A varicocele (VAR-ih-koe-seel) is an enlargement of the veins within the loose bag of skin that holds the testicles (scrotum). These veins transport oxygen-depleted blood from the testicles. A varicocele occurs when blood pools in the veins rather than circulating efficiently out of the scrotum.

Varicoceles usually form during puberty and develop over time. They may cause some discomfort or pain, but they often result in no symptoms or complications.

A varicocele may cause poor development of a testicle, low sperm production or other problems that may lead to infertility. Surgery to treat varicocele may be recommended to address these complications.

A varicocele usually occurs on the left side of the scrotum and often produces no signs or symptoms. Possible signs and symptoms may include:

• Pain. A dull, aching pain or discomfort is more likely when standing or late in the day. Lying down often relieves pain.
• A mass in the scrotum. If a varicocele is large enough, a mass like a “bag of worms” may be visible above the testicle. A smaller varicocele may be too small to see but noticeable by touch.
• Differently sized testicles. The affected testicle may be noticeably smaller than the other testicle.
• Infertility. A varicocele may lead to difficulty fathering a child, but not all varicoceles cause infertility.

When to see a doctor

Annual wellness visits for boys are important for monitoring the development and health of testicles. It’s important to schedule and keep these appointments.