Can Testicular Infections Be Detected on Ultrasound?
Yes, testicular infections including epididymitis, orchitis, and testicular abscesses can be reliably detected and characterized on ultrasound examination, making it the imaging modality of choice for evaluating suspected scrotal infections. 1
Ultrasound as First-Line Imaging
Ultrasound with Duplex Doppler is the established first-line imaging modality for all scrotal pathology, including infectious processes. 1, 2 The combination of grayscale and color-power Doppler US significantly improves diagnostic accuracy for characterizing scrotal lesions and is particularly useful for diagnosing focal inflammatory processes such as epididymitis and testicular abscess. 1
Specific Ultrasound Findings in Testicular Infections
Epididymitis/Epididymo-orchitis
- Enlarged epididymis with markedly increased blood flow on color Doppler (hyperemia with sensitivity near 100% for detecting scrotal inflammation) 1, 3
- Scrotal wall thickening and reactive hydrocele 3
- Up to 20% of cases have concomitant orchitis 3
- Gradual onset of pain clinically distinguishes this from torsion 3
Testicular Abscess
- Focal inflammatory processes presenting as palpable scrotal masses can be accurately depicted on grayscale US 1
- Heterogeneous, hypoechoic echotexture of the involved testicle 1
- Variable Doppler flow patterns depending on extent of involvement 1
Orchitis
- Heterogeneous testicular echotexture with increased vascularity 4
- Less common than epididymitis as a primary infection 5
- Blood-borne dissemination is the major route of testicular infection 5
Advanced Imaging Techniques
Contrast-enhanced ultrasound (CEUS) has been demonstrated to be particularly useful in patients with acute scrotal pain in the setting of infection, improving early diagnosis and detection of postinfectious complications. 1 CEUS can unequivocally differentiate between hypervascular, hypovascular, and avascular scrotal lesions. 1
Clinical Context and Epidemiology
In sexually active young to middle-aged men, epididymitis/epididymo-orchitis is overwhelmingly the most common cause of testicular pain, representing approximately 600,000 cases annually in the United States. 3 Sexually transmitted epididymitis (caused by Chlamydia trachomatis or Neisseria gonorrhoeae) represents the most frequent cause of acute scrotal swelling in men younger than 35 years of age. 5
Critical Diagnostic Pitfalls
- Normal urinalysis does not exclude epididymitis - infection can be present despite normal urine studies 3
- Duplex US cannot definitively differentiate malignancies from certain inflammatory conditions (orchitis, granuloma, focal fibrosis) - these can mimic cancer, lowering specificity 1
- Severe epididymitis with venous infarction can occasionally show absent or reversed diastolic flow, potentially mimicking torsion, though complete absence of all arterial flow is uncommon 3
- In the acute setting with high clinical suspicion for torsion, do not delay surgical consultation while waiting for imaging, as testicular viability is compromised after 6-8 hours 3
Practical Imaging Protocol
The ultrasound examination should include:
- High-frequency linear array transducer (12-17 MHz) for excellent anatomic detail 6
- Grayscale examination to assess testicular homogeneity, size, and echotexture 3
- Color/Power Doppler assessment to evaluate perfusion patterns (Power Doppler is particularly useful for detecting low-flow states) 3
- Comparison to the contralateral testis as an internal control 3
- Spectral Doppler analysis when indicated to characterize flow patterns 3