Although prostatitis is the most common urologic diagnosis in males younger than 50 years and the third most common diagnosis in men older than 50 years (after benign prostatic hyperplasia [BPH] and prostate cancer), acute prostatitis is rare. Acute prostatitis is easier to identify than chronic prostatitis, however, because of its more uniform clinical presentation.

Acute prostatitis presents as an acute urinary tract infection (UTI). It is usually associated with predisposing risk factors, including bladder outlet obstruction secondary to benign prostatic hyperplasia (BPH) or an immunosuppressed state. Approximately 5% of cases of acute bacterial prostatitis (ABP) progress to chronic prostatitis. ^[1]

Pathologic definition of prostatitis

Pathologically, prostatitis is defined as an increased number of inflammatory cells within the prostate gland. The inflammatory process may be infectious or inflammatory in origin. The most common histologic pattern is a lymphocytic infiltrate in the stroma immediately adjacent to the prostatic acini

Prostatitis occurs in distinct forms that have separate causes, clinical features, and outcomes. Four clinical entities have been described: acute bacterial prostatitis, chronic bacterial prostatitis, nonbacterial or abacterial prostatitis, and prostatodynia.

NIH classification and definition of prostatitis

The National Institutes of Health (NIH) classification and definition of the categories of prostatitis are as follows:

• Category I – Acute bacterial prostatitis (ie, acute infection of the prostate)
• Category II – Chronic bacterial prostatitis (ie, recurrent urinary tract infection and/or chronic infection of the prostate)
• Category III – Chronic abacterial prostatitis/chronic pelvic pain syndrome (ie, discomfort or pain in the pelvic region for at least 3 mo with variable voiding and sexual symptoms and/or no demonstrable infection; by definition, the syndrome becomes chronic after 3 mo)
• Category IIIA – Inflammatory chronic pelvic pain syndrome (ie, white blood cells in semen and/or expressed prostatic secretions and/or third midstream bladder specimen)
• Category IIIB – Noninflammatory chronic pelvic pain syndrome (ie, no white blood cells in semen and/or expressed prostatic secretions)
• Category IV – Asymptomatic inflammatory prostatitis (ie, evidence of inflammation in biopsy samples, semen and/or expressed prostatic secretions, but no symptoms)

Historical and epidemiologic data

In 1978-1979, symptoms due to acute and chronic prostatitis accounted for 25% of outpatient urinary conditions in the United States. In 1985, according to Nickel, acute and chronic prostatitis accounted for more office visits than BPH or prostate cancer. Most of these visits were for chronic prostatitis. In the early 1990s, the diagnosis of prostatitis resulted in slightly more than 2 million office visits per year.

The international prevalence rate of prostatitis is similar to that in the United States. In one report, of 600 men diagnosed with prostatitis, 5% had bacterial prostatitis, 64% had nonbacterial prostatitis, and 31% had pelvic-perineal pain syndrome or prostatodynia.

Relevant anatomy

The prostate is an extraperitoneal organ that encircles the neck of the bladder and urethra. In an adult, this organ is divided into four distinct zones or regions: periurethral, central, transitional, and peripheral. Prostate carcinoma arises more often in the peripheral zone than the other zones. However, the distribution of prostatic inflammation among the various zones is not clear.

A normal prostate gland is approximately 20 g in volume, 3 cm in length, 4 cm wide, and 2 cm in depth. As men get older, the prostate gland often enlarges because of BPH.

The gland is located posterior to the pubic symphysis, superior to the perineal membrane, inferior to the bladder, and anterior to the rectum. The base of the prostate is in continuity with the bladder and the prostate ends at the apex before becoming the striated external urethral sphincter. The sphincter is a vertically oriented tubular sheath that surrounds the membranous urethra and prostate.