Primary Bladder Neck Obstruction

Primary bladder neck obstruction is failure of the bladder neck to open adequately during voiding without prostatic enlargement, stricture or neurological disease, producing high detrusor pressure with low flow. It is also called bladder neck dysfunction, or Marion disease in older literature.

It affects mainly men aged 20 to 50 and is an uncommon but important cause of obstructive symptoms in younger men with a small prostate. It also occurs in women, less often.

Pathophysiology. Proposed mechanisms are sympathetic overactivity at the alpha-adrenergic-rich bladder neck, failure of smooth muscle relaxation, bladder neck hypertrophy or fibrosis, and a congenital abnormality of muscle or collagen.

Chronic obstruction leads to detrusor hypertrophy, trabeculation, diverticula and, in late cases, decompensation.

Hesitancy, weak and intermittent stream, straining, incomplete emptying, frequency, urgency, nocturia, recurrent urinary tract infection, and suprapubic or perineal discomfort. Reduced ejaculate volume, painful ejaculation and difficulty with fertility may be present. Examination is normal, with a normal sized prostate and no neurological signs.

• Uroflowmetry: peak flow under 15 mL/s with a voided volume over 150 mL, often with a prolonged or flattened curve.
• Post-void residual by bladder scan.
• Prostate ultrasound: normal or small volume. Bladder wall thickening and trabeculation may be present.
• Cystoscopy: elevated or high bladder neck, trabeculation, with no stricture, valve or prostatic obstruction.
• Video urodynamics are the definitive test. They show high detrusor pressure at low flow with a poorly opening bladder neck while the distal sphincter relaxes and the urethra is normal.
• Urine culture, creatinine and upper tract ultrasound. Spinal imaging if neurological features are present.

Differential diagnosis.

• Urethral stricture
• Adult posterior urethral valves
• Benign prostatic enlargement
• Chronic prostatitis or pelvic pain syndrome
• Detrusor sphincter dyssynergia
• Dysfunctional voiding from external sphincter overactivity
• Detrusor underactivity
• Bladder stone
• Neurogenic bladder
• Drug induced retention (alpha agonists, anticholinergics)
• Psychogenic retention

• First line is an alpha blocker. Options: tamsulosin 400 micrograms orally once daily after the same meal each day, or alfuzosin prolonged release 10 mg orally once daily after a meal. Assess response at 4 to 6 weeks, and continue if symptoms and flow improve. Relapse on stopping is common, so long term use is often needed.
• Alfuzosin is contraindicated in moderate to severe liver impairment and with strong CYP3A4 inhibitors such as ketoconazole and ritonavir, and it can prolong the QT interval. Both drugs cause orthostatic hypotension and reduced or retrograde ejaculation. Warn patients about intraoperative floppy iris syndrome, and tell the ophthalmologist before any cataract surgery.
• Behavioural measures: relaxed posture and unhurried voiding, double voiding, avoidance of sympathomimetic decongestants.
• Transurethral incision of the bladder neck for failed or intolerant medical therapy. Incision is made at the 5 and 7 o'clock positions, or at 6 o'clock, down to perivesical fat, with or without resection of fibrous tissue. Retrograde ejaculation is common after it, so offer sperm storage to men who plan children. Catheter drainage is usually needed for 1 to 3 days.
• Botulinum toxin injection into the bladder neck is used off label in selected patients, with limited evidence.

Special groups. In women, alpha blockers are off label and used when video urodynamics confirm the diagnosis. Men desiring fertility should have a semen analysis and counselling before any surgery.

Monitoring. Symptom score, peak flow and residual at 4 to 6 weeks after starting a drug and at 3 months after surgery. Repeat upper tract ultrasound if trabeculation is marked or residual is high.

Referral and escalation. Refer to urology with video urodynamic capability. Urgent referral for retention, hydronephrosis or renal impairment.