What are the diagnostic criteria for prostatitis?

Diagnosis of Prostatitis: Diagnostic Criteria and Approach

The diagnosis of prostatitis requires specific laboratory tests including the Meares-Stamey 4-glass test or its 2-glass variant, along with clinical assessment of symptoms and physical examination findings. 1

Classification of Prostatitis

Prostatitis is classified into four categories according to the National Institutes of Health (NIH) system:

1. Category I: Acute Bacterial Prostatitis (ABP)

   • Characterized by acute onset of symptoms
   • Systemic infection signs (fever, chills)
   • Lower urinary tract symptoms

2. Category II: Chronic Bacterial Prostatitis (CBP)

   • Recurrent UTIs with the same pathogen
   • Persistent symptoms for >3 months

3. Category III: Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS)

   • Chronic pelvic pain without evidence of infection
   • Subdivided into:
     • Category IIIA: Inflammatory (WBCs in semen/EPS/VB3)
     • Category IIIB: Non-inflammatory (no WBCs)

4. Category IV: Asymptomatic Inflammatory Prostatitis

   • Incidental finding during evaluation for other conditions
   • Inflammatory cells present without symptoms

Diagnostic Criteria and Tests

For Acute Bacterial Prostatitis:

• Clinical presentation: Fever, chills, dysuria, frequency, urgency, perineal pain
• Physical examination: Tender, swollen, warm prostate on digital rectal examination (DRE)
• Laboratory tests:
  • Midstream urine dipstick (nitrites and leukocytes) 1
  • Midstream urine culture to identify pathogens 1
  • Blood cultures and complete blood count 1
  • Note: Prostatic massage is contraindicated in ABP due to risk of bacteremia 1

For Chronic Bacterial Prostatitis:

• Gold standard: Meares-Stamey 4-glass test 1, 2

  • Collection of four specimens:
    1. First-void urine (VB1): represents urethral specimen
    2. Midstream urine (VB2): represents bladder specimen
    3. Expressed prostatic secretions (EPS): obtained after prostatic massage
    4. Post-massage urine (VB3): first-void urine after prostatic massage
  • Positive result: 10-fold higher bacterial count in EPS/VB3 than in VB1/VB2 1

• 2-glass variant (simplified version):

  • Involves only midstream urine and post-massage urine specimens 1
  • More practical for office-based settings 3

For Chronic Prostatitis/Chronic Pelvic Pain Syndrome:

• Mandatory evaluations:

  • History and physical examination
  • Urinalysis and urine culture 2

• Recommended evaluations:

  • Lower urinary tract localization tests
  • NIH Chronic Prostatitis Symptom Index
  • Uroflowmetry
  • Post-void residual measurement
  • Urine cytology 2

• Optional evaluations (based on clinical presentation):

  • Semen analysis and culture
  • Urethral swab
  • Urodynamics
  • Cystoscopy
  • Imaging studies
  • PSA determination 2

Microbiological Considerations

Common Pathogens:

• Acute bacterial prostatitis:

  • Escherichia coli and other Enterobacterales
  • Pseudomonas species
  • Staphylococcus aureus
  • Enterococcus
  • Group B streptococci 1

• Chronic bacterial prostatitis:

  • Similar pathogens as acute bacterial prostatitis
  • Consider atypical pathogens such as Chlamydia trachomatis and Mycoplasma species 1, 4

Specimen Collection and Transport:

• Specimens should be collected in closed sterile containers
• Transport to laboratory within 1 hour or refrigerate at 4°C if delayed 1
• For fungal or mycobacterial cultures, special media and processing are required 1

Imaging in Prostatitis

• Transrectal ultrasound (TRUS):

  • Recommended in selected cases to rule out prostatic abscess 1
  • May detect calcifications, cysts, or other structural abnormalities 1

• MRI:

  • Consider when TRUS results are negative or inconclusive 1
  • Better for anatomic abnormalities of the prostate and ejaculatory tract 1

Common Pitfalls in Diagnosis

1. Failure to distinguish between prostatitis categories:

   • Different categories require different diagnostic approaches and treatments

2. Relying solely on symptoms without laboratory confirmation:

   • Symptoms of prostatitis overlap with other urological conditions

3. Performing prostatic massage in acute bacterial prostatitis:

   • Can lead to bacteremia and sepsis 1

4. Inadequate specimen collection or transport:

   • May lead to false-negative cultures or contamination

5. Not considering non-bacterial causes in chronic pelvic pain syndrome:

   • Chronic prostatitis/chronic pelvic pain syndrome is often not caused by culturable infectious agents 1

Differential Diagnosis

• Benign prostatic hyperplasia
• Urinary tract infection
• Urinary tract stones
• Bladder cancer
• Prostatic abscess
• Urethral stricture
• Neurogenic bladder dysfunction 5

In summary, the diagnosis of prostatitis requires a systematic approach using specific laboratory tests, particularly the Meares-Stamey 4-glass test or its 2-glass variant, along with careful clinical assessment. The diagnostic criteria differ based on the category of prostatitis, with acute bacterial prostatitis diagnosed primarily through clinical presentation and urine culture, while chronic bacterial prostatitis requires more specialized testing to localize the infection to the prostate.