Abstract
The use of ureteral stent in a human was first reported by Zimskind et al. in far 1967. 1 Its use has been increased dramatically over time, becoming a basic armamentarium in current urologic practice. Nonetheless, there are several aspects of the clinical use of ureteral stents that remain undiscovered.
Discoloration of the ureteral stents is a common phenomenon. Question that arises observing any kind of ureteral stent discoloration is whether it has any negative effect on patients' health and whether additional care should be provided to those patients. The study by Chew et al. addresses important points on indwelling stent discoloration and its correlation to bacterial adhesion and encrustation on the stent surface. 2 The authors conducted a well-designed experimental study examining overall 40 ureteral stents (20 Polaris Ultra and 20 Percuflex Plus; Boston Scientific Corporation, Natick, MA). Stents with various degree of discoloration were collected from patients who were having the stent for >48 hours without specific inclusion/exclusion criteria regarding the underlying disease. The authors performed in vitro stent discoloration of unused stent pieces and observed that color change was related to the presence of bismuth sulfide (black powder) formation. A separate in vitro testing of bacterial adhesion and encrustation was carried out for both indwelling and nonused stents. What the authors were able to show was that discoloration affected neither the encrustation nor the bacterial adhesion on the surface of the stent.
Nonetheless, there are several limitations of the study that dictate the careful interpretation of the presented results. The extrapolation of the results to all ureteral stents may not correlate as only 2 stent types were tested. In fact, this could be one of the reasons for discrepancies between the results of this study and previously reported clinical studies by Kawahara et al. 3,4 Although Kawahara et al. found an increased likelihood of encrustation and positive urine culture in patients with discolored ureteral stents, the specifications of used stents were not provided. 3,4 Moreover, all stents were retrieved from patients with stone diseases, 3,4 whereas Chew et al. examined ureteral stents regardless of patients' diagnosis. 2 Finally, the discoloration itself may not be a predictor of any condition, rather the condition and specific environment might provoke the ureteral stents' discoloration.
The authors concluded that “Stent discoloration is therefore believed to be a cosmetic change in stents containing bismuth subcarbonate as the radiopacifying agent, and is unlikely to have clinical consequences.” 2 Drawn from the conclusion, hypothetical questions arise. How could we prove that the presence of the bismuth subcarbonate and subsequent discoloration does not have any effect in the clinical practice? How often is the phenomenon present on stents? Does the presence of discoloration influence the duration of the indwelling period or stent-related complications in a clinical setting? Does the radiopacity of the stent change with its discoloration and could it have any prognostic value? All these questions require further investigation and this study seems to have succeeded in intriguing the scientific thought.