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

This proof-of-concept study demonstrates the feasibility of a magnetic resonance imaging-based kidney stress test using oral protein loading. Phase-contrast magnetic resonance imaging detected reproducible renal blood flow increases after animal protein loading. With further validation, magnetic resonance imaging-based kidney stress testing may provide a noninvasive assessment of renal functional reserve.

This prospective feasibility study evaluated a noninvasive kidney stress test using multiparametric magnetic resonance imaging (MRI) combined with an oral protein challenge to assess the renal blood flow (RBF) 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 after oral ingestion of animal protein (0.7 g/kg). MRI measurements included RBF, T2* mapping, kidney volume, and cortical thickness. A subset of participants underwent a plant-based protein control experiment and test-retest studies at short-term 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 RBF at all postprandial time points (mean change: +11%±6%, P < 0.001), with an early response observed within 30-60 minutes. Cortical T 2 * 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 RBF response to acute stress (intraclass correlation coefficient=0.81).

Multiparametric MRI combined with oral protein loading provides a feasible, noninvasive approach to assess renal functional reserve. The RBF 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.

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