One Testicle Bigger Than the Other? Is It Normal or Problematic?

It is more common than many people may think to have one testicle bigger than the other. In fact, according to a study on genital asymmetry in men, the right testicle is usually somewhat larger than the left. This is because in humans, the testes on the right seem to develop more quickly than on the left. In addition, growth favors the development of the testicle on the right in a fetus in utero. For females, this phenomenon is the opposite, with the ovaries developing first on the left.

Not only is it normal to have one testicle that is slightly bigger than the other, but it’s also common to have one that hangs a bit lower than the other one in the scrotum.

But it’s not always normal for one testicle to be bigger than the other, and it’s important to know the difference between normal asymmetrical testicle size and what may constitute something more serious.

Before one can screen for testicular problems, it’s important to learn about their normal structure and function:

A testicle (also called testis) is a small oval-shaped gland. It produces sperm and male sex hormones.

The scrotum is the sac that surrounds the testicles. It is located outside of the body because sperm requires a lower-than-normal body temperature to be produced.

The epididymis is a chain of small tube-like structures located behind the testicles. Its function is to collect and store the sperm that is produced in the testicles. The epididymis links up with the vas deferens—a larger tube-like structure that carries the sperm out of the body during ejaculation.  

One of the most indicative signs that having asymmetrical testicle size is not normal is when there is pain, redness, or swelling. The other telltale sign that there could be a problem is if one testicle is a different shape than the other.

Knowing the normal anatomy of the testes and other parts of the male reproductive system is important in self-examination. Being familiar with the normal shape, appearance, and the feel of the testes will help a person to notice when a change occurs. General tips on normal anatomy of the testes and scrotum include:

• Each testicle should feel like a firm, smooth egg.
• Adult testicles should be approximately 2 to 3 inches in length and 1 inch in width.
• It’s normal for one testicle to be slightly larger than the other and for one to hang slightly below the other.
• There should not be any pain or discomfort when the testicles are gently examined.

Self-examination of the testicles should be performed monthly. Testicular self-examination steps from the Victoria State Government in Melbourne, Australia include:

1. Shower or take a bath to ensure the scrotum is relaxed and warm.
2. Stand in front of a mirror if that helps to visualize the process.
3. Examine each testicle separately, one after the other.
4. Use the fingers and thumbs on both hands to gently roll the testicle, check for lumps, protrusions, or any painful areas.
5. Palpate (feel) along the underneath of the scrotum to locate the epididymis (it should feel like a bundle of tightly coiled tubules). 
6. Examine the other testicle.

The examination should not result in any unusual findings, such as:

• Pain
• Lumps
• Swelling
• Change in size or shape (since the last exam)
• Change in feel or consistency (since the last exam)

Common conditions involving lumps, pain, or swelling of the testicle that are not life-threatening, but require medical attention include:

• Cysts—an abnormal, but harmless, fluid collection
• Blood clots—caused by trauma or injury
• Varicose veins
• Orchitis—inflammation of the testicle caused by an infection
• Testicular torsion—twisting of the cord that attaches the testicle to the body, causing excruciating pain. This may result in loss of the testicle.

Noticing or experiencing symptoms of any of these may feel frightening, but it's important to get them checked out so that the symptoms do not progress.

Performing monthly self-examinations is an important part of early testicular cancer screening. Symptoms of testicular cancer include lumps, new growths, and sometimes pain.

Having one testicle that is slightly larger than the other is completely normal. However, swelling, pain, redness, and lumps are not. It’s important to note that testicular cancer is rare, and although it’s vital to seek medical attention when a lump, pain, or other abnormality is noted, there is no need to panic. The symptoms are more than likely a result of a less serious condition.