Techniques of pancreas and islet transplantation

Techniques for vascularized pancreas transplantation are relatively standardized, whereas those for human islet isolation and transplantation are rapidly changing and evolving. The commonest method for transplanting the vascularized pancreas is to use the entire pancreas together with a segment of donor duodenum, and to anastomose this to the recipient bladder. This technique offers the advantages of technical ease, the maximum beta-cell mass is transplanted and graft function can be monitored by measuring urinary amylase levels. Human islet isolation requires that the pancreas is dissociated, the islets purified and then transplanted to a well-vascularized location. The pancreas is dispersed by a combination of the intraductal injection of collagenase and gentle mechanical agitation, and the islets separated from contaminating exocrine tissue by density-gradient centrifugation. Once purified, the islets can be placed into tissue culture or cryopreserved. The commonest site for human islet transplantation is intraportal injection so that the islets are embolized throughout the liver. Alternatives include transplantation to the renal subcapsular space or the spleen.