Comparison of Ultrasound-Guided and Nerve Stimulator-Guided Obturator Nerve Block during Transurethral Resection of Bladder Tumour: A Prospective Randomized Single-Blinded Study

Abstract

Background: Transurethral resection of bladder tumour involving the lateral and posterolateral bladder wall may provoke an obturator reflex despite adequate spinal anaesthesia. The resulting adductor contraction can interrupt resection and may contribute to bleeding, bladder perforation, or incomplete tumour clearance. Obturator nerve block is therefore given in addition to spinal anaesthesia to suppress this reflex, but the most practical localisation technique remains clinically relevant in routine operating rooms.

Objective: To compare ultrasound-guided and nerve stimulator-guided obturator nerve block during TURBT under spinal anaesthesia, with emphasis on obturator reflex prevention, ease of approach, intraoperative interruptions, complications, and patient satisfaction.

Methods: This prospective randomized single-blinded comparative study included 60 patients scheduled for elective TURBT under subarachnoid block. Patients were randomized into two equal groups: Group U received obturator nerve block after ultrasound localisation, and Group N received the block after nerve stimulator localisation. Both groups received 20 mL of 0.5% bupivacaine. Ease of approach was classified according to the number of needle passes/redirections, and intraoperative outcomes were recorded after a 20-minute waiting period following the block. Continuous variables were compared using an independent samples t-test, while categorical variables were analysed using chi-square or Fisher’s exact test as appropriate.

Results: Baseline characteristics were comparable between groups. Mean needle passes were significantly fewer in Group U than Group N (1.97 ± 1.96 vs 5.97 ± 4.60; p<0.001). An easy approach was achieved in 26/30 patients in Group U compared with 9/30 in Group N (p<0.001). Adductor reflex occurred in 2/30 patients in Group U and 8/30 in Group N (p=0.038). Resection was hampered in the same proportions. Bleeding and bladder perforation were also less frequent in Group U, with bladder perforation limited to 2/30 patients in Group N. Patient satisfaction was higher with ultrasound guidance (4.30 ± 0.99 vs 3.13 ± 1.38; p<0.001).

Conclusion: Ultrasound-guided obturator nerve block offered better procedural ease and lower obturator reflex-related intraoperative events than nerve stimulator-guided block in patients undergoing TURBT under spinal anaesthesia. The findings support ultrasound localisation as a useful adjunct for improving surgical stability during lateral and posterolateral bladder wall tumour resection.