Bladder outlet obstruction (BOO) is a blockage at the base of the bladder that reduces or prevents the flow of urine into the urethra, the tube that carries urine out of the body.

Bladder outlet obstruction can have many different causes, including:

• Benign prostatic hyperplasia (BPH)
• Bladder stones
• Bladder tumors (cancer)
• Pelvic tumors (cervix, prostate, uterus, rectum)
• Urethral stricture (scar tissue)

Less common causes of bladder outlet obstruction include:

• Cystocele
• Foreign objects
• Posterior urethral valves (congenital birth defect)
• Urethral spasms
• Urethral diverticula

Bladder outlet obstruction is most common in aging men. It is often caused by BPH. Bladder stones and bladder cancer are also more commonly seen in men than women. As a man ages, the chance of developing these diseases increases dramatically.

See also:

• Benign prostatic hypertrophy
• Bladder stones
• Obstructive nephropathy
• Reflux nephropathy