A 3 years old girl is having high fever for last 10 days with h/o nausea. There is no organomegaly. Her CBC, mp card., typhidot, urine are wnl.

LFT is nad, her blood urea is raised 42 mg% but creatinine is 0.7. urine NAD,Accepting orally. What could be the cause of raisd blood urea?