Overview

Portal vein embolization (PVE) is performed preoperatively to reduce the risk of extensive surgery in patients with small anticipated remnant livers (Makuuchi et al, 1990; de Baere et al, 1993; Abdalla et al, 2002; Madoff et al, 2005a; see Chapter 30a). PVE redirects portal blood flow to the intended future liver remnant (FLR) in an attempt to initiate hypertrophy of the nonembolized segments, and it has been shown to improve the functional reserve of the FLR before surgery. In appropriately selected patients, PVE has also been shown to reduce perioperative morbidity, and it allows for safe, potentially curative hepatectomy for patients previously considered ineligible for resection based on anticipated small remnant livers (Azoulay et al, 2000; Madoff et al, 2005a; Abulkhir et al, 2008). For this reason, PVE is now performed at many comprehensive hepatobiliary centers worldwide prior to major hepatectomy. This section details the techniques currently used to perform PVE, discusses their advantages and disadvantages, and reviews the potential complications that can occur from this procedure.

Technical Aspects of Portal Vein Embolization

Access Routes to the Portal Venous System

PVE can be performed by any of three standard approaches: 1) the intraoperative transileocolic venous approach, 2) the transhepatic contralateral approach (i.e., percutaneous portal vein is accessed via the FLR), and 3) the transhepatic ipsilateral approach (i.e., percutaneous portal access is via the liver to be resected; Madoff et al, 2005a). It is important to note that the approach to the portal vein is chosen at the discretion of the operator, and the decision may be based on multiple factors, including the extent of the embolization and surgery, the operator’s preference for a specific embolic agent, tumor burden within the liver, and the operator’s level of experience with one technique over another (Avritscher et al, 2008). An alternative approach, portal vein ligation, is typically performed intraoperatively during the first stage of a two-stage resection for hepatic colorectal metastases, and it has been reported to be as effective as percutaneous embolization methods (Aussilhou et al, 2008). Regardless of the technique used, the operator must be aware of variations in portal venous anatomy that may impact the conduct of the procedure (see Chapter 1B).

Transileocolic Venous Approach

The transileocolic venous approach was the first approach described for performing preoperative PVE, and it is still used in many Asian centers. This technique is performed at laparotomy by direct cannulation of the ileocolic vein and introduction of a catheter into the portal system for embolization (Abdalla et al, 2002). Conventional teaching has been that this approach is performed when additional treatment is needed during the same surgical exploration, when a percutaneous approach is not considered feasible, or when an interventional radiology suite is not available (Azoulay et al, 1995; Denys et al, 2002).

The disadvantages of this method are the need for general anesthesia and laparotomy, with their inherent risks, and the inferior imaging equipment often available in the operating room, compared with the state-of-the-art imaging equipment available in most modern interventional radiology suites; however, as more minimally invasive techniques have become favored, and as the equipment used—imaging equipment, catheter systems, embolic agents, and so on—has become more sophisticated, the reasons for using this technique apply in very limited situations, such that the transileocolic venous approach is being used less often than the techniques described below.

Percutaneous Transhepatic Ipsilateral Approach

The percutaneous transhepatic ipsilateral approach was first described by Nagino and coworkers (1996), and it is now advocated by many other investigators (Madoff et al, 2003, 2005b; Gibo et al, 2007; Tsuda et al, 2006). With this approach, access is obtained through the portal branches within the tumor-bearing liver (Fig. 93B.1). A distinct advantage of the ipsilateral approach is that the FLR is not instrumented. It also allows for straightforward catheterization of segment IV branches, should embolization of segment IV be required. When planning the puncture, the anterior segment of the right portal vein is preferred, because its use is associated with a lower complication rate (Kodama et al, 2002); however, catheterizing the right portal branches can be challenging, owing to the sharp angulation of the right portal veins, which often necessitates using reverse-curve catheters or balloon occlusion catheters with multiple lumina (Nagino et al, 1996, 2000a).

FIGURE 93B.1 Schematic representation of the ipsilateral approach for right portal vein embolization (PVE) and segment IV as described by Nagino and coworkers. Different balloon catheters are used for antegrade embolization of segment IV veins (A) and for retrograde delivery of the embolic agent into the right portal system (B).

In Nagino’s approach (see Fig. 93B.1), the right anterior portal vein is punctured using sonographic guidance, and a 6-Fr sheath is introduced into the right portal vein system (Nagino et al, 2000a). To make this procedure feasible, the authors designed two types of 5.5-Fr triple-lumen balloon catheters. The first catheter, “type 1,” was designed with one lumen connected to the balloon and two lumina connected to the tip. The second catheter, “type 2,” had two separate lumina opening proximal to the balloon, and the balloons were used to prevent any backflow of embolic material. Both catheters had two separate lumina so that fibrin glue and iodized oil could be injected simultaneously. To facilitate resection, the authors advocated that a proximal right portal vein segment at least 1 cm in length remain patent. Depending on the portal vein anatomy, and the need to spare the proximal right portal vein, type 1 or type 2 catheters were used for embolization. The type 1 catheter was used for embolization of branches distal to the catheter tip, whereas the type 2 catheter was used for embolization of branches proximal to the catheter tip, as mandated by each patient’s portal vein anatomy.

In a recent study, Gibo and coworkers (2007) reported on a modified technique utilizing a four-lumen balloon catheter in eight patients. The authors recommended using this modified catheter because of its larger occlusion balloon and lumina, which allow for safer and easier embolization using fibrin glue. Unfortunately, neither the original nor the modified catheters are available in the United States.

In the early 2000s, Madoff and coworkers (2003, 2005b) described a technique using angiographic catheters commercially available worldwide (Figs. 93B.2 and 93B.3). Under sonographic guidance, a 22-gauge Chiba needle (Neff Percutaneous Access Set; Cook Medical, Bloomington, IN) is used to puncture a distal branch of the right portal system. Subsequently, a 5- or 6-Fr vascular sheath is advanced over a guidewire into the right portal vein branch to aid with subsequent catheter exchanges. Flush portography is performed with a 5-Fr angiographic flush catheter placed within the main portal vein. Anteroposterior and craniocaudal projections are obtained as needed to delineate the portal anatomy.

FIGURE 93B.2 Schematic representation shows modification of the ipsilateral technique for right portal vein embolization (RPVE) extended to segment IV. A, Placement of a 6-Fr vascular sheath into the right portal branch. An angled 5-Fr catheter is placed into the left portal system with coaxial placement of a microcatheter into a segment IV branch. Particulate embolization is performed followed by placement of coils, until all the branches are occluded. B, After segment IV embolization is completely occluded, a 5-Fr reverse-curve catheter is used for RPVE. C, After embolization of the right and segment IV portal veins are complete, the access tract is embolized with coils to prevent subcapsular hemorrhage.

FIGURE 93B.3 A 67-year-old man with pancreatic insulinoma metastatic to the liver who had transhepatic ipsilateral right portal vein embolization (RPVE) with particles and coils prior to right hepatectomy. A, Contrast-enhanced computed tomographic (CT) scan of the liver shows a hypervascular mass in the right liver consistent with metastatic disease (arrow). B, Contrast-enhanced CT scan of the liver shows a small left liver within the shaded area (functional liver remnant/total estimated liver volume ratio [FLR/TELV] of 16%). C, Anteroposterior flush digital subtraction portogram shows a 6-Fr vascular sheath (arrowheads) in a right portal vein branch and a 5-Fr flush catheter (arrow) in the main portal vein. D, Postprocedure anteroposterior flush portogram shows occlusion of the portal vein branches to segments V through VIII (white arrows) with continued patency of the vein supplying the left liver (black arrow). An arrowhead shows subtracted contrast within a right portal vein branch overlying the left liver. E, A later phase of portogram confirms persistent flow to the left liver (arrows). F, Contrast-enhanced CT scan of the liver performed 1 month after RPVE shows hypertrophy of the left liver within the shaded area (FLR/TELV of 34%). The patient soon after underwent an uneventful right hepatectomy.

When embolization of the right portal vein is extended to segment IV (Fig. 93B.4), segment IV embolization should be performed first (Madoff et al, 2005b). This sequence is advocated because of the potential difficulty of exchanging catheters through a previously embolized right portal system and the possible dislodgement of embolic material from the right liver during the subsequent treatment of segment IV, which is usually embolized with a 3-Fr microcatheter placed coaxially through a selective 5-Fr angiographic catheter.

FIGURE 93B.4 A 38-year-old man with metastatic colorectal cancer to the liver who had transhepatic ipsilateral right portal vein embolization with particles and coils extended to segment IV prior to extended right hepatectomy. A, Contrast-enhanced computed tomography (CT) scan of the liver shows a small left lateral liver (functional liver remnant/total estimated liver volume ratio [FLR/TELV] of 16.9%; shaded area). B, Anterior–posterior flush portogram from the ipsilateral approach shows a 6-Fr vascular sheath in a right portal vein branch and a 5-Fr flush catheter (arrow) in the main portal vein. C, Postprocedure portogram shows complete occlusion, with particles and coils, of the portal vein branches to segment IV (arrowheads) and the right liver (arrows) with continued patency of the veins supplying the left lateral liver. D, A later phase of portogram confirms persistent flow to the left liver (arrows). E, Contrast-enhanced CT scan performed 4 weeks after portal vein embolization shows hypertrophy of the left lateral liver (FLR/TELV is now 27.2%, a degree of hypertrophy of 10.3%) with rounded margins (shaded area). A coil within segment IV (arrowhead) and coils within the right liver are seen. F, Contrast-enhanced CT scan of the liver performed after successful extended right hepatectomy shows hypertrophy of the liver remnant.

Early on, polyvinyl alcohol (PVA) particles (Contour SE Microspheres; Boston Scientific, Natick, MA) were the embolic agents of choice (Madoff et al, 2003). PVA was administered in a stepwise fashion: smaller particles (355 to 500 µm) were used first to occlude the distal branches, and larger particles (up to 1000 µm) were used subsequently to occlude branches more proximally. Larger particles were not used until the forward portal blood flow was considerably reduced. Additional embolization with the larger particles was then performed, until near complete stasis was achieved. Later, with the advent of spherical embolic agents, tris-acryl gelatin microspheres (EmboGold Microspheres; Biosphere Medical, Rockland, MA) became the embolic agent of choice (Madoff et al, 2005b). EmboGold microspheres ranging from 100 to 700 µm in diameter are administered in a stepwise fashion, similar to the method used for the PVA particles. After particulate embolization is complete, platinum microcoils (Boston Scientific) are placed within the proximal segment IV branches to further reduce portal blood inflow that could lead to recanalization.

For right PVE (RPVE), the working catheter is exchanged for a 5-Fr reverse-curve catheter (Sos-2, AngioDynamics, Latham, NY) to enable delivery of the particulate embolic agent. These catheters are chosen for their ease of manipulation into the right portal branches, given the severe angulation of the right portal tree with the ipsilateral approach. As with segment IV embolization, smaller particles are used first to occlude the distal, smaller portal branches, and the larger particles are used later to occlude the more proximal, larger branches. After near complete stasis is achieved, 0.035- or 0.038-inch embolization coils (Gianturco, Cook Medical) are placed within the secondary portal branches to further reduce portal inflow that could lead to recanalization. A final portogram is obtained with the flush catheter positioned within the main portal vein to assess completeness of the embolization. At the completion of the procedure, the access tract is embolized with coils and/or Gelfoam to minimize the risk of bleeding at the liver puncture site.

Overall, the ipsilateral approach is safe and effective for achieving FLR hypertrophy preoperatively. Although disadvantages of the ipsilateral approach do exist, they are minor. As mentioned above, catheterization and embolization of the right portal vein branches may be challenging because of the severe angulations between right portal branches; however, this is rarely a problem when reverse-curve catheters are used. Operators also need to be aware that the ipsilateral approach carries the risk of puncture through tumor tissue when multiple or large tumors are present, which could theoretically lead to bleeding or tumor seeding.