Experimental Liver Embolization with Four Different Spherical Embolic Materials: Impact on Inflammatory Tissue and Foreign Body Reaction

We sought to describe and compare material specific inflammatory and foreign body reactions after porcine liver embolization with spherical embolic agents. In 40 animals, superselective liver embolization was performed with four different spherical embolic agents of various sizes: 40-120 mu m (Embozene, Embosphere), and 100-300 mu m, 500-700 mu m, and 700-900 mu m (Embozene, Embosphere, Bead Block, and Contour SE, respectively). After 4 or 12 weeks, inflammatory reactions were evaluated microscopically according to the Banff 97 classification. For investigation of foreign body reactions, a newly designed giant cell score was applied. Banff 97 and giant cell scores closely correlated. At 4 weeks, small Embosphere particles (100-300 mu m) had a significantly higher Banff 97 score than Embozene, Bead Block, and Contour SE of the corresponding size. After 12 weeks, the calculated differences were not statistically significant. Comparison between the 4-week results and the 12-week results revealed a statistically higher Banff 97 score for Embosphere 100-300 mu m after 4 weeks than after 12 weeks (P = 0.02). The overall foreign body reaction was pronounced after embolization with smaller particles, especially in small Embosphere particles. Giant cell numbers with Embosphere 100-300 mu m were statistically higher compared with the other materials of corresponding size (P < 0.0001). Inflammatory and giant cell reactions after embolization procedures depend on the embolic material. The overall inflammatory reaction was low. However, marked inflammation was associated with small Embosphere particles at 4 weeks, a finding that might be caused by the allogeneic overcoat. Correspondingly, giant cells indicating a foreign body reaction were more frequently associated with small particle sizes, especially after embolization with small Embosphere particles.