Aims: The need for an indwelling transurethral catheter in patients with postoperative thoracic epidural analgesia (TEA) is a matter of controversy. Subjective observations are ambivalent and the literature addressing this issue is scarce. As segmental blockade can be achieved with epidural analgesia, we hypothesized that analgesia within segments T4–T11 has no or minimal influence on lower urinary tract function. Thus, we evaluated the effect of TEA on lower urinary tract function by urodynamic studies. Methods: In 13 women with no preoperative lower urinary tract symptoms undergoing open kidney surgery by lumbotomy under TEA, we prospectively assessed changes in urodynamic parameters the day before and 2–3 days after surgery with the patients under TEA. Results: Before versus during TEA, there was a significant increase in postvoid residual (median, 5 ml vs. 220 ml, P < 0.001) and a significant decrease in maximum detrusor pressure (median, 23 cmH2O vs. 5 cmH2O, P = 0.001), detrusor pressure at maximum flow rate (median, 18 cmH2O vs. 5 cmH2O, P = 0.001), maximum flow rate (median, 12 ml/sec vs. 3 ml/sec, P < 0.001), and voided volume (median, 250 ml vs. 40 ml, P < 0.001). In addition, maximum urethral closure pressure at rest decreased significantly under TEA from median 75 cmH2O to 56 cmH2O (P = 0.002). Bladder sensation, maximum cystometric capacity, compliance, and functional profile length at rest were not influenced by TEA. Conclusions: TEA has a significant effect on bladder emptying with clinically relevant postvoid residual (PVR) necessitating (indwelling or intermittent) catheterization or monitoring of PVR. Neurourol. Urodyn. 30:121–125, 2011. © 2010 Wiley-Liss, Inc.