Portal Vein Embolization as an Oncosurgical Strategy Prior to Major Hepatic Resection: Anatomic, Surgical, and Technical Considerations

Abstract

Preoperative portal vein embolization (PVE) is used to extend the indications for major hepatic resection, and it has become the standard of care for selected patients with hepatic malignancies treated at major hepatobiliary centers. To date, various techniques with different embolic materials have been used with similar results in the degree of liver hypertrophy. Regardless of the specific strategy used, both surgeons and interventional radiologists must be familiar with each other's techniques to be able to create the optimal plan for each individual patient. Knowledge of the segmental anatomy of the liver is paramount to fully understand the liver segments that need to be embolized and resected. Understanding the portal vein anatomy and the branching variations, along with the techniques used to transect the portal vein during hepatic resection, is important because these variables can affect the PVE procedure and the eventual surgical resection. Comprehension of the advantages and disadvantages of approaches to the portal venous system and the various embolic materials used for PVE is essential to best tailor the procedures for each patient and to avoid complications. Before PVE, meticulous assessment of the portal vein branching anatomy is performed with cross-sectional imaging, and embolization strategies are developed based on the patient's anatomy. The PVE procedure consists of several technical steps, and knowledge of these technical tips, potential complications, and how to avoid the complications in each step is of great importance for safe and successful PVE and ultimately successful hepatectomy. Because PVE is used as an adjunct to planned hepatic resection, priority must always be placed on safety, without compromising the integrity of the future liver remnant, and close collaboration between interventional radiologists and hepatobiliary surgeons is essential to achieve successful outcomes.

Keywords: hepatectomy; liver resection; liver tumors; oncosurgical strategy; portal vein embolization.

Figure 1

Illustration of the segmental anatomy of the liver based on the third-order portal vein branching (Couinaud’s classification system) and the portal vein and hepatic vein branches. IVC: inferior vena cava and PV: portal vein.

Figure 2

Representative hepatic resections. (A) Right hepatectomy or right hemihepatectomy (resection of segments 5–8) and left hepatectomy or left hemihepatectomy (resection of segments 2–4). (B) Right trisectionectomy or extended right hepatectomy (resection of segments 4–8) and left lateral sectionectomy or bisegmentectomy 2 and 3 (resection of segments 2 and 3). (C) Segmentectomy 6 (resection of segment 6). (D) Bisegmentectomy 5 and 6 (resection of segments 5 and 6).

Figure 3

Standard portal vein branching and main portal vein branching variations. (A) Standard portal vein branching. (B) Trifurcation of the main portal vein. (C) The right posterior portal vein arising as the first branch of the main portal vein. MPV, main portal vein; LPV, left portal vein; RPV, right portal vein; RAPV, right anterior portal vein; and RPPV, right posterior portal vein.

Figure 4

Right portal vein branching variations. (A–C) Trifurcation of the right portal vein. (D) Quadrification of the right portal vein. (E,F) Proximal origin of the segmental branch from the right portal vein. (G,H) Proximal origin of the subsegmental branch from the right portal vein.

Figure 5

Drawing illustrates the right anterior portal vein that arises from the left portal vein in an anomaly with the right-sided ligamentum teres that is juxtaposed to the gallbladder. In this anomaly, the umbilical portion of the left portal vein is also deviated to the right. UP, umbilical portion; LT, ligamentum teres (dotted line); and GB, gall bladder.

Figure 6

Segmental or subsegmental portal vein branches that cross the midplane of the liver. (A) A Sg 4 branch that arises from the right anterior portal vein. (B) A Sg 8 branch that arises from the left portal vein. (C) A subsegmental branch that arises from the right anterior portal vein but supplies Sg 4. (D) A subsegmental branch that arises from the left portal vein but supplies Sg 8.

Figure 7

Surgical techniques used for the control of inflow to the liver in a right hepatectomy. (A) Extrahepatic dissection and ligation. The hilar plate (arrow) is dissected and the right hepatic artery and right portal vein are ligated and dissected individually. A vascular stapler is used to divide the right portal vein. (B) Intrahepatic pedicle ligation. Arrow indicates the site of a hepatotomy made at the inferior surface of the liver to expose the intrahepatic main right portal pedicle. A vascular stapler which is inserted into the liver parenchyma divides the main right portal pedicle.

Figure 8

Right PVE strategies based on portal vein branching anatomy. In each drawing, black lines indicate the most proximal site or sites where embolic materials can be placed when the length of the right portal vein is more than 1 cm. The dotted black lines indicate the most proximal site or sites where embolic materials can be placed when no right portal vein exists or the length of the right portal vein is less than 1 cm. (A) A case with standard portal vein anatomy. (B) A case with trifurcation of the main portal vein. (C) A case with a Sg 6 branch arising from the proximal 1-cm portion of the right portal vein.

Figure 9

Right PVE extended to segment 4. (A) Intraprocedural ultrasound image shows a 22-gauge Chiba needle (arrowheads) placed within the branch of the right portal vein. A metal introducer set was subsequently introduced into the right portal system over a 0.018 guidewire (not shown). (B) Flush portogram shows a 5-Fr pigtail catheter (arrow) introduced through a 6-Fr sheath (arrowhead) and placed within the main portal vein. No variant main portal vein branching is demonstrated. (C) Selective right portogram, using a 5-Fr reverse curved catheter, shows right portal vein branches. Note the metallic coils placed within the Sg 4 branches. (D) Selective right portogram following delivery of PVA particles into the right portal vein branches shows embolized subsegmental branches within the right liver. (E) Final portogram shows successful embolization of the right portal vein and Sg 4 branches, with preserved blood flow to the FLR (Sg 2 and 3). Note the metallic coils placed within the proximal right anterior and posterior branches (arrowheads).

Figure 10

Right PVE in a patient with complex right portal vein branching anatomy. (A) Flush portogram shows the right posterior portal vein arising as the first branch of the main portal vein (large arrow). The Sg 7 branch arises from the proximal right posterior portal vein (small arrow). The common trunk (large arrowhead) of the left portal vein and the right anterior portal vein trifurcate into the left portal vein and two right anterior portal vein branches (small arrowheads). Based on this right portal vein branching anatomy, the four right portal vein branches are separately embolized with PVA particles and metallic coils. (B) Final portogram shows successful right PVE, with preserved blood flow to the left liver. Note the metallic coils placed in the proximal portion of each branch.

Figure 11

A questionable subsegmental portal vein branch crossing the midplane of the liver in a patient referred for right PVE. (A) Flush portogram shows a subsegmental branch directing to the left (small arrow) that is arising from the segmental branch directing to the dome of the liver (large arrow). (B) Selective right portogram clearly shows the subsegmental branch that possibly supplies segment 4 (small arrow). (C,D) Axial, (A) sagittal, and (B) reformatted C-arm cone-beam CT images during selective right portogram show the segmental branch supplying segment 7 (arrowheads). The subsegmental branch that was considered to be possibly supplying segment 4 was shown to be supplying segment 7. This segmental branch was then confidently embolized with PVA particles and coils. Note that artifact from the metallic coils placed in the right liver during the PVE procedure.

Figure 12

Right PVE via a contralateral approach in a patient with a large hepatocellular carcinoma. (A) Contrast-enhanced T1-weighted coronal MR images show a large tumor in the right liver. Marked distortions of the anterior (arrows) and posterior (arrowheads) branches of the right portal vein caused by the tumor are noted. The patient was referred for right PVE prior to a right hepatectomy. An ipsilateral approach was initially planned; however, no portal branches were identified for safe access within the right liver during the procedure. Access to the Sg4 portal vein branch was then obtained with a 22-gauge Chiba needle (not shown). (B) Flush portogram shows a 5-Fr pigtail catheter placed within the main portal vein through a 6-Fr sheath (arrow). (C) Final portogram shows successful occlusion of the right portal vein branches, with preserved blood flow to the left portal vein branches.