In most children with this health issue, it Is not known why the testicles fail to drop. It may be because the testicles are not normal to start with. In other cases, there is a mechanical problem. The testicles drop but miss the scrotum, ending up next to the scrotum instead. These are called "ectopic testicles." Or it may be that the baby's hormones can't stimulate the testicles normally. No studies have shown that the problem is caused by something the mother did or ate during pregnancy.

Sometimes the testicles drop but don't attach in the scrotum. Then, when the boy grows, it becomes clear that the testicles are not attached. About 1 of every 5 cases of undescended testicles are found once the boy is no longer a baby. For this reason, all boys should have the location of their testicles checked during each annual physical exam.

A testicle that can't be felt in a physical exam is called "nonpalpable." Nonpalpable testicles may be in the abdomen (undescended), absent, or very small ("atrophic"). It is important to find out whether there is a testicle that has not dropped. An undescended testicle left inside the abdomen could form a tumor later in life. Such a tumor might not be noticed until it becomes quite large or causes symptoms. Unfortunately, there' is no test, such as an ultrasound, that can definitively show whether a testicle is there.

there are three test by which undescended testicle can be diagnose

1. Blind-ending testicular blood vessels – proving there is no testicle
2. Vessels leaving the abdomen – proving there's no testicle in the abdomen
3. A testicle in the abdomen. If a testicle is found, it is brought down into the scrotum or removed, based on its condition.