Weak or interrupted urinary stream

Specialty: Nephrology and urology.

• decreased urinary stream
• interrupted jet
• intermittent urination
• fine jet

Why it occurs

• Benign prostatic hyperplasia (adenomatous enlargement of the prostate mechanically compresses the prostatic urethra and increases resistance to outflow)
• Urethral stricture (fibrous narrowing of the lumen of the urethra secondary to previous infections, surgeries or trauma)
• Detrusor hypocontractility (weakness of the bladder muscles due to denervation or cellular aging, preventing sustained contraction)
• Detrusor-sphincter dyssynergia (lack of neurological coordination where the external urethral sphincter contracts synchronously with the contraction of the detrusor, common in multiple sclerosis or spinal cord injuries)
• Stenosis of the external urethral meatus (scarring or congenital narrowing of the meatus that mechanically restricts urine output)

Initial workup

Simple urinary flowmetry (to observe the maximum flow - Qmax - and the jet pattern, where a Qmax <10 ml/s is highly indicative of detrusor obstruction or weakness); pre- and post-void vesicoprostatic ultrasound to determine post-void residual and estimate prostate volume; diagnostic urethrocystoscopy or retrograde urethrography if urethral stricture is suspected.

Standard management

• Tamsulosin — 0.4 mg daily orally at night; blocks alpha-1a adrenergic receptors causing relaxation of smooth muscle in the prostate and bladder neck, improving urinary flow
• Dutasteride — 0.5 mg daily orally, 5-alpha reductase inhibitor that progressively reduces the size of the prostate by reducing the synthesis of dihydrotestosterone; requires 3 to 6 months for significant clinical effect
• Bethanechol (10-25 mg every 8 hours orally, cholinergic agonist that stimulates detrusor contraction, to be used with caution and only if mechanical obstruction of the urinary tract has been ruled out).