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

The symptoms of bladder outlet obstruction may vary, but can include:

• Abdominal pain
• Continuous feeling of a full bladder
• Delayed onset of urination (urinary hesitancy)
• Frequent urination
• Inability to urinate (acute urinary retention)
• Pain on urination (dysuria)
• Slow urine flow
• Urinary tract infection
• Urine stream starts and stops (urinary intermittency)

If bladder outlet obstruction is suspected, your health care provider will take a thorough history of your problems. During a physical exam, your provider may find one or more of the following possible causes:

• Abdominal mass
• Cystocele (women)
• Distended bladder
• Enlarged prostate (men)

Tests may include:

• Blood chemistries to reveal kidney damage
• Cystoscopy and retrograde urethrogram (x-ray to look for urethral narrowing)
• Ultrasound to locate the blockage of urine, and find out how well the bladder empties
• Urinalysis to look for blood or infection
• Urine culture to show an infection
• Uroflowmetry to determine how fast the urine flows out
• Urodynamic testing to see how much the urine flow is blocked and how well the bladder contracts

Treatment of bladder outlet obstruction depends on the cause of the problem. For most cases, a Foley catheter (a tube inserted through the urethra into the bladder) will relieve the obstruction temporarily.

Occasionally, a suprapubic catheter (a catheter through the abdomen into the bladder) is needed to drain the bladder.

Long-term treatment of bladder outlet obstruction usually involves surgery. However, medical treatment options are available for many of the diseases that cause BOO. Discuss treatment options with your health care provider.

If diagnosed early, most causes of BOO can be treated with great success. However, if diagnosis is delayed, permanent damage can result.

Complications of BOO can be devastating. Long-term or high-grade bladder outlet obstruction can permanently damage all parts of the urinary system.

Complications of BOO include:

• Bladder and kidney stones
• Kidney failure
• Recurrent urinary tract infections
• Urinary incontinence
• Urinary retention

If you have symptoms of bladder outlet obstruction, call your provider. Early diagnosis is important and can often lead to a simple and effective cure.

The condition may be prevented by identifying and treating the cause of the blockage.