Abstract
As the author pointed out, the definitions of encrustation and incrustation were not strictly objective. To assess the details of the encrustation, an objective method for measuring the quantity is needed. From the clinical point of view, however, our determination of encrustation and incrustation were similar to practices used in the clinical setting. In fact, our determination was similar to that used by most urologists. Although our definition was not strictly objective, this definition is able to be used in the clinical setting and at no cost. Therefore, the investigation can become widespread and also might result in a larger number of investigations.
The ureteral stent encrustation, incrustation, and resistance to removal were influenced by multiple factors, including the indwelling time, pregnancy, chemotherapy, infection, size, and composition of the ureteral stent, etc. Ideally, an investigation should be performed in persons with exactly the same background. In our present study, almost all of the patients had stone disease, so we believe that our patients' backgrounds were suitable to represent standard stone patients.
As the author noted, the indwelling ureteral stent times were long compared with those of the patients who received ureteral stents in our hospital. Our institute is the third referral stone disease center, and we treat about 300 patients by shockwave lithotripsy (SWL), 300 by ureteroscopy, and 100 by percutaneous nephrolithotomy per year. In addition, patients whose disease was resistant to SWL and sometimes have ureteral stents with a long indwelling time come to our institute for treatment. Because of the wide range of indwelling times, we were able to confirm the relationship between the encrustation and stent time.
Of course, further studies are needed to determine the detailed risk factors underlying ureteral stent encrustation. We believe that this article, however, is a milestone investigation for ureteral stent encrustation. At our institute, we are now performing a randomized study on the differentiated type of ureteral stents and ureteral stent encrustation.