Change in Toddler daughters urine

I have started to potty train my daughter from past 1 month and i observed that when my daughter pees in the toilet bowl (adult toilet pot)..there are some bubbles in her urine and most of them disappear and some slight foam stays back until i flush .
I got her urine tests to rule out any infections or other things ...Dr said me that every body is different and should not worry ...But i am unable to come out of this stress...not sure why this has affected me so much ...i would like to request if any parents here can help observe the toilet bowl after their kids pee and let me know if this kind of slight foam or bubbles is normal ..that if some bubbles dont dissapear and stay for few seconds ...
Basically i am looking for any mommies who had noticed teh same slight foamy urine with their toddler daughters ..