Chapter 91

Acute renal failure (ARF) is the deterioration of renal function over hours or days resulting in the accumulation of toxic wastes and the loss of internal homeostasis. The Risk, Injury, Failure, Loss, and End-Stage Renal Disease (RIFLE) classification established three grades of renal compromise of increasing severity (Table 91-1).1

Table 91-1 Risk, Injury, Failure, Loss, and End-Stage Renal Disease (RIFLE) Classification of Acute Renal Failure1

The diagnosis of ARF is complicated by the fact that acute declines in renal function, especially early in their course, are asymptomatic. The first step is to differentiate the cause of the renal insult as prerenal, intrinsic, or postrenal. Prerenal causes involve decreased perfusion of a normal kidney, intrinsic causes entail pathologic changes within the kidney itself, and postrenal causes involve obstruction to the urinary outflow tract. The underlying primary disease process that triggered renal failure usually dominates the clinical picture. The ED goals are to identify patients at risk for ARF and those with asymptomatic disease, and to correct metabolic effects of renal failure, decrease ongoing renal injury, and prevent iatrogenic injury.

The distinction between community- and hospital-acquired ARF is important for the differential diagnosis, treatment, and eventual outcome (Table 91-2). The annual incidence of community-acquired ARF is approximately 100 per 1 million population2 and is diagnosed in only 1% of hospital admissions at presentation.3 When the RIFLE criteria were used, hospital-acquired ARF was found to manifest as renal risk in 9%, renal injury in 5%, and renal failure in 4% of admissions in a large, single-center study.4 Among admissions to critical care units, approximately 17%, 12%, and 7% were found to have risk, injury, and failure, respectively, according to the RIFLE criteria.5,6 This high incidence of hospital-acquired ARF is multifactorial. Factors include an aging population at increased risk of ARF, the high prevalence of nephrotoxic exposures possible in a hospital setting, and increasing severity of illness in hospitalized patients.

Table 91-2 Causes of Community-Acquired and Hospital-Acquired Acute Renal Failure

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