Detrusor activity is impaired during thoracic epidural analgesia after open renal surgery

There are no data on lower urinary tract function during postoperative thoracic epidural analgesia (TEA). Because selected segmental blockade can be achieved with epidural analgesia, we hypothesized that lower urinary tract function remains unchanged during TEA within segments T4-T11 after open renal surgery.

In a prospective, open, observational, follow-up study, 13 male patients with no preexisting lower urinary tract symptoms (International Prostate Symptom Score < or =7) and postvoid residual less than 100 ml underwent urodynamic investigations the day before open renal surgery (lumbotomy) and 2-3 days postoperatively during TEA. Primary outcome was the difference in postvoid residual before versus after surgery during TEA.

The median postvoid residual increased from 25 ml before surgery (range, 0-95) to 420 ml (15-1020) 2-3 days postoperatively (P = 0.002). Maximum detrusor pressure, detrusor pressure at maximum flow rate, and maximum flow rate were significantly reduced during TEA (37 [28-84] to 27 cm H2O [13-51], P = 0.004; 31 [27-52] to 19 cm H2O [0-33], P = 0.003; and 14 [4-35] to 4 ml/s [0-13], P = 0.001), respectively. Bladder capacity and sensation were not changed during TEA. All patients had a postvoid residual determined by ultrasound of less than 100 ml 1 day after removal of the epidural catheter.

In contrast to our initial hypothesis, detrusor activity was significantly impaired during TEA after open renal surgery. This resulted in clinically relevant postvoid residuals.