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A 72-year-old man, recently treated for resistant Escherichia coli urosepsis, is sent to the emergency department from his nursing home because of new left-sided hemiparesis. He has a past history of chronic kidney disease (CKD), hypertension, and osteoarthritis. Medications include lisinopril 20 mg daily and naproxen 400 mg twice a day. On physical examination, he has a low-grade fever of 38°C (100.4°F), his initial blood pressure is 130/66 mm Hg, and his heart rate is 88 bpm. He is breathing at 28 breaths/min, and his hemoglobin oxygen saturation by pulse oximetry is 89% on supplemental oxygen by nasal cannula. He has a flaccid left hemiparesis and is stuporous.

He undergoes a computed tomogram (CT) of the head, which shows no hemorrhage. He has a CT angiogram of the chest, which shows no evidence of pulmonary embolism. His temperature rises quickly to 38.9°C (102°F), the blood pressure falls to 78/50 mm Hg, and the heart rate rises to 120 bpm. His initial white blood cell count is 29.9 with 44% bands, and a urine analysis shows pyuria and bacteriuria. Treatment is initiated with vancomycin, gentamicin, and cefepime. Intravenous normal saline is given by rapid infusion, according to the sepsis protocol. The patient is intubated and placed on mechanical ventilation. The serum creatinine, 1.6 mg/dL on arrival, increases to 2.0 mg/dL by the following day, and the blood urea nitrogen (BUN) has risen from 22 mg/dL to 36 mg/dL. Urine output has been about 20 mL/h for the past 8 hours.


The patient's daughter, a registered nurse, is in the room when you make rounds. She is aware of his history of chronic kidney disease, and wants to know if he is in “kidney failure.” What do you tell her?


Although acute renal failure (ARF) is conceptually simple to characterize as “an abrupt decrease in renal function,” a commonly accepted definition of ARF emerged only very recently.


An international group of experts convened in 2002 to develop a consensus definition of ARF in order to advance research in the field. They devised a staging classification for ARF—using changes in serum creatinine concentration and hourly urine output—and gave it the acronym RIFLE (Risk, Injury, Failure, Loss, and End-Stage) (Table 41-1).1 Many investigators have since validated that classification scheme in various clinical settings, and a recent meta-analysis showed a graded impact on mortality by RIFLE stage.2

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Table 41-1.Comparison of RIFLE and AKIN Criteria

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