Self-expanding stents were used first to reduce the risk of an endoluminal restricturation after balloon dilatation .
Soon afterwards, urologists began to treat strictures in the urethra with this technique. Both permanently as well as short-term implanted stents were inserted and examined in the treatment of recurrent urethral strictures. These stents, due to their elastic, radial expanding power, are supposed to press against the wall of the urethra, thus on the one hand keeping the lumen open, and on the other hand not slipping.
The basic construction of a urethral stent consists of a woven, self-expanding wire mesh (see O Figs. 13.1, 13.2). Due to its biocompatibility, already known in other fields, and its being stainless, the material generally in use is stainless steel, nitinol, and titan. Urethral stents are available in different lengths and a large variety of diameters. Thermolabile materials are also used [92, 97]. At body temperature, the material expands and thus should lead to improved anchoring in the urethra. Nonmetallic materials such as polyurethane are also used for temporary stents,
in order to avoid incrustations . There is no long-term experience in the use of either of these materials.
Although urethral stents can also be placed in position using radiological guidance, endoscopic positioning is to be preferred. To start with, a guidewire is pushed forward past the urethral stricture into the bladder. Afterwards, the stricture is opened endoscopically [4, 86, 88]. The length of the stricture can be measured with the cystoscope and suitable catheters. Urethral stents are delivered in compressed form on an application tool. With the help of a 0°-optic, the exact position of the stent is checked, before the stent is unloaded. Most systems allow for a correction of the position as long as the stent has not been completely thrown off.
Furthermore, we should keep in mind that the stent contracts after delivery. Stents ought to be placed at least 0.5 cm away from the extern sphincter, to avoid incontinence . In cases of longer strictures, the stents can by all means be placed above each other, or overlapping .
Postoperatively, catheter insertions are not necessary, as most patients are able to void immediately. The epithe-lialization of the stent through its mesh happens within the following 6 months; the stent thus becomes incorporated into the urethral wall.
Besides these permanent stents, other stents have recently become, which are applied in the treatment of recurrence urethral strictures [80, 125-127]. The idea behind this development is that by doing so, no materials foreign to the body are left permanently in the urethra. These stents, also made of biocompatible material, are only supposed to keep the urethra open during the process of healing after urethrotomy interna, and can then be removed after a period of 9-14 months (□ Fig. 13.2).
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