The impact of clinically insignificant residual fragments following endourological management of urolithiasis: a systematic review of complications and re-intervention rates
Alberto Quarà, Letizia Maria Ippolita Jannello, Alejandra Bravo‐Balado, Stefano Moretto, Federico Zorzi, Ugo Gradilone, H. Werth, Mariela Corrales, M.L. Letouche, Luigi Candela, Steeve Doizi, Frédéric Panthier, Cristian Fiori, Olivier Traxer
Abstract
INTRODUCTION: Achieving stone-free status (SFS) is a key goal of endourological treatment, yet definitions of SFS and clinically insignificant residual fragments (CIRF) remain controversial. While CIRF is frequently defined as residual fragments ≤4 mm, there is no consensus on its clinical significance regarding complications and re-intervention needs. We evaluate the risk of complications and the need for re-intervention associated with the presence of CIRF following endourological treatment for urolithiasis. EVIDENCE ACQUISITION: PubMed/Medline, Scopus, Web Of Science, and Embase databases were searched for articles relating to SFS and CIRF definitions and outcomes, in February 2025, using keyword combinations: "stone-free rate," "residual fragments," "clinically insignificant residual fragments," "urinary calculi," "urolithiasis," "complications," and "outcome". Inclusion criteria were all studies with SFS/CIRF definition and complications associated with residual fragments following treatment (shock wave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy). EVIDENCE SYNTHESIS: Fifty-two studies met inclusion criteria. From the pooled analysis the probability of spontaneous expulsion of CIRF≤4 mm was 33% (95% CI: 12-50%; P<0.001), while regrowth occurred in 32% (95% CI: 23-40%; P<0.001). CIRF-related complications were observed in 27% (95% CI: 21-34%; P<0.001), and the re-intervention rate was 21% (95% CI: 16-26%; P<0.001). Within a variable mean follow-up ranging from 3 to 59 months. The risk of bias was moderate overall, with single-arm studies exhibiting the highest bias risk. CONCLUSIONS: Patients with CIRF≤4 mm should be monitored closely and informed about the non-neglectable likelihood of complications and of re-intervention. On the other hand, they have one probability out of three of spontaneous passage. Endourologist and patients should be aware of these outcomes to better plan the management, follow-up, and the "insignificant" nature of residual fragments. Hence, the aim of surgeries should be achieving the complete SFS, especially in high-risk stone former patients.