Pancreas transplant

A pancreas transplant is a procedure performed in some medical centers in which a donor pancreas is transplanted to a recipient.  The donor pancreas is typically cadaveric, but ismay rarely be a segment from a living donor ¹.  The transplant is meant to establish normoglycemia in patients with diabetes mellitus -- typically type 1, though similar outcomes may be acheivedachieved with type 2 patients ².

The most common types of pancreas transplants are ³:

• SPK: simultaneous pancreas and kidney transplant (78(~78% of cases)
• PAK: pancreas after kidney transplant (16(~16% of cases)
• PTA: pancreas transplant alone (7(~7% of cases)

Indications

TypicallyTransplants are typically performed in patients with diabetic complications or hyperlabile diabetes. The risk ofTo be a candidate for transplant, the diabetesrisks and complications must be considered more of a risk than complications from the procedure orpatient's diabetes must outweigh the risk from surgical complications and post procedure immunosuppression, which must be continued for life ⁴.

Pancreas transplants may be performed infor both type 1 and type 2 diabetes, although it is currently more commonly performed for type 1. Patients with type 1 diabetes often have absent or minimal serum levels of c-peptide (<1mg;1 mg/ml), and are considered better surgical candidates ⁵.

Indications for pancreas transplant and simultaneous pancreas and kidney transplant are continually evolving. The American Diabetes Association 2006 indications for pancreas transplant are ⁴:

• hyperlabile diabetes defined by frequent acute severe metabolic complications (hypoglycemia, marked hyperglycemia, and ketoacidosis) requiring medical attention
• clinical and emotional problems with insulin therapy that are incapacitating
• consistent failure of insulin based management to prevent complications
• presence of (two or more) diabetic complications that are progressive and unresponsive to intensive insulin therapy
• early diabetic nephropathy
• proliferative retinopathy
• symptomatic peripheral or autonomic neuropathy
• vasculopathy with accelerated atherosclerosis

The indications for a pancreas and kidney transplant are:

• CKD stages 4 or 5 (creatinine clearance <30 ml/min) with type 1 diabetes and with other diabetic complications
• prior renal transplant which is failing in a type 1 diabetic

Procedure

Technique

The pancreas is procured from the donor in a variety of ways, depending on the operative needs. The second portion of the duodenum (containing the ampulla of Vater) is recovered with the pancreas.

The technique generally consists of ³:

• incision and exposure: intraperitoneal or retroperitoneal approaches possible
• donor portal vein mobilization: to confluence of splenic vein and superior mesenteric vein
• arterial reconstruction, involving either:
  • donor Y-graft:
    • donor internal iliac artery is anastomosed end-to-end with the recipient external iliac artery
    • the other ends of the donor internal iliac artery bifurcation are anastomosed end-to-end with the donor pancreas superior mesenteric artery (SMA) and splenic artery
    • systemic venous drainage
  • direct splenic artery to SMA
    • donor SMA is anastomosed to recipient external iliac artery
    • donor splenic artery is anastomosed end-to-side with the donor SMA
    • portal venous drainage
• end-to-side or side-to-side anastomosis of the donor duodenal segment with recipient jejunum

Radiographic features

Ultrasound

Ultrasound is considered the first-line modality in evaluating the transplanted pancreas and vasculature ³, demonstrating the following features:

• grayscale:
  • transplant is hypoechoic relative to mesenteric fat
  • useful to evaluate for peripancreatic fluid collections
• colour Doppler / power Doppler:
  • evaluate flow to all parts of the transplant parenchyma
  • evaluation of patency of arterial and venous anastomoses
• spectral Doppler
  • arterial waveforms: sharp upstroke with continuous diastolic flow
  • venous waveforms: monophasic

Ultrasound may be limited by the presence of overlying bowel gas, which is common due to the frequent anastomosis to the small bowel. 

One of the primary roles of ultrasound is to exclude thrombosis. Ultrasound has limited ability to diagnose rejection. Rejection and pancreatitis may appear similarly. One of the primary roles of ultrasound is to exclude thrombosis.

CT

CT is superior to ultrasound in cases of suspected abdominal infections, bowel complications, graft rejection, or pancreatitis ³.  It is typically performed with oral contrast.

MRI

Given the common presence of contraindications to IV contrast material in donor recipients, MR is superior to CT in assessing vascular complications ³. 

Complications

Vascular complications of a pancreas transplant are conceptually similar to renal transplant, and include ³:

• graft rejection
• anastomotic breakdown and hemorrhage
• stenosis or thrombosis of the arterial inflow or venous outflow

Bowel complications may also occur ³:

• small bowel obstruction
• anastomotic exocrine leak
• colitis, specifically pseudomembranous and cytomegalovirus colitis

Other complications include ³:

• fluid collections, especially peripancreatic fluid collection
• post-transplant lymphoproliferative/lymphoproliferation disorder (PTLP)

Post-grafting pancreatitis is also possible.

Outcomes

Unadjusted patient survival rates ⁶:

• SPK:
  • 1 year: 95-98%
  • 3 years: 91-93%
  • 5 years: 87%
  • 10 years: 70%
• PAK:
  • 1 year: 95-98%
  • 3 years: 91-93%
  • 5 years: 84%
  • 10 years: 65%
• PTA:
  • 1 year: 95-98%
  • 3 years: 91-93%
  • 5 years: 89%
  • 10 years: 73%

SPK patients demonstrate the best pancreas graft survival rates.