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 110-1Criteria for Diagnosis of Acute Kidney Injury |Favorite Table|Download (.pdf) TABLE 110-1 Criteria for Diagnosis of Acute Kidney Injury
| ||Creatinine/GFR Criteria ||Urine Output Criteria |
|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 |
|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 |
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 so an early normal value may not reflect ongoing and potentially severe injury. In children, it is even more difficult as often the baseline creatinine level for a patient is not known and a rise from the baseline may still fall within the ...