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Erschienen in:
01.04.2007 | LABORATORY INVESTIGATION
Experimental Evaluation of Early and Long-Term Effects of Microparticle Embolization in Two Different Mini-Pig Models. Part I: Kidney
Erschienen in: CardioVascular and Interventional Radiology | Ausgabe 2/2007
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Purpose
Using a pig model: (1) to evaluate the vascular distribution pattern, including the homogeneity and completeness of the intra-arterial microsphere distribution, of 40–120-μm trisacryl-gelatin microspheres (Embospheres) in acute whole-kidney embolization; (2) to evaluate the durability and biocompatibility of 40–120-μm trisacryl-gelatin microspheres (Embospheres) in chronic partial kidney embolization.
Methods
Twenty-two animals were divided into four groups: group 1 (n = 4) underwent total arterial renal occlusion with immediate euthanasia. Groups 2–4 had chronic superselective and partial renal embolization with increasing follow-up times: group 2 (n = 2), 1 week; group 3 (n = 7), 4 weeks; and group 4 (n = 9), 14 weeks. Key endpoints in group 1 were homogeneity and completeness of acute embolizations. In groups 2–4 the key endpoints were durability of embolization and particle-related inflammation in chronic partial embolizations as assessed by quantitative angiography or histomorphometry. A numerical angiographic occlusion score (0.0 to 4.0, where 3.0 is optimal) was developed to assess and quantify the angiographic durability of superselective embolizations (groups 2–4).
Results
In group 1, a relatively homogeneous distribution of the particles from segmental arteries to the precapillary level was shown by histomorphometry. Some particles reached the glomerular vas afferens (10 μm diameter). In groups 2–4, a mild recanalization appeared during follow-up. The immediate average postembolization occlusion score of 3.18 ± 0.73 was reduced to 1.44 ± 0.73 (statistically significant). Microscopy revealed subtotal necrosis but no foreign body granuloma formation. The intra-arterial appearance of giant cells closely attaching to the surface of the embolic spheres inside the vessel lumen was noted. Vessel walls showed major ischemic reactions.
Conclusion
Microspheres 40–120 μm in diameter might achieve total occlusion of the arterial kidney vasculature when injected centrally as a result of their fairly homogeneous distribution. Segmental renal infarction occurs after chronic partial embolization despite recanalizations during follow-up. Only mild specific intra-arterial foreign body reactions were found.