High BUN and Creatinine Levels

My 10.5 month old Germans Shepherd Rottweiler puppy went in for her preoperative bloodwork on Sunday prior to her spay that should have been today. My vet called and said her BUN was high at 40 and creatinine was high at 1.9. So they redid the blood work and it came back still high at 49 and 2.0. They did a urinalysis to see if she had a kidney infection but that came back clear. Now we are waiting on ultrasound scheduled for Friday. She has had two previous UTI at 9 weeks and 6 months old. She does not act sick. She is an energetic and happy pup. Zero signs of any kidney problems other than this weird blood work. She had her first heat in April and that went off with no issues. Has anyone experienced this before? Is it really possible she has a kidney issue or could it just be some weird anomaly? I’m so scared because I love her so much and she is literally my world. I’m just so confused as to how all of this is happening and she is so healthy otherwise.