Ethylene-vinyl alcohol copolymer: Histopathological findings after pre-surgical right portal vein embolisation

To describe the gross and microscopic histopathological changes observed in human liver tissue resected after pre-surgical portal vein embolization (PVE) performed exclusively with ethylene-vinyl alcohol copolymer (EVOH).

This retrospectively study reviewed 12 consecutive patients who underwent right PVE with EVOH as the sole embolic before right hemi-hepatectomy. Demographics, peri-procedural data, and future liver remnant (FLR) volumetry were collected. Gross and microscopic examinations were performed on liver parenchyma from resected specimens using hematoxylin-eosin (H&E) and Masson's trichrome stains. The distribution of EVOH within the portal venous tree and parenchymal changes were assessed.

All patients achieved liver hypertrophy and underwent right hepatectomy 4-8 weeks after PVE. Mean pre-PVE FLR was 21.3% ± 4.8. Mean post-PVE FLR was 35.6% ± 5.5. There was no unwanted migration of EVOH into left portal vein. There were no EVOH-related complications. EVOH completely occluded targeted macro- and micro-portal branches without recanalization. The material reached portal venules within the portal triads in all cases and, in two cases, was also identified within sinusoids/centrilobular veins without associated inflammatory reaction. Histology showed a foreign-body type response with multinucleated giant cells and mild perivascular fibrosis confined to occluded portal veins. There was no acute inflammation, hepatocellular necrosis, or cholangiolar injury.

EVOH penetrates deeply into the macro and microscopic branches of the portal vein. It produces effective short-term occlusion with limited, localized foreign-body reaction and no evidence of hepatocellular injury. It facilitates adequate FLR hypertrophy and subsequent right hepatectomy.