Understanding Causes for Admission in Planned Ambulatory Percutaneous Nephrolithotomy.

Introduction: For treatment of nephrolithiasis, ambulatory percutaneous nephrolithotomy (aPCNL) is growing in popularity for select patients. The aim of this study was to investigate the safety and efficacy of a set of aPCNL selection criteria as well as search for predictors of failed aPCNL resulting in inpatient admission. Materials and Methods: We reviewed all percutaneous nephrolithotomy (PCNL) patients from 2016 to 2020. A total of 175 met selection criteria for aPCNL and were included. Primary outcome was safety and efficacy, and secondary outcome was to identify predictors of inpatient stay. Demographic and perioperative data were analyzed with both descriptive and inferential statistics. Results: In total, between 2016 and 2020, 552 patients underwent PCNL, with 175 of them meeting criteria for aPCNL. One hundred thirty-four of the 175 (76.6%) of these patients were discharged the same day as the surgery and 41 patients were admitted. On univariate analysis, patients who required upper pole access or multiple accesses ( p  = 0.038) American Society of Anesthesiologists >2 ( p  = 0.005), or postoperative nephrostomy (PCN) tube ( p  < 0.001) were more likely to be admitted after surgery. On multivariate analysis, only postoperative PCN was significantly associated with admission ( p  = 0.015). Regarding reasons for unsuccessful aPCNL, 19.5% of admissions were attributed to intraoperative complications, 7% to social causes, 12.2% to postoperative complications, 14.6% to uncontrolled pain, and 34.1% to unexpected intraoperative procedures. Conclusions: aPCNL using selection criteria is safe and effective, with postoperative PCN predicting the possible necessity for conversion to inpatient admission. Furthermore, our study provides a practical algorithm for those opting to provide aPCNL to patients.