Is a slight discrepancy in testicular size, with the left testicle being smaller than the right, considered normal?

Slight Testicular Size Discrepancy with Left Smaller than Right is Normal

A slight discrepancy in testicular size, with the left testicle being smaller than the right, is considered normal and does not require medical intervention in the absence of other symptoms or risk factors. 1, 2

Normal Testicular Size Variation

• Studies have shown that there are no statistically significant differences between the dimensions of right and left testes in healthy males 2
• However, in clinical practice, slight variations are commonly observed, particularly with the left testicle being slightly smaller than the right 3
• This slight asymmetry is not considered pathological when the difference is minimal and not associated with other symptoms 1

When to Be Concerned

• Testicular volumes less than 12 ml are generally considered small or atrophic and may warrant further investigation 1
• A size difference greater than 2 ml or 20% between testes that persists on repeated examinations (6 months apart) may be clinically significant, particularly in adolescents 4
• Significant testicular size discrepancy may be associated with conditions such as varicocele, which is more common on the left side 3, 5

Varicocele and Testicular Size

• Left varicocele can be associated with loss of left testicular volume, with the degree of hypotrophy proportional to the clinical grade of varicocele 3
• In men with left varicocele, mean left testicular volume is often less than right testicular volume (12.7 vs. 13.8 mL), a finding not observed in men without varicocele 3
• The European Association of Urology recommends treating varicocele in adolescents when associated with a persistent small testis (size difference >2 ml or 20%), confirmed on two subsequent visits 6 months apart 6, 4

Clinical Implications

• Bilateral testicular hypotrophy is more concerning than unilateral hypotrophy in terms of potential impact on fertility 7
• Unilateral hypotrophy alone does not necessarily predict impaired semen quality 7
• When evaluating testicular size, ultrasound is more accurate than external measurements, as the latter may overestimate dimensions 2

Monitoring Recommendations

• Regular testicular self-examination is recommended, especially for men with risk factors such as testicular microcalcification, even if the size discrepancy is minimal 6
• If concerned about a size discrepancy, follow-up evaluation should include physical examination and possibly ultrasound to accurately measure testicular volumes 6, 1
• Ultrasound is the established first-line imaging modality for scrotal evaluation when there are concerns 6

When to Seek Medical Attention

• Seek medical attention if the size discrepancy is accompanied by pain, swelling, or other symptoms 6
• Medical evaluation is warranted if there is a sudden change in testicular size or if the size difference is significant (>2 ml or 20%) 6, 4
• Consider evaluation if there are other risk factors such as infertility, cryptorchidism (history of undescended testicles), or family history of testicular cancer 6, 1

In conclusion, while a slight discrepancy in testicular size with the left being smaller than the right is generally normal, significant differences or changes should be evaluated by a healthcare provider, particularly when accompanied by other symptoms or risk factors.