Kidney Preservation (TTS Congress, Berlin July 2012)

I was greatly impressed with the Transplantation Society Congress in Berlin last month. The venues and organisation were first class. There were also many high level presentations and discussions that have both informed and stimulated interested minds. Given my own interests, a personal highlight was the session on Organ Procurement and Preservation, where much good discussion and interaction took place. The demand for more organs to meet the requirements of waiting lists has prompted the investigation of many new and exciting techniques. There were presentations touching on the wide complexity of preservation methods from static cold storage through to normothermic resuscitation of marginal kidneys.

Lazslo Szabo (Cardiff) presented a retrospective review of DCD kidneys transplanted at one institution. The cold ischemic time experienced by kidneys preserved by machine perfusion was considerably longer than that for statically stored kidneys in this non-randomized cohort. Machine perfusion was associated with a reduction in DGF from 70% to 40%. Michael Goldstein (New York) further expanded upon machine perfusion for deceased donor kidney preservation. In New York all kidneys are preserved by machine perfusion and he presented results for 1181 kidneys between 2007 and 2009. Interestingly the Machine Measured Renal Resistance (MMRR) correlated well with biopsy results (tubular interstitial scarring in particular) as well as renal function at 1 year, and 1 year graft survival. What is to be done with kidneys from young donors with good biopsy results that do not pump well? They may have better outcomes than the MMRR would suggest, so an absolute cut-off cannot be set and each case should be judged independently.

Moving from cold storage through to normothermic preservation, Ivo Post (Amsterdam) presented results from an in vitro study at increasing temperatures. The preservation effect of various solutions was examined using endothelial barrier function as an endpoint, measured by electrical impedance. University of Wisconsin solution appeared to be the best at maintaining endothelial function at 15 and 20 degrees centigrade, for up to 20 hours. At temperatures above this, only cell growth medium preserved function. HTK, Ringer’s Lactate and Polysol only functioned at 4 degrees centigrade in this study. Chris Ray (Newcastle) presented results of an experimental study investigating the role of an oxygenated flush (with RSI Aqix solution) prior to static cold storage.  Across outcomes as diverse as serum lactate, MMRR, apoptotic cell count on biopsy and podocyte foot process width there was no difference between the study groups.

Normothermic perfusion in kidney preservation has so far been developed to its greatest extent by the Leicester group. Sarah Hosgood presented the results of 19 marginal kidneys that have been resuscitated prior to transplantation. Following cold storage, kidneys are perfused in a normothermic and oxygenated system with a red cell solution for approximately 60 minutes. They are then cold flushed and immediately implanted. The results so far are excellent with only one case of DGF and no PNF. Nine cases have been followed up to one year with just one graft loss. This of course prompted the question of whether or not implanting the kidneys and reperfusing them an hour earlier would have the same benefit? It is unclear. It is possible that protective mechanisms are upregulated prior to implantation. However, TPN, dexamethasone and prostacyclin are administered during the perfusion period and these should have a beneficial effect as well. The perfusate is also leuko-depleted, possibly reducing IRI. I’m certainly looking forward to hearing more about this work.

At this session I also presented our recent systematic review of hypothermic machine perfusion in comparison with static cold storage. In meta-analysis of seven RCTs we found a slight benefit of machine perfusion in reducing DGF. Meta-analysis for graft survival was not possible and there was not a clear impact of the preservation modality on this outcome.