Pancreas
Initial methods for pancreas preservation were based on those developed for kidney. The pancreas is more vulnerable to mechanical damage during retrieval, but is no more sensitive to either warm ischaemia or cold storage. The problems encountered in pancreatic grafting relate to its low circulatory flow rate and to vascular damage on storage and reperfusion. Thrombosis of vascular anastomses is more likely in organs subjected to poor preservation.
In early clinical studies, EuroCollins solution was successful, albeit for short periods of ischaemia: only about 10 per cent of grafts were preserved for longer than 12 h. Experimental preservation of the canine pancreas has been successful for 72 h (UW), and rat pancreas has been preserved for 48 h (UW, hydroxyethyl starch-free UW, and Citrate). Preservation times have been extended clinically using UW solution; this has markedly facilitated organization of transplant programmes. Clinically, graft survival has not been affected by extending preservation times to 24 h, although grafts stored for over 30 h show somewhat decreased graft survival. Retrospective analysis of transplant registry results showed that patients with better HLA-DR matching had significantly better graft survival. Prolonged effective preservation would allow allocation of grafts after matching.
Perfusion storage is inherently more difficult in the pancreas because of its low circulatory flow rate. Early studies using machinery designed for kidney perfusion were unsuccessful. Perfusion storage at low flow rates with UW-based solutions may in the future extend and improve pancreatic storage.
The interdependence of exocrine and endocrine cells has not been assessed. Ablation of the exocrine cells by polymer injection of the pancreatic duct does not appear to have any detrimental effect on 1-year graft survival, but long-term endocrine function may be compromised. Other transplant techniques involve reconstitution of pancreatic drainage via the intestine or the urinary bladder. Effective preservation of acinar cells helps minimize pancreatitis: elevated serum amylase is a common occurrence, and the level relates to preservation time. Acinar cell preservation provides a reliable and sensitive test of rejection. Monitoring of urinary amylase in bladder-drained pancreas transplants has become an accepted early indicator of rejection: falling urinary amylase indicates a need for more vigorous immunosuppression.
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