Predictors of Epidural Depth in Percutaneous Nephrolithotomy and Model Development

Accurate estimation of epidural depth is critical for safe epidural anesthesia during percutaneous nephrolithotomy (PCNL). Although various imaging modalities can predict epidural depth, they increase healthcare burden and are not always feasible in emergency or bedside settings. Identifying simple, easily obtainable clinical parameters-such as sex, age, and body mass index (BMI)-for predicting epidural depth has become a research priority. However, systematic investigations specifically targeting the Chinese population remain scarce. This retrospective study aims to identify independent factors influencing epidural depth in PCNL patients and to develop simple, level-specific predictive models for different puncture sites, thereby providing a practical reference for clinical epidural anesthesia.