According McNeal’s model of the prostate [7], four different anatomical zones may be distinguished that have anatomo-clinical correlation (Figure 2):
1) The peripheral zone : is the area forming the postero-inferior aspect of the gland and represents 70% of the prostatic volume. It is the zone where the majority (60-70%) of prostate cancers form.
2) The central zone : represents 25% of the prostate volume and contains the ejaculatory ducts. It is the zone which usually gives rise to inflammatory processes (eg prostatitis).
3) The transitional zone : this represents only 5% of the total prostatic volume. This is the zone where benign prostatic hypertrophy occurs and consists of two lateral lobes together with periurethral glands. Approximately 25% of prostatic adenocarcinomas also occur it this zone.
4) The anterior zone : predominantly fibromuscular with no glandular structures.
The prostate weighs approximately 20g by the age of 20 and has the shape of an inverted cone, with the base at the bladder neck and the apex at the urogenital diaphragm [8].The prostatic urethra does not follow a straight line as it runs through the centre of the prostate gland but it is actually bent anteriorly approximately 35 degrees at the verumontanum (where the ejaculatory ducts joins the prostate) [9].