eMedicine Specialties > Urology > Infections and Related Inflammatory Conditions

Prostatitis, Bacterial

Author: Joe D Mobley III, MD, MPH, Chief Resident Physician, Department of Surgery, Division of Urology, University of Tennessee Graduate School of Medicine/University of Tennessee Medical Center
Coauthor(s): Edward David Kim, MD, FACS, Professor of Surgery, Division of Urology, University of Tennessee Graduate School of Medicine; Consulting Staff, University of Tennessee Medical Center
Contributor Information and Disclosures

Updated: Oct 8, 2009

Introduction

Background

Chronic bacterial prostatitis represents an infection of the prostate gland. By definition, this condition is characterized by bacterial growth in culture of the expressed prostatic fluid, semen, or postmassage urine specimen. The expressed prostatic secretion (EPS) usually contains more than 10 white blood cells (WBCs) per high-power field (HPF) and macrophages.

The hallmark of chronic bacterial prostatitis is the occurrence of relapsing urinary tract infections, usually involving the same pathogen. Chronic bacterial prostatitis is often confused with nonbacterial prostatitis, chronic pelvic pain syndrome (CPPS), and prostatodynia.

Pathophysiology

The prostate gland is an accessory sex gland, providing approximately 15% of the ejaculate. The base of the prostate abuts the bladder neck, while the apex is in continuity with the membranous urethra, resting on the urogenital diaphragm.

The adult prostate weighs approximately 20 g but may grow dramatically with age (see Prostate Hyperplasia, Benign). The approximate dimensions are 4.4 cm transversely at the base, 3.4 cm in length, and 2.6 cm in anteroposterior diameter. Antibacterial factors within the prostate, such as zinc, help to prevent infection.

Frequency

United States

Prostatitis accounts for approximately 2 million annual visits. Twenty-five percent of all men evaluated for urologic problems in the United States are estimated to have symptoms of prostatitis. Approximately 50% of men experience symptoms of prostatitis at some time in their life. However, less than 5-10% of men with symptoms of prostatitis have bacterial prostatitis. Evaluation for these symptoms makes up approximately 8% of all urology visits.

International

Worldwide, 8 million prostatitis-related visits are reported annually.

Mortality/Morbidity

• Chronic bacterial prostatitis is not associated with mortality. However, acute bacterial prostatitis (discussed in Acute Bacterial Prostatitis and Prostatic Abscess) represents a potentially lethal process if untreated.
• The morbidity associated with chronic bacterial prostatitis is related to its relapsing nature. Chronic bacterial prostatitis may be difficult to eradicate because of the persistence of bacteria within the prostatic acini. Factors that contribute to bacterial persistence include (1) a poor ductal drainage system within the prostate, which can lead to congestion of prostatic secretions, and (2) the tendency for urine to reflux into the prostatic ducts, which may cause irritation and inflammation.

Race

No racial predilections have been identified.

Sex

Bacterial prostatitis affects in males.

Age

Chronic bacterial prostatitis typically affects men aged 40-70 years. Benign prostatic hyperplasia typically affects the same age group.

Clinical

History

Relapsing urinary tract infections, interspersed with asymptomatic periods, are common in persons with chronic bacterial prostatitis. Although some men are diagnosed because of asymptomatic bacteriuria, most have varying degrees of irritative voiding symptoms, such as dysuria, frequency, and urgency.

In addition, some patients report feelings of a vague discomfort in the pelvis and perineum. Fevers and chills are uncommon. Rectal palpation of the prostate is not painful and produces no specific findings. Prostatic fluid and postmassage urine cultures, which should be obtained for precise diagnosis, demonstrate bacterial growth.

• Characteristics of chronic bacterial prostatitis include the following:
  • Chronic bacterial prostatitis is the most common cause of relapsing urinary tract infection in males.
  • Asymptomatic periods are interspersed between episodes of recurrent bacteriuria.
  • Obstructive or irritative voiding symptoms may occur.
  • Vague discomfort in pelvis, perineum, lower abdomen, back and testicles is reported.
  • Physical findings on palpation are often unremarkable.
  • EPS, postmassage urine culture, or semen culture must be obtained for a precise diagnosis.
• Symptoms of prostatitis include the following:
  • Genitourinary pain
  • Dysuria and hematospermia
  • Clear urethral discharge
  • Recurrent urinary tract infection
• The spectrum of organisms grown in culture in chronic bacterial prostatitis is essentially the same as in acute bacterial prostatitis. Most infections are caused by a single pathogen, but a polymicrobial infection is not unusual. Obligate anaerobic bacteria rarely cause prostatic infection.
• Localization cultures do not need to demonstrate greater than 100,000 colony-forming units (CFU) per milliliter to establish the diagnosis. Instead, the presence of a greater than 10-fold bacterial growth in the EPS or the third midstream bladder specimen (VB₃) compared with the first voided bladder specimen (VB₁) and the second midstream bladder specimen (VB₂) is important.
• Common bacterial pathogens, predominated by gram-negative rods, include the following:  
  • Escherichia coli (80%)
    
    

    

    Urine culture with greater than 100,000 colony-forming units (CFU) of Escherichia coli, the most common pathogen in acute and chronic prostatitis. Chronic bacterial prostatitis must be confirmed and diagnosed using a urine culture.

    [ CLOSE WINDOW ]

    

    Urine culture with greater than 100,000 colony-forming units (CFU) of Escherichia coli, the most common pathogen in acute and chronic prostatitis. Chronic bacterial prostatitis must be confirmed and diagnosed using a urine culture.

  • Klebsiella species
  • Enterobacter species
  • Proteus enterococci species
  • Pseudomonas species
  • Staphylococcus species

Physical

The physical examination findings, including the findings on prostate examination via digital rectal examination, are typically normal.

• The prostate may have areas of firmness related to chronic inflammation. While prostatic calculi are associated with a higher risk of chronic bacterial prostatitis, they are rarely palpable on prostate examination because of their location, which is typically deep within the prostate gland.
• In contrast, acute bacterial prostatitis is characterized by a very tender, warm, swollen, firm gland. When acute bacterial prostatitis is suspected, prostate massage should be avoided because of the risk of causing bacteremia.
• While chronic bacterial prostatitis may be associated with symptoms of perineal, scrotal, and low back discomfort, the physical examination findings are typically normal.

Causes

The actual routes of prostatic infection are unknown in most cases, but various etiologies may be found. Ascending urethral infection is a known route because of the frequency of previous gonococcal prostatitis, as well as the finding of identical organisms in prostatic fluid and vaginal culture in many couples. Intraprostatic urinary reflux has been demonstrated in human cadavers and may play a role.

• Routes of infection include the following:
  • Ascending urethral infection
  • Reflux of infected urine into prostatic ducts
  • Migration of rectal bacteria via direct extension or lymphogenous spread
  • Hematogenous infection
• The relapsing nature of bacterial prostatitis is due in part to the ductal anatomy of the prostate’s peripheral zone, which prevents dependent drainage of secretions. This can lead to congestion and thickening of prostatic secretions and provides a nidus for recurrent infections. Ductal fibrosis and prostatic calculi, if present, further inhibit the drainage of secretions.
• E coli infection accounts for 80% of cases of chronic bacterial prostatitis. The other members of the Enterobacteriaceae family, Klebsiella species, Pseudomonas aeruginosa, and Proteus species are also known pathogens. Chlamydia trachomatis has been implicated as a cause of chronic bacterial prostatitis.¹ However, this organism is unlikely to play a major role in the etiology of chronic bacterial prostatitis.
• The role of the gram-positive organisms Staphylococcus epidermitis and Staphylococcus saprophyticus is controversial. These organisms typically colonize the anterior urethra and likely represent contamination when positive in a culture specimen. Only patients in whom a second culture result is positive should receive antibiotic treatment.
• Prostatic calculi, although an unspecific finding, often develop in men with chronic bacterial prostatitis; prostatic calculi may serve as a nidus for recurrent infection. A newly described entity termed nanobacteria is thought to play a significant role in urologic stone disease, including prostatic calculi.² Nanobacteria may play a role in the chronic nature of this condition. Studies are currently underway to further delineate the role of these organisms in chronic bacterial prostatitis.
• The National Institutes of Health (NIH) classification of prostatitis: Based on specific etiologies, the NIH classified the various forms of prostatitis in 1995.³ The most common type of prostatitis is type III, the chronic pelvic pain syndrome (CPPS) category.
  • Type I - Acute bacterial prostatitis
    • Well-defined infectious disease of the lower urinary tract
    • Bacterial cause, most commonly E coli infection
    • Frequently presents with bacteremia
  • Type II - Chronic bacterial prostatitis (focus of this article)
  • Type III - Chronic abacterial prostatitis (inflammatory CPPS and noninflammatory CPPS)
    • Most common prostatitis (90% of cases)
    • Nonbacterial
    • Diagnosed based on EPS findings, clinical findings, and culture results
    • Empiric trial of antimicrobials usually warranted (fluoroquinolone or trimethoprim-sulfamethoxazole [TMP-SMZ])
  • Type IV - Asymptomatic inflammatory prostatitis
    • Often diagnosed based on results of biopsies, surgical specimens, or semen analysis obtained for other reasons
    • No treatment warranted
    • Biopsy typically indicated because of elevated prostate-specific antigen (PSA) level

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