patient detals: Name - Aditya, 2year 3 months male Medical history: PUV with biletaral hydro uretero Nephrosys and bileteral vesico uretheric reflex (Grade v) PUV fulgarated at 40 days of age. Current Status: good Urine stream, No reflux seen in latest MCUG,and DRCG. latest GFR:57ml (last GFR=42ml 9months back).DMSA -left kindey- normal size with scar on both poles,right kidney - normal size with scar on upper pole laterally. Current problem: as part of uro dynamic study, the baby was catherized for 4hours ,day before yesterday. The urine routine examination report today revealed Pus cells= 12-14, but RBC = Nil, Epithelial cells = 0-1, Bacteria=Nil. in The same test done 3 days back , the count of pus cells was just 1-2. Please let me know the possible reason?