Testes are referred to as undescended (or cryptorchid) if they are absent from the scrotum. This is usually picked up in children at routine health checks. It is very common in premature babies (up to 30%) and found in about 3% of full term male infants. Only about 1% of boys at the age of 1 year still have this problem and it is unlikely to improve after 1 year. Rarely descended testes can disappear from the scrotum.
Testes normally develop inside the body and descend into the scrotum, where the reduced temperature allows them to work better. Testes that fail to decend have a slightly increased risk of testicular cancer and if they are left undescended (especially past puberty) are unlikely to make sperm (for fertility). If a testis is undescended several things might have happenend to it:
-it may be trapped inside the abdomen (see picture taken at laparoscopy showing a testis inside the abdomen very close to the groin). If this is detected in a child it may be possible to bring it down into the scrotum, but if this is detected in an adult it is probably better to surgically remove it (click to view surgical video).
-it may be trapped in the groin or thigh. If this is the case, it is usually possible to surgically relocate it to the scrotum (orchiopexy) in a child, although in an adult it may be better to remove it; possibly replacing it with an artificial testicle. An orchidopexy operation involves an operation under general anaesthetic, with a cut in the groin and often a second cut in the scrotum. There are small risks of bruising, bleeding, infection, damage to the testis or very rare risks associated with any operation under general anaesthetic such as heart, lung or thrombosis problems.
-it may have not formed properly and be very small. This type of tissue should be removed as it still has a cancer risk.
-it may have become damaged and disappeared. This condition is not really an undescended testis but might need an operation to diagnose.
It is important to diganose why a testis is missing from the scrotum so that it can be either brought down into the scrotum as soon as possible (probably best at or before 1 year old for future fertility) or removed to avoid the risk of cancer. The later the time a testis is relocated into the scrotum the lower the chance of fertility from that testis. All undescended testes (even if surgically brought down into the scrotum) have a cancer risk unless they are surgically removed; especially those within the abdomen and those that have failed to develop properly (but not those that have been damaged and disappeared).
It might be possible to feel an undescended testis or locate it by ultrasound scan or MRI. An operation to look inside the abdomen with a camera (laparoscopy) can show whether the testis is inside the abdomen (see above) or has descended into the groin (see adjacent picture, showing the vessels that lead to the testis going to the groin with no visible testis inside the abdomen). If the vessels lead to the groin then even if the scans show no testis in the groin it is usually worth an operation to check that there are no remnant of the testis that should be removed, to avoid the risk of cancer.