Clinical Connection: Intersex

Because expression errors from a single gene (like SRY) are always possible, it should not surprise you that individuals exist whose gonad development is somewhere in between male and female. These individuals used to be called hermaphrodites or pseudohermaphrodites; the current term is intersex. They are born with reproductive anatomy that doesn’t fit typical definitions of male or female. For example, a person might appear to be female on the outside but have male-typical anatomy on the inside, or vice-versa. Some appear have both male and female external genitalia and/or may have both ovarian and testicular tissue. A surprisingly large number of people are born intersex — about 1.7% of the population or 5.6 million people in the US (about as common as having red hair). Some are identified at birth, more won’t show up until later in life, and some live their entire life unaware.

Clinical Connection: Cryptorchidism

The descent of male testes from an embryonic position in the abdomen into the scrotal sac is important clinically for two primary reasons. During fetal growth, testes move first to the inguinal canal between weeks 8 and 12, then downward through the inguinal canal during weeks 12 to 28, and finally from the inguinal canal into the scrotum during weeks 28 through 40. The failure of one or both testes to descend fully into the scrotum by birth is called cryptorchidism or, more simply, undescended testis (UDT).

Cryptorchidism occurs in 3-4% of full-term male births; about three-quarters of these are unilateral (left-sided more common than right) and about one-quarter are bilateral (both testes fail to descend fully). In pre-term male births, the 3-4% figure increases to 30% (by the time these infants reach what would have been their birth dates, most have resolved and the prevalence is once again about 3-4%). In about 75% of cases, the missing testis completes its descent into the scrotum by the age of three months; about 25% will require surgery, usually done between six and twelve months of age.

Resolving cryptorchidism is important because the condition increases the risk, later in life, of the following conditions:

• Testicular cancer – An undescended testis has an eight times greater risk of developing testicular cancer. While this increase is significant, the risk of testicular cancer is remains below 1 per 100.
• Testicular torsion – While rare, testicular torsion is ten times more likely in an undescended testis.
• Infertility – Because sperm production functions best at 2-3°C below body temperature, an undescended testis is too warm to carry out this process efficiently. While bilateral cryptorchidism clearly presents a significant challenge to male fertility, even a unilateral case can lower sperm count enough to prevent successful conception.

Clinical Connection: Inguinal Hernia

The second reason the descent of male testes through the inguinal canal into the scrotal sac is important clinically relates to the risk of inguinal hernia. After passage of the testis, the inguinal canal becomes the spermatic cord and remains, mechanically, a weak point in the lower abdominal wall. An inguinal hernia occurs when a loop of bowel finds its way into the remnants of the inguinal canal. It stands to reason, then, that inguinal hernias are seven times more common in men than women (oddly, they occur 4.5 times more frequently on the left side than the right).

Sometimes, the herniated loop of bowel can be carefully reduced manually (pushed out of the inguinal canal back into the abdominal cavity), but will frequently herniate again, necessitating surgery. Herniated tissue that becomes trapped quickly becomes a medical emergency resolved only by abdominal surgery to reduce the hernia, resect a section of necrotic bowel (often), and structurally reinforce the body wall to prevent recurrence.