Causes
This can be due to:
- One testicle not descending into the scrotum during normal embryonic or fetal development (3–4% of 'normal' live births), also known as: undescended testis or cryptorchidism. In this case the testis is within the abdominal cavity, somewhere along the normal route of descent — most commonly, within the inguinal canal. Such a testis has an increased risk of malignancy.
- One testicle may disappear during development (the so-called vanishing testis) due to some intrauterine insult. This is thought to be most likely vascular, such as testicular torsion.
- One testicle being surgically removed through orchidectomy.
- One testicle may be injured.
Read more about this topic: Monorchism