Benign prostatic hyperplasia (BPH) is a nodular, irregular enlargement of the prostate, a walnut-size gland located just below the bladder in men, which produces about 30 percent of the fluid portion of semen.

Because the prostate surrounds the urethra (the passageway through which urine empties from the bladder), enlargement of the prostate may eventually constrict the urethra and thus interfere with urination. An enlarged prostate may also cause the muscular bladder wall to thicken, as stronger contractions are necessary to push urine through a narrowed urethra. Increased thickness of the wall of the bladder can reduce its ability to store urine and can result in frequent need for urination and sudden strong urges to urinate.
 
BPH is common, and its incidence increases with age: Evidence of BPH is present in over 50 percent of men by age 60.
 
There is no evidence that BPH leads to prostate cancer; however, symptoms of both disorders are similar, and it is possible to have BPH and prostate cancer at the same time. BPH responds well to treatment.