Q: One of my testicles is much larger than the other. Is this a concern?

A: Although one testicle is usually a bit lower in the scrotum, healthy testicles are nearly identical in size. So you should be concerned if yours differ substantially – but that doesn't mean you should be alarmed or panicky.

In adults, testicles average about two inches in length and about 1/3 ounce in weight. They have a smooth surface and a firm but slightly spongy texture.

Men who've had orchitis (inflammation of a testicle due to mumps or another cause) on one side will be left with one small testicle. But if one testicle is normal and the other is larger, something else is responsible for the difference. Most often, it's a hydrocele; a benign collection of fluid around a normal testicle. A simple test called transillumination can tell doctors when fluid is present, since a bright light will pass though fluid but not a solid mass. Acute infections can cause a testicle to enlarge, but since these conditions are very painful and the swollen structures are red, warm and tender, you'd have already seen a doctor for the problem.

The most serious possibility is testicular cancer, which typically produces a hard, non-tender lump or mass. Fortunately, the disease is highly curable – just ask Lance Armstrong. A painless, safe testicular ultrasound test is the way to start evaluating this possibility – and it's also an excellent way to check out the other possible causes of an enlarged testicle.

Since testicular cancer is a disease of young men, we encourage males under age 35 to check their testicles every month or so. I'm glad you noticed this and reported it. Now make an appointment to see your doctor. You're likely to get good news, but it's important to be sure.