Pancreas Transplantation with Systemic Venous Drainage
Randall S. Sung
DEFINITION
Pancreas transplantation is the preferred method of insulin replacement therapy for selected patients with type 1 diabetes.
Compared to insulin therapy, advantages of pancreas transplantation include improved quality of life and impact on secondary complications of diabetes.1 Survival is dramatically improved in recipients of combined kidney and pancreas transplants compared with dialysis and insulin; the survival benefit of the isolated pancreas transplant is controversial.2
Systemic venous drainage of the pancreas transplant is the most common method employed in the United States and is performed in about 85% of cases.3
In the alternative method, portal venous drainage, the portal vein of the pancreas is anastomosed to the portal vein or superior mesenteric vein (SMV) of the recipient.
Recipients of pancreas transplants with portal venous drainage do not exhibit the systemic hyperinsulinemia observed in recipients of transplants with systemic venous drainage.4
Because hyperinsulinemia has been associated with accelerated atherosclerosis and metabolic syndrome in patients without pancreas transplants, the purported advantage of portal venous drainage is a reduction in cardiovascular disease. However, over the long term, improvements in cardiovascular endpoints have not been demonstrated with portal venous drainage, and the use of this method has been declining in the past several years.5,6
PATIENT HISTORY AND PHYSICAL FINDINGS
As with other types of transplants, pancreas transplants can only be performed at accredited transplant centers.
Most potential candidates for pancreas transplantation also have chronic kidney disease (CKD) or end-stage renal disease (ESRD) and are potential kidney transplant candidates. As such, the evaluation process is similar to kidney transplant candidates. A thorough history should be performed, including assessments of cardiovascular disease, psychosocial risks, functional status, and kidney function.
A history of early onset of diabetes, with initial treatment with insulin, is suggestive of type 1 diabetes. Type 2 diabetes is associated with late age of onset, obesity, initial treatment with oral hypoglycemic agents or diet, or high insulin requirements. There is considerable overlap with respect to age of onset and body mass index (BMI).
The adequacy of current diabetes therapy and degree of glycemic control should be assessed. A history of secondary complications of diabetes such as peripheral neuropathy, autonomic neuropathy, retinopathy, cardiovascular disease, and gastroparesis should be obtained. Hypoglycemic unawareness, especially if not able to be managed by the patient, is a significant short-term risk of insulin therapy in those with autonomic neuropathy.
In general, due to the increased surgical risk of pancreas transplantation compared with kidney transplantation, selection criteria are more stringent than for kidney transplant candidates, especially with respect to functional status and cardiovascular disease.
Selection criteria vary widely regarding diabetes control and secondary complications of diabetes. Some centers require hypoglycemic unawareness for candidacy but many do not. Transplantation of recipients with BMI greater than 30 is unusual, and BMI greater than 35 is very rare.
A majority of transplant centers have far more stringent criteria for diabetes control, secondary complications, and hypoglycemic unawareness for pancreas transplant alone (PTA) candidates (those without ESRD) compared with either simultaneous pancreas-kidney (SPK) transplant or pancreas after kidney (PAK) transplant. This is due to the added risk of immunosuppression for the PTA recipient that is already assumed by the SPK or PAK recipient regardless of pancreas transplant status.
All pancreas candidates should be counseled with respect to the surgical risks and benefits of pancreas transplantation. Given the controversy over the survival benefit specifically attributable to a pancreas transplant compared with a kidney transplant, the anticipated benefit in quality of life that the patient envisions is an important patient-dependent consideration. There should be a discussion of alternative treatments, including optimization of insulin therapy.
A full physical exam should be performed with particular attention to the vascular exam.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Diagnostic studies are similar to those for kidney transplant candidates with diabetes, especially with respect to cardiovascular disease. Some centers perform cardiac catheterization and/or computed tomography (CT) imaging of the pelvic vessels in all candidates, whereas other selectively perform them based on history, physical findings, or the results of noninvasive cardiac screening.
Absence of C-peptide confirms lack of pancreatic function, which is a requirement for most centers and insurers.
SURGICAL MANAGEMENT
Preoperative Planning and Positioning
The transplant is performed under general anesthesia with the patient in the supine position. Most centers use an intraperitoneal approach, although a retroperitoneal approach through a lower quadrant incision use for kidney transplants has been used. When a retroperitoneal approach is used, the peritoneum is usually opened after reperfusion to allow drainage of pancreatic secretions or to facilitate exocrine drainage.
Standard skin preparation should be used. Broad-spectrum antibiotic prophylaxis is indicated.
TECHNIQUES
BACKBENCH OF THE PANCREAS
The pancreas is prepared under sterile conditions on ice.
The parenchyma is inspected for injury, integrity of vascular structures, and fat content. The backbench procedure is detailed in Chapter 38.
Some surgeons use a portal vein extension graft of donor iliac vein to permit greater length of the vein to facilitate anastomosis (FIG 1).
Most commonly, a Y-graft of donor iliac artery is used to anastomose the donor superior mesenteric artery (SMA) and splenic artery on the back table.
The duodenum should be shortened with a stapler as appropriate to the technique of exocrine drainage employed.
 FIG 1 • Venous extension graft of donor iliac vein to donor portal vein. This can relieve tension on the vein and potentially reduce the risk of thrombosis when appropriately used. |
INTRAPERITONEAL APPROACH
A lower midline incision is used that usually extends above the umbilicus. If a kidney transplant is not being performed simultaneously, the incision does not need to extend to the pubic symphysis.
The pancreas transplant is usually placed on the right side given the greater options available for portal vein anastomosis; however, it can be placed on the left if there is not a venous target on the right.
On the right side, the pancreas can be oriented with the head directed down (duodenum toward the pelvis) or head up. The author performs most transplants with the head down. The pancreas cannot usually be oriented with the head up on the left due to the distal location of the accessible iliac vein.
The venous anastomosis can be performed on the external iliac vein, common iliac vein, or vena cava. Head-up transplants are anastomosed to the vena cava.
The underlying principle should be to seat the pancreas so as to avoid tension on the portal vein, which may result in increased resistance to outflow. This can come from a short or poorly mobilized donor vein, a deep or poorly mobilized recipient vein, or the right colon (or its mesentery) pushing the pancreas laterally. The most superficial venous target should be used to achieve this goal.Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
