Enfamil AR

So my LO was having vomiting and spit up issues majorly!  Her Dr finally decided to switch her formula from Enfamil Newborn to Enfamil AR!  I have already noticed a huge difference in 1 day no spit up or vomit at all!  Her Dr wanted me to take her for a ultrasound for the muscle in her stomach Pyloric Stenosis but ok wondering if that's even needed because the problem has stopped!  My insurance will not cover it and I'm ok with that just wondering if it's needed since it seems the problem is no longer there