Is testicular asymmetry on ultrasound (ultrasound) normal?

Testicular Asymmetry on Ultrasound: Normal Variant vs. Pathology

Testicular asymmetry on ultrasound is a common finding that can be normal, but requires careful evaluation to exclude underlying pathology such as varicocele, hydrocele, or testicular masses. The clinical context, degree of asymmetry, and associated ultrasound findings determine whether further workup or intervention is needed.

Understanding Normal vs. Pathologic Asymmetry

Mild testicular asymmetry is frequently observed in healthy males and does not automatically indicate disease. However, the threshold for concern and the underlying causes vary significantly by age and clinical presentation:

Key Diagnostic Considerations

• Testicular ultrasound serves to confirm the presence of testicular masses and explore the contralateral testis, making it essential for evaluating asymmetry 1
• The contralateral asymptomatic testicle should be used as an internal control during ultrasound evaluation to assess for true pathologic asymmetry 2
• Ultrasound is the established first-line imaging modality for scrotal evaluation due to its high resolution, Doppler capabilities, and availability 1, 3

Common Causes of Testicular Asymmetry

Varicocele (Most Common Pathologic Cause)

• Varicoceles are the most frequent cause of testicular asymmetry in adolescents and young adults, occurring in approximately 15% of this population 4
• Asymmetry of 15% or greater is considered clinically significant, with 50-67% of adolescents with varicocele presenting with this degree of asymmetry at Tanner stages 1-3 5
• Intratesticular varicoceles occur in approximately 0.9-2% of cases and are associated with progressive testicular asymmetry over time, warranting surgical intervention rather than observation 4
• Left-sided varicoceles occur in 95% of cases, with bilateral involvement in only 5% 6

Hydrocele

• Hydrocele accounts for testicular asymmetry in a significant proportion of pediatric cases, representing the cause in approximately 67% (16 of 24) of boys presenting with asymmetry in one study 6
• Hydroceles can create photon-deficient areas on imaging that may complicate interpretation 1

Other Pathologic Causes

• Testicular masses must be excluded, as a painless solid testicular mass is pathognomonic for testicular tumor 1
• Suspicious intratesticular abnormalities include hypoechoic masses or macrocalcifications, which warrant biopsy consideration 1
• Microcalcifications without other abnormalities can be observed and do not require biopsy 1

Clinical Algorithm for Evaluation

Initial Assessment

• Determine if asymmetry is associated with pain, swelling, or palpable abnormalities on physical examination 1
• Document the patient's age and Tanner stage, as this influences the differential diagnosis and natural history 5
• Perform grayscale ultrasound to assess testicular homogeneity, size, and echotexture 1

Doppler Evaluation

• Color Doppler and power Doppler assessment should be performed to evaluate testicular perfusion and identify varicoceles 1
• Power Doppler is more sensitive for detecting low-flow states 1, 2
• Spectral Doppler analysis should be performed in the upper, mid, and lower poles of each testicle to detect subtle perfusion abnormalities 1

Management Based on Findings

For varicocele with ≥15% asymmetry:

• Adolescents at earlier Tanner stages (1-3) have a 64% incidence of significant asymmetry and lower rates of spontaneous catch-up growth (27%) 5
• Surgical intervention should be considered rather than observation, particularly if intratesticular varicoceles are present or asymmetry is worsening over time 4, 5
• Those at later Tanner stages (4-5) show a trend toward higher catch-up growth rates (53%), though this may still warrant intervention if asymmetry persists 5

For hydrocele:

• Most cases can be observed unless causing significant asymmetry or discomfort 6

For suspicious masses:

• Any hypoechoic mass or macrocalcification requires further evaluation with tumor markers (AFP, β-HCG, LDH) and consideration of inguinal orchiectomy 1

Critical Pitfalls to Avoid

• Do not dismiss asymmetry as normal without Doppler evaluation, as significant pathology may be present despite normal grayscale appearance 1, 6
• Asymmetry in the setting of acute pain requires urgent evaluation to exclude testicular torsion, even if blood flow appears present on initial Doppler (partial torsion can show preserved flow) 1, 7
• Serial ultrasounds may be necessary to document progression or resolution of asymmetry, particularly in adolescents with varicocele 4, 5
• Spectral waveform analysis showing asymmetry in resistive index or reversal of diastolic plateau between testes may indicate partial torsion even when color Doppler is indeterminate 7