Memokath Stent is a semi-permanent metal prosthesis which can be used as an alternative and minimally invasive treatment in stenosischronic ureteral disease of different etiologies, both benign and malignant.
This semi-permanent metal prosthesis with thermo-expandable properties and it is made of a nickel-titanium alloy. It is manufactured in different sizesthat allow their adaptation to the length of the stenosis, but all have aninner diameter of 8.1 mm, one outer diameter of 10.5 mm, and a visible cylinder-shaped structure formed by a 0.4 mm wirediameter that rolls up on itself. Due to this tightly wound spiral,these stents are resistant to extrinsic compressive forces, allowing to follow thecontouring the ureter and reducing the risk of ischemic mucosal injury without abolishingproximal peristalsis.
Regarding its placement, it can be inserted both antegradeas retrograde, playing a very important role the mentioned propertiesThermal that facilitate installation or removal, if necessary.
Its peculiarity lies in the deployment of a 20 mm crown at the endproximal of the prosthesis with the instillation of hot serum at about 50 degrees Celsiusthus avoiding the migration of it. For the withdrawal, an instillation withcold serum, around 10 degrees, causing the crown to retract.
Finally, the choice of the prosthesis length will depend on the size of thestenosis, in a directly proportional way, and also of the forecast that exists of theureter to be treated. In patients with retroperitoneal fibrosis, as it is a diseaseprogressive, or in cases of tumorcompressions with a high probability ofevolution, an attempt is made to cover as much ureter length as possible with the stent. This measureis adopted early so that disease progression does not lead tonew areas of stenosis where there is no prosthesis.
Metallic ureteral stents are currently used as an alternative in cases of obstruction or stenosis not subsidiary to other treatments,but few studies have been published on this therapeutic option. The possibility toobtain an optimal result through a minimally invasive procedure, sosafe and effective, has aroused interest in this device, being necessarydemonstrate its suitability in the short and long term.
Although this study was conducted with a small series of patients, there arepublications that support the use of the Memokath 051® prosthesis in the management ofstenosis, generating few adverse effects and being very well tolerated in themost cases. The most important fact to highlight in this work is thatstudied ureteral prostheses maintain patency of the ureter without complicationssevere, and when they occur, they are mild or moderate. In case of beingnecessary, the removal of the stent is a minimally invasive procedure and does not hinder or preventthe use of other materials or alternative urinary diversion techniques.
The main disadvantage that has been observed has been the migration of the device.Resolution of this incident is not difficult, but little is known about the causesresponsible, as well as the circumstances that influence anchorage and stabilityof the prosthesis in the ureter. One of the factors that can contribute to this complicationis the initial overestimation of the caliber of the stenosis, being necessary to consider amore detailed observation of intraoperative pyelography in determining thelocation and length of stenosis for best results.
Another aspect to consider is the cost of the prosthesis. The initial outlay canbe seen as an investment for the future, since these semi-permanent prostheses do notneed continuous replacement as happened with double J catheters, option moreused in the management of ureteral obstruction so far. Although these the latter are cheaper, the need for replacement every 6-12 months makesultimately lead to higher costs.
As already mentioned, the limitation of this study is centeredmainly in the low sample number and the highly variable duration of follow-upbetween some patients and others. This situation does not prevent us from talking about the prosthesis