In the early 1980s, prenatal ultrasound imaging opened the curtains to a “real-time” view of fetal anatomy. What we saw helped limit invasive diagnosis and therapy to those that benefited our unborn patient, and taught us that patiently waiting until after delivery was often the best approach to abnormalities detected in the womb. In other words, wanting to know was no longer a good reason for pursuing an immediate answer; needing to know, to benefit the child, was the rule to follow.

So, let’s skip over 40 years of “boring” fetal diagnostics, genetic testing, treatment, surgeries, and other distractions and talk about the great mystery on everyone’s mind, the hunt for the impalpable testicle—or as I call it, “following the bouncing ball”.

Every fetal sonographer knows what a testicle nestled in the scrotum looks like and will often be required to quickly gloss over the classic image in order to avoid the unwelcome or undesired “reveal”. As depicted in the diagram below, imaging after 20 weeks may show the scrotum (B) and after 30 weeks (C) may show “ball in sac” if the rest of the child behaves. If, however, the testicle(s) are not cooperative, nobody panics.

But after birth, if one or both testicles fail to stare the waiting observer in the eye, or happily make themselves easily ballotable in their pocket, the alarms go off and rational processes falter. In this vacuum of clinical reason, the reflex order for an ultrasound (US) emerges and sadly obscures best care of both the child and parents. Why should you wait to order an US? Because I am a pediatric Urologist and I said so! If that answer doesn’t suffice, as it never has for me at home or office, let me try and explain.

Case 1

Both testicles are absent to examination at birth. Well, if a newborn of male appearance and yet unknown genotype has no testicles, that neonate is a girl until proven otherwise. Genetic testing will answer that and other potential questions of chromosomal gender.

The lone cry in the wilderness that ultrasound can “find” nonpalpable testes, ignores the literature that shows that in an examination, a specialist will feel the previously un-felt testicle in over 80% of children, which is equivalent to US success. Add to that the false-positive rate of 15% (generous here) where an immobile abdominal or clinically absent gonad is “found” in the groin on US and we are rapidly approaching the poster-child for unwarranted examinations. I do not deny the HUGE contribution of US to the work-up of ambiguous genitalia and intersex conditions, supplanting fluoroscopy and even MRI in many centers, but please do not confuse garden-variety “lost balls” with these more complex issues.

Case 2

The infant or child has one or no balls in their pocket on subsequent examination after birth. Referral to a specialist often comes after US, MRI, and even CT scans seeking to see “where” the ball has strayed along its path to the scrotum. MR and CT for this concern are unjustified as a result of their expense and risk exposure, so I will speak of them no further.

If we go back to our rule that imaging is done to help the child or parents, how does the pre-specialty referral US play out? If the US finds a testis, I would have found it anyway, but the US will not define whether it is retractile (normal with a reflex requiring observation, not surgery), or truly undescended, where surgery is warranted after 6 months of age.

If US fails to find a testicle, I will need to do surgery for certainty (US false negatives on intrabdominal gonad are 10%—again generous) as testicular cancer is possible in undescended testes at 5 times the rate of the general population and direct surgical inspection is as near to 100% certainty of whether a testicle exists or not, as one can get.

So, tell me, where’s the harm in noninvasive, nonpainful, nonionizing, inexpensive imaging. Well? I’m waiting. Never mind. Let me tell you.

Imagine you are a parent. Testicles are absent on US, where does your mind go? Testicles are in the inguinal canal, where does your mind go? Now remember, not because I say so; not because I am some gifted guy; but because of my training and experience, I eliminate the worry after 60 seconds in the office and reverse the concerns set in motion in over 90% of visits after imaging. I would say that’s a lot of “Google-worry-stress time” avoided, so, it is therefore worth foregoing US before the specialist exam.

Finally, in the worst-case scenario, US finds testicles, and, as a result, the primary care physician tells the parents it’s OK, and an infant is denied time-sensitive surgery to maximize testicular function and possibly decrease cancer risk simply because the “presence” was interpreted as “normal”. The US window to gonadal and urogenital anatomy is evolving and brilliant, with contrast-enhanced ultrasound (CEUS), molecular imaging, and elastography promising even more advances. Our common goal is to have our tools create better outcomes and minimize the potential for harm.

Robert Mevorach, MD, is Chief of Pediatric Urology at the University of South Alabama, Mobile, and is Secretary of the American Institute of Ultrasound in Medicine (AIUM) Urology Community (2021–2023).

Interested in learning more about urologic ultrasound? Check out the following resources from the AIUM:

• AIUM Practice Guideline for the Performance of an Ultrasound Examination in the Practice of Urology
• AIUM Accreditation in Urologic Ultrasound
• Article in the Journal of Ultrasound in Medicine (JUM): Epididymal Appearance in Congenital Absence of Vas Deferens