Presented by: Christopher Carlisi MD
University of Rochester

Introduction

Stone-free status (SF) is considered important to achieve in percutaneous nephrolithotomy (PCNL), as it may affect risk for unplanned stone procedures. PCNL literature has traditionally defined SF to be <2 mm on post-op CT scan. However, we know from URS studies that the reoperation rate can be as high as 17% within 1 year. We analyzed whether being truly SF with a post-op stone burden of 0 mm confers a lower risk of unplanned stone procedure following PCNL.

Materials

We performed a retrospective review of adults undergoing PCNL by a single surgeon between 10/11/2018 and 7/7/2022. Patients underwent PCNL in the prone split-leg position with endoscopic-guided access, using a 24 Fr access sheath. A post-op day 1 CT (POD1 CT) was routinely performed. Exclusion criteria included no POD1 CT, planned secondary procedure intraoperatively or after POD1 CT, known residual stones with no plans to treat, and patients undergoing PCNL with a pre-op CT scan over 1 year old. Stone burden was defined as the sum of the longest dimensions of all stones or fragments. Patients were classified as SF if there were no residual fragments identified. Univariate and multivariate logistic regression was performed.

Results

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We identified 209 subjects undergoing PCNL. 130 of them were included (51.5% female, mean BMI 31.2, mean age 59.8). 45 patients were excluded due to no POD1 CT, 22 due to planned secondary procedure, and 12 for other reasons. The median preop stone burden was 34.45 mm (IQR 23.8-52.65). 38 patients (29.2%) were SF. 50 patients (38.5%) would be considered SF by the 2 mm cutoff. The median post-op stone burden was 3.5 mm (IQR 0-7.7), and median size of largest residual stone fragment was 2.3 mm (IQR 0-4.1). At a median follow up period of 23 months (IQR 14-31), there were 3 (7.9%) and 13 (14.1%) patients who underwent unplanned secondary procedures in the SF and residual stone groups, respectively. However, this was not statistically significant (OR=1.48, p=0.66). Median length of time to secondary procedure was 15 months (IQR 12-18.25).

Conclusion

There is a very low rate of unplanned secondary procedures following PCNL at a median follow up time of 23 months, suggesting that small residual stone burden does not negatively impact the patient in this time frame. Being completely SF may be important with longer follow up, but more data is needed to confirm this.

Funding

None

Co-Authors

Karen Doersch, MD, PhD
University of Rochester

Galen Cheng, MD
University of Rochester

Scott Quarrier, MD, MPH
University of Rochester

Rajat Jain, MD
University of Rochester