Predictors of Persistent Residual Stones After Second Look Percutaneous Nephrolithotomy

Area of Science:

• Urology
• Nephrology
• Endourology

Background:

• Percutaneous nephrolithotomy (PCNL) is a primary treatment for kidney stones.
• Residual fragments (RFs) can persist after PCNL, necessitating further intervention.
• Second look flexible nephroscopy (SLFN) is often employed to address RFs post-PCNL.

Purpose of the Study:

• To determine the incidence of persistent RFs after SLFN for post-PCNL RFs.
• To identify predictors of persistent RFs following SLFN.

Main Methods:

• Retrospective analysis of 201 renal units undergoing SLFN for RFs post-PCNL (1/2016-5/2020).
• Analysis of patient demographics, stone characteristics, and perioperative parameters.
• Multivariable logistic regression (MVA) to identify predictors of persistent fragments on follow-up imaging within 3 months.

Main Results:

• The stone-free rate after SLFN was 60.7%.
• Median largest RF size at SLFN was 5 mm; median cumulative RF stone size was 8 mm.
• MVA identified bilateral preoperative stones and greater RF stone burden at SLFN as independent predictors of post-SLFN fragments.

Conclusions:

• Approximately 60% of patients with RFs after PCNL become stone-free following SLFN.
• Bilateral stones and larger residual stone burden are associated with persistent fragments despite aggressive treatment.
• The clinical significance and risk of adverse events from these inaccessible fragments remain uncertain.