Detrusor Sphincter Dyssynergia

Detrusor sphincter dyssynergia (DSD) is the loss of normal coordinated relaxation of the urethral sphincter during detrusor contraction. It results from a suprasacral spinal cord lesion that disrupts the pontine micturition centre pathways. It causes functional bladder outlet obstruction and risks upper tract damage.

During voiding the detrusor contracts while the external urethral sphincter (striated) contracts, instead of relaxing. This causes functional obstruction, high voiding pressures (above 40 cm H2O), poor emptying and risk of upper tract damage.

It is found in about 50 to 70 percent of patients with multiple sclerosis and with suprasacral spinal cord injury (traumatic, transverse myelitis, tumours, spina bifida). It also occurs in other neurological diseases.

It does not occur in suprapontine lesions (stroke, Parkinson disease), where sphincter coordination is maintained, nor in lesions below S2.

Types:

• Type 1: sphincter contraction increases as the detrusor contracts and relaxes suddenly, then voiding occurs.
• Type 2: sphincter contractions occur sporadically throughout detrusor contraction.
• Type 3: sustained sphincter contraction through the whole detrusor contraction, causing obstruction.

The consequences include recurrent infection, vesicoureteral reflux, hydronephrosis, bladder trabeculation, diverticula, stones, autonomic dysreflexia and renal failure.

• Difficulty initiating urination, interrupted or weak stream, hesitancy, incomplete emptying, and straining to void.
• Urinary frequency and urgency (from detrusor overactivity), urgency incontinence, and recurrent urinary tract infections.
• Urinary retention and large post-void residual.
• Autonomic dysreflexia in those with lesions above T6.
• Neurological signs: spasticity, hyperreflexia, upgoing plantar responses, impaired sensation, and sexual and bowel dysfunction.
• Epididymitis in men with spinal cord injury.

• Videourodynamics (the gold standard): simultaneous detrusor pressure, sphincter electromyography and fluoroscopy shows a high detrusor pressure (above 40 cm H2O) with a low flow, increased electromyographic sphincter activity during the detrusor contraction, and a closed bladder neck and sphincter area of narrowing on voiding cystourethrogram ("spinning top" urethra); and vesicoureteral reflux.
• Uroflowmetry: interrupted or low flow with residual; post-void residual above 100 mL.
• Renal and bladder ultrasound: hydronephrosis, trabeculated or thick walled bladder, diverticula and stones.
• Blood: creatinine, eGFR; urine culture.
• Neurological assessment and MRI of the spine to identify the lesion level.

The goal is low pressure bladder storage and emptying to prevent renal damage and to restore continence.

• Clean intermittent catheterisation every 4 to 6 hours with hydrophilic catheters (the cornerstone for those with sufficient hand function), with anticholinergics to reduce detrusor pressure.
• Antimuscarinics: oxybutynin 5 mg two to three times daily (extended release 10 to 30 mg once daily), solifenacin 5 to 10 mg daily, tolterodine 4 mg daily, trospium 20 mg twice daily, fesoterodine 4 to 8 mg daily. Mirabegron 50 mg daily is an alternative or add on.
• Alpha blockers (tamsulosin 0.4 to 0.8 mg daily, alfuzosin 10 mg daily, silodosin 8 mg daily) may reduce outlet resistance with modest benefit.
• Baclofen 5 to 20 mg three times daily or diazepam 2 to 5 mg for striated sphincter spasticity (limited efficacy; watch sedation).
• Botulinum toxin injection into the external sphincter (onabotulinumtoxinA 100 units in 4 sites, transperineal or transurethral), effective in about 50 to 70 percent for 3 to 6 months (repeat). Intradetrusor botulinum toxin (200 to 300 units) for detrusor overactivity.
• Surgical options for men with an adequate bladder: external sphincterotomy (endoscopic, laser or electrocautery, cutting at 12 o'clock in the sphincter) with condom catheter drainage. It reduces voiding pressure in about 70 to 80 percent, but has risks (bleeding, erectile dysfunction, stricture, need for repeat in 30 to 50 percent). Alternatively, urethral sphincter stents (the stent is placed in the bulbar urethra).
• Bladder augmentation (clam cystoplasty), continent catheterisable channel (Mitrofanoff), urinary diversion (ileal conduit) or suprapubic catheter for failure or in women with severe disease.
• Treat infections (symptomatic only) and monitor for dysreflexia: sit up, remove triggers, and give nifedipine 10 mg or glyceryl trinitrate 0.4 mg sublingual for severe hypertension.
• Long term surveillance: renal ultrasound and creatinine yearly, urodynamics every 1 to 2 years if high risk, and cystoscopy yearly after 10 years of indwelling catheter use.
• Treat the underlying neurological disease (disease modifying therapy for multiple sclerosis), physiotherapy and rehabilitation.