How is prostatitis assessed and diagnosed?

Assessment of Prostatitis

The diagnosis of prostatitis requires a focused clinical evaluation combining history, physical examination, urinalysis, and the Meares-Stamey test (4-glass or 2-specimen variant) to differentiate bacterial from non-bacterial forms, with a positive result defined as a 10-fold higher bacterial count in expressed prostatic secretions compared to midstream urine. 1

Initial Clinical Assessment

History and Symptom Evaluation

• Obtain a detailed history focusing on urinary symptoms (dysuria, frequency, urgency, retention), pelvic pain (location, duration, severity), and ejaculatory pain 1, 2
• Document symptom duration: acute (<3 months) versus chronic (≥3 months) 2, 3
• Use the NIH Chronic Prostatitis Symptom Index (NIH-CPSI) to quantify symptom severity (scale 0-43, with 6-point change being clinically meaningful) 2
• Assess for systemic symptoms including fever, chills, nausea, or malaise, which suggest acute bacterial prostatitis 2, 4
• Document history of recurrent urinary tract infections with the same organism, which suggests chronic bacterial prostatitis 2, 3

Physical Examination

• Perform digital rectal examination (DRE) to assess for prostate tenderness, enlargement, or boggy consistency 1, 4
• Critical pitfall: Avoid vigorous prostatic massage or aggressive DRE in suspected acute bacterial prostatitis due to risk of bacteremia 1, 5
• Examine abdomen and genitalia to exclude alternative diagnoses like epididymitis (epididymal tenderness rather than prostate tenderness) 5

Laboratory Diagnostic Testing

Essential Initial Tests

• Urinalysis to identify urinary tract infection, proteinuria, hematuria, or glycosuria 1
• Midstream urine culture to identify causative organisms in acute bacterial prostatitis 5, 2
• Blood cultures in febrile patients with suspected acute bacterial prostatitis 5
• Complete blood count to assess for leukocytosis in acute presentations 5

Gold Standard Localization Testing

For chronic bacterial prostatitis, the Meares-Stamey 4-glass test is the gold standard diagnostic procedure 1, 5:

1. First-void urine (VB1): Initial 10 mL of voided urine
2. Midstream urine (VB2): Midstream clean-catch specimen
3. Expressed prostatic secretions (EPS): Obtained via prostatic massage
4. Post-massage urine (VB3): First 10 mL voided after massage

Simplified 2-specimen variant: Collect only midstream urine and EPS specimens 1, 5

Interpretation:

• Perform Gram stain or cell counts to identify inflammatory cells 1
• Perform aerobic culture of all specimens 1
• Positive diagnosis requires a 10-fold higher bacterial count in EPS compared to midstream urine 1, 5

Common Bacterial Pathogens

• Acute bacterial prostatitis: Gram-negative bacteria in 80-97% of cases (E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa); Gram-positive organisms include Staphylococcus aureus, Enterococcus species 5, 2
• Chronic bacterial prostatitis: Up to 74% are Gram-negative organisms (E. coli most common), also Proteus mirabilis, Enterobacter species, Serratia marcescens 1, 5, 2

Additional Diagnostic Studies

When to Obtain Imaging

• Transrectal ultrasound (TRUS): Perform in selected cases to assess prostate volume and rule out prostatic abscess in acute bacterial prostatitis 1, 5
• TRUS is more accurate than DRE for estimating prostate volume 1

Functional Urologic Testing

• Uroflowmetry: Correlate symptoms with objective voiding dysfunction 1
• Post-void residual measurement: Assess for urinary retention 2
• Bladder diary (minimum 3 days): Recommended for patients with storage symptoms or nocturia 1

Diagnostic Algorithm by Prostatitis Category

Acute Bacterial Prostatitis

• Clinical diagnosis based on acute onset of urinary symptoms + systemic symptoms + tender prostate on gentle DRE 4
• Confirm with midstream urine culture 5, 2
• Avoid prostatic massage 1, 5

Chronic Bacterial Prostatitis

• Requires Meares-Stamey test showing 10-fold higher bacterial count in EPS versus midstream urine 1, 5
• Consider testing for atypical pathogens (Chlamydia trachomatis, Mycoplasma species) as these require specific antimicrobial therapy 5

Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS)

• Diagnosis of exclusion: Pelvic pain ≥3 months with urinary symptoms but negative cultures 2, 3
• Perform Meares-Stamey test to rule out bacterial infection 5
• CP/CPPS is not frequently caused by culturable infectious agents 1, 5
• Exclude other causes: infection, cancer, urinary obstruction, urinary retention 2

Asymptomatic Inflammatory Prostatitis

• Incidental finding during evaluation for infertility or prostate cancer 3, 6
• Does not require treatment 6, 7

Critical Diagnostic Pitfalls

• Never perform vigorous prostatic massage in acute prostatitis due to bacteremia risk 1, 5
• Distinguish between bacterial prostatitis (requires antibiotics) and CP/CPPS (requires symptom-focused management) using localization cultures 1, 5
• Local antibiotic resistance patterns should guide empiric therapy selection 5
• Stopping antibiotics prematurely in acute bacterial prostatitis can lead to chronic bacterial prostatitis 5