Baby with UTI

Hi, all. FTM here and freaking out a bit. Last week after spiking a fever of almost 105, I took my 12 week old daughter to the doctor where we discovered she had a UTI. Her pediatrician said UTIs are uncommon in children under two and ordered an ultrasound of kidneys and bladder to check for any structural problems. Should I be concerned? After 24 hours on the antibiotics, she bounced back and is back to normal. Anyone else been through this with a child under 2?