LAUSR

The use of a metallic ureteral stent was first reported in 2006 by Borin et al. Metallic ureteral stents can be exchanged less frequently due to the use of metallic materials and the stent’s spiral form [1]. Metallic ureteral stents are currently widely used in daily urological practice and their efficacy and safety have been confirmed [2, 3]. In our institute, a total of 120 metallic ureteral stents have been used. Among these cases, we only encountered one case involving a heavily encrusted metallic ureteral stent. A 82-year-old inserted a metallic ureteral stent for the purpose of protecting the renal function and started prednisolone therapy at a dose of 25 mg/body for retroperitoneal tumor, which was then gradually decreased. We then attempted to remove the metallic ureteral stent under cystoscopic guidance in an outpatient clinic. However, the metallic ureteral stent was heavily encrusted and could not be removed. We then planned to remove the metallic ureteral stent under general anesthesia. Under general anesthesia, in the lithotomy position, we first inserted a guidewire beside the metallic ureteral stent and confirmed that the proximal side of the guidewire was placed in the renal pelvis. We then inserted a cystoscope and grasped the distal end of the metallic stent using forceps and removed it from the external urinary orifice (Fig. 1a). Next, we inserted a 6.5/8Fr rigid ureteroscope to confirm that there was no adhesion and that no encrusted stones remained in the ureter; then an 11/13Fr 28-cm ureteral access sheath (UAS) (Navigator HD, Boston Scientific, Marlborough, MA, USA) was inserted into the ureter. Because of the firm material of the metallic ureteral stent, we used a single-use digital flexible ureteroscope (LithoVue, Boston Scientific, Marlborough, MA, USA) to avoid damaging an expensive digital ureteroscope. Ureteroscopy confirmed the site of encrustation at the distal loop of the metallic stent (Fig. 1b, c). Then Ho:YAG laser lithotripsy with a 200-μm fiber (Slim Line, Boston Scientific, Marlborough, MA, USA) was performed using a Versa Pulse Select 80:100 (Lumenis, San Jose, CA, USA). During lithotripsy, the metallic ureteral stent seemed to be damaged; thus, we were careful to only apply the laser fiber (setting: 0.5 J, 5 Hz) to the site of encrustation to avoid injury when removing the metallic stent (Fig. 1d). In the present case, we used a disposable ureteroscope instead of a digital flexible ureteroscope as we did not wish to risk damaging a digital flexible ureteroscope. The metallic ureteral stent was composed of a metal alloy (MP35N) and had a spiral form, and we considered that it might damage the vinyl cover of a flexible ureteroscope. In this procedure, the metallic ureteral stent was easily damaged by Ho:YAG laser during lithotripsy targeting the surface encrustation. After the removal of metallic ureteral stent, we investigated the durability of the metallic ureteral stent. The metallic ureteral stent was easily cut by Ho:YAG laser at a setting of 2.0 J 5 Hz (Fig. 1e).