Undescended Testis (UDT)
The most common congenital urologic problem is undescended testis (UDT). This occurs in about 3% of newborns. By six months of age, only 1% of those born with UDT still have it. In other words, two-thirds of UDT come down to the scrotum on their own by six months of age. The 1% of UDT that remain undescended by six months of age will almost never come down on their own and will need surgery.
Medical concerns related to UDT include:
Paternity rates for men with unilateral (one) UDT that has been operated on previously are similar to those of men with two normal testicles. So, having one UDT is usually not a concern as far as fertility goes. On the other hand, paternity rates for men with bilateral (two) UDT are considerably lower at around 60%.
The risk of cancer was overestimated in the past, where biased studies were used to make the calculations. The best estimate we have now about cancer risk comes from a study done in Sweden that looked at more than 16,000 patients that had UDT surgery, of which only 56 developed testicular cancer (0.3%) (Pettersen, et al 2007, NEJM). Compared to the Swedish general population, when surgery was done before the age of 13 years, the risk of cancer was twice as high. And when the surgery was done after the age of 13 years, the risk of cancer was about five times higher. Although “twice the risk” sounds scary, the absolute numbers are not (0.3%).
- Cosmesis and comfort
I think this should be obvious.
Ascending Testis (AT)
The ascending testis (AT) refers to a patient that at birth, had a documented physical exam by an experienced provider in which both testicles were found to be in the scrotum, but on subsequent medical check-ups, one or both testicles are found to be out of the scrotum (undescended).
Some prepubertal boys have an underdeveloped scrotum where the pubic fat, penis, and scrotum all mix into one unit, whereas in the adult, the scrotum is completely separate from the body and “hangs out”. Prepubertal boys also have very small testis (less than 2 cm in length) compared to adult testis (4-5 cm in length). The cremasteric muscles surround the blood vessels going to the testicles and when they contract, they pull the testicles up into the groin (for instance, when cold, etc.). The cremasteric muscles are well developed in prepubertal boys and can easily pull up a small testicle into the groin. These characteristics may make prepubertal boys appear to have ascending testicles when in fact all they have is a retractile testicle. Retractile testicles do not require treatment.
Only an experienced examiner can distinguish between a retractile and an ascending testicle (retractile testicles can still be manipulated into the scrotum without tension, whereas the true AT testis cannot be manipulated down). Only birth medical records can distinguish an ascending from an undescended testicle.
Is there a difference between Undescended Testicles (UDT) and Ascending Testicles (AT)?
Yes. The health consequences of undescended testicles that I described above have been well studied. We know nothing about the health consequences of ascending testicles (Cancer? Infertility?).
There is one good study done in the Netherlands where patients with documented ascending testicles were followed without surgery until puberty. They found that in 75% of the cases, the testicles descended spontaneously (without surgery) by the time the boy reached puberty. (Sijstermans 2006, International Journal of Andrology).