Experimental study of Wallstent self-expandable metal stent in ureteral implantation.

In regard to the risk of stent obstruction, there are persistent controversies concerning the use of the Wallstent self-expandable metal stents in the ureter. Only a few clinical trials have been published to date, and, from a technical point of view, no success predictors have been identified. In an experimental study using a pig model, we have shown that neither the length of the stent (5 or 10 cm) nor an initial 1-month intubation had any influence on the outcome of the stents. Among the eight implantations studied (four 5-cm and four 10-cm stents), only one 5-cm stent was perfectly patent at 35 days. In all the remaining stents, after 35 or 90 days, constant failure was related to distal narrowing at the edge of the stent, with no difference between the 5- and 10-cm stents or between the intubated and the nonintubated stents. This distal narrowing, probably attributable to a functional discrepancy between an adynamic stented ureter and a normal underlying ureter, demands extreme caution in human applications when the ureter is normally peristaltic.