The presence of a varicocele is perhaps the most common identified anatomically correctable abnormality associated with male infertility. A varicocele is an abnormal dilatation of the testicular veins within the spermatic cord, generally due to increased back pressure in these vessels. Some 15% of healthy fertile men in the general population have a detectable varicocele. In the infertile population, up to 40% of men have reportedly been found to have a varicocele so there seems to be an association with infertility. The evidence that has been collected suggests that varicoceles cause a progressive injury to spermatogenic function in the testes. This relationship may explain why many young men with a varicocele are fertile and then develop secondary infertility as the effect of the varicocele progresses. The elevation of testicular temperature secondary to increased arterial blood flow around a varicocele results in the spermatogenic dysfunction.
Recognized authorities in Urology report that about 90% of varicoceles are limited to the left side. The reason for the higher incidence of left sided varicoceles is suggested by the normal male anatomy. There are differences between the left and right testicular veins. The left testicular vein drains into the left renal vein while the right testicular vein drains directly into the vena cava. The increased resistance to flow into the smaller renal vein as compared to the vena cava is one potential reason for increased pressure on the left. The left testicular vein has a higher incidence of absent valves and is about 10 cm longer than on the right, also adding to the increased resistance and greater pressure on the left side. The left renal vein may become compressed (to further increase resistance to flow) during its course as it travels between the superior mesenteric artery and the aorta, a process playfully referred to as the “nutcracker phenomenon.”
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