If you use watchful waiting, the most serious problem that you need to be wary of is the complete blockage of urinary flow—called acute urinary retention. (This complication also can arise if you undergo treatment.) Contact your doctor at the first hint of an increase in the severity of symptoms, including:

• increased slowing of the urine stream (more dribbling)
• more frequent urination at night
• more difficulty starting or stopping urination
• painful or burning urination
• painful ejaculation
• aching pain in the penis, scrotum, testicles, anus, lower abdomen, or lower back
• blood in the urine

Acute urinary retention is a very disturbing and painful condition that can have dangerous consequences if not treated rapidly. If the obstruction is left untreated, there is a chance that bladder dysfunction, bladder stones, or kidney damage could result. And, the condition is terribly uncomfortable.

Inserting a tube, called a catheter, through the penis into the bladder, easily treats the condition, but the procedure requires immediate access to medical care. So, if you live or work far from a medical facility, you may not want to use watchful waiting because of the danger of developing this complication.

Although the chance of developing acute urinary retention is very low, it increases with age, regardless of how severe the patient’s symptoms are. Men under the age of 50 with mild symptoms of BPH have about a 0.26% (1 in 400) chance per year of developing acute urinary retention, while the risk for men in their 70s who have mild symptoms increases to only 0.93% per year (still less than 1 in 100). The chance of developing the condition is still very low for men under the age of 50 with moderate-to-severe symptoms (0.3% per year, or 1 in 333); but for men between the ages of 70 to 79 with similar symptoms, the chance increases to 3.47% per year (1 in 29).

The risk for men with low peak urinary flow rates (<12 ml/sec)—an indication that an obstruction is present—is 3.9 times greater than men with normal peak flow rates. And, having an enlarged prostate gland (>40 ml) increases the risk of urinary retention threefold over men with normal-sized prostates.

Treatment of Acute Urinary Retention

Having surgery reduces the chance of acute urinary retention. One study found that 2.9% of men who had moderate symptoms and no treatment had an episode of urinary retention after three years, whereas only 0.4% of men with moderate symptoms but who had surgery developed this condition.

Finasteride (Proscar®) also has been shown to reduce the risk of acute urinary retention—a benefit that may be caused by the ability of the drug to shrink the size of the prostate. One study showed that the rate of acute urinary retention after two years was 1% for patients taking finasteride, while the rate was 2.5% in patients who took a placebo. A second study showed that the rate of acute urinary retention after four years was 3% for patients taking finasteride, versus 7% for patients on placebo.