High resolution real-time ultrasonography in the localization of the undescended testis.

In a prospective study ultrasound was compared to palpation in 41 instances in which a testis was not present in the scrotum. A testis was palpable in 20 of these instances and not palpated in 21. Of 20 palpable undescended testes 14 (70 per cent) were identified by ultrasound. Of the 21 instances in which a testis was not palpated 3 intra-abdominal and 5 inguinal testes were identified at exploration. One of these organs (an inguinal testis) was identified by ultrasound. Two false positive sonograms in which a gubernacular structure mimicked an undescended testis occurred. Sonography cannot satisfactorily stand alone as a screening modality in the management of the undescended testis.