ACR Codes: 8.1
Anatomy: The undescended testicle is often smaller than the normal descended testicle. In a small number, testicular agenesis is present.
The most common ectopic site is the inguinal canal. However, undescended testicles may be located in the abdomen, pelvis, or high in the scrotum.
Incidence: Up to 20% of premature and preterm males are born with undescended testes. In most, normal descent occurs within the first few weeks or months of life. In less than 3%, persistent lack of descent occurs. The condition is more commonly unilateral.
Associated features: Other urogenital anomalies such as renal agenesis or ectopia, prune belly syndrome, and epispadias.
Etiology: Failure to descend may be due to hormonal dysfunction or mechanical obstruction.
The testis may be abnormal resulting in a lack of testosterone production which is necessary to stimulate normal descent.
There may be abnormal production of adenohypophyseal gonadotrophin which controls fetal production of testosterone. Or gonadotrophin secretion may be normal, but the normal response of the gubernaculum in guiding the testes into the scrotum is lacking.
If hormonal secretion is normal, mechanical obstruction may be responsible for arrested descent. This may be due to obstruction of the process vaginales or to the formation of a septum at the scrotal neck.
Complications: Malignant change - incidence is high... 2:100,000 in the normal male population; 10:100,000 in inguinally placed testes; and higher still in abdominal or pelvic testes.
Other complications include sterility, testicular torsion, and vulnerability to accidental injury.
Ultrasound: useful for detection of inguinal testes, useless for abdominal or pelvic testes, unless malingnant change has produced a mass. An asymmetric mass in the inguinal region with the echogenic characteristics of normal testes is seen. The mediastinum testes must be identified. An atrophic testis may be difficult to identify since its echogenicity is variable, and the epididymis may not be seen. Malignant change will be seen as a mass of indefinable echogenicity.
Rarely, the pars infravaginales gubernaculi may be confused with an undescended testis in the inguinal canal whereas in fact the testis is higher up in the pelvis. However, this structure does not show the characteristic mediastinum testes.
CT: Asymmetry with a small mass on the affected side is seen. An asymmetric mass larger than the expected testicular size should raise the possibility of malignant change.
CT is accurate in detecting undescended testes in any position adjacent to the inguinal canal. Oral and transrectal contrast is necessary to delineate bowel. IV contrast is useful to increase the density of the undescended testicle. Tomographic cuts are obtained every 5mm from the scrotum until the iliac crests.
Spermatic venography: useful to localize non-palpable (abdominal or pelvic) testes - the pampiniform plexus is visualized as a collection of linear coalescing vessels. The epidymal veins are distinguished by being much lower in the abdomen or pelvis since the vas deferens and epididymis descend ahead of the testes. The pampiniform plexus is demonstrated 80% of the time on the left, but only 60% on the right. This is because the right spermatic vein is more difficult to catheterize and has valves.
Agenesis of the testis is diagnosed when no pampiniform plexus is seen and the spermatic vein terminates in a blind end.
Herniography: Injection of dilute water-soluble contrast (10-60 ml depending on body weight) into the peritoneal cavity. Radiographs are taken with the patient prone and head of the table elevated 35 degrees. 80% of boys with undescended testis show a patent processus vaginalis or hernia sac, with a filling defect in the contrast-filled hernia sac in the inguinal canal representing the undescended testicle.
Reference(s): Dunnick, N. Reed, Textbook of Uroradiology, Williams & Wilkins, Baltimore, MD, 1991
Use this for Comments and SuggestionsMedPix® is sponsored by the Department of Radiology and Radiological Sciences, USUHS, Bethesda, MD We do not accept paid advertisements.
Disease Topic 3752 
Click Here for MedPix®-2
for Comments and Suggestions
