Use of a shape-memory alloy (nitinol) in a removable prostate stent.

An easily removable prostate stent would be useful in various clinical situations but is not currently available. Thus, we studied the safety, tolerability, and ease of removal of a nitinol (nickel-titanium alloy) prostate stent in 10 men with symptomatic benign prostatic hyperplasia. The circular-coil stent becomes hourglass in shape following deployment, with the narrowest diameter approximately 35F. A working hypothesis was that the temperature-sensitive shape memory of nitinol would allow for its easy removal vis-à-vis other available stents. Using several modifications of a prototype insertion device, we found that the nitinol stents were easily inserted, retained their shape during retention periods of 1 to 4 weeks, caused no gross tissue reaction, and were removed easily with gentle traction after in situ cooling with iced saline lavage. Stent migration was observed in two patients, but otherwise, the stents were well tolerated. Nitinol prostate stents appear to fulfill a theoretical promise of being biologically inert, "superelastic," and pliable when cooled, allowing for easy removal. Further clinical investigation appears warranted.