William Aiken
The prostate gland is not essential for life but is an accessory organ of reproduction in the man. It is located at the base of the urinary bladder, deep in the pelvis, in front of the rectum and behind the pubic bones.
The urethra, which transports urine and semen in men, on leaving the bladder, passes through the prostate gland which surrounds it. The prostate gland is made up of glands which secrete, glandular (smooth) muscle which contracts, and fibrous tissue which provides a supporting framework for the glands and muscle.
The prostate has a secretary and closing (sphincteric) muscular function. The prostate secretes copiously during sexual arousal and ejaculation and its secretions accounts for up to 30 per cent of seminal fluid. This fluid contains various proteins and sugars and other chemicals which, among other things, are important in reproduction as well as preventing infection.
The muscular contractions of the prostate which occur during ejaculation are important in closing off the urethra's communication with the bladder, thereby preventing semen from flowing upwards into the bladder.
Enlarged prostate
Benign prostatic hyperplasia (BPH) is an extremely common condition affecting the prostate gland as men age, and may result in non-cancerous prostate enlargement which can cause obstruction of the urethra as well as a number of complications, such as recurrent urinary tract infections, bleeding, bladder stones and kidney failure. When BPH results in enlargement of the prostate gland, it can obstruct the urethra by two mechanisms: the sheer encroachment of the increased gland size on the urethral channel and ongoing muscular contraction of the prostate gland squeezing and narrowing the urethra as it passes through the prostate.
Together, these result in increased resistance to the flow of urine from the bladder, causing it to have to push harder to empty itself of urine. The muscle of the urinary bladder thickens like any other muscle in the body when faced with an increased workload (similar to biceps curls producing big biceps) to compensate for the increased resistance caused by the enlarged prostate.
By generating a higher pressure gradient through increased force of contraction, the bladder initially maintains the flow of urine. The bladder muscle may eventually decompensate and fatigue after a variable period of time and become inefficient at emptying itself. At this point the force and continuity of the stream of urine may be adversely affected and urine may be left behind in the bladder after urinating.
Another effect of obstruction by the prostate gland on the bladder is that the muscle of the bladder may become 'irritable'. This results in unwanted bladder contractions occurring frequently at very low volumes, giving the urgent sensation of needing to urinate which cannot be postponed. If a bathroom is not available this may result in uncontrolled loss of urine causing social embarrassment.
The symptoms of an obstructing prostate are therefore an urgent need to urinate that cannot be deferred, going frequently to pass small volumes of urine both day and night, involuntary loss of urine preceded by an urgent desire to urinate, taking a long time to start urinating, a weak flow of urine, interrupted (stop-start) urine flow and a sensation of not completely emptying the bladder once urination is finished.
These symptoms may be punctuated by an episode of acute urinary retention ('stoppage of water') which is the sudden painful inability to pass urine. This may be precipitated by over-the-counter cold medicines, alcohol, holding the urine for too long, cold weather, severe constipation, blood in the urine and inflammation of the prostate (prostatitis).
Dr. William Aiken is the head of urology at the University Hospital of the West Indies
and president of the Jamaica Urological Society; email: yourhealth@gleanerjm.com.
