Why does varicocele cause male infertility? Varicocele is one of the most common causes of male infertility, and according to statistics, 40% of men with infertility suffer from this condition. This disease can affect testicular function in several ways: when the veins become thickened, the mechanism that prevents blood from flowing backwards fails and blood that should otherwise return to the heart flows to the scrotum under the influence of gravity. These backflow blood will increase the pressure in the scrotum, so that the testes are compressed; at the same time, some metabolic wastes in the veins, especially toxic substances from the kidneys, will accumulate and poison the testes, and when one side of the varicose stagnation, these toxic wastes will also be transferred to the opposite side, so that the other side of the testes are also damaged; at the same time, the testes are intolerant of high temperature, and usually the temperature in the scrotum is 1-2 degrees lower than in the abdominal cavity. It is relatively cool, but due to the stagnation of venous blood in the patient’s scrotum, the temperature then rises, and this can also lead to a decrease in testicular function. The testes have two most important functions – the synthesis of androgens and the production of sperm. If androgen production decreases, this may indirectly cause sexual dysfunction; and a decrease in sperm production capacity may also affect the quality of the patient’s semen. Although it cannot be said that varicocele necessarily causes oligozoospermia, many of the patients with infertility due to decreased sperm concentration as well as motility suffer from varicocele. Therefore varicocele is likely to affect fertility and lead to infertility. Varicocele is very slow to damage the testicles, and if left untreated, it may remain uneventful for many years, or after ten or twenty years, for example, some patients in their fifties or sixties, whose testicles have been compressed by varicocele for many years, may experience testicular atrophy. It should also be noted here that azoospermia will not be caused by varicocele. Azoospermia is divided into obstructive azoospermia and non-obstructive azoospermia, etc. Obstructive azoospermia is caused by obstruction of the vas deferens, which is not related to varicocele, and the sperm of such patients is normal in most cases; non-obstructive azoospermia may be caused by various factors, and varicocele is not the main cause, but it can further aggravate the condition of azoospermia. Therefore, non-obstructive azoospermia may also be improved to some extent if varicocele is surgically treated.