Retractile and Ascending Testes

A retractile testis is a normally developed testis that can be brought into a stable position at the bottom of the scrotum during physical examination, but can also move into the groin by the cremasteric reflex.

As many as 35% of children's testes are thought to be retractile, with a peak incidence between the ages of 5 and 6 years. A retractile testis can transiently lie between the inguinal canal and scrotum and appear as a lump on physical examination and on imaging. Retractile testes usually descend completely by puberty, and there are no implications for fertility.

An ascending testis, also known as an ascended testis, ascensus testis, secondary cryptorchidism, and acquired cryptorchidism, is one that had previously been in the scrotum, but which can now be classified as undescended. Ascending testes are more frequently seen on the left, and many patients have associated disorders.

The majority of patients with an ascending testis can be shown to have had a history of a retractile testis and about 1/3 of boys with retractile testes go on to have ascending testes. The high position of the testis causes the same damage as seen with congenitally undescended testes and can lead to adverse effects on germ cell development and fertility.

Physical examination criteria have been proposed to differentiate an incompletely descended testis from a retractile testis on a single examination:

• An incompletely descended testis is smaller than the contralateral testis
• The incompletely descended testis rapidly retracts out of the scrotum when it is released.
• Pain is elicited when the incompletely descended testis is manipulated into the scrotum.

Of these, only the first can be applied to imaging, and may be helpful in differentiating an incompletely descended testis from a retractile or ascending testis on a single imaging study. Physical examination is then needed to differentiate a retractile testis from an ascending testis.

The images above are from a 7-year-old boy who in 2010 had descended testes bilaterally. His most recent MRI (in 2011) reveals that the left testis (pink arrow) has moved up into the inguinal canal. Note that the testes are about the same size.

References

• Guven A, Kogan BA. Undescended testis in older boys: further evidence that ascending testes are common. J Pediatr Surg. 2008 Sep;43(9):1700-4.
• Kidney DD, Cohen AJ, Seville P. Retractile testis: an incidental CT finding in trauma patients. AJR Am J Roentgenol. 1997 May;168(5):1233-4.
• Shadbolt CL, Heinze SB, Dietrich RB. Imaging of groin masses: inguinal anatomy and pathologic conditions revisited. Radiographics. 2001 Oct;21 Spec No:S261-71.
• Shapiro E. The risk of retractile testes becoming ascending testes. Rev Urol. 2006 Fall;8(4):231-2.
• Yoshida T, Ohno K, Morotomi Y, Nakamura T, Azuma T, Yamada H, Hayashi H, Suehiro S. Clinical and pathological features of ascending testis. Osaka City Med J. 2009 Dec;55(2):81-7.