PD50-10: Evaluating the encrustation features due to the short-term ureteral stent placement using micro-computed tomography: The results from a prospective study

Shinji Fukui*, Takashi Yoshida, Kuniko Takemoto, Hidefumi Kinoshita, Hirakata, Japan

Introduction: To evaluate the short-term encrustation formation and encrustation volume of the ureteral stent, focusing on the major stone components (i.e., calcium oxalate and calcium phosphate).

Methods: Eighty-four patients requiring ureteral stent placement after retrograde intrarenal surgery (RIRS) were enrolled. After stent removal on postoperative day 14, the encrustation volume on the stent surface was measured by micro-computed tomography. Of the 84 patients, 71 were eligible for this study, excluding seven patients with no encrustation, two patients with uric acid (1 patient) and cystine (1 patient), and four patients with no available data. The encrustation volume was evaluated by micro-CT, and the stone components and the component ratio were determined using infrared spectroscopy.

Results: All included patients had encrustation in the inner lumen of the stent. Compared to this, encrustation on the outer surface was observed only in 3 (4.2%) patients (p < 0.001). Sixty-seven patients (94%) had calcium oxalate as the primary stone component, 42 (62%) of whom had pure calcium oxalate. Four patients (6%) had pure calcium phosphate as the primary stone component, three of whom had mixed stone with calcium phosphate. Cases with calcium oxalate showed a higher prevalence of stone components than those with calcium phosphate (p < 0.001). However, cases with calcium phosphate stone had a significantly greater median inner encrustation volume compared to those with calcium oxalate stone (3.66 mm3 vs. 1.11 mm3; p<0.001). There was no difference observed in the encrustation volume on the outer surface between the two stone components (p=0.86). In multivariate analysis, crystalluria (p=0.013) and primary calcium phosphate component (p < 0.001) were significantly associated with the increased total encrustation volume on the stent.

Conclusions: This study revealed that the encrustation volume on the stent was significantly greater for calcium phosphate compared to calcium oxalate with the short-term indwelling ureteral stent. Thus, early stent removal may be recommended for patients with calcium phosphate stones.

Source of Funding: No source of funding