Anatomic limitations of prostatic urethra in using cylindrical stents.

The use of metal stents for the relief of prostate obstruction in the elderly has increased in popularity since 1980. The finding that fine metal wire stents become covered with prostatic epithelium led to the recent use of stents that can be left in place permanently. Because the prostatic urethra does not always conform to the cylindrical shape of these stents, and because the bladder neck/urethral angle is not a right angle and may not be circular in outline, problems may occur with positioning and subsequent inadequate epithelial covering. Three-dimensional imaging of the prostatic urethra using transrectal ultrasound scanning during voiding may give additional help in defining the variety of possible shapes of this area, but more work on the compliance of prostate tissue and the shape of the prostatic urethral lumen is essential in order to improve stent design and reduce the risks and complications of these useful devices.