Acute tubular necrosis

A 45-year-old man is brought to the emergency department for evaluation following a motor vehicle accident. Trauma chest/abdomen/pelvis CT-imaging demonstrates multiple bilateral fractures, a right humeral shaft fracture, as well as splenic and liver lacerations with ongoing internal hemorrhage. The patient is resuscitated with type O negative blood and is taken to the operating room for repair of the aforementioned injuries. His condition remains stable postoperatively. Following surgery, his temperature is 38.0°C (100.4°F), pulse is 95/min, respirations are 20/min, and blood pressure is 115/70 mmHg. On his second day of hospitalization, his urine output decreases. Urine microscopy demonstrates granular casts and a calculated fractional excretion of sodium (FENa) of 3%. On the patient’s eighth day of hospitalization, a significant increase in urine output is noted. Serum creatinine charting is shown:

 
 

Laboratory value	Result
Urinalysis
	On admission	Day 2	Day 8
Creatinine	1.1 mg/dL	3.5 mg/dL	2.3 mg/dL

   In the coming days, this patient is at highest risk of developing which of the following findings?