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

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.

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.

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).

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.