Experimental study of self-expandable metallic inferior vena caval stent crossing the renal vein in rabbits. Radiologic-pathologic correlation.

RATIONALE AND OBJECTIVES The authors evaluate in the rabbit the radiologic-pathologic changes of the inferior vena cava and the renal vein and the functional changes of the kidneys after placement of a self-expandable metallic stent in the inferior vena cava where the renal vein empties. METHODS One self-expandable metallic stent was placed in the inferior vena cava in each of 12 rabbits; the rabbits were divided into four groups of three rabbits each. The inferior vena cava and renal vein were examined angiographically and pathologically at intervals of 1 week, 2 weeks, 1 month, and 3 months. Vena cavography was performed to evaluate changes in the inferior vena cava before and after stenting. Laboratory tests were performed to determine blood urea nitrogen and creatinine levels, and radioisotope renal scans were performed to evaluate possible changes in renal function before and after stenting. RESULTS No stent migration was noted in 11 of 12 rabbits; however, migration of the stent to the subdiaphragmatic level was noted in 1 rabbit. All stents were patent angiographically. Statistical analysis showed no significant change in renal function after stenting (blood urea nitrogen, P = 0.9; creatinine P = 0.5). In addition, radioisotope scans revealed no abnormal findings in perfusion and excretion. Pathologic examination of both kidneys showed no abnormal findings. Neointimal proliferation over the stent was first noted at 1 week after the stent was placed, was most prominent at 1 month, and regressed substantially by 3 months. CONCLUSIONS The self-expandable metallic stent was relatively well adapted to the inferior vena cava. Renal function was not affected by the inferior vena cava stent, which crossed the orifice of renal vein.