Assessment of in situ renal transplant viability by 31P-MRS: experimental study in canines

In 14 in situ canine renal transplants, intracellular phosphorus metabolites were evaluated by phosphorus-31 magnetic resonance spectroscopy (31P-MRS), performed using surface coils to investigate the usefulness of this technique for assessing renal viability in situ. Group I control kidneys (n = 5) were autografts, as were Group II (n = 5) kidneys: the latter group were subjected to surgically induced vascular ischemia and thrombosis. Group III kidneys (n = 4) were rejecting allografts. Renal flow and function, as measured by 99mTc-DTPA, and findings on histologic examination were correlated with 31P-MRS spectra. Group I kidneys showed excellent viability on both 99mTc-DTPA studies and biopsy evaluation, and their 31P-MRS-derived ratios of phosphomonoesters/inorganic phosphate (PME/Pi) and adenosine triphosphate/Pi (ATP/Pi) were high (1.32 +/- 0.23 and 0.90 +/- 0.36, respectively). In contrast, Group II kidneys demonstrated poor flow and function, histologic evidence of severe ischemia from venous and arterial thrombosis, and significantly (P < 0.005) less viability than controls, as monitored by 31P-MRS PME/Pi (0.58 +/- 0.30) and ATP/Pi (0.20 +/- 0.13) ratios. Group III kidneys also demonstrated poor flow and function with 99mTc-DTPA, and the associated histologically injury was noted to be caused by accelerated rejection and severe vascular damage. PME/Pi (0.24 +/- 0.22) and ATP/Pi (0.10 +/- 0.01) ratios were also significantly (P < 0.005) less than those in controls, reflecting nonviability. The 31P-MRS-derived PME/Pi and ATP/Pi ratios enable a qualitative noninvasive assessment of blood flow-dependent renal viability, but with currently used localization techniques the differentiation between severe ischemia and severe acute rejection was not possible.