A 7-year-old boy is brought to the physician because of a 4-day history of diarrhea and vomiting. He has not voided during the past 24 hours. Examination shows dry mucous membranes and poor skin turgor. Which of the following is most likely to be seen in this patient?
2+ blood on dipstick with 0-1 RBCs/hpf on light microscopy
Fractional excretion of sodium of 0.5%
Granular casts
Urine osmolality of 280 mOsmol/kg
Urine specific gravity of 1.012
