Weight increase during machine perfusion may be an indicator of organ and in particular, vascular damage.

OBJECTIVES: Hypothermic machine perfusion preservation has been shown to improve the outcome of renal grafts from non-heartbeating donors. We have noticed that organs gain a variable amount of weight during perfusion. METHODS: All grafts, whether used or discarded, were assessed with respect to their weight gain. Primary outcome measures were the results of viability testing. Secondary outcomes were early transplant variables including incidence and duration of delayed graft function and histological examination of protocol graft biopsies. RESULTS: Weight increase data was available on 97 grafts. There were no significant differences in weight gain between kidneys used and discarded (17% vs 20%). 14 patients received grafts which gained over 30% of their initial retrieval weight. There were no significant differences in secondary outcome measures between this group of recipients and patients who had received less "waterlogged" kidneys. Histological changes including endothelial inflammation and oedema were observed. CONCLUSIONS: Kidney grafts which have gained over 30% of weight on hypothermic machine perfusion preservation can be transplanted successfully. Complex interactions between the period of warm ischaemia, in situ flushing, perfusion pressures and perfusate probably lead to the phenomenon of excessive graft weight gain.