Varicocele is a condition where the veins within the scrotum become enlarged and dilated. The exact cause of varicocele is unknown, but it is believed to be caused by defective valves in the veins within the scrotum, just above the testicles. Normally, these valves regulate the flow of blood to and from the testicles. When normal flow doesn’t occur, the blood backs up, causing the veins to dilate (enlarge) . 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. Varicoceles are more common on the left side of the scrotum, and in about 85% of cases, it occurs in the left testicle area. Varicoceles can cause poor development of a testicle, low sperm production, or other problems that may lead to infertility. Varicoceles rarely produce symptoms, but when they do, they tend to be felt as a dull ache or feeling of heaviness in the testicle, which gets worse during the day, particularly in hot weather or after physical exertion. Varicocele treatment is generally necessary only for infertility, or if the varicocele causes persistent pain or discomfort or significant testicular atrophy.