Is it normal for the right testicle to be larger than the left testicle?

Normal Anatomical Variation in Testicular Size

Yes, it is normal for the right testicle to be slightly larger than the left testicle in most men. This anatomical variation is considered a normal finding and generally does not indicate any pathology.

Anatomical Basis for Size Difference

The size difference between testicles has several anatomical explanations:

• Vascular anatomy: The left spermatic vein drains into the left renal vein at a 90-degree angle, while the right spermatic vein drains directly into the inferior vena cava. This anatomical difference in venous drainage may contribute to the size discrepancy 1.

• Embryological development: During development, the right and left testes may grow at slightly different rates, leading to a small but noticeable size difference in adulthood.

Normal Testicular Measurements

• The normal adult testicular volume ranges from 14-35 ml, with an average of approximately:

  • 18-20 ml for the right testicle
  • 16-18 ml for the left testicle 2

• Normal testicular size correlates with testicular function, including sperm production and hormone levels 3.

Clinical Significance

• No clinical concern: A slight size difference between testicles is not associated with any increased risk of morbidity or mortality.

• When to be concerned: Medical evaluation should be considered if:

  1. The size discrepancy is significant (>20% difference)
  2. There is a sudden change in size of either testicle
  3. The size difference is accompanied by pain, swelling, or lumps
  4. Either testicle is abnormally small (<14 ml) 3

Examination Technique

When examining the testicles, healthcare providers should:

• Perform examination in a warm room to minimize cremasteric reflex
• Have the patient in standing position initially
• Palpate each testicle separately between thumb and first two fingers
• Note any differences in:
  • Size
  • Consistency (should be firm but not hard)
  • Surface characteristics (should be smooth)
  • Tenderness 1

Differential Considerations

If concerned about abnormal testicular size differences, consider:

• Varicocele: Dilated veins in the scrotum (more common on left side)
• Hydrocele: Fluid collection around the testicle
• Testicular atrophy: From prior infection, trauma, or torsion
• Cryptorchidism: History of undescended testicle (can lead to smaller size)
• Testicular mass: Requires urgent evaluation 1

When Imaging Is Indicated

Ultrasound is not routinely needed to evaluate normal size variations but may be indicated if:

• There is suspicion of a testicular mass
• Acute onset of pain
• Significant or concerning size discrepancy
• Nonpalpable testicle 1

Remember that routine testicular self-examination has not been shown to improve outcomes according to the U.S. Preventive Services Task Force, but being familiar with your normal anatomy can help identify concerning changes 4.