Supplementary Material for: Optimal Timing of Removal of Epidural and Urethral Catheters to Avoid Postoperative Urinary Retention Undergoing Abdominal Surgery

Background/Aims: Postoperative urinary retention (POUR) is one of the most frequent complications of epidural anesthesia. This study aims to clarify risk factors of POUR and to estimate the appropriate timing of urethral catheter removal. Methods: Between September and December 2014, a retrospective cohort study was conducted on 120 patients who underwent epidural anesthesia and major abdominal surgery. To observe trends in incidence of POUR, we analyzed the order and interval of removal of epidural and urethral catheters using Cochran-Armitage trend test. Results: In this study, 40 patients were diagnosed with POUR (33.3%). Median removal of epidural catheters was 4 postoperative days in the POUR group and 3.5 postoperative days in the non-POUR group (p = 0.04). When the urethral catheter was removed before epidural catheter, incidence of POUR was comparatively greater (p < 0.001). There were no statistical differences in surgical fields, operation approach, epidural catheter levels, or epidural opioid use. No patients had urinary tract infections. Conclusion: We demonstrated that removal of urethral catheter before epidural catheter contributed to increasing trends in incidence of POUR. The optimal order and interval of removal of epidural and urethral catheters should be considered to avoid POUR after abdominal surgery.