Q. A 35-year-old male patient was admitted last night with symptoms of nausea, vomiting, and abdominal pain. The patient has a history of diabetes mellitus, which is poorly controlled. A CT scan of the patient’s abdomen and pelvis (with and without contrast) was performed on admission. This morning, the patient is experiencing more severe nausea and vomiting, and his urine output is less than 0.5 mL/kg/h since admission. On physical examination, the patient's skin is warm and moist, and he is afebrile. His blood pressure is 110/80 mm Hg, heart rate 90/min, respiratory rate 20/min, and oxygen saturation is 98 percent on room air. Chest auscultation demonstrates a normal cardiopulmonary examination. Assessment of his abdomen reveals diffuse abdominal tenderness, with no ascites or palpable masses detected. You review the following blood work and chemistry values before proceeding. Laboratory Results: Serum creatinine: 4.5 mg/dL Blood urea nitrogen: 60 mg/dL Urine specific gravity: 1.010 Urine osmolality: 300 mOsmol/kg The presence of which of the following would be most suggestive of acute tubular necrosis as the cause of this patient’s symptoms?