The undescended testis is a very common urologic problem, observed in 0.8% of boys at 1 year of age. It is considered a developmental defect and places the affected testis at higher risk of developing cancer. Although the newborn undescended testis is morphologically fairly normal, deterioration in early germ cell numbers is often seen by 2 years of age. The contralateral, normally descended testis is also at increased risk of harboring germ cell abnormalities. Thus, males with either unilaterally or bilaterally undescended testes are at risk for infertility later in life. Prophylactic orchidopexy is generally performed by 2 years of age to allow the testis to be palpated for cancer detection. It is unclear whether orchidopexy alters fertility potential in cryptorchidism.

Varicocele

A varicocele is defined as dilated and tortuous veins within the pampiniform plexus of scrotal veins. It is the most surgically correctable cause of male subfertility. The varicocele is a disease of puberty and is only rarely detected in boys under 10 years of age. A left-sided varicocele is found in 15% of healthy young men. In contrast, the incidence of a left varicocele in subfertile men approaches 40%. Bilateral varicoceles are uncommon in healthy men (< 10%) but are palpated in up to 20% of subfertile men. In general, varicoceles do not spontaneously regress. The cornerstone of varicocele diagnosis rests on an accurate physical examination.

Several anatomic features contribute to the predominance of left-sided varicoceles. The left internal spermatic vein is longer than the right; in addition, it usually joins the left renal vein at right angles. The right internal spermatic vein has a more oblique insertion into the inferior vena cava. This particular anatomy in the standing man may cause higher venous pressures to be transmitted to the left scrotal veins and result in retrograde reflux of blood into the pampiniform plexus.

Varicoceles are associated with testicular atrophy. It has also been demonstrated that varicocele correction can reverse atrophy in adolescents. There is indisputable evidence that the varicocele affects semen quality. In fact, based on the work of MacLeod and Gold (1951), a classic semen analysis pattern has been attributed to varicoceles in which low sperm count and motility is found in conjunction with abnormal sperm shapes. The finding of semen abnormalities constitutes the main indication for varicocele surgery in infertile men.

Precisely how a varicocele exerts an effect on the testicle remains unclear. Several theories have been postulated; it is likely that a combination of effects results in infertility. Pituitary-gonadal hormonal dysfunction, internal spermatic vein reflux of renal or adrenal metabolites, and an increase in hydrostatic pressure associated with venous reflux are also postulated effects of a varicocele. The most intriguing theory of how varicoceles affect testis function invokes an inhibition of spermatogenesis through the reflux of warm corporeal blood around the testis, with disruption of the normal countercurrent heat exchange balance and elevation of intratesticular temperature.

Idiopathic

It has been estimated that at least 25%-50% of male infertility has no identifiable cause. As our knowledge expands, it is likely that genetic and environmental factors will explain many of these cases.