Ultrasound is Not Useful To Diagnose Undescended Testis

Scrotal ultrasounds are not clinically useful in the management of the undescended testis. This is not just my rogue opinion but the consensus of the American Medical Association and the American Urologic Association.

Scrotal ultrasounds cannot distinguish a retractile from an undescended testis

The ultrasound can only show where the testis is at the time of the test; it cannot distinguish a retractile testis from an undescended testis since both can be in the groin at any given time. A retractile testis is one that is extra-scrotal at the time of the exam but that can be manipulated into the scrotum, staying there for a few moments under no tension. The undescended testis cannot be manipulated into the scrotum without tension or without it immediately retracting back into the groin.  Only a physical exam can distinguish a retractile from an undescended testis.

Scrotal/groin ultrasounds are not clinically helpful for non-palpable testis

Many non-palpable testes are indeed palpable when examined with proper technique  — patient in frog leg position, KY jelly using 4 fingers starting at the internal ring moving down towards the external ring and then ending in the scrotum.

Pediatric urologists recommend surgery for the true non-palpable testis regardless of any ultrasound, CT, MRI or nuclear medicine scan finding. Surgery reveals a nubbin or intraabdominal testis in 60 and 40% of cases respectively.  Surgeons bring Intraabdominal testis down into the scrotum and remove testicular nubbins due to their malignant potential.

For the sake of argument, one could question the need to remove testicular nubbins since I know of no case reports confirming their malignant potential. Imaging diagnosing a nubbin could allow the primary care doctor to avoid referral. However, a testicular nubbin would have to be diagnosed with a high degree of certainty to avoid leaving a viable intraabdominal testis behind. Even MRI’s can miss 10% of intra-abdominal testis, and therein lies the problem. Even leaving 1/100 intraabdominal testis behind would be too much.

Rare cases where a scrotal ultrasound can be clinically useful

There are 2 situations where a scrotal ultrasound could be useful for some surgeons (not for me):

  1. In cases of the unilateral non-palpable testis, if the surgeon wants to decide between a scrotal exploration or laparoscopy. Scrotal ultrasounds are good at visualizing non-palpable testis in the inguinal canal. That finding could allow a surgeon to chose inguinal exploration over laparoscopic exploration.
  2. Very obese older boys where the testis is non-palpable, also in the hopes of avoiding exploratory laparoscopy if the testis is visible in the groin.


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