Discussion

In this study, we investigated the effects of an obturator nerve blockade on oncological outcomes in patients who underwent TUR-BT. The results revealed that ultrasound-guided obturator nerve blockade combined with spinal anaesthesia was associated with lower rates of tumour recurrence, better rates of RFS, tumour size, adequate muscle tissue and complete resection. Ultrasound-guided obturator nerve blockade combined with spinal anaesthesia had a positive correlation with tumour size, adequate muscle tissue sampling and complete resection rates and a negative correlation with tumour recurrence and persistent obturator reflex.
TUR-BT is the gold standard method for both the initial diagnosis and treatment of patients with NMIBC. The frequency of severe adductor muscle contractions during the transurethral resection of laterally located bladder tumours has been stated to be approximately 20% (13). Major complications such as bladder perforation and excessive haemorrhage, incomplete resection of tumour and inadequate sampling of muscle tissue in the surgical specimens may occur during resection due to adductor muscle contractions via stimulation of the obturator nerve (14). In order to prevent this undesirable adductor reflex, obturator nerve blockade with ultrasound guidance has been recommended in several studies (6, 15, 16). First, Labat described the obturator nerve blockade with nerve stimulator in 1922 (17). Afterwards, Wassef described the inter-adductor approach (18), Khorammi described the transvesical approach using a nerve stimulator (2), Choquet studied the inguinal approach to block the obturator nerve (19), and several studies compared sonographic demonstrations of obturator nerve-to-nerve stimulation methods (20). In a recent study, Smith reported a combined ultrasound and nerve stimulator approach (21). Despite all of these techniques effectively blocking the obturator nerve, undesirable adductor muscle spasms may still occur during TUR-BT even when an obturator nerve block is performed correctly due to variations in the obturator nerve’s ramifications (22). The efficacy rate of obturator nerve blockade is between 84% and 96%, according to several studies (23, 24). In our study, we performed a combination of ultrasound guidance and nerve stimulator to block the obturator nerve, and our efficacy rate was 92.1%, meaning it was as effective as the rates reported in other studies.
Although an obturator nerve blockade is an intervention that reassures the surgeon during surgery and reduces the rate of peroperative complications, its contribution to oncological outcomes is not yet clear. Erbay showed that patients with lateral wall localized NMIBC who underwent spinal anaesthesia combined with obturator nerve blockade had longer RFS than patients who received only spinal anaesthesia (25). Additionally, rates of complete resection and the presence of muscle tissue in the surgical specimen were higher in patients who received an obturator nerve blockade combined with spinal anaesthesia (25). Tekgul reported that patients with lateral wall localized bladder tumour had a prolonged time to recurrence than patients without an obturator nerve blockade. They reported that bladder perforation was reported in two patients without obturator nerve block, whereas none of the patients who did not undergo obturator nerve block developed bladder perforation. Authors also reported that they did not observe tumor progression during the study (16). We observed a significantly increased RFS in patients who received an obturator nerve blockade, but we did not find any significant difference in prolonged time to recurrence. Similar to Tekgül’s study, while we observed bladder perforation in three patients without obturator nerve block, we did not observe perforation in any of the patients who underwent obturator nerve block. Authors also did not observe tumor progression in their study in three years period. In our study, although we observed tumor progression in 8 (14.5%) patients in group 1 and 2 (3.9%) patients in groups 2, that result was insignificant statistically.
The presence of detrusor muscle tissue in the specimen provides accurate pathologic staging that allows the determination of an adequate follow-up protocol and potential adjuvant treatment according to tumour grade and invasiveness. Additionally, a complete resection of all tumour tissues significantly reduces the risk of NMIBC recurrence and progression. Understaging of NMIBCs at first resection due to failure of the presence of detrusor muscle in the resected specimen is reported in up to 49% of patients, compared with 14% for patients with adequate muscle tissue sampling (26, 27). In our study, we found lower inadequate muscle tissue sampling and higher detrusor muscle complete resection rates in the obturator nerve blockade group.
After an incomplete resection, the recurrence rate is 15%–61% in Ta and T1 tumours in the first year (12). The presence of residual tumour tissue after a TUR-BT procedure increases the recurrence rates and decreases the RFS. One study investigating the presence of residual tumour in the marginal resection after a complete TUR-BT of Ta/T1 transitional urinary bladder cancer reported that 26% of patients had residual tumour tissue after a complete resection of Ta/T1 bladder tumours (28). This possibility particularly increases in undesirable conditions such as obturator reflex during the resection of tumours located in the lateral wall of the bladder, and our results were similar. In our study, RFS was longer in patients who underwent spinal anaesthesia combined with obturator nerve blockade, and no patients had tumour progression. Moreover, we observed that patients who received an obturator nerve blockade had a higher pathological T stage according to TNM classification and decreased recurrence rates as compared with patients who did not receive an obturator nerve blockade.
Another challenging complication due to adductor spasm from stimulation of the obturator nerve during resection is bladder perforation. Several studies have reported bladder perforation due to obturator reflex in ranges between 0.9% and 5% (29, 30). Extravesical dissemination of the tumour may occur due to bladder perforation (31). In our study, only three patients (2.8%) had extraperitoneal bladder perforation, and they were treated with only a urinary catheter. All these three patients underwent TUR-BT with only spinal anaesthesia. Open laparotomy was not required in any of the patients with bladder perforation, and no pelvic mass was observed at follow-ups due to extravesical tumour dissemination. Although perioperative complication rates were not statistically significant, consider that difference between groups in terms of perioperative complication rates were clinically significant.
This study has some limitations. First, due to the retrospective design of the study, randomization could not be included. Second, the study population was small, and we may not have reached statistical significance in terms of some variables such as time to recurrence, tumor progression, and perioperative complication rates due to population size.