What does ketones trace mean?

lab urinalysys says color yellow: refrence range apperance clear refrance clearleuk. esterase negative refrance range negative PH 6.0 5-8 protein negative referance range negative glucose negative referance range negative ketones negative Trace referance range negative. my general dr looked those over and said it is something to do with the kidney so he did ultrasounds but I was reading online and it says something about diabetic issue? now why would my dr say it was something else? he said it was very microscopic blood found in my urine and that it was kidney or uti issues?? anyone wanna inlighten me?