Have Pediatric Questions? Ask a Pediatrician.
Hi there, you have very good questions regarding this; I hope I can help you out. First off, it is encouraging to hear that his pediatrician has felt them on his exams in the past. This is important- one thing you wouldn't want to miss here is what's called an undescended testicle. He most likely had what's called a hydrocele; this is where fluid collects in the layers of the testicle at birth, making them appear very large; this usually resolves on its own by 1 year.
Now, at this time, the fluid has resorbed, and the normal, smaller testes are left behind. Add this to the fact that toddlers have a strong cremasteric muscle (the muscle that pulls the testicles upwards) and the scrotum can appear flattened or "empty." The important thing that should be checked at his exams is that his testicles are still able to be felt, even if they are a little higher in the area above the scrotum. If he is running around and playing, doesn't seem bothered by it, and there isn't redness or swelling, then it sounds very appropriate. Just be sure to bring it up at his next visit so he can be rechecked. I hope this helps and I wish your daughter good luck with college! She should be praised for sticking with it!