Varicocele is a varicose vein in the scrotum that prevents sperm from developing properly and can be treated with surgery. Testicles that fail to descend from the abdomen into the scrotum during fetal development causes a higher internal body temperature and sperm production can be affected. Additional testicular problems include: blocked ejaculatory ducts and or a lack of vas deferens (the tube that carries sperm from the testicle through the penis). Ejaculatory problems can include retrograde ejaculation—when semen enters the bladder during orgasm rather than through the penis. This can be caused by diabetes, prostate or urinary issues and by some medications.