Portal vein embolization for induction of selective hepatic hypertrophy prior to major hepatectomy: rationale, techniques, outcomes and future directions

Abstract

The ability to modulate the future liver remnant (FLR) is a key component of modern oncologic hepatobiliary surgery practice and has extended surgical candidacy for patients who may have been previously thought unable to survive liver resection. Multiple techniques have been developed to augment the FLR including portal vein embolization (PVE), associating liver partition and portal vein ligation (ALPPS), and the recently reported transhepatic liver venous deprivation (LVD). PVE is a well-established means to improve the safety of liver resection by redirecting blood flow to the FLR in an effort to selectively hypertrophy and ultimately improve functional reserve of the FLR. This article discusses the current practice of PVE with focus on summarizing the large number of published reports from which outcomes based practices have been developed. Both technical aspects of PVE including volumetry, approaches, and embolization agents; and clinical aspects of PVE including data supporting indications, and its role in conjunction with chemotherapy and transarterial embolization will be highlighted. PVE remains an important aspect of oncologic care; in large part due to the substantial foundation of information available demonstrating its clear clinical benefit for hepatic resection candidates with small anticipated FLRs.

Keywords: Portal vein; embolization; future liver remnant; hepatocellular carcinoma; hypertrophy; liver cancer; liver metastases; liver regeneration.

1

Degree of hypertrophy of the sFLR over time after PVE with kinetics of FLR growth, plotted as median degree of hypertrophy after PVE (with interquartile ranges). The shaded zone, days 22-56 after PVE, represents the “plateau” period during which the degree of hypertrophy did not change significantly between measurement points. Used with permission from Ref..

2

Hypertrophy of the FLR after PVE as determined by three-dimensional reconstruction of CT images. (A) Three-dimensional volumetric measurements are determined by outlining the hepatic segmental contours and then calculating the volumes from the surface measurements of each slice. (B) The formula for calculating total liver volume is based on the patient’s body surface area. (C) Before embolization, the volume of segments 2 and 3 was 283 cm³, or 14% of the total liver volume (2, 036 cm³). After embolization, the volume of segments 2 and 4 was 440 cm³, or 21% of the total liver volume (a degree of hypertrophy of 7%). B was modified from Vauthey et al. and C was modified from Vauthey et al. with permission.

3

Receiver operating characteristic curves for measured volume parameters in the prediction of postoperative hepatic insufficiency. Area under the curve (AUC) calculated for kinetic growth rate (KGR), degree of hypertrophy (DH), and sFLR. P values represent asymptotic significance (null hypothesis, AUC = 0.500). Modified with permission from Ref.

4

Schematic representation of the contralateral approach. An occlusion balloon catheter is placed from the left lobe into right portal branch, with delivery of the embolic agent in the anterograde direction.

5

Schematic representation of the ipsilateral approach for RPVE and segment 4 as described by Nagino et al.. Different portions of the balloon catheter are used for antegrade embolization of segment 4 veins (A) and for retrograde delivery of the embolic agent into the right portal system (B).

6

Schematic representation shows modification of the ipsilateral technique for RPVE extended to segment 4. (A) Placement of a 6F vascular sheath into the right portal branch. An angled 5F catheter is placed into the left portal system with coaxial placement of a microcatheter into a segment 4 branch. Particulate embolization is performed, followed by placement of coils, until all the branches are occluded. (B) After segment 4 embolization is completely occluded, a 5F reverse-curve catheter is used for RPVE. (C) After PVE is complete, the access tract is embolized with coils and/or gelfoam to prevent subcapsular hemorrhage.

7

Transhepatic ipsilateral RPVE in an 87 year old male with two segment 7 colorectal metastases prior to right hepactectomy. (A) Axial contrast enhanced MRI demonstrating two colorectal metastases in segment 7 prior to RPVE. (B) Pre-embolization portogram demonstrates patent conventional portal anatomy. (C) Intra-procedural fluoroscopic image demonstrating reduction of segment 7 flow after embolization with tris-acryl microspheres and coils. (D) Post-embolization portogram shows complete occlusion of branches of the right portal vein and patency of the left portal vein. (E) A single image from post-PVE contrast-enhanced CT scan shows hypertrophy of the left liver. The FLR/TELV increased to 43%. (F) Axial contrast enhanced MRI status after right hepatectomy demonstrates hypertrophied left liver with no evidence of disease.

8

Transhepatic ipsilateral right PVE extended to segment 4 using tris-acryl particles and coils performed in a 48 year old male with cholangiocarcinoma involving segments 4 and 5. (A) Contrast-enhanced coronal CT image of the liver demonstrated an enhancing mass centered in segment 5 (black arrow) and the normal appearing left lateral liver (white arrow) prior to PVE. (B) Anteroposterior flush portogram obtained through a 5-F flush catheter within the main portal vein via ipsilateral approach demonstrates patent conventional portal anatomy. (C) Intraprocedural fluoroscopic image from PVE depicts coil placement into segment 4 branches via a microcatheter. (D) Final portogram shows occlusion of the portal vein branches to segments 4-8 with continued patency of the veins supplying the left lateral liver. (E) CT obtained after PVE demonstrates massive hypertrophy of the FLR (White arrow; Left lateral liver volume increased from 157 to 457 mL).

9

Presence of hepatic dysfunction by sFLR volume and degree of hypertrophy. Used with permission from Ref..

10

Rates of hepatic insufficiency (A) and death (B) by preoperative sFLR volume. Modified with permission from Ref..

11

Postoperative liver insufficiency and mortality from liver failure in patients who underwent extended right hepatectomy in the setting of colorectal metastases, stratified to those undergoing no chemotherapy, chemotherapy, or long duration (> 12weeks) chemotherapy. sFLR > 20% cut-off (A) and sFLR > 30% cut-off (B) for resection eligibility. Used with permission from Ref..

12

A 55-year-old man with hepatitis C cirrhosis complicated by a 12 cm hepatocellular carcinoma replacing the entire right liver who underwent sequential TAE followed 1 month later by RPVE prior to a right hepatectomy. (A) Contrast enhanced axial image of the liver demonstrated a 12 cm enhancing mass replacing the right liver and normal appearing of left lateral liver prior to embolization and PVE. (B) Intraprocedural digital subtraction selective angiography demonstrates hypervascular tumor with successful particle embolization. (C) Anteroposterior flush portogram obtained through a 5-F flush catheter within the main portal vein via ipsilateral approach demonstrates patent conventional portal anatomy. (D) Intraprocedural fluoroscopic image from PVE depicts complete occlusion of all branches to right portal vein. (E) Final portogram shows occlusion of the portal vein branches to segments 4–8 with continued patency of the veins supplying the left lateral liver. (F) A single image from post-PVE contrast-enhanced CT scan demonstrates profound necrosis of the tumor (white arrow) and massive hypertrophy of the left lateral liver. The patient underwent uncomplicated right hepatectomy.