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Chapter 110: Acute Renal Failure

Lindsay Chase

BACKGROUND

Acute renal failure (ARF) is the sudden decline in renal function resulting in increase in metabolic waste products in the blood and dysregulation of extracellular electrolytes and volumes. This is usually marked by elevations in serum creatinine and increased, normal, or decreased urine output. The terms polyuria, oliguria, and anuria sometimes are used to characterize the type of failure. The term acute kidney injury (AKI) has replaced acute renal failure in the literature in an effort to better characterize the spectrum of impairment in renal function before complete failure.

In order to better characterize the spectrum of acute kidney injury or renal failure, two classification systems were developed to standardize assessment of acute kidney injury for clinical and research purposes. Both use creatinine and urine output criteria to stratify renal injury (Table 110-1). The AKIN criteria were developed by the Acute Kidney Injury Network and consist of three stages. AKIN classification has not been validated in children and does not capture milder cases of acute renal injury.1 The other system, called pRIFLE, was developed by modifying existing adult RIFLE criteria. pRIFLE consists of categories of increasing severity: Risk, Injury, Failure, Loss, and End Stage Renal Disease.2,3

TABLE 110-1*Criteria for Diagnosis of Acute Kidney Injury
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TABLE 110-1 Criteria for Diagnosis of Acute Kidney Injury
Creatinine/GFR Criteria Urine Output Criteria
AKIN
Stage 1 Cr increase >0.3 mg/dL or 1.5 to 2 times baseline <0.5 mL/kg/hour for 6 hours
Stage 2 Cr increase 2 to 3 times baseline <0.5 mL/kg/hour for 12 hours
Stage 3 Cr increase 3 times baseline <0.3 mL/kg/hour for 24 hours or anuria for 12 hours
RIFLE
Risk eCrCl* decrease by >25% <0.5 mL/kg/hour for 8 hours
Injury eCrCl decrease by >50% <0.5 mL/kg/hour for 16 hours
Failure eCrCl decrease by >75% or eCrCl <35 mL/min per 1.73m2 <0.3 mL/kg/hour for 24 hours or anuria for 12 hours
Loss Persistent failure >4 weeks Need for RRT
End Stage Persistent failure >3 months Need for RRT

Sources: Data from Mehta RL, Kellum JA, Shah SV, et al. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care. 2007;11:R31; Reproduced with permission from Akcan-Arikan A, Zappitelli M, Loftis LL, et al. Modified RIFLE criteria in critically ill children with acute kidney injury. Kidney Int. 2007;71:1028-1035. © 2007 International Society of Nephrology.

Cr, serum creatinine; GFR, glomerular filtration rate; eCrCL, estimated creatinine clearance; RRT, renal replacement therapy.

*

Estimated using the Schwartz formula. If no baseline then use 100 mL/min per 1.73m2 for baseline value.

Traditionally, elevated serum creatinine is used to make the diagnosis of renal failure. This is problematic for several reasons. Serum creatinine is an isolated measurement and does not accurately reflect ongoing changes in renal function. Creatinine takes time to accumulate ...

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