How To Treat Cyst And Pelviectasis Of Both Kidneys?

I recently was in the ER with severe lower back pain and also symptoms of a UTI. UA showed UTI and renal ulrasound showed a cyst on one of.my kidneys and both kidneys were "full" pelviectasis. I was put on Keflex, Pyridium, and Motrin. Could this have been the start of ?pyelonephritis. Do you recommend a follow up ultrasound or CAT scan? Thank you!