Is it normal for one testicle to be smaller than the other?

Testicular Size Asymmetry: Normal Variation vs. Pathology

Yes, it is normal for one testicle to be slightly smaller than the other, with the left testicle typically being smaller in approximately 59% of healthy adolescent males.

Normal Testicular Asymmetry

• Testicular asymmetry is a common finding in healthy males
• In a study of 345 healthy adolescent boys, 58.84% had a smaller left testicle compared to the right 1
• This asymmetry is particularly noticeable during puberty, especially in Tanner stage 3 of development 1

When Asymmetry is Normal

• Mild asymmetry without other symptoms is generally not concerning
• Normal asymmetry typically involves:
  • Minimal size difference
  • No pain or discomfort
  • No changes in testicular consistency
  • No history of trauma or infection
  • No swelling or lumps

When Asymmetry May Indicate a Problem

Testicular asymmetry may warrant medical evaluation in these circumstances:

• Significant size difference (Testicular Atrophy Index >20% or volume difference >2mL) 1
• Recent change in size difference
• Associated symptoms:
  • Pain or discomfort
  • Swelling
  • Lumps or masses
  • Changes in consistency

Common Causes of Pathological Testicular Asymmetry

1. Varicocele: Dilated veins in the scrotum (most common in left testicle)

   • Can cause progressive loss of testicular volume proportional to varicocele grade 2
   • More common on the left side due to anatomical differences in venous drainage

2. Cryptorchidism (Undescended testicle)

   • Can lead to an "incompetent" smaller testicle even after surgical correction 3
   • May result from prenatal testicular damage or injury to blood vessels during orchiopexy 3

3. Testicular atrophy from:

   • Previous infection (e.g., mumps orchitis)
   • Previous trauma or torsion
   • Radiation exposure
   • Certain medications (chemotherapy, immunosuppressants) 3
   • Systemic conditions (liver cirrhosis, chronic alcoholism) 3

Evaluation of Concerning Testicular Asymmetry

If you have concerns about testicular asymmetry, especially if accompanied by pain, swelling, or recent changes:

1. Seek medical evaluation from a primary care provider or urologist

2. Physical examination will typically be performed to assess:

   • Testicular size, position, and consistency
   • Presence of masses or tenderness
   • Signs of infection or inflammation

3. Ultrasound may be ordered if:

   • There is suspicion of a mass
   • Physical examination findings are unclear
   • There is significant asymmetry with concerning features

Key Takeaways

• Mild testicular asymmetry is common and normal in most males
• The left testicle is more commonly the smaller one
• Significant asymmetry, especially when accompanied by other symptoms, warrants medical evaluation
• Regular testicular self-examination can help identify concerning changes

Remember that while asymmetry is often normal, any sudden change in testicular size, pain, or the discovery of lumps should prompt immediate medical attention to rule out serious conditions like testicular torsion or cancer.