Schematic model.

Operative animation, External sphincterotomy

External sphincterotomy for detrusor sphincter dyssynergia

Indications

  • Detrusor sphincter dyssynergia in a man with a spinal cord injury, shown on video-urodynamics.
  • High bladder pressures, autonomic dysreflexia, infections or upper tract dilatation from the obstruction.
  • A man who will manage a sheath catheter and cannot, or will not, catheterise.

Alternatives

  • Intermittent catheterisation with botulinum toxin to the detrusor.
  • Botulinum toxin injected into the sphincter, which wears off.
  • A urethral stent across the sphincter.
  • A suprapubic catheter or a urinary diversion.

Risks

  • Bleeding, from the spongiosum or a venous sinus.
  • Infection.
  • Recurrent obstruction and a repeat incision.
  • Erectile dysfunction; incontinence into the sheath is the intended result.

A permanent endoscopic incision of the external urethral sphincter for a man with a spinal cord injury whose sphincter contracts against his bladder. The bladder then empties by reflex at low pressure into a sheath catheter.

Shown is the resectoscope view: the sphincter ring and the verumontanum, then a cut at twelve o’clock from just distal to the verumontanum through the full thickness of the sphincter into the bulbar urethra, and the ring opening.

The lesson is depth: all of the sphincter, and none of the venous plexus above it or the spongiosum beyond it.

Advanced tier FRCS neuro-urology, spinal cord injury, bladder outlet Interactive 3D
Schematic scene preview: External sphincterotomy
Preparing the 3D anatomy…

UrOops3D · UroRef · © Nity G

How to use this module. Play the seven steps, or use Back and Next. The scope view is the resectoscope; the cutaways are seen from the patient’s left. Watch the cut on the roof deepen until the ring parts and opens. The triggers show bleeding, dysreflexia, a recurrence and the nerves behind erectile dysfunction.

Click me next Section 2 of 8 Anatomy The structures this operation works between, and the one it must not cross.

The structures in the scene

External sphincterotomy: how the structures relateThe external sphincter from the resectoscope, and what lies round it. External sphincter round the membranous urethra: the cut starts just distal to it Verumontanum on the floor. External sphincter round the membranous urethra: cut runs on into it, shallow there Bulbar urethra and corpus spongiosum (danger). External sphincter round the membranous urethra: just beyond its full thickness Venous plexus at twelve o’clock (danger). External sphincter round the membranous urethra: why the cut stays at twelve o’clock Cavernous nerves behind and to each side (danger). External sphincter round the membranous urethra: a second level of obstruction to check Bladder neck and ureteric orifices.External sphincterround the membranousurethraVerumontanum on thefloor!Bulbar urethra andcorpus spongiosum!Venous plexus attwelve o’clock!Cavernous nervesbehind and to eachsideBladder neck andureteric orificesthe cut starts justdistal to itcut runs on intoit, shallow therejust beyond itsfull thicknesswhy the cut staysat twelve o’clocka second level ofobstruction tocheckTargetDangerLandmarkContext
The external sphincter from the resectoscope, and what lies round it. Schematic, not to scale; relationships only.
  • The resectoscope looks up the urethra from the bulbar segment toward the bladder: twelve o’clock is the top of the picture and the verumontanum sits on the floor ahead.
  • The sphincter is a muscular ring round the membranous urethra just distal to the verumontanum.
  • The cut runs along the roof from the level of the verumontanum, through the ring, into the bulbar urethra.
  • In the cutaway, seen from the patient’s left, the venous plexus lies above the sphincter, the spongiosum surrounds the urethra distal to it, and the cavernous nerves run behind and to each side of it.
  • ›External urethral sphincter - the striated muscle round the membranous urethra, distal to the verumontanum; in dyssynergia it contracts as the bladder does.
  • ›Verumontanum - on the floor of the prostatic urethra; the incision starts just distal to it.
  • ›Twelve o’clock - the roof of the urethra, opposite the verumontanum: the line of the cut.
  • ›Bulbar urethra - distal to the sphincter; the cut runs on into it and stays shallow there.
  • ›Venous plexus - the veins over the front of the sphincter and the apex of the prostate: the depth limit at twelve o’clock.
  • ›Corpus spongiosum - the erectile tissue round the bulbar urethra; entering it bleeds.
  • ›Cavernous nerves - beside the membranous urethra, behind and to each side of it, on their way to the corpora cavernosa.
  • ›Bladder neck - a second possible level of obstruction; incised as well when it obstructs.
  • ›Ureteric orifices - checked at cystoscopy; reflux into them is one reason the outlet is being opened.
Click me next Section 3 of 8 Steps The operation in order, with the landmark that guards each move.

Operative steps

  1. The patient and the study A man with a spinal cord injury and detrusor sphincter dyssynergia. Video-urodynamics shows a high-pressure contraction with the sphincter firing against it and the posterior urethra ballooning above it. He will manage a sheath catheter and does not want, or cannot do, intermittent catheterisation.
    where it bites: the incision cannot be undone, so the sheath catheter has to be a plan he accepts.
  2. The level of the obstruction Under anaesthesia, with the blood pressure monitored, the resectoscope is passed under vision. The sphincter is seen as a ring closing the lumen distal to the verumontanum. In the bladder the trabeculated wall, both orifices and the bladder neck are checked, because the neck can be a second level of obstruction.
    where it bites: a lesion at or above the sixth thoracic level can bring on autonomic dysreflexia during the cystoscopy.
  3. The line at twelve o’clock The Collings knife is turned to twelve o’clock, the roof of the urethra opposite the verumontanum. The line runs from just distal to the verumontanum, through the sphincter, to the bulbar urethra. Twelve o’clock is where the EAU guideline places the incision with the fewest complications.
    where it bites: a cut proximal to the verumontanum, or moved off twelve o’clock, reaches tissue that this incision is not meant to open.
  4. The incision With cutting current the knife is drawn from the verumontanum toward the meatus, through the ring of the sphincter and on into the bulbar urethra, where the cut stays shallow. The scope returns to the start and the second pass deepens the same line.
    where it bites: in the bulbar urethra the spongiosum lies just beneath the mucosa; the cut there stays shallow.
  5. Through the full thickness The line is deepened until the fibres of the sphincter part and the ring opens at twelve o’clock. The incision goes through the full thickness of the sphincter and no further. Beyond it lie the venous plexus over the sphincter and, distally, the corpus spongiosum.
    where it bites: too shallow leaves the obstruction; too deep enters the venous plexus or the spongiosum and bleeds.
  6. Haemostasis and drainage The cut is inspected with the irrigation slowed, and bleeding points are touched with the roller rather than run along the cut. The verumontanum and the bladder neck are seen intact. With the scope out, pressure on the full bladder gives a free stream through the open sphincter.
    where it bites: heavy coagulation along the cut adds heat close to the nerves to the erectile tissue.
  7. Catheter, sheath and follow-up A catheter is left with its balloon in the bladder and comes out after a day or two. Then the bladder empties by reflex into a sheath catheter and a leg bag. Follow-up is lifelong: video-urodynamics and ultrasound of the upper tracts, because the sphincter can close again.
    where it bites: a residual or a pressure that rises again is a recurrence until proved otherwise.
Click me next Section 4 of 8 Danger zones Where this operation bites, and why it bites there.
Critical relationship

Danger zones

The spatial relationships the animation is built to make automatic. Before you read each one, ask yourself: at this point in the operation, what is about to go wrong, and what is my first move? The save for each sits in the Complications tab.

  • RiskThe external sphincter and the erectile tissue beside it - the cut goes through the whole sphincter and stops; the cavernous nerves lie behind and to each side of the membranous urethra, so the cut stays at twelve o’clock.
  • RiskThe venous plexus at twelve o’clock - just beyond the full thickness of the sphincter; entering it is where bleeding at this depth comes from.
  • RiskThe corpus spongiosum in the bulbar urethra - directly under the mucosa distal to the sphincter; the cut there is shallow. Around an implanted stent the same tissue can be eroded.
  • RiskThe bladder neck and the ureteric orifices - seen at cystoscopy and left intact unless the neck itself obstructs and is incised as a separate decision.
  • RiskAutonomic dysreflexia - in a lesion at or above the sixth thoracic level, a full bladder or the scope can raise the blood pressure sharply; it is watched throughout.
Practise it Take me into the scene Opens the animation at a danger moment and asks you to predict the mechanism and your first move before it reveals.
Click me next Section 5 of 8 Complications The save for each one: the first move, the escalation trigger, the op-note line.

Complications and immediate saves

Trigger each of these live in the Animation tab, then read the save: the first move, the escalation trigger, and the line that goes in the op note.

Bleeding from the spongiosum or a sinus

  • a cut carried too deep in the bulbar urethra opens the spongiosum, and one too deep over the sphincter opens the venous plexus; the field fills with blood.
  • Haemorrhage is one of the recognised risks of the operation.
The save
  1. Stop cutting. Slow the irrigation and find the point; coagulate a point that can be seen, with a touch, not a run along the cut. first move
  2. If it will not settle, pass a catheter, put it on traction so that the balloon presses the outlet, and let the bleeding settle.
  3. Once it has, go back in with the resectoscope to look and to finish haemostasis.
  4. Bleeding that continues on traction, or a falling haemoglobin, means senior help and a return to theatre. escalation trigger
  5. Op note: where the bleeding came from, how deep the cut was there, how it was controlled, and the catheter plan. document

Autonomic dysreflexia during the procedure

  • in a lesion at or above the sixth thoracic level, the full bladder or the scope triggers a surge of blood pressure, often with a slow pulse, headache, sweating and flushing above the lesion.
  • The EAU guideline defines it as a rise in systolic pressure of more than 20 mmHg from baseline.
The save
  1. Stop: take the instrument out of the urethra and empty the bladder, which removes the trigger. first move
  2. Sit him up, or tilt the head of the table up, and loosen anything tight.
  3. The anaesthetist treats a pressure that stays high: deeper anaesthesia, or a short-acting antihypertensive.
  4. A pressure that does not respond, chest pain, or a fit, is a medical emergency: call for help at once. escalation trigger
  5. Op note: the trigger, the highest pressure, what was given, and the plan to prevent it next time. document

Recurrent obstruction

  • the sphincter closes again over a healed cut, or the bladder neck obstructs; the residual, the pressures, the infections or the dysreflexia return.
  • Many men need a repeat incision.
The save
  1. Repeat video-urodynamics to show where the obstruction is and how high the pressure is. first move
  2. A repeat incision on the same twelve o’clock line, through the full thickness again.
  3. If the neck is the level, a bladder neck incision is added.
  4. Upper tract dilatation, or failure after repeat incisions, goes to the neuro-urology team for another bladder management. escalation trigger
  5. Op note: the number of previous incisions, the findings and the level treated. document

Erectile dysfunction

  • a listed risk of the operation.
  • The cavernous nerves run beside the membranous urethra, behind and to each side of it, which is why the cut is placed at twelve o’clock, kept to the sphincter, and coagulated sparingly.
The save
  1. Prevention is the save: the twelve o’clock line, the sphincter only, and points touched, not the cut run with current. first move
  2. Consent names it, with what the man’s erections are like before the operation.
  3. Erectile dysfunction afterwards goes to the andrology or spinal injuries team for the usual treatments. escalation trigger
  4. Op note: the clock position of the cut, its extent, and the coagulation used. document
Click me next Section 6 of 8 Troubleshooting When the case turns: the problem, then the next move.

Intra-operative troubleshooting

When the case turns: the problem, then the next move.

  • ActionThe pressure rises as the scope goes in - that is autonomic dysreflexia until shown otherwise. Stop, empty the bladder and sit him up while the anaesthetist treats the pressure; carry on only once it has settled.
  • ActionThe sphincter cannot be told from the bulbar urethra - find the verumontanum and come back from it: the sphincter is the ring just distal to it.
  • ActionThe ring does not open after two passes - the cut has not crossed the full thickness. Deepen the same line at twelve o’clock rather than starting a new one beside it.
  • ActionThe bladder neck looks tight - it may be a second level of obstruction; the EAU guideline describes secondary narrowing of the neck after sphincterotomy and a bladder neck incision for it.
  • ActionA laser is to be used - Perkash describes a contact laser incision on the same twelve o’clock line from the verumontanum to the bulbous urethra; the line and the depth do not change with the energy.
  • ActionThe man is not sure he can manage a sheath - do not operate. The incision cannot be undone, and intermittent catheterisation with botulinum toxin to the bladder, a stent, or a suprapubic catheter are the alternatives.
Click me next Section 7 of 8 FRCS viva Say it out loud, then mark yourself against the model answer.

FRCS viva questions

The examiner stems this scene prepares you for. Try to answer out loud first, then reveal, and learn the discriminator, the detail that turns a pass into a strong pass.

QA man with a cervical spinal cord injury has recurrent infections and dysreflexia. Video-urodynamics shows detrusor sphincter dyssynergia. What are his options?reveal answer
  • The aim is a bladder that stores and empties at low pressure, to protect the upper tracts.
  • I would first ask how he manages now, what his hand function is, who looks after him and what he wants.
  • Intermittent catheterisation with botulinum toxin to the detrusor is the usual first choice when it is possible, with an indwelling or suprapubic catheter for some.
  • If he cannot catheterise and will use a sheath, I would offer to lower the outlet resistance.
  • The EAU guideline describes external sphincterotomy, a urethral stent and botulinum toxin into the sphincter.
  • Sphincterotomy is irreversible and limited to men who can use a condom catheter, and the toxin wears off.
  • I would name the risks: bleeding, a repeat incision, and erectile dysfunction.
Strong pass

Say all three

  • Choosing by bladder management
  • Hands and wishes first
  • Saying that sphincterotomy commits him to a sheath for good
Examiner note
Choosing by bladder management, hands and wishes first, and saying that sphincterotomy commits him to a sheath for good.
QDescribe how you would do the incision.reveal answer
  • Under anaesthesia, with the blood pressure monitored, I would pass a resectoscope under vision and identify the verumontanum, the sphincter ring and the bladder neck, and inspect the bladder.
  • I would turn a Collings knife to twelve o’clock and make one incision from just distal to the verumontanum through the sphincter into the bulbar urethra, deepening the same line until the fibres part and the ring opens.
  • The guideline says the twelve o’clock cold-knife incision has the fewest complications; Perkash describes the same twelve o’clock line from the verumontanum to the bulbous urethra with a contact laser.
  • I would stay shallow in the bulbar urethra, touch the bleeding points, and leave a catheter for a day or two.
Strong pass

Twelve o’clock, the verumontanum to the bulbar urethra, full thickness of the sphincter and no deeper.

QHow well does it work, and how often does it need repeating?reveal answer
  • It works for most men but it is often repeated.
  • The EAU guideline says it resolves dysreflexia, hydronephrosis and recurrent infection and lowers detrusor pressure and the residual, but must be repeated at regular intervals in many patients.
  • Perkash reported 76 men treated with a contact laser: 69, 92 per cent, voided adequately at a mean of 27 months, and seven needed a repeat within two to five months.
  • In a French series of 51 men, Lepoittevin and colleagues found reflex voiding kept in 80 per cent at a median of 4.6 years, with a second incision in 39 per cent; dysreflexia fell from 26 men to seven.
  • These are retrospective single-centre series.
  • Kim and colleagues found a leak point pressure over 40 cmH2O after the operation went with upper tract damage, so I judge success on the trace, not only on symptoms.
Strong pass

Say both

  • Quoting a repeat rate alongside the success rate
  • Judging success by pressure on urodynamics
Examiner note
Quoting a repeat rate alongside the success rate, and judging success by pressure on urodynamics.
QDuring the cystoscopy his blood pressure climbs and his pulse slows. What is happening and what do you do?reveal answer
  • This is autonomic dysreflexia: an exaggerated sympathetic response to a stimulus below a lesion at or above the sixth thoracic level, here the scope and a full bladder.
  • The EAU guideline defines it as a rise in systolic pressure of more than 20 mmHg from baseline and warns that it can be life-threatening.
  • I would stop, take the instrument out and empty the bladder, sit him up or tilt the table head up, and loosen anything tight.
  • The anaesthetist treats a pressure that stays high.
  • The review by Krassioukov and colleagues supports upright positioning and removing the trigger by consensus, and a short-acting antihypertensive such as nifedipine if the pressure stays up.
  • I would start again only once it has settled, and record the event.
Strong pass

Say all three

  • Removing the trigger first
  • By emptying the bladder
  • Before reaching for a drug
Examiner note
Removing the trigger first, by emptying the bladder, before reaching for a drug.
QHow do you follow him up?reveal answer
  • For life, because the sphincter can close again and the bladder can change.
  • The EAU guideline recommends assessing the upper tracts at regular intervals in high-risk patients, with ultrasound about every six months, and urodynamics as a baseline and repeated at intervals of no more than one to two years.
  • Physical examination and urine tests are yearly.
  • I would ask about dysreflexia, infections and how the sheath stays on, measure the residual, and repeat video-urodynamics if anything changes.
  • A rising pressure or new dilatation means a recurrence until shown otherwise: a repeat incision, a bladder neck incision, or another way of managing the bladder.
Strong pass

Upper tracts on ultrasound and pressures on urodynamics, for life, with a rising pressure treated as recurrence.

Click me next Section 8 of 8 Evidence The guidance each of these answers is built on.

Evidence and guidance

Operative Dictations in Urologic Surgery
Armenakas NA, Fracchia JA, Golan R. Operative Dictations in Urologic Surgery. Wiley, 2019
Searched in full for this operation, 19 October 2026: the book has no chapter on external sphincterotomy, detrusor sphincter dyssynergia or a urethral stent. Its augmentation cystoplasty chapter lists intractable autonomic dysreflexia as an indication for augmentation. The page therefore follows the hub sequence, the EAU guideline and the papers below; every danger line, every first, escalate and document line, and the troubleshooting moves not attributed to a source are general practice.
Open guideline
EAU Guidelines
Neuro-Urology, chapter 3, The Guideline: bladder neck and urethral procedures, autonomic dysreflexia and follow-up, read 19 October 2026
Reducing outlet resistance may be necessary to protect the upper tracts. Sphincterotomy resolves autonomic dysreflexia, hydronephrosis and recurrent infection and lowers detrusor pressure, residual and reflux; it is irreversible and limited to men who can use a condom catheter; the twelve o’clock cold-knife incision has the fewest complications; it must be repeated at regular intervals in many patients; secondary narrowing of the bladder neck may need a combined bladder neck incision. Stents give comparable results but complications and reinterventions limit them; botulinum toxin into the sphincter treats dyssynergia. Dysreflexia: lesions at or above Th 6, a systolic rise of more than 20 mmHg. Follow-up: ultrasound about every six months in high-risk patients, urodynamics within one to two years. Read through a summarising fetch tool, not the raw page.
Open guideline
Spinal Cord
Perkash I. Contact laser sphincterotomy: further experience and longer follow-up. Spinal Cord 1996;34:227-233
Abstract read 19 October 2026. 76 consecutive men with spinal cord injury, 89% with dyssynergia; a twelve o’clock incision from the verumontanum to the bulbous urethra with a contact laser; a catheter for about a day. At a mean of 27 months 69 (92%) had adequate voiding with minimal or no dysreflexia; seven needed repeat laser surgery within two to five months. Source of the line of the cut and of the first figures in the viva.
Open guideline
Progrès en Urologie
Lepoittevin L, Leon G, Perrouin-Verbe B, et al. External sphincterotomy in neurological patients with detrusor sphincter dyssynergia: short and mid-term results. Prog Urol 2021;31:40-46
Abstract read 19 October 2026. Retrospective, single centre: 51 patients with a first sphincterotomy, median follow-up 4.6 years. Reflex voiding kept in 80%; a second sphincterotomy in 39%; dysreflexia fell from 26 patients to 7, infections from 31 to 15, and the residual from 200 to 50 ml. The authors ask for long-term follow-up for recurrent obstruction.
Open guideline
The Journal of Urology
Kim YH, Kattan MW, Boone TB. Bladder leak point pressure: the measure for sphincterotomy success in spinal cord injured patients with external detrusor-sphincter dyssynergia. J Urol 1998;159:493-497
Abstract read 19 October 2026. 55 men after one or more sphincter resections, a mean of 11 years before; a leak point pressure over 40 cmH2O went with more upper tract damage and persisting dyssynergia. Behind judging success on the trace in the third viva answer.
Open guideline
Nature Clinical Practice Urology
Ahmed HU, Shergill IS, Arya M, Shah PJR. Management of detrusor-external sphincter dyssynergia. Nat Clin Pract Urol 2006;3:368-380
Abstract read 19 October 2026. A review: external sphincterotomy carries significant risks, including haemorrhage, erectile dysfunction and the need for repeat procedures, and urethral stents and botulinum toxin have been studied as alternatives. Source of the risks named on the page; the anatomical reason given for erectile dysfunction is general anatomy, not from this review.
Open guideline
Archives of Physical Medicine and Rehabilitation
Krassioukov A, Warburton DE, Teasell R, Eng JJ. A systematic review of the management of autonomic dysreflexia after spinal cord injury. Arch Phys Med Rehabil 2009;90:682-695
Abstract read 19 October 2026. 31 studies. The acute non-drug management (sitting the patient up, loosening tight clothing, removing the trigger) rests on clinical consensus and physiology; antihypertensives for a sustained high pressure rest on trials of prazosin and nifedipine. No doses are given on the page.
Open guideline

Curriculum. Supports learning relevant to the ISCP Urology Curriculum special interest module Female, functional and reconstructive urology. Not a workplace-based assessment and not evidence of competence.

Two minutes

Close the lap: recall it before you leave.

Say it aloud, then reveal. Reading is not remembering.

  1. 01 The relationship Say the critical spatial relationship out loud, then reveal. reveal
    Memory frame

    The resectoscope looks up the urethra from the bulbar segment toward the bladder

    Why?
    The resectoscope looks up the urethra from the bulbar segment toward the bladder: twelve o’clock is the top of the picture and the verumontanum sits on the floor ahead. The sphincter is a muscular ring round the membranous urethra just distal to the verumontanum. The cut runs along the roof from the level of the verumontanum, through the ring, into the bulbar urethra. In the cutaway, seen from the patient’s left, the venous plexus lies above the sphincter, the spongiosum surrounds the urethra distal to it, and the cavernous nerves run behind and to each side of it.
  2. 02 The first move Bleeding from the spongiosum or a sinus. Your first move? reveal
    First move

    Stop cutting.

    More detail
    Slow the irrigation and find the point; coagulate a point that can be seen, with a touch, not a run along the cut.
  3. 03 The escalation trigger Bleeding from the spongiosum or a sinus. What makes you call for help? reveal
    Escalate when

    Bleeding that continues on traction, or a falling haemoglobin, means senior help and a return to theatre.

  4. 04 The discriminator What turns a pass into a strong pass? reveal
    Strong pass

    Say all three

    • Choosing by bladder management
    • Hands and wishes first
    • Saying that sphincterotomy commits him to a sheath for good
    Examiner note
    Choosing by bladder management, hands and wishes first, and saying that sphincterotomy commits him to a sheath for good.
  5. 05 The pitfall Where does this operation bite first? reveal
    Pitfall

    The external sphincter and the erectile tissue beside it

    Why?
    the cut goes through the whole sphincter and stops; the cavernous nerves lie behind and to each side of the membranous urethra, so the cut stays at twelve o’clock.

Revision practice with self-marked answers, not an assessment of clinical competence. Kept in this browser only; it does not sync between devices.