Nuclear magnetic resonance assessment of renal perfusion and preservation for transplantation.

The feasibility of using proton nuclear magnetic resonance (NMR) relaxation measurement to monitor organ perfusion and preservation was studied using a rat model. Intact kidneys were assessed with NMR following various periods of cold storage. Bilateral en bloc donor nephrectomy was performed on Sprague-Dawley rats with prior in situ flushing with Euro-collins', dextrose and other test solutions via a plastic cannula in the aorta. A paramagnetic agent, gadolinium-DPTA, dissolved in perfusion fluid was then injected into the renal vasculature. NMR analysis was repeated and the kidneys were reflushed with perfusion fluid to remove the gadolinium, followed by another NMR analysis. By sequential flushing and NMR measurement after 24, 48 and 72 hours of cold storage, the thoroughness of flushing, the patency of intrarenal vasculature and capillary integrity could be assessed. With the D5W, the T1 relaxation of kidneys dropped 56% with prolonged cold storage, indicating gadolinium accumulation in the interstitium, in effect loss of capillary integrity. With the Euro-collins', the T1 showed a small drop (23%) and almost complete flush-out, indicating superior tissue preservation and patency of vasculature. The addition of trifluoperazine, (TFP, a calmodulin inhibitor) to the Euro-collins' resulted in only a 9% drop in T1 after 72 hours. This possibly indicates TFP has additional protective action on cold ischemic damage. Using the small animal model presented here, proton NMR spectroscopy appears to be a sensitive technique in assessing renal vascular patency after cold storage and provides a useful tool for the investigation of other agents for organ preservation for transplantation.