Assessment of Residual Stone Fragments After Retrograde Intrarenal Surgery

Abstract

Objectives: To define the most suitable approach to assess residual stone fragments after retrograde intrarenal surgery (RIRS). Methods: Ninety-two patients (115 renal units) submitted to RIRS for symptomatic kidney stones >5mm and <20mm or <15mm in the lower Calyx diagnosed by noncontrast CT (NCCT) were prospectively studied. Residual fragments were assessed by endoscopic evaluation (END) at the end of the procedure and by NCCT, ultrasonography (US), and kidney, ureter, and bladder radiograph (KUB) on the 90th postoperative day (POD). NCCT was considered the gold standard for the evaluation of residual fragments after RIRS. Results: The 90th POD NCCT resulted in stone-free status in 74.8% (86/115), 0-2mm in 8.7% (10/115), and >2mm residual fragments in 16.5% (19/115) renal units. Stone-free status by END at the end of RIRS was coincident with NCCT in 93.0% of the cases (40/43). There were no cases of residual fragments >2mm on NCCT if END resulted in stone-free status. In all cases where END resulted in residual fragments >2mm, US proved to be correct according to NCCT. Neither US nor KUB was able to identify residual fragments between 0 and 2mm. KUB had only 31.6% (6/19) sensitivity to detect residual fragments >2mm and did not add sensitivity or specificity to US. Conclusions: In the follow-up imaging after RIRS, we suggest that if END resulted in residual fragments <2mm, a 90th POD NCCT should be performed. US may be used if END showed fragments >2mm.