Functional evaluation of transplanted kidneys in normal function and acute rejection using BOLD MR imaging.

Area of Science:

• Nephrology
• Radiology
• Transplant Medicine

Background:

• Assessing transplanted kidney function is crucial for patient outcomes.
• Distinguishing acute rejection from normal function is clinically significant.
• Oxygen metabolism plays a role in kidney graft health.

Purpose of the Study:

• To evaluate Blood-Oxygen-Level-Dependent (BOLD) MRI for assessing oxygen metabolism in transplanted kidneys.
• To differentiate acute graft rejection from normal kidney transplant function using BOLD MRI.
• To identify imaging biomarkers for normal kidney graft function and rejection.

Main Methods:

• BOLD MRI was performed on 122 subjects: 20 volunteers, 72 patients with normal functioning transplants, and 21 with acute rejection.
• R2 values (1/s) in the cortex and medulla, and the medulla-to-cortex (M/C) R2 ratio were measured.
• Analysis compared R2 values and ratios between volunteers, normal function grafts, and acute rejection grafts.

Main Results:

• Normal function grafts and volunteers exhibited higher R2 values in the medulla than the cortex, with a steep M/C R2 ratio (>1.1).
• Patients with acute rejection showed significantly lower R2 values in both cortex and medulla compared to normal function grafts (P<0.001).
• In 9 patients with initially normal grafts that later showed dysfunction, R2 values varied, but M/C ratios remained similar to the normal function group.

Conclusions:

• BOLD MRI, specifically decreased R2 values and M/C ratio, can indicate acute renal graft rejection.
• A steep M/C R2 ratio (>1.1) is associated with maintaining normal clinical kidney graft function.
• BOLD MRI offers a non-invasive method to assess oxygen metabolism and graft status.