[Medical Q&A] Why is varicocele more likely to occur on the left side?

Planner: Chinese Medical Association

Reviewer: Zhuang Jintao, deputy chief physician, First Affiliated Hospital of Sun Yat-sen University

The spermatic cord is a soft, cord-like structure (one on each side) that runs from the internal ring of the inguinal canal to the upper end of the testicle. Its structure is relatively complex, including blood vessels, lymphatic vessels, nerves, vas deferens, etc. Similar to the varicose veins of the lower limbs that everyone has heard of, if the spermatic vein is abnormally dilated, elongated, and tortuous, it is varicocele, which is an important cause of male infertility. Varicocele often occurs on the left side, which is mainly related to the anatomical structure of the human body.

First, the left spermatic vein is longer than the right one, which to some extent causes the left spermatic vein pressure to be greater than that of the right one. Secondly, the left spermatic vein flows vertically upward into the left renal vein (the left renal vein crosses between the abdominal aorta and the superior mesenteric artery to reach the inferior vena cava), and the journey is long. This vertical upward path makes blood return relatively difficult, especially when standing or when abdominal pressure increases, which is more likely to cause blood stasis and increased venous pressure. In addition, the left renal vein flows into the inferior vena cava at an angle close to 90 degrees, which further increases the resistance to blood flow and aggravates the pressure of the left spermatic vein. Thirdly, the left spermatic vein is located behind the sigmoid colon and is more susceptible to intestinal compression, which affects its patency. Finally, the valve defects or incomplete closure in the left spermatic vein are more than those on the right side, which cannot effectively prevent blood reflux and is more likely to cause venous dilatation. Of course, some other factors (such as congenital vascular dysplasia, long-term heavy physical labor, etc.) may also promote the occurrence of varicocele to a certain extent.