The symptoms caused by BPH can be obstructive and irritative. Obstructive symptoms result from the mechanical obstruction of the flow of urine caused by the prostate. As a man's bladder contracts to empty, it has to overcome the obstruction caused by the enlarged prostate. Irritative symptoms are often a combination of the mechanical obstruction and the effects of obstruction. Because the prostate is enlarged, the bladder must work harder to empty. In doing so it undergoes a series of changes that result in a "hypersensitive bladder". The hypersensitive bladder then partly causes some of the irritative symptoms discussed below.

Obstructive Symptoms

• Hesitancy/straining - When the urethra is obstructed, it is often difficult to start urinating despite the urge. Men strain or bear down, as if attempting to have a bowel movement, to start their urinary stream.

• Weak stream/intermittency - Flow of urine may be slow or diminished and urination may be characterized by a repeated start-stop pattern that requires additional straining.

Irritative Symptoms

• Frequency - Due to changes in the bladder wall, as well as incomplete emptying of the bladder, needs to urinate frequently.

• Nocturia - Nighttime frequency, this symptom describes the inability to sleep through the night without having to get up to urinate.

• Urgency - The sudden, intense and sometimes uncontrollable urge to urinate that results from having a hypersensitive bladder.