Undescended testis

What it is

An empty scrotum has four causes:

• Retractile testis: normally descended, retracted up when the child cries or is irritable, due to dartos muscle hyperactivity
• Ectopic testis, for example in the thigh
• Absent testis: agenesis, or a vanishing testis after intrauterine testicular torsion, where no testis is found but the vessels are present
• True undescended testis, which is either palpable or non palpable. A palpable undescended testis is inguinal, ectopic or retractile; a non palpable one is inguinal, ectopic, intra-abdominal or absent, and an absent testis is either agenesis or a vanishing testis

Undescended testis also sits in the differential diagnosis of groin swelling, with communicating hydrocele, cystic hydrocele, inguinal hernia and testicular torsion. Cryptorchidism by definition is a hidden testis: one that is not within the scrotum and does not descend spontaneously into the scrotum by four months of age, or corrected age in premature infants, and the cryptorchid testis may be absent or undescended. A true undescended testis stops short along its normal path of descent and may remain in the abdominal cavity, or be palpable in the inguinal canal (intracanalicular) or just outside the external ring (suprascrotal). An absent testis is agenesis, or atrophy secondary to intrauterine vascular compromise such as prenatal testicular torsion, known as the vanishing testis syndrome or testicular regression syndrome; bilaterally absent testes are anorchia. A retractile testis is pulled into a suprascrotal position by the cremasteric reflex and can be brought into a dependent scrotal position, where it stays if the cremasteric reflex is overcome, for example by holding the testis in the scrotum for at least one minute. An ascending testis was in a scrotal position in early childhood and then ascends, an acquired undescended testis. In development the testes appear on the urogenital ridge in the second month, the coelomic cavity evaginates into the scrotal swelling to form the processus vaginalis in the middle of the third month, the testes begin their descent guided by the gubernaculum in the seventh month, and the processus vaginalis obliterates spontaneously shortly after birth.