Do elevated intrarenal pressures during mini percutaneous nephrolithotomy increase postoperative pain??

Introduction: High intrarenal pressures (IRP) during mini-PCNL have been postulated to result in increased postoperative pain but no studies have evaluated this to our knowledge. We sought to determine if there is a correlation between IRP and immediate postoperative pain when using different tract sizes.

Methods: Patients were enrolled and assigned for standard (s-PCNL, 24fr), suctioning-mini (sm-PCNL, 16fr) and non-suctioning-mini (nsm-PCNL, 17.5fr) PCNLs. IRP was measured continuously with a novel technique of real-time monitoring using a 0.014 single-use pressure-sensing COMET™ guidewire. Postoperative pain was documented at the PACU using the VAS pain score. Correlation tests were used to evaluate the association between maximal IRP or tract size and postoperative pain.

Results: The study cohort consisted of 30 patients with 10 patients in each group. The median age was 59 and the median stone volume was 438 mm³. None of the patients were pre-stented. Baseline characteristics were comparable across the groups. The median average IRP of the entire cohort was 7 mmHg (IQR 5-11), and the median maximal pressure was 50 mmHg (IQR 30-66). There were no IRP differences between the groups (p = 0.67 for average; p = 0.35 for maximal). Average and maximal VAS pain scores were not different between the tract size groups (p = 0.09 and p = 0.17, respectively), and no significant association was found between maximal IRP and pain scores.

Conclusion: The IRP range during PCNL is relatively low, regardless of the tract size. There was no association between the level of maximal IRP and postoperative pain. Our findings provide new in-vivo evidence challenging the commonly cited 30 mmHg IRP threshold and support its reevaluation, given the lack of strong clinical validation.