Why obturator nerve block is given in TURBT surgery

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obturator nerve block TURBT obturator jerk bladder perforation guideline

Quick answer

Obturator nerve block is given during TURBT, especially for tumors on the lateral bladder wall, to prevent the obturator reflex or “obturator jerk.”

During electrocautery resection, current can stimulate the nearby obturator nerve through the bladder wall. This causes sudden, forceful contraction of the thigh adductor muscles, leading to abrupt leg adduction.

That sudden movement can cause:

Bladder wall perforation, often extraperitoneal
Bleeding
Incomplete tumor resection
Injury to adjacent structures and possible tumor cell spillage

A regional obturator nerve block interrupts the motor supply to the adductor muscles, preventing this reflex. It is particularly useful if spinal anesthesia is used without sufficient neuromuscular paralysis.

Find recent guidelines on anesthesia for TURBT

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EAU guidelines 2026 non-muscle-invasive bladder cancer TURBT anaesthesia obturator nerve block

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guideline anaesthesia transurethral resection bladder tumour TURBT obturator nerve block society

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https://uroweb.org/guidelines/urological-trauma/chapter/urog…

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PMID: 42477956

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PMID: 36341572

Recent guidance relevant to anesthesia for TURBT

There is no single major anesthesia-society guideline devoted exclusively to TURBT anesthesia. Current recommendations are mainly found in urology guidance and in TURBT consensus documents.

EAU Guidelines on Urological Trauma, current online guidance
- For a lateral-wall bladder tumor, use either an obturator nerve block (ONB) or adequate neuromuscular relaxation to reduce the obturator jerk and the risk of intraoperative bladder injury/perforation.
- The EAU notes that evidence that bipolar TURBT alone prevents the obturator jerk is conflicting. See the EAU prevention guidance.
EAU Non-muscle-invasive Bladder Cancer Guidelines 2026
- These are the most current EAU TURBT guidelines. They focus chiefly on oncologic and technical quality of TURBT rather than prescribing one anesthetic technique.
- Therefore, anesthesia should be planned around tumor location, especially lateral-wall involvement, comorbidities, and whether obturator-reflex prophylaxis is needed. The 2026 EAU NMIBC guideline update confirms the current edition.
Japanese Society of Urologic Oncology consensus checklist, 2026
- This practice-guideline level consensus explicitly includes documentation of the anesthesia method and obturator-reflex prophylaxis in TURBT planning.
- It supports making anesthesia choice and ONB planning deliberate preoperative checklist items rather than routine afterthoughts. Taoka et al. (2026), International Journal of Urology, PMID: 42477956.

Practical anesthesia interpretation

Spinal anesthesia is commonly appropriate for TURBT, but it does not reliably block the obturator nerve.
For a lateral or inferolateral wall lesion, add an obturator nerve block under regional anesthesia, or choose general anesthesia with sufficient neuromuscular blockade.
General anesthesia may be preferable when regional anesthesia is contraindicated, the procedure is expected to be prolonged/complex, patient cooperation or positioning is difficult, or reliable paralysis is desired.
Preoperatively assess standard anesthetic risks, particularly anticoagulant/antiplatelet use, cardiopulmonary disease, renal function, anemia, infection, and whether intravesical therapy is planned.

Supporting evidence: a 2023 network meta-analysis found that ONB techniques used with spinal anesthesia reduce obturator reflex and bladder-perforation risk, though the optimal approach depends on expertise and patient/tumor factors. Wu et al. (2023), Cancer Medicine, PMID: 36341572.

Bottom line: For routine TURBT, either spinal or general anesthesia may be used. The key guideline-linked decision is that lateral-wall TURBT requires planned obturator-jerk prevention with ONB or adequate muscle relaxation.

Compare obturator nerve block techniques for TURBT

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obturator nerve block TURBT techniques proximal distal ultrasound nerve stimulation systematic review 2023

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PMID: 42286464

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PMID: 38863316

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https://pmc.ncbi.nlm.nih.gov/articles/PMC10028043

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Obturator nerve block techniques for TURBT

ONB is used chiefly for lateral or posterolateral wall tumors to prevent electrocautery-induced adductor contraction, the obturator jerk. It is usually added to spinal anesthesia. It is not primarily an analgesic block for TURBT.

Technique	Target and method	Main strengths	Main limitations
Classic pubic / landmark block	Needle advanced near the pubic tubercle toward the obturator foramen, often using nerve stimulation to elicit adductor twitch	Familiar traditional approach; can block the common nerve before branching	Deeper needle path, proximity to pubic ramus and vessels, more technically demanding; blind technique has lower reliability
Inguinal approach	More lateral/proximal approach near the groin, with landmark, ultrasound, or nerve-stimulator localization	Better success and fewer attempts than classic pubic technique in a meta-analysis	Still relies on accurate deep anatomy; may be less practical than a straightforward medial-thigh approach
Distal interadductor / medial thigh block	At proximal medial thigh, block anterior branch between adductor longus and brevis and posterior branch between adductor brevis and magnus	Common ultrasound-guided approach; superficial, avoids pelvic needle path; each branch can be identified and blocked separately	Requires two interfascial injections and the posterior branch can be difficult to visualize, creating a risk of incomplete block
Proximal ultrasound-guided block	Single injection near the common nerve before division, between pectineus and obturator externus	Can cover both divisions with one injection; ranked best for preventing perforation in one network meta-analysis	More technically difficult, deeper, and potentially greater vascular-puncture risk
Transvesical block	Injection directed toward the nerve from inside the bladder during cystoscopy, with or without a needle electrode/stimulation	Performed by the surgeon during TURBT, potentially avoids a separate external block	Less commonly used; needs specialized instrumentation and surgical experience; limited comparative evidence

Guidance methods

Guidance	Advantages	Limitations
Ultrasound alone	Visualizes adductor fascial planes, local-anesthetic spread, and vessels. Helps reduce blind vascular puncture.	The nerve, especially the posterior branch, may not be seen clearly. Seeing spread does not guarantee motor blockade.
Peripheral nerve stimulation alone	Confirms the functional endpoint: adductor twitch. Useful when the nerve is poorly visualized.	Does not visualize vessels or needle trajectory.
Ultrasound plus nerve stimulation	Combines anatomical safety with functional confirmation. Has the strongest practical rationale when a failed block would be consequential.	Takes slightly longer and requires both equipment and familiarity.
Landmark-only	Fast and equipment-free.	Least reliable and more operator-dependent. A 2024 RCT found absence of adductor contraction in 91.4% with ultrasound versus 76.6% with blind ONB. Yasar et al., 2024

What does the evidence suggest?

ONB plus spinal anesthesia is better than spinal anesthesia alone for lateral-wall TURBT. A systematic review/meta-analysis reported lower obturator reflex and bladder perforation with ONB, though the underlying trials were relatively small. Krishan et al., 2021
In a 2023 network meta-analysis, distal ONB with nerve stimulation ranked best for preventing the obturator reflex, while proximal ultrasound-guided ONB ranked best for preventing bladder perforation. These are indirect comparative rankings, so they should not be interpreted as proof that one technique is universally superior. Wu et al., 2023
For inguinal versus classic pubic blocks, a 2022 meta-analysis of five RCTs found the inguinal technique had higher success, fewer puncture attempts, and shorter procedure time. Chou et al., 2022
A recent randomized study in TURBT found a nonsignificant trend toward more cephalad injectate spread into the obturator canal with ultrasound-guided than nerve-stimulation-guided interadductor block. Uchino et al., 2026

Practical choice

Most practical default: ultrasound-guided distal interadductor block, targeting both anterior and posterior divisions.
If complete motor block is particularly important: add nerve stimulation to confirm adductor response before injection.
If using a single-injection proximal block: it can cover both branches, but should be done by an operator comfortable with the deeper anatomy and vascular risk.
Avoid landmark-only techniques when ultrasound or nerve stimulation expertise is available, particularly for high-risk lateral-wall resection.

At the medial thigh, the anterior branch lies between adductor longus and brevis, and the posterior branch lies between adductor brevis and magnus. This is the anatomic basis for the distal two-injection technique. Morgan and Mikhail's Clinical Anesthesiology, 7e, p. 1919. The obturator artery can lie close to the unbranched nerve, so aspiration and vascular visualization are important. Barash, Cullen, and Stoelting’s Clinical Anesthesia, 9e, p. 3017.

Anatomy of obturator nerve around urinary bladder

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Obturator nerve anatomy in relation to the urinary bladder

The obturator nerve is a somatic nerve from the anterior divisions of L2-L4. Its pelvic course places it close to the inferolateral bladder wall and bladder neck, which is why it is clinically important during TURBT.

Course

Origin
- Arises within the psoas major muscle from L2, L3, and L4 anterior rami.
Pelvic course
- Emerges from the medial border of psoas major.
- Descends on the lateral pelvic wall, over the obturator internus fascia.
- It lies lateral and posterolateral to the bladder, travelling toward the obturator canal.
- At this level, it is close enough to the lateral and inferolateral bladder wall for electrical current from a resectoscope to stimulate it.
Exit from pelvis
- Passes through the obturator canal at the superior part of the obturator foramen, accompanied by the obturator vessels.
- It then enters the medial thigh and usually divides into anterior and posterior branches.
Branches in the thigh
- Anterior branch: passes between adductor longus and adductor brevis.
- Posterior branch: passes between adductor brevis and adductor magnus.

Functional anatomy

The obturator nerve supplies:

Motor: adductor longus, adductor brevis, adductor magnus adductor part, gracilis, and obturator externus. Its key visible action is thigh adduction.
Sensory: variable cutaneous sensation over the medial thigh, plus articular branches to the hip and knee.

Relevance during TURBT

A tumor on the lateral bladder wall may overlie the pelvic course of the nerve. During monopolar or bipolar electrocautery, current can spread through the thin bladder wall to stimulate the obturator nerve.

Sequence:

Electrocautery near lateral bladder wall
→ obturator nerve stimulation
→ powerful adductor contraction
→ sudden leg movement, termed obturator jerk
→ risk of bladder perforation, bleeding, and incomplete resection

Spinal anesthesia blocks pelvic visceral sensation but may not reliably prevent this somatic motor reflex. Thus, for lateral-wall TURBT, an obturator nerve block or general anesthesia with adequate neuromuscular blockade is considered to prevent the jerk.

Campbell-Walsh-Wein Urology, p. 2240, describes the nerve origin from L2-L4, its descent toward the obturator canal, and its importance in lateral TURBT. Morgan and Mikhail's Clinical Anesthesiology, 7e, p. 1316, notes that lateral bladder tumors may lie close to the obturator nerve and cautery can trigger leg adduction.

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