An abnormal dilatation of the veins surrounding the testes. A varicocele, present in 25% of infertile males, causes blood to pool in the veins of the testes. This pooling presents a problem for some men because the presence of excess blood raises testicular temperature, which can be detrimental to sperm. The surgical correction of a varicocele is minor, and performed in order to ligate the dilated vessels or veins. However, the success of treatment is controversial. Pregnancy rates after surgery are reported to be in the range of 30-50%.