Long-term assessment of posttransplant renal prognosis with 31P magnetic resonance spectroscopy

Background. 31 P-magnetic resonance spectroscopy (MRS) has been widely used to study pretransplantation renal viability, and although some had discussed posttransplant renal viability, no one has examined long-term posttransplant renal prognosis. We discuss the use of 31 P-MRS to assess the long-term prognosis from the time when MRS was performed. Methods. We studied 20 patients with renal allografts. 1.5 Tesla clinical magnetic resonance imaging (MRI) and 15 cm surface coil was used for 31 P-MRS. Localized 31 P-MRS was done using image selected in vivo spectroscopy (ISIS) method. Individual peaks were fitted by Lorenzian line-shapes with a least square method and peak area ratios were calculated. Results. A β-adenosine triphosphate/inorganic phosphate (β-ATP/Pi) ratio >1.2 had sensitivity of 92.8%, specificity of 100%, and accuracy of 95% for predicting 3-year renal survival; a β-ATP/Pi ratio > 1.2 had sensitivity of 90.9%, specificity of 66.7%, and accuracy of 76.9% for predicting 5-year renal survival. We compared 31 P-MRS spectra data between the survived group and failed group. The survived group had significantly higher β-ATP/Pi, α-ATP/Pi, and phosphodiester (PDE)/Pi ratios than the failed group. Conclusions. We discussed the β-ATP/Pi value as a parameter for predicting long-term survival of a transplanted kidney from the time when MRS was performed. A value above 1.2 suggests a high probability of 3-year renal survival, whereas a value over 2.5 indicates that the transplanted kidney could survive over 5 years. 31 P-MRS may be useful for predicting long-term survival of transplanted kidneys, but additional studies are needed.