This article is part of our Bladder Health After Spinal Cord Injury series, building on our overview of neurogenic bladder after SCI with a closer look at one of the most common and most dangerous bladder complications after suprasacral injury.
What Is Detrusor Sphincter Dyssynergia?
After a , the bladder and the muscle that guards its exit lose their ability to work as a team. The bladder squeezes to push urine out, but the external urethral sphincter clamps shut at the same moment instead of relaxing. Urine gets trapped under rising pressure with nowhere to go. This condition is called detrusor sphincter dyssynergia, or DSD, and it affects 70% to 100% of people with suprasacral SCI, depending on injury level and when urodynamic testing is performed [1][4][6].
The International Continence Society defines DSD as involuntary contraction of the striated urethral sphincter during an involuntary detrusor contraction [2]. In plain terms, two muscles that should take turns are firing at the same time, and the bladder pays the price.
Think of a garden hose with a squeeze nozzle. When you turn on the faucet, the nozzle is supposed to release so water flows through. Now picture the nozzle with a mind of its own, clamping down tight every time water pressure kicks in. The harder the faucet pushes, the harder the nozzle grips. Pressure builds inside the hose with no way out.
The bladder is the faucet. The external urethral sphincter is the nozzle. Before the injury, the brainstem sent a signal down the spinal cord that told the sphincter to open when the bladder squeezed. After a suprasacral SCI, that signal path is cut. The bladder still gets the local reflex to contract, but the sphincter never receives the instruction to let go. Both fire at once, and urine gets trapped under rising pressure [1][5].
DSD is not the same condition as neurogenic detrusor overactivity (NDO), though both frequently appear together after suprasacral spinal cord injury. NDO describes involuntary bladder contractions during filling. DSD refers to what happens during those contractions. The sphincter fights the bladder instead of opening, and the result is a pressurized, obstructed system [1][3]. Of all bladder dysfunction patterns after SCI, DSD carries the greatest risk to kidney health because it generates the highest sustained pressures [4][1].
How the Bladder and Sphincter Lose Coordination
Normal urination depends on a relay system with three stations. Think of it like a chain of command in air traffic control. The tower (brainstem) clears the plane for landing, the ground crew (sacral cord) opens the runway gate, and the pilot (the person) decides when to begin the descent. Every station must send its signal at the right time, or the landing fails.
At the top of this chain sits the pontine micturition center in the brainstem. When the bladder fills to capacity, the pontine center signals the detrusor to contract and the external urethral sphincter to relax at the same moment [5]. The sacral micturition center at S2-S4 directly activates the detrusor and contains Onuf's nucleus, the nerve cluster governing the external sphincter. Higher up, the cerebral cortex adds voluntary control, allowing a person to delay or start urination based on circumstance [5].
Spinal cord injury above the sacral segments severs the line between the tower and the ground crew. The local reflex arc between bladder and sacral nerves survives, so the bladder starts contracting on its own once spinal shock resolves (usually 6 to 12 weeks after injury). Without brainstem coordination, the sphincter never receives the signal to relax during bladder contraction. Instead, it fires its own reflex contraction, creating a closed outlet against a pressurizing bladder [1][5].
Three DSD Patterns on EMG
Electromyography during urodynamic testing reveals three DSD patterns, first described by Blaivas and colleagues [7]. Each one reflects a different version of the same broken coordination.
The pattern a person develops depends on where the spinal cord was damaged and how completely the injury disrupted nerve traffic between the brainstem and sacral cord.
Which Injuries Cause DSD
DSD occurs almost exclusively after suprasacral spinal cord injuries (above the S2 segment). Reported prevalence ranges from 70% to 100% of people with suprasacral SCI, depending on the study population and when urodynamic testing was performed [6][4].
| Injury Level | DSD Prevalence | Notes |
|---|---|---|
| Cervical (C1-C8) | Up to 96% | Highest incidence; autonomic dysreflexia complicates management |
| Thoracic (T1-T12) | 70-90% | AD risk present with injuries at T6 and above |
| Upper Lumbar (L1-L2) | Variable | Mixed patterns possible; conus involvement creates unpredictable presentations |
| Sacral and Below (S2+) | 0% | Reflex arc destroyed; bladder becomes flaccid |
Injuries at or below S2 destroy the sacral reflex arc entirely. The bladder becomes flaccid and cannot generate contractions. Without detrusor activity, DSD cannot develop [3][6].
Because DSD prevalence is so high across cervical and thoracic injuries, the question for most people with suprasacral SCI is not whether they have DSD, but how severe it is and what pressures it generates. Answering that takes testing.
Diagnosing DSD After Spinal Cord Injury
Symptoms alone cannot confirm DSD. A person with SCI may report incomplete emptying, high post-void residual volumes, or frequent urinary tract infections, but these findings overlap with many other bladder conditions. Urodynamic testing with simultaneous electromyography of the external urethral sphincter is the accepted diagnostic method [1][7].
| Finding | What It Shows | Why It Matters |
|---|---|---|
| Sphincter EMG during detrusor contraction | Increased or sustained EMG activity when the bladder contracts | Confirms DSD and rules out coordinated voiding |
| Maximum detrusor pressure | Pressures often reach 60-90+ cm H₂O during DSD episodes | Pressures above 40 cm H₂O threaten kidney health |
| Post-void residual volume | Large volumes remain after voiding attempts | Raises UTI risk and increases overdistension injury |
| Vesicoureteral reflux on fluoroscopy | Urine forced backward toward kidneys during high-pressure events | Direct evidence that the upper urinary tract is at risk |
Video urodynamics combines pressure measurement with fluoroscopic imaging, providing the most complete diagnostic picture. The 2021 AUA/SUFU guidelines recommend urodynamic evaluation for all people with neurogenic lower urinary tract dysfunction, with the goal of catching dangerous patterns before organ damage starts [9].
Ask your urologist about scheduling urodynamic testing if you have a suprasacral SCI. Symptoms do not predict bladder pressures reliably. Dangerously high pressures can exist without warning signs, and kidney damage may already be underway before a person notices anything wrong [8][9].
The numbers that come back from urodynamic testing matter because they predict what is happening upstream, in the ureters and kidneys. When the bladder cannot empty past a locked sphincter, that pressure has to go somewhere.
Why DSD Threatens Kidney Health
The 1981 McGuire study established that sustained detrusor leak point pressures above 40 cm H₂O damage the upper urinary tract. In that study, 81% of patients with pressures above this threshold had ureteral dilation, and 68% had vesicoureteral reflux [8]. DSD routinely produces pressures well above this cutoff, with some patients reaching 80 to 90 cm H₂O during voiding attempts [1].
On its own, 40 cm H₂O is a modest amount of pressure. You generate more force squeezing a stress ball. But the kidneys and ureters are soft tissue, and they were never built to absorb hydraulic force like that over and over. When DSD pushes bladder pressure to 80 or 90 cm H₂O, more than double the safety threshold, the system breaks at its weakest points. Urine forces its way backward into the ureters and toward the kidneys, and the damage starts accumulating [8].
Repeated pressure spikes cause hydronephrosis (kidney swelling from backed-up urine), recurrent pyelonephritis (kidney infections), progressive renal scarring, and chronic kidney disease. A 45-year follow-up study found that 58% of people with SCI developed moderate renal deterioration and 29% developed severe deterioration. Upper urinary tract dilation was a strong independent predictor of kidney decline [10].
The 40 cm H₂O Safety Cutoff
Bladder pressures above 40 cm H₂O mark the threshold for upper tract damage. DSD regularly exceeds this number. Because high pressures can exist without symptoms, urodynamic surveillance and renal imaging should be part of ongoing care for anyone living with DSD after spinal cord injury [8][9].
Kidney damage from DSD develops gradually over months and years. But for people with injuries at T6 and above, a locked sphincter can also trigger a medical emergency within minutes.
The Autonomic Dysreflexia Connection
Autonomic dysreflexia (AD) affects 48% to 90% of people with injuries at T6 and above. Bladder distension is the single most common trigger, responsible for up to 85% of AD episodes [11]. DSD contributes directly to this risk by preventing the bladder from draining. A sphincter that stays closed during bladder contraction traps urine, the bladder fills rapidly, and the resulting stretch signals set off the dangerous blood pressure surge that defines AD.
AD can also occur during urodynamic testing itself. Clinicians performing urodynamics on patients with cervical or high thoracic injuries must monitor blood pressure throughout the procedure and be prepared to stop the study if systolic pressure rises more than 20 mmHg above baseline [11].
Read about autonomic dysreflexia warning signs and emergency response steps →
The urgency behind treating DSD comes from both of these directions. Left unmanaged, it quietly erodes kidney function over years while also threatening sudden AD crises in the short term. Treatment aims to break that cycle.
Treating Detrusor Sphincter Dyssynergia After Spinal Cord Injury
Treatment targets two goals. The first is reducing bladder outlet resistance so the bladder can drain. The second is protecting the upper urinary tract from pressure-related damage. Most people with DSD after SCI use clean intermittent catheterization (CIC) as their main bladder management method, combined with additional interventions based on urodynamic findings [9].
Alpha-Adrenergic Blockers
Medications like tamsulosin, terazosin, and prazosin relax smooth muscle at the bladder neck and proximal urethra. They are often the first medication tried because they carry fewer risks than procedural treatments [1]. But there is an anatomical mismatch that limits how much they can do for DSD.
The bladder outlet has two muscle layers. The inner layer at the bladder neck is smooth muscle, controlled by the autonomic nervous system through alpha-adrenergic receptors. Alpha-blockers work well here. The outer layer, the external urethral sphincter, is striated muscle controlled by the pudendal nerve through a separate neural pathway. Alpha-blockers cannot reach it [1].
Think of it like a door with two deadbolts. Alpha-blockers have the key to the first deadbolt (the bladder neck) but not the second (the external sphincter). Unlocking one reduces some resistance, and some people notice lower post-void residual volumes and fewer AD episodes. But the second deadbolt, the one DSD jams shut, stays locked [1].
This distinction matters because people on SCI forums frequently ask whether alpha-blockers actually treat DSD. The honest answer is that they reduce part of the outlet resistance but do not fix the mismatch between bladder and sphincter that defines the condition. For some people, that partial relief is enough. For others, the sphincter remains the bottleneck, and procedural treatment is needed.
Botulinum Toxin Injection into the External Sphincter
OnabotulinumtoxinA (Botox) injected into the external urethral sphincter temporarily weakens the dyssynergic muscle. A double-blind study by Dykstra and colleagues was among the first to confirm this approach, demonstrating measurable denervation of the sphincter with reduced voiding pressures [12]. Later studies have refined both dosing and injection technique.
Sphincter Botox Outcomes
| Post-void residual reduction | 63% decrease (227 mL to 97 mL) [13] |
| Response rate | 60-88% depending on DSD type [12][13] |
| Duration per injection | 3-9 months |
| Best response by DSD type | Type 1 (65.7% success) vs. Type 2 (14.3%) [13] |
Sphincter Botox is not the same as detrusor Botox, and the confusion between them trips up a lot of people researching their options. Detrusor Botox (200 units injected into the bladder wall) calms an overactive bladder muscle. Sphincter Botox (typically 100 units into the external sphincter) relaxes the gate that DSD keeps locked shut. One treats the squeeze. The other treats the blockade. Patients with both NDO and DSD may benefit from treatment at both sites, but these are separate injections with different targets and different effects [1][13].
External Sphincterotomy
Surgical incision of the external urethral sphincter permanently reduces outlet resistance. This procedure is limited to males who choose reflex voiding into a condom catheter with an external collection system. Sphincterotomy creates permanent incontinence by design and has a 30% to 60% reoperation rate. A prospective randomized trial comparing sphincterotomy to urethral stent placement found that many men continued to experience elevated renal pressures and AD episodes after the procedure [14].
Sphincterotomy cannot be reversed. Discuss the decision thoroughly with your urologist before proceeding. Candidates should understand the need for lifelong condom catheter use and external drainage. Urodynamic testing before and after surgery confirms whether outlet resistance dropped enough to protect the kidneys [1][14].
Choosing Between Sphincter Botox and Sphincterotomy
The two procedures that directly target the external sphincter offer very different tradeoffs. Botox wears off in 3 to 9 months, which means repeat injections for as long as treatment continues. Some people see that as a disadvantage because the commitment never ends. Others see it as a safety net because if the results are poor, the effect fades on its own. Sphincterotomy is permanent, which means no repeat procedures if it works, but no reversal if it does not [12][14].
Sphincterotomy is available only to males because it requires condom catheter collection, and it rules out CIC as a future option. Botox preserves all existing management methods and works for any patient regardless of sex. Response rates for Botox depend heavily on DSD type. Type 1 responds best (65.7% success rate), while Type 2 responds poorly (14.3%) [13]. Sphincterotomy works across DSD types but carries a 30-60% reoperation rate and does not always bring pressures below the 40 cm H₂O threshold [14].
| Factor | Sphincter Botox | Sphincterotomy |
|---|---|---|
| Duration | 3-9 months per injection | Permanent |
| Reversibility | Yes (effect wears off) | No |
| Who can receive it | All patients with DSD after SCI | Males choosing condom catheter drainage |
| Effect on CIC | CIC continues as before | CIC no longer possible |
| Reoperation rate | Repeat injection every 3-9 months | 30-60% require revision surgery |
| Effect on erections | No reported impact | Erectile dysfunction reported in some cases [1][14] |
A Note on Women with DSD After Spinal Cord Injury
Most published research on DSD treatment after SCI has been conducted in male patients, and sphincterotomy is anatomically limited to males. Women with suprasacral SCI develop DSD at rates comparable to men [4], but the treatment literature rarely addresses sex-based differences in outcomes for this population. Botox and alpha-blockers remain available regardless of sex. Women with DSD after SCI should discuss the full range of options with a urologist experienced in neurogenic bladder care, and should not assume that treatment data drawn primarily from male study populations will apply without adjustment.
Long-Term Management and Monitoring
DSD is a lifelong condition for most people with suprasacral SCI. The bladder pattern that develops after spinal shock resolves can shift over years as the bladder wall remodels, compliance decreases, or new complications appear. A management plan that works at two years post-injury may fall short at ten years [10].
| Assessment | Frequency | Purpose |
|---|---|---|
| Renal function (cystatin-C preferred) | Annually | Detects kidney decline early; creatinine is unreliable in SCI |
| Renal ultrasound | Every 1-2 years | Identifies hydronephrosis and structural changes |
| Urodynamic study | When clinically indicated | Reassesses bladder pressures and sphincter coordination |
| Urine cultures | Only with symptoms | Asymptomatic bacteriuria does not need antibiotic treatment |
Serum creatinine readings run falsely low in people with SCI because muscle loss reduces the amount of creatinine the body produces. Cystatin-C gives a more accurate picture of kidney function. Studies show that 22.4% of people with SCI meet criteria for chronic kidney disease when cystatin-C is used, a rate more than three times higher than in the general population [15].
Revisit your management plan any time voiding patterns change, spasticity worsens, autonomic dysreflexia episodes become more frequent, or kidney infections recur. These shifts may signal that bladder compliance has deteriorated or that current treatment is no longer keeping pressures in a safe range [9].
References
The following citations provide the scientific foundation for information presented in this article. Sources include peer-reviewed medical journals, clinical practice guidelines, and authoritative medical institutions.
- Stoffel JT. Detrusor sphincter dyssynergia: a review of physiology, diagnosis, and treatment strategies. Transl Androl Urol. 2016;5(1):127-135. doi:10.3978/j.issn.2223-4683.2016.01.08
- Abrams P, Cardozo L, Fall M, et al. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourol Urodyn. 2002;21(2):167-178. doi:10.1002/nau.10052
- Panicker JN, Fowler CJ, Kessler TM. Lower urinary tract dysfunction in the neurological patient: clinical assessment and management. Lancet Neurol. 2015;14(7):720-732. doi:10.1016/S1474-4422(15)00070-8
- Hamid R, Averbeck MA, Chiang H, et al. Epidemiology and pathophysiology of neurogenic bladder after spinal cord injury. World J Urol. 2018;36(10):1517-1527. doi:10.1007/s00345-018-2301-z
- Fowler CJ, Griffiths D, de Groat WC. The neural control of micturition. Nat Rev Neurosci. 2008;9(6):453-466. doi:10.1038/nrn2401
- Weld KJ, Dmochowski RR. Association of level of injury and bladder behavior in patients with post-traumatic spinal cord injury. Urology. 2000;55(4):490-494. doi:10.1016/s0090-4295(99)00553-1
- Bacsu CD, Chan L, Tse V. Diagnosing detrusor sphincter dyssynergia in the neurological patient. BJU Int. 2012;109 Suppl 3:31-36. doi:10.1111/j.1464-410X.2012.11042.x
- McGuire EJ, Woodside JR, Borden TA, Weiss RM. Prognostic value of urodynamic testing in myelodysplastic patients. J Urol. 1981;126(2):205-209. doi:10.1016/s0022-5347(17)54449-3
- Ginsberg DA, Boone TB, Cameron AP, et al. The AUA/SUFU Guideline on Adult Neurogenic Lower Urinary Tract Dysfunction: Treatment and Follow-up. J Urol. 2021;206(5):1106-1117. doi:10.1097/JU.0000000000002239
- Elmelund M, Oturai PS, Topping-Jensen B, Pedersen SB, Biering-Sørensen F. Forty-five-year follow-up on the renal function after spinal cord injury. Spinal Cord. 2016;54(1):27-32. doi:10.1038/sc.2015.137
- Krassioukov A, Warburton DE, Teasell R, Eng JJ; Spinal Cord Injury Rehabilitation Evidence Research Team. A systematic review of the management of autonomic dysreflexia after spinal cord injury. Arch Phys Med Rehabil. 2009;90(4):682-695. doi:10.1016/j.apmr.2008.10.017
- Dykstra DD, Sidi AA, Scott AB, Pagel JM, Goldish GD. Effects of botulinum A toxin on detrusor-sphincter dyssynergia in spinal cord injury patients. J Urol. 1988;139(5):919-922. doi:10.1016/s0022-5347(17)42668-7
- Kuo HC. Therapeutic outcome and quality of life between urethral and detrusor botulinum toxin treatment for patients with spinal cord lesions and detrusor sphincter dyssynergia. Int J Clin Pract. 2013;67(10):1044-1049. doi:10.1111/ijcp.12174
- Chancellor MB, Bennett C, Simoneau AR, et al. Sphincteric stent versus external sphincterotomy in spinal cord injured men: prospective randomized multicenter trial. J Urol. 1999;161(6):1893-1898. doi:10.1016/s0022-5347(05)68830-2
- Patel DP, Herrick JS, Stoffel JT, et al. Chronic kidney disease progression in individuals with spinal cord injury or disease. Spinal Cord. 2021;59:726-733. doi:10.1038/s41393-021-00616-6
How to Cite This Article
North American Spinal Cord Injury Consortium (NASCIC). Detrusor Sphincter Dyssynergia After Spinal Cord Injury: Causes, Diagnosis, and Treatment. NASCIC Knowledge Base. Published February 2025. Available at: https://nascic.org/detrusor-sphincter-dyssynergia/
Clinical Disclaimer: This article is intended for educational purposes. Individual bladder management should be developed with your healthcare team based on urodynamic findings, injury characteristics, and personal factors. This content does not replace professional medical advice.
