Transsinusoidal portal vein embolization with ethylene vinyl alcohol copolymer (Onyx): a feasibility study in pigs

Abstract

Purpose: Portal vein embolization is performed to increase the future liver remnant before liver surgery in patients with liver malignancies. This study assesses the feasibility of a transsinusoidal approach for portal vein embolization (PVE) with the ethylene vinyl alcohol copolymer, Onyx.

Methods: Indirect portography through contrast injection in the cranial mesenteric artery was performed in eight healthy pigs. Onyx was slowly injected through a microcatheter from a wedged position in the hepatic vein and advanced through the liver lobules into the portal system. The progression of Onyx was followed under fluoroscopy, and the extent of embolization was monitored by indirect portography. The pigs were euthanized immediately (n = 2), at 7 days (n = 4), or at 21 days postprocedure (n = 2). All pigs underwent necropsy and the ex vivo livers were grossly and histopathologically analyzed.

Results: Transsinusoidal PVE was successfully performed in five of eight pigs (63%). In 14 of 21 injections (67%), a segmental portal vein could be filled completely. A mean of 1.6 liver lobes per pig was embolized (range 1-2 lobes). There were no periprocedural adverse events. Focal capsular scarring was visible on the surface of two resected livers, yet the capsules remained intact. Histopathological examination showed no signs of recanalization or abscess formation. Mild inflammatory reaction to Onyx was observed in the perivascular parenchyma.

Conclusions: The porcine portal vein can be embolized through injection of Onyx from a wedged position in the hepatic vein. Possible complications of transsinusoidal PVE and the effect on contralateral hypertrophy need further study.

Fig. 1

A Preembolization portogram showing the portal supply to the right lateral lobe (RL), the right medial lobe (RM), the left medial lobe (LM), and the left lateral lobe (LL), and the position of the arterial catheter in the cranial mesenteric artery (*). B Injection of Onyx from a wedged catheter position in the hepatic vein. C Onyx cast is visible at portography after first injection (injection position marked by the black short arrow). This injection was unsuccessful, because the segmental portal vein was not embolized up to its origin (white long arrow). D Onyx cast during the second injection (injection position marked by the white short arrow) successfully embolizing the RL portal vein. E Final portography shows a successfully embolized right hemiliver after the RM portal vein had been embolized by the third injection (injection position marked by the black arrowhead). Note that the Onyx cast from the second injection extends into the portal trunk (white long arrow). The diameter of the portal vein has markedly decreased compared with the preembolization portogram (A)

Fig. 2

Pathway of Onyx (arrows) from the wedged microcatheter (M) in the hepatic vein trough the central veins (CV) and the sinusoids (S) of the hexagonal shaped liver lobules, into the portal venules (PVV) and branches of the portal vein (PV)

Fig. 3

A Macroscopic view of a capsular lesion (arrow), consistent with B a superficial injection site (arrow) under fluoroscopy. C Microscopic view (H&E, original magnification ×40) of the same region shows capsular fibrosis (arrow) around the injection site

Fig. 4

A Macroscopic image of a resected liver with (B) the related radiographic image. C Close-up of injection area in (A). D Microscopic view (H&E, original magnification ×40) near the injection site shows a combination of lobules with normal-sized central veins and Onyx-filled sinusoids (arrowheads) and lobules with dilated central veins and empty, suppressed sinusoids (arrows). E Lobules near the injection site (H&E, original magnification ×40); Onyx is present in the central veins (thin arrows), in the sinusoids (arrowheads), and in the portal veins (thick arrows)