A varicocele is a network of swollen or enlarged veins in the scrotum. Varicoceles are a common condition, presenting in 20% of men. In some cases, only minor symptoms are present, though for some men a varicocele can be extremely painful and can interfere with normal activities. Varicoceles generally form during puberty and can grow over time. A varicocele may cause problems such as low sperm production contributing to infertility.