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.