The effects of crossing porcine renal artery ostia with various endovascular stents

Objectives: to compare the effects of crossing renal artery ostia with various stents. Methods: the renal artery ostia of 24 large white pigs were coveted with a Wallstent(R) (nine ostia), a Palmaz(R) stent (nine ostia) and a Memotherm(R) stent (13 ostia). After an interval of 6-15 weeks, aortography, renal pressure and blood samples were performed and the pigs then sacrificed for histological examination. Results: histological examination revealed an organised collagen matrix with endothelial cells coveting the struts in contact with the aorta. This occurred with all stents but was most organised with the Wallstent. This matrix did not involve the renal artery ostia crossed by Wallstents, but in one Palmaz stent and in 12/13 Memotherm stents, a disorganised acellular matrix caused partial ostial occlusion. There was no mean fall in renal artery pressure but traces were damped in 8/13 cases of partial occlusion. There was a rise in serum creatinine in two cases rising the Palmaz stent. Conclusions: covering renal arteries with the Wallstent appears to be safe in the short-term. Placement of stents with larger struts across renal arteries will require imaging methods, such as intravascular ultrasound (IVUS) to ensure that the ostia are not obstructed.