What lab results are typically elevated in epididymitis?

Laboratory Findings in Epididymitis

In epididymitis, the most commonly elevated laboratory findings include white blood cell count (WBC), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and positive cultures for causative pathogens from urine or urethral discharge. 1

Key Laboratory Abnormalities

Inflammatory Markers

• White blood cell count (WBC): Elevated in systemic inflammatory response
• Erythrocyte sedimentation rate (ESR): Typically elevated 2
• C-reactive protein (CRP): Commonly elevated, indicating acute inflammation 2

Urinalysis Findings

• Urine leukocyte esterase: Positive in cases with urinary tract involvement 3
• Urine nitrites: More commonly positive in men ≥35 years with bacterial infection 3
• Urine white blood cells: Increased counts, particularly with urinary tract infections 3
• Urine bacteria: Visible on microscopic examination 3

Microbiological Testing

• Urine culture: Positive in approximately 20% of cases, with E. coli being the most common pathogen (especially in men ≥35 years) 3
• Urethral swab/discharge:
  • Gram-stained smear: May show inflammatory cells and bacteria 1
  • Nucleic acid amplification tests (NAATs): Positive for sexually transmitted infections in younger patients 1

Specific Pathogen Detection

• Chlamydia trachomatis: Found in approximately 12.3% of cases, more common in men <35 years 3
• Neisseria gonorrhoeae: Present in about 3.1% of cases 3
• Trichomonas: Found in approximately 8.8% of tested cases 3

Age-Related Differences in Laboratory Findings

Younger Men (<35 years)

• More likely to have positive tests for sexually transmitted infections, particularly Chlamydia trachomatis 3
• Lower rates of positive urine cultures 3

Older Men (≥35 years)

• Higher rates of positive urine cultures (predominantly E. coli) 3
• More likely to have elevated urine WBCs, bacteria, leukocyte esterase, and nitrites 3

Clinical Pearls and Pitfalls

• Only about 50% of men diagnosed with epididymitis are tested for gonorrhea and chlamydia during their clinical encounter, representing a significant gap in diagnostic evaluation 3
• In approximately 30% of cases, no causative pathogen is identified despite comprehensive testing 4
• 16S ribosomal DNA analysis can increase pathogen detection rates by approximately 10% in challenging cases 4
• Viral causes of epididymitis (such as enteroviruses) are rare, found in only about 1% of cases 4
• In patients with persistent symptoms despite appropriate antibiotic therapy, consider fungal causes (particularly in immunocompromised or diabetic patients) 5
• Laboratory testing should include both STI screening and urine culture regardless of age, as pathogens don't strictly follow age-based patterns 4

Remember that laboratory findings should be interpreted in the context of clinical presentation, and negative results don't rule out epididymitis when clinical suspicion is high.