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 may have been surgically removed through orchiectomy. * One testicle may be injured.
Monorchism
Clonorchiasis
Opisthorchiasis
Taeniasis
Trichiasis
Trichuriasis
Cyclosporiasis
Thelaziasis