Varicocele is a disease of the testis – namely the pampiniform plexus of veins (the network of veins that drain blood from the testes). Recall the testes are the male gonads responsible for sex hormone and sperm production. The condition occurs due to an incompetence of the valves within the veins of the spermatic cord. This causes the veins to expand, resulting in a localised venous lump (or varicocele) near the testis. It is much more common on the left and thought to be caused due to the anatomical relationship of the veins. This is one of the causes for infertility.