(a) Above the left renal vein, the isolated superior mesenteric artery (arrow) arises from the aorta; (b) schematic representation
The gastrocolic ligament is then divided between the stomach and transverse colon up to the splenic flexure, looking inside for the middle colic vein: following it, the superior mesenteric vein (SMV) can be reached and isolated as far as the splenomesenteric confluence into the portal vein (the origin of the inferior pancreaticoduodenal vein must be preserved in the case of pancreas harvesting, so the SMV must be isolated up to the first jejunal vessels in order to be cut there, saving the middle colic vein). The Treitz ligament can be cut now.
The proximal part of the first jejunal loop is encircled and transected with a GIA 75 stapler in order to obtain the proximal part of the graft.
On the anatomical left side of the middle colic vessels which are going to be preserved the transverse colon is encircled and transected with a GIA 75 stapler in order to obtain the distal part of the graft. The colon is necessary to orientate the graft and can sometimes be used with the graft in order to improve electrolyte and fluid balance of the recipient, but is highly immunogenic and can be responsible for posttransplantation lymphoproliferative disorder. The warm phase can be concluded separating the mesenterium from the body ligating small lymphatic and vascular vessels, in order to progress to the cold phase with the bowel connected to the body by the superior mesenteric vessels only.
After heparinization and cross-clamping and venting maneuvers, cold perfusion is performed giving an average infusion volume of 50–100 mL/Kg, carefully watching the intestine as it blanches homogeneously. Ice must be put on the towel, wrapped around the small bowel to avoid burns. Notably, cold perfusion reaches the small bowel through the SMA only (the inferior mesenteric artery is usually tied), and vein drainage is ensured by the SMV through the portal vein.
After liver harvesting and without pancreas procurement, the pancreatic head en bloc with the duodenum is separated from the SMV and SMA, starting from the pancreatic head (cut previously by liver surgeons) and going towards the right anatomical direction: during this maneuver small head pancreatic veins must be tied. With pancreas harvesting, the pancreaticoduodenal block must be removed from the mesenterium, keeping the superior mesenteric artery and vein small cuffs with the inferior pancreaticoduodenal vessels with the pancreas.
Finally, the SMA is cut at the aortic origin (above the right branch if present or above the inferior pancreaticoduodenal artery in the event of pancreas harvesting), and the SMV is cut at the splenomesenteric confluence (or above the inferior pancreaticoduodenal vein in the event of pancreas harvesting), putting a monofilament stitch on the anterior wall (or corner) of the vessels for orientation. Enterectomy is then completed, and perfusion of the bowel with cold perfusion is performed through the SMA.
A good suggestion is to perfuse all the abdominal viscera, at the end of the warm phase, only from the aorta, thus avoiding perfusion of the liver from the inferior mesenteric vein to prevent high outflow pressure into the superior mesenteric vein. In cadaveric donors the superior mesenteric artery is cut proximally to the middle colic artery, and the superior mesenteric vein is cut centrally to the emergence of the first jejunal vein. Care must be taken to avoid traction on the delicate jejunal veins.
The isolated intestinal graft after harvesting includes the entire small bowel and the right colon with the stump of the superior mesenteric artery and the superior mesenteric vein. At the back-table care must be taken in suturing the large lymphatic vessels around the mesenteric artery and to provide good hemostasis; bleeding from the mesentery around the SMA after reperfusion can be difficult, and excessive traction on the mesentery can cause tearing of the first jejunal veins. A modification of the isolated intestinal transplant together with the pancreas en bloc has recently been described. The major difference is that the small bowel is harvested en bloc with the duodenum and pancreas. The superior mesenteric artery is harvested possibly with an aortic patch, and the splenic artery is anastomosed to a Y-iliac graft together with the superior mesenteric artery. The donor iliac artery will then be implanted end-to-side to the aorta. The venous outflow of the entire composite graft is constituted by the portal vein, and venous reconstruction will be performed with an end-to-end anastomosis between the donor and recipient’s portal vein .
24.3.2 Combined Liver-Intestine Graft: Donor Procedure
After cross-clamping, all the celomatic organs in the donor should be perfused only through the aorta. After harvesting of the liver en bloc with gastro-pancreatic-intestinal viscera, the donor surgeon performs the total pancreatectomy together with gastrectomy and duodenectomy at the back-table. Of course the total pancreatectomy and gastrectomy of the donor can be performed before cross-clamping, but in this case the procedure can be time-consuming, can cause blood loss, and can become dangerous for the subsequent function of the liver and intestinal grafts. At the end of the donor and back-table procedures, the composite allograft should consist of the liver with the inferior vena cava and the bile duct cut at the usual level as in the isolated liver harvesting procedure. The liver remains connected to the small bowel plus the right colon through the portal vein which is intact. The arterial vascular supply of the composite graft is through the hepatic artery and superior mesenteric artery which are kept connected if possible with an aortic patch surrounding the takeoff of the celiac axis and SMA.