Cavernous transformation of the portal vein in pancreatic cancer surgery—venous bypass graft first

To assess the possibility of a “venous bypass graft first” operation in patients with a cavernous transformation of the MPA after complete occlusion of the splenic-mesenteric confluence, the anatomy of the PV and the SMV has to be carefully analyzed in preoperative contrast-enhanced CT or MRI scans (Fig. 1a–d). It is quintessential to have a patent albeit short extrahepatic portal vein as well as a patent SMV or in case of tumor infiltration into the mesentery, a large tributary branch of the SMV proximal to the occlusion to enable a venous bypass using a graft; therefore, preoperatively, a thrombosis of or occlusion of the extrahepatic portal vein needs to be ruled out.

The operation begins with the initial exploration as in a conventional partial pancreaticoduodenectomy. High blood loss due to the cavernous transformation with excessive varicose veins should be avoided. During the exploration phase, excessive varicose veins can be visible around the stomach and in the greater omentum (Fig. 2a). After separation of the greater omentum from the transverse colon, the right colic flexure is mobilized to gain access to the head of the pancreas. To provide sufficient access and flexibility of the mesenteric root, the complete right hemicolon and the mesenteric root can be mobilized. The aim in the first stage of the operation is to identify suitable venous vessels to perform the “venous bypass graft first” approach. This includes the identification of the superior mesenteric vein or one of its branches as well as the portal vein in the hepatoduodenal ligament, often close to the liver hilum. A potential vein for the proximal intestinal part of the bypass should be secured with a vessel loop. This might be the superior mesenteric vein itself or one or more of its dilated tributaries. To assess the resectability of the tumor, an extended Kocher’s maneuver is performed. This includes the identification of the left renal vein and its junction with the inferior vena cava. Additionally, the root of the superior mesenteric artery should be secured at its aortic origin [15, 16]. In the next step, the dissection of the hepatoduodenal ligament is performed (Fig. 2b). If possible, the proper hepatic artery with the left and right hepatic arteries is identified and secured with vessel loops. After securing arterial inflow control to the liver, the extrahepatic portal vein close to the liver hilum should be secured with a vessel loop as this serves as the distal anastomotic location of the venous bypass. The common bile duct with its varicose transformed veins can be a challenge when accessing the extrahepatic portal vein.

The superior mesenteric vein or a large branch is transected after a vascular clamp is applied. The pancreatic side of the SMV is suture ligated and, on the mesenteric side, an end-to-end anastomosis is performed (i.e., 5–0 monofilament non-resorbable running suture) with a ring-enforced polytetrafluoroethylene (PTFE) Gore-Tex prosthesis of 10 or 12 mm diameter depending on the SMV or SMV branch size. The prosthesis is placed around the dorsal part of the pancreatic head with a sufficient length to enable further resection of the tumor. The portal vein is transected after the application of vascular clamps and a suture ligation towards the pancreatic head is placed. The prosthesis is flushed with heparinized saline solution and an end-to-end anastomosis is performed to the portal vein in the liver hilum (Fig. 2c, d). After the release of the vascular clamps, flow is measured and the intestine is observed for venous congestion. Postoperatively, a standard thrombosis prophylaxis is performed with low molecular weight heparin.

The common hepatic artery is followed towards the CA and the gastroduodenal artery is identified. The gastroduodenal artery is severed as well as the right gastroepiploic vessels. The distal stomach or duodenum (pylorus-preserving PD) is transected and the remnant stomach is placed in the left upper quadrant. During this phase of the operation, the left gastric vein is usually severed due to portal vein infiltration. The left gastric vein is tagged for potential re-anastomosis. The jejunum is transected 10 cm after the ligament of Treitz. The proximal jejunum is devascularized and transposed via the opened ligament of Treitz into the right upper quadrant. Afterward, the uncinate process is mobilized from the superior mesenteric artery analogous to the uncinate first approach [14].

To perform the portal vein resection, the pancreas is divided left to the normal resection plane of the SMV. The splenic artery is identified and preserved at its location at the superior border of the pancreas. After the division of the pancreas, the splenic vein is identified and divided. During the resection phase, the dissection of the pancreatic head is performed according to the previously published “artery first” and “uncinate” approaches [14, 16]. The vascular approach during this phase of the operation was described previously [15]. Finally, the pancreatic head is resected in a right to left and posterior to anterior fashion and the mesopancreas is resected up to the transection plane of the pancreas. For a complete oncologic resection, we perform additionally a resection of the potentially tumor-infiltrated lymph node and neural tissue in the triangular space between the CA, aorta, and SMA [15]. The anterior border of the “triangle” consists usually of the portal vein, but is resected in this approach. Due to the extensive tumor infiltration, total pancreatectomy is often warranted. To relieve the gastric congestion, the left gastric vein, or the right gastroepiploic vein, can be implanted into the left renal vein. Alternatively, the splenic vein can be implanted into the left renal vein. If these approaches are not possible, a subtotal gastrectomy should be considered.

Before reconstruction, the venous bypass graft should be shortened to the correct length. This is important to avoid graft kinking and venous thrombosis. In some cases, the complete graft can be removed if an end-to-end anastomosis of the SMV and PV is possible; however, this is limited by potential kinking of the SMA, which needs to be avoided. The shortening of the venous graft completes the resection phase of the operation. To avoid left-sided portal hypertension, a splenorenal shunt or a shunt from the left gastric vein to the left renal vein should be considered (Fig. 3a, b).