Comparison of computed tomography with high-resolution real-time ultrasound in the localization of the impalpable undescended testis.

Localization of an undescended testis was attempted in 23 instances in 20 patients using both computed tomography (CT) and high-resolution real-time ultrasonography. The testis was identified and correctly localized 16 times by CT and 15 times by ultrasound. There was one false-negative diagnosis by CT and two by ultrasound. False-positive diagnoses were not made with either modality in the six cases in which the testis was not found during exploratory surgery. CT showed 94% sensitivity, 100% specificity, and 96% accuracy; ultrasound resulted in 88% sensitivity, 100% specificity, and 91% accuracy. The authors recommend high-resolution real-time ultrasound as the modality of choice for this procedure because it is simple, accurate, and avoids the use of ionizing radiation. CT may be used when ultrasound findings are negative or equivocal. Angiography should rarely be required.