Abstract
Thank you for the Editorial Comment. It should be noted that in the Kawahara et al. article (2015), discolored stents had a statistically significant longer indwell time (p = 0.01) than the nondiscolored stents. This does not allow for a direct comparison between the two groups, as the discolored group is biased by a longer indwell time that is known to increase infection rate and discoloration. Furthermore, it is conceivable that the biomaterial we studied may have decreased infectivity compared with the various materials used in the Kawahara study. With regard to the question of whether we can prove if subsequent discoloration has any effect in clinical practice, our study was designed to attempt to answer this exact translational scientific question. To give clinical relevance, the majority of the stents used in our study were removed from patients (i.e., clinical samples), and subsequent tests were standardized to determine whether discoloration resulted in increased encrustation and/or bacterial adhesion rates as suggested by others in the literature. The finding that neither encrustation nor bacterial adhesion/colonization was increased by the discoloration of stents removed from patients has definite clinical implications: stent discoloration does not increase the rate of two common stent-associated complications. One limitation of the Kawahara article was the lack of scientific investigations to back up the claims that stent discoloration changed stent characteristics in a way that compromise their use, which our current study addressed using stents removed from patients.
Furthermore, the statement that “discoloration itself may not be a predictor of any condition, rather the condition and specific environment might provoke the ureteral stents' discoloration” is consistent with our comment that it is the specific overall urinary environment that leads to discoloration rather than a specific medical condition. This is precisely why we chose not to focus our study on stents removed from stone patients only, but rather patients having a stent inserted for other indications. In addition, the question of whether the presence of discoloration influences indwelling time is answered by the fact that stent discoloration is most often a coincidental finding upon removal of the stent after the planned indwelling time rather than the stent having been removed because of stent-associated complications. Finally, no noticeable depreciation in radiopacity was noted in our series.