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

Objectives: to compare the effects of crossing renal artery ostia with vari ous 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 pre ssure and blood samples were performed and the pigs then sacrificed for his tological examination. Results: histological examination revealed an organised collagen matrix wit h endothelial cells coveting the struts in contact with the aorta. This occ urred with all stents but was most organised with the Wallstent. This matri x 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 pr essure 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 arte ries will require imaging methods, such as intravascular ultrasound (IVUS) to ensure that the ostia are not obstructed.