Changing Perspectives in Portal Vein Thrombosis and Liver Transplantation

Portal Vein Thrombosis in Adults Undergoing Liver Transplantation. Risk Factors, Screening, Management, and Outcome. Transplantation 2000; 69: 1873. Yerdel MA, Gunson B, Mirza D, Karayalçin K, Olliff S, Buckels J, Mayer D, McMaster P, and Pirenne J. In the initial experience of liver transplantation complete thrombosis and occlusion of the portal vein was regarded as an absolute contraindication to liver transplantation because it was believed that it would not be possible to provide a satisfactory portal inflow for the graft (1). Portal vein thrombosis is most common in patients with previous shunt surgery, previous splenectomy, hepatic malignancy, Budd Chiari syndrome, and postnecrotic cirrhosis (2). As experience in hepatic transplantation grew, surgeons rose to the challenge of performing transplantations on such patients, and reports soon appeared describing techniques to overcome this problem. Portal vein thrombosis can result in obstruction of varying proportions of the splanchnic venous system. A number of different classifications of the degree and extent of portal obstruction produced by the thrombotic process have been described; they vary from those purely based on the anatomy of the thrombosis to others more directly relevant to possible surgical approaches (2–4). In summarizing these classifications from a practical viewpoint, portal vein thrombosis can be broken down into cases with the following features: 1) thrombosis confined to the portal vein beyond the splenomesenteric confluence, which may be either partial or complete, 2) thrombosis extending into the proximal superior mesenteric venous system but with a patent vessel in the mesentery, 3) diffuse thrombosis of the splanchnic venous system but with large accessible collaterals and, 4) extensive thrombosis of the splanchnic venous system but with only fine collaterals. Different approaches have been developed to address each of these situations; these are summarized in the Table. Table: Approaches to different classifications of portal vein thrombosisThe first and most obvious method was to perform a venous thrombectomy using a Fogarty catheter. More sophisticated and controlled variations of this technique such as eversion thrombectomy (5) are still the most commonly applied technique for partial portal vein thrombosis and segmental thrombosis localized to the portal vein itself. Alternative approaches include formal dissection back to the confluence of the splenic and superior mesenteric veins to allow anastomosis of the donor portal vein directly to this point if it is sufficiently long or with the use of an interposition graft of donor iliac vein if it is not (6). This provides a solution to the problem in cases where the superior mesenteric vein and splenic vein are patent, but this solution is not applicable to the group of patients with more extensive thrombosis involving the main trunk of the superior mesenteric vein. The introduction of venous jump grafts using the donor iliac vein to provide a conduit from the more distal patent parts of the superior mesenteric system provided a means of transplantation for these patients (3), with satisfactory long term outcomes. In this technique, a venous graft is anastomosed to the distal superior mesenteric vein and brought up through the mesocolon to lie in front of the pancreas passing behind the pylorus for anastomosis to the donor portal vein (Fig. 1). In cases with extensive thrombosis where this technique cannot be applied, anastomosis to the coronary vein or to a large venous collateral may be possible and provide long-term satisfactory portal decompression and hepatic inflow (3). In the most challenging cases where there is no vessel available for portal inflow, replacement of the entire portal system along with the liver can be achieved by combined liver/small bowel or multivisceral transplantation (9). More recently, an alternative approach for these very difficult cases has been reported (10). This is based on the extensive early work by Child and then Starzl and co-workers where caval blood was diverted to the liver as partial or complete replacement of portal inflow with maintenance of satisfactory liver function (1112). Early outcomes after this procedure seem satisfactory, although there remains the issue of the persisting obstructed portal system in these patients and the continuing possibility of portal hypertensive hemorrhage. Figure 1: A venous jump graft fashioned from a donor iliac vein anastomosed to the superior mesenteric vein and brought up in front of the pancreas and behind the pylorus for anastomosis to the portal vein of the donor liver.Choice of the optimal approach to be used in an individual case is clearly dependent on accurate pre-operative diagnosis. Ultrasound and, subsequently, Doppler ultrasound have been extensively used as a screening device, with additional information provided by CT and accurate anatomical detail for operative planning obtained by conventional contrast angiography or, increasingly, by magnetic resonance angiography (13). Increased surgical skill and the application of innovative techniques have transformed the outlook for patients whose liver disease has been complicated by portal vein thrombosis. A number of large series, including the current study, have documented the excellent outcome that can currently be achieved in such cases. The outlook for patients with thrombosis confined to the portal vein proper is now comparable to that of patients without portal vein thrombosis. Even where there is more extensive thrombosis, use of the innovative techniques of jump grafts to the superior mesenteric vein or anastomosis to large collateral vessels has resulted in excellent medium and long-term survival (14–16). The most complex and difficult cases remain those with diffuse thrombosis of the splanchnic system with only fine collateral vessels, and further follow-up of patients undergoing multivisceral grafting or cavoportal hemitransposition for this indication will allow assessment of the relative merits of these two approaches.