I have testicular atrophy but the scrotal ultrasound did not show epididymitis; is it unlikely that I have an infection?

Testicular Atrophy Without Ultrasound Evidence of Epididymitis: Infection Likelihood

If your scrotal ultrasound shows testicular atrophy but no signs of epididymitis, an active infection is unlikely, but this does NOT rule out past infection, chronic inflammation, or other serious pathology that requires further evaluation. 1, 2

Understanding the Ultrasound Findings

What Epididymitis Looks Like on Ultrasound

• Acute epididymitis has a near 100% sensitivity on color Doppler ultrasound, showing marked hyperemia (increased blood flow) in the epididymis 2
• The epididymis appears enlarged with either increased or decreased echogenicity, accompanied by scrotal wall thickening and often a reactive hydrocele 3, 2
• If your ultrasound showed none of these findings—no epididymal enlargement, no hyperemia, no reactive hydrocele—then acute epididymitis is effectively ruled out 2, 4

Testicular Atrophy: What It Means

• Testicular atrophy represents chronic testicular damage and volume loss, which can result from previous infection (including resolved epididymo-orchitis), testicular torsion with partial infarction, trauma, varicocele, or hormonal disorders 4
• Importantly, a study of 134 patients with acute epididymitis found that ultrasound parameters normalized after treatment without evidence of testicular atrophy, even in patients with epididymal abscess or concomitant orchitis 4
• This suggests that if you have testicular atrophy, it likely represents a chronic process rather than acute infection

Critical Differential Diagnoses to Consider

Past Infection or Chronic Inflammation

• Up to 20% of patients with epididymitis develop concomitant orchitis (epididymo-orchitis), which can lead to testicular damage if severe or untreated 3, 2
• Chronic or recurrent epididymitis may have resolved by the time of your ultrasound but could have caused permanent testicular damage
• Tuberculosis and fungal infections (Blastomyces, Histoplasma, Coccidioides) can involve the testis and epididymis with minimal acute inflammatory findings, especially in immunocompromised patients 2

Testicular Torsion (Past or Intermittent)

• Previous testicular torsion with spontaneous detorsion can cause segmental or global testicular infarction leading to atrophy 1
• The "bell-clapper" deformity is found in 82% of patients with intermittent testicular torsion and predisposes to recurrent episodes 1
• If you have a history of sudden severe scrotal pain that resolved spontaneously, this should raise suspicion for past torsion 1

Testicular Tumor (Critical Not to Miss)

• A retrospective study of 118 patients with acute epididymitis found that 4 patients (3.4%) had underlying testicular cancer that was initially overseen 5
• Patients under 50 years of age without bacteriuria and those with persistent symptoms after antibiotic treatment should be referred to a urologist for re-evaluation or follow-up ultrasound 5
• Testicular atrophy itself can be associated with increased cancer risk in certain contexts (cryptorchidism, prior trauma)

Recommended Diagnostic Algorithm

Immediate Steps

1. Review your ultrasound report carefully for:

   • Testicular volume measurements (normal is approximately 12-15 mL) 4
   • Presence or absence of testicular masses or focal lesions
   • Doppler flow patterns (normal, increased, or decreased)
   • Any mention of microlithiasis, which increases tumor surveillance needs 6

2. Obtain age-appropriate microbiologic testing even with negative ultrasound:

   • If you are under 35 years old: nucleic acid amplification testing (NAAT) for Chlamydia trachomatis and Neisseria gonorrhoeae on first-void urine, as these organisms often don't grow on routine culture 2
   • If you are 35 years or older: urine culture for enteric gram-negative bacteria (E. coli) and evaluation for urologic abnormalities 2

3. Consider serologic testing for viral causes:

   • Mumps virus is the most common viral cause of orchitis and typically shows normal inflammatory markers; diagnosis relies on IgM/IgG serology 2
   • Other viruses (Coxsackie, Epstein-Barr, varicella-zoster) can also cause orchitis with minimal acute findings 2

Follow-Up Imaging

• If you are under 50 years old, have no clear infectious etiology, or have persistent symptoms, you need urologic referral and consideration of repeat ultrasound in 6-8 weeks 1, 5
• MRI may be helpful if ultrasound findings are equivocal or if there is concern for tumor versus chronic inflammation 3

Common Pitfalls to Avoid

• Do not assume that normal inflammatory markers (CRP, ESR, white blood cell count) rule out infection—sexually transmitted infections and viral orchitis frequently present with normal labs 2
• Do not dismiss testicular atrophy as benign without ruling out underlying tumor, especially if you are under 50 years old 5
• Do not delay urologic consultation if you have had recurrent episodes of scrotal pain, as this may indicate intermittent torsion requiring bilateral orchiopexy 1
• In immunocompromised patients (HIV, transplant recipients, chronic steroid use), fungal and mycobacterial infections must be considered even with normal ultrasound and inflammatory markers 2

Bottom Line

Your negative ultrasound for epididymitis makes acute bacterial infection unlikely, but testicular atrophy demands investigation for past infection, resolved torsion, chronic inflammation, or underlying tumor. You need urologic evaluation with age-appropriate infectious workup, consideration of viral/atypical pathogens, and close follow-up imaging to exclude malignancy. 1, 2, 5