Sadowski EA et al. (2005) Assessment of acute renal transplant rejection with blood oxygen level-dependent MR imaging: initial experience. Radiology 236: 911–919

Determination of the cause of early graft dysfunction (which occurs in approximately 30% of patients who have undergone renal transplantation) facilitates prompt treatment and prevention of nephron and graft loss. Graft dysfunction is currently assessed by percutaneous renal biopsy, an invasive, painful procedure with a risk of complications. Sadowski et al. have demonstrated the feasibility of measuring the oxygenation state of transplanted kidneys by BLOOD OXYGEN LEVEL-DEPENDENT (BOLD) MRI. This technique potentially represents an alternative means of determining the cause of early graft dysfunction.

This prospective, single-center study enrolled 20 patients (age range 21–70 years) with graft dysfunction (as determined by the transplant nephrologist) who had undergone renal transplantation during the preceding 3 months. Renal biopsy showed that six patients had normally functioning transplants, eight had acute rejection and six had ACUTE TUBULAR NECROSIS. The intensity of the BOLD MRI signal (which decreases with decreasing tissue oxygenation) in the renal medulla was able to differentiate the three states. Rates of signal loss were lower in acute tubular necrosis than in functioning transplants, and lower still in transplants undergoing rejection.

The study was limited by sample size, the fact that patients were scanned at only one time point, and potential intra-observer variability; however, larger studies addressing these points are warranted because a noninvasive technique for clarifying the cause of dysfunction is much needed.