The prostate gland, which is set beneath the bladder and partly encloses the urethra in men and boys, can become enlarged in various ways. The commonest is a benign tumour (adenoma). The tumour grows slowly, and replaces normal prostate tissue. Because the urethra runs through the prostate the first noticeable symptoms occur when urinating. The urethra is constricted by the tumour, making urination more difficult; there is no force behind the stream, and urine often dribbles out. The patient can thus pass only a little urine at a time, and often has to get up in the night for the purpose. Because the condition develops slowly, many men do not consult a doctor. The disorder is said to be an old man’s disease, but it can have serious consequences in the long run. The bladder can no longer be fully emptied, which can cause infection of the urethra and even damage to the kidneys.