Experimental evaluation of early and long-term effects of microparticle embolization in two different mini-pig models. Part I: kidney.
OBJECTIVE
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-microm trisacryl-gelatin microspheres (Embospheres) in acute whole-kidney embolization; (2) to evaluate the durability and biocompatibility of 40-120-microm 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 microm 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.


CONCLUSIONS
Microspheres 40-120 microm 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.
Stampfl
S
S
Department of Diagnostic Radiology, University of Heidelberg, Im Neuenheimer Feld 110, 69120 Heidelberg, Germany.
Stampfl
U
U
Rehnitz
C
C
Schnabel
Ph
P
Satzl
S
S
Christoph
P
P
Henn
C
C
Thomas
F
F
Kauffmann
G W
GW
Richter
G M
GM
D000180:Acrylic Resins / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D016461:Chemoembolization, Therapeutic / Q000009:adverse effects; D004195:Disease Models, Animal; D004389:Durable Medical Equipment; D005780:Gelatin / Q000378:metabolism / Q000494:pharmacology*; D007238:Infarction / Q000000981:diagnostic imaging / Q000209:etiology; D007668:Kidney / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000378:metabolism; D008422:Materials Testing; D010316:Particle Size; D011859:Radiography; D012078:Renal Artery Obstruction / Q000000981:diagnostic imaging / Q000473:pathology / Q000628:therapy; D012079:Renal Circulation; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors
D000180:Acrylic Resins; C496735:trisacryl gelatin microspheres; D005780:Gelatin