Double Embolization for Rapid Liver Hypertrophy : The Endovascular ALPPS

P ortal vein embolization (PVE) with gelatin sponge and cyanoacrylate is a well-established approach to divert portal flow from one side of the liver to the future liver remnant (FLR) to prepare the liver for extended resections.1 When more than 70% of the liver has to be removed, most often due to extensive tumor load, PVE can help to prepare the small FLR to tolerate the hemodynamic stress of the portomesenteric blood flow and metabolic requirements of the organism and increase the liver volume of the FLR by up to 50%.2,3 This process of conditioning the FLR usually takes about 6 weeks but is not successful in all patients. In some patients, the FLR fails to grow in volume, or cancer progression during the waiting period makes the planned resection impossible. Overall, up to 27% of patients fail to achieve resectability using this strategy, even in the most experienced centers.4 Due to its unreliability and the necessary waiting period, PVE is not a popular option at some centers. Randomized studies have not been able to consistently prove an outcome advantage for all patients, but some subgroups, such as those with cirrhosis undergoing extensive resections, have had improved outcomes over extended resections without preconditioning.5 In 2012, associating liver partition and portal vein ligation for staged hepatectomy (ALPPS), a surgical procedure, was proposed to replace interventional PVE.6 In ALPPS, the portal vein is ligated but not embolized, and the liver parenchyma is transected to separate the deportalized liver and the FLR.7 ALPPS both accelerates the time the liver takes to hypertrophy and increases the amount of liver volume achieved when compared to PVE.8 The novel operation was hailed to increase the resectability of liver tumors and expand the indications for surgical resection.6 Not surprisingly, complications and mortality were higher in a surgical procedure requiring laparotomy instead of a radiologic intervention,9 but in bilobar multifocal liver metastases, which require two surgical procedures for resection anyway, the ALPPS procedure continued to garner support.10 A Scandinavian randomized study recently showed that the complication rate associated with resection of bilobar colorectal liver metastases in a two-stage hepatectomy, using PVE in between, is comparable to that of the two ALPPS stages.11 However, more patients proceed to complete resection with the ALPPS procedure than with PVE.11 In contrast, reports of high complication rates for most other indications for liver resection such as hepatocellular carcinoma and biliary tumors have challenged the potential of ALPPS to replace PVE.12-14 ALPPS remains a second-line intervention behind PVE for all indications for liver resection to increase the function and volume of the FLR except for very extensive colorectal liver metastases.15,16 To maintain the advantages of rapid hypertrophy while reducing the high morbidity and mortality rate of ALPPS, attempts have been made to return to the interventional paradigm. ALPPS reformists proposed interventional embolization of the portal vein instead of ligation (also called hybrid ALPPS),17 as well as interventional transection of the parenchyma using transcutaneous radiofrequency ablation combined with PVE (also called radiofrequency-assisted ALPPS or RALPPS)18 Double Embolization for Rapid Liver Hypertrophy: The Endovascular ALPPS