, reproducible and can be captured within 60 minutes of scan time. This imaging-based stress test offers a practical alternative to traditional methods and may enable early detection of impaired kidney function.