FEATURED ABSTRACTTargeting and recanalization with rapidly resorbable microspheres versus gelatin sponge particles in a pig kidney model

Purpose Resorbable embolization microspheres (REM) must have a time of resorption quick enough to provide a functional recanalization, and to avoid chronic vascular remodeling. We synthesized calibrated REM that resorbed in less than 24 hours and evaluated the performances of REM of 3 sizes (300-500μm, 500-700μm, and 700-900μm) in terms of targeting and recanalization, by comparison to handcut 1mm gelatin sponge particles (GSP). Materials and Methods Eight pigs underwent polar renal artery embolization with either REM of the 3 sizes or GSP. Angiograms were recorded before embolization, 10 minutes and before pig sacrifice 1 week after embolization. On each angiogram, the number of opacified segments of arteries at each bifurcation level was quantified. We analyzed the partition of the opacified segments and determined the level of occlusion, the percentage of occlusion and the recanalization rate for each product. In pathology, the distribution of GSP was assessed. Results REM 300-500μm occluded distal vessels, in interlobular arterioles in the deep cortex. REM 500-700μm and 700-900μm located more proximally, in the junctional arteries which are anastomotic arteries located at the junction between medulla and cortex. GSP occluded the interlobar arteries, proximally. At D7, recanalization rate of the larger REM was 105%, whereas for the two smaller sizes (500-700μm and 300-500μm) it was respectively 62% and 57%. GSP recanalized at 79%. Conclusion Embolizations with calibrated REM were successful and enabled a precise targeting of the occlusion. REM of different sizes targeted different levels of occlusion in kidney arteries. Within less than one week REM were completely resorbed, left no residual material and inflammation and the arteries recanalized between 60% and 100%. By comparison, handcut GSP provided a variable level of occlusion without actual targeting. They were partly degraded and accompanied by a foreign body reaction and the recanalization rate was important but never complete.