Portal versus systemic delivery of insulin: immunologic benefits for pancreas transplantation:

Are there still roles for exocrine bladder drainage and portal venous drainage for pancreatic allografts?

PURPOSE OF REVIEW

Controversy remains regarding the best methodology of handling exocrine pancreatic fluid and pancreatic venous effluent. Bladder drainage has given way to enteric drainage. However, is there an instance in which bladder drainage is preferable? Also, hyperinsulinemia, as a result of systemic venous drainage (SVD), is claimed to be proatherosclerotic, whereas portal venous drainage (PVD) is more physiologic and less atherosclerotic.

RECENT FINDINGS

Bladder drainage remains a viable method of exocrine pancreas drainage, but evidence is sparse that measuring urinary amylase has a substantial benefit in the early detection of acute rejection in all types of pancreas transplants. Currently, there is no incontrovertible evidence that systemic hyperinsulinemia is proatherosclerotic, whereas recent metabolic studies on SVD and PVD showed that there was no benefit to PVD.

SUMMARY

Given the advent of newer immunosuppressive agents and overall lower acute rejection rates, the perceived benefit of bladder drainage as a means to measure urinary amylase as an early marker of rejection has not been substantiated. However, there may be a selective role for bladder drainage in 'high risk' pancreases. Also, without a clear-cut metabolic benefit to PVD over SVD, it remains the surgeon's choice as to which method to use.

The current state of pancreas-kidney transplantation in China: the indications, surgical techniques and outcome

It is currently estimated that 50 million Chinese have diabetic mellitus (DM) with more than 90% of these being afflicted with type 2 DM. Concomitantly, the socio-economic improvements in China are supporting the adoption of pancreas-kidney transplantations as a treatment option for these patients. Recipient candidate pool has yet to be expanded and the final effect to be improved in clinical practice. To date, more than 250 pancreas-kidney transplants have been performed on patients with type 1 and type 2 DM. To improve the outcome, a new surgical technique that involves anastomosis of the graft duodenum to recipient jejunum side-to-side but not Roux-en-Y, has been devised for enteric drainage. Furthermore, the systemic venous drainage (SVD) has been used as the method of choice for endocrine secretions. Graft and recipient long-term survival in China was similar to that in America and Europe. Three-year survival rate of pancreas and kidney grafts was 92.2% and 90.2%, respectively, in our center. No difference in survival and graft function between type 1 and type 2 DM recipients was noted. It is concluded that pancreas-kidney transplantation is an effective way for the treatment of type 1 DM and some type 2 DM complicated with uremia.

A novel model of portal vein transplantation in mice using two-cuff technique

Allogeneic portal vein (PV) grafts have been widely used for vascular reconstruction in the aggressive biliary-pancreatic surgery and partial liver transplantation. We developed a novel PV transplantation model aimed at studying the pathologic alteration of the grafts and further managements. The PV graft was implanted orthotopically into the recipient using two-cuff technique. A total of 80 PV transplants have been performed, and the overall survival rate for the recipients was 91.3% (73/80). Mice were randomly separated into isografts group, allografts group, and allografts group treated with CTLA4-Ig. PV grafts were harvested on the 1st, 2nd, 4th, and 8th postoperative week. The isografts remained intact vascular structure, and the allografts developed marked rejection with significant increase in wall thickness (95 +/- 19 microm vs. 49 +/- 7 microm; P < 0.01) and decrease in lumen area (1.9 +/- 1.1 x 10(4) microm(2) vs. 7.7 +/- 3.1 x 10(4) microm(2); P < 0.01) on the 4th week. In the CTLA4-Ig treated group, the vascular thickness and lumen area were significantly improved when compared with the untreated allografts (wall-thickness: 53 +/- 3 microm vs. 95 +/- 19 microm, P < 0.01; lumen area: 8.8 +/- 2.4 x 10(4) microm(2) vs. 1.9 +/- 1.1 x 10(4) microm(2), P < 0.01) on the 4th week. In conclusion, the PV transplantation model in mice using two-cuff technique is a feasible procedure with a high survival rate. The PV allografts responded well to the CTLA4-Ig therapy in our preliminary research by the model.

Management of hyperglycaemia after pancreas transplantation: are new immunosuppressants the answer?

Pancreas transplantation is considered the optimal therapy for patients with diabetes mellitus who reach end-stage renal disease. Despite achievement of euglycaemia after this procedure, the progression to impaired pancreatic function and metabolic exhaustion still represents one of the major concerns that increase the risk of graft loss. This paper reviews the possible mechanisms that can induce post-transplant hyperglycaemia, including those related to immunosuppression and those non-related, and the new strategies available for minimising or preventing this complication. Different aetiologies can induce pancreatic dysfunction. Technical complications, acute pancreatitis and delayed graft function, mostly related to impaired insulin secretion, are considered the early causes for abnormal glucose control. In general, acute rejection does not affect the endocrine portion of the pancreas graft because islet destruction occurs later than the inflammation of the exocrine components. Hyperinsulinaemia and insulin resistance represent the main concern for the progression of blood glucose intolerance. The anastomotic techniques of the exocrine portion of the pancreas and the immunosuppressive regimens are of critical importance for the development of impaired glucose metabolism. Hyperinsulinaemia, as a result of the fact that systemic-enteric or systemic-bladder drainages reducing the hepatic clearance of insulin, has led to the introduction of more physiological techniques using portal drainage of the endocrine secretions. Experimental and clinical data have shown that many of the current immunosuppressants account, to a large degree, for the increased risk of the development of post-transplant hyperglycaemia. The most common maintenance regimen in pancreatic transplantation still consists of triple therapy with a combination of corticosteroids, calcineurin inhibitors (either ciclosporin [cyclosporine] or tacrolimus), and mycophenolate mofetil (MMF).The diabetogenic effects of corticosteroids and calcineurin inhibitors have resulted in the need for protocols able to minimise their use. Recent studies have shown the safety and efficacy of steroid-sparing or -free regimens. Sirolimus has shown powerful immunosuppressive potency in absence of nephrotoxicity and diabetogenicity. Multicentre and single-centre reports have demonstrated that both calcineurin inhibitor withdrawal and avoidance were possible when sirolimus was used in a concentration-controlled fashion, with low-dose corticosteroids and MMF. Although the experience with sirolimus in pancreatic transplantation is still limited, the results are promising. Patients affected by diabetic gastroparesis seem to better tolerate a regimen with sirolimus and low-dose tacrolimus than one with tacrolimus in combination with MMF.For successful, long-term results of pancreatic transplantation, it is crucial to combine donor selection, technical aspects, modified anastomotic techniques and new therapeutic approaches designed to minimise the metabolic and non-metabolic adverse effects of the immunosuppressive regimens.