RIFLE Renal Failure Classifications

Acute renal failure (ARF) is a serious complication following cardiac surgery, in which blood pressure drops and can often lead to death. The RIFLE acronym classifies the increasing severity of ARF and two possible outcomes. Specifically, R, I and F denote risk, injury and failure, while L and E represent loss and end-stage kidney disease.

RIFLE Renal Classification System

• The RIFLE renal classification system was first published in 2004 and aimed to describe the severity of ARF; however, a universal definition is lacking. Each classification is interpreted differently, which may be dependent upon the criteria used by medical personnel in diagnosing the patient and the perceived outcome of treatments. Nonetheless, several groups are currently working to formulate standard definitions for the classification and diagnosis of ARF using the RIFLE system.

Morbidity and Mortality of Patients with ARF

• A study published in the October 2006 issue of "Critical Care" evaluated more than 5,000 patients who were admitted to intensive care units over a one-year period. The researchers found that upon admission, 12 percent were classified as "R" or "risk," 27 percent as "I" or "injury" and 28 percent as "F" or "failure." Of these patients, a mortality of 8.8 percent occurred in the R-class, 11.4 percent in the I-class and 26.3 percent in the F-class. The authors concluded that the RIFLE classification system was efficient in predicting the morbidity and mortality of patients with ARF.

Alternative RIFLE Criteria

• According to an article appearing in the July 2009 issue of "The American Journal of Surgery," since 2004, more than 30 clinical studies have applied the RIFLE classification somewhat differently. To reach a consensus, the author suggests using risk ratios (RRs) based on serum creatinine levels and reduction in urine output to estimate the morbidity and mortality of patients. In this classification, an RR value of 2.4 would indicate risk, 4.15 for injury and 6.37 for failure.

Comparison of RIFLE to Other Parameters

• Researchers at the Helsinki (Finland) University Hospital analyzed more than 813 patients undergoing cardiac surgery and classified them into three groups based on the RIFLE system. Their findings, published in the July 2005 issue of the "Annals of Thoracic Surgery," showed a 90-day mortality of 8, 21 and 32 percent for patients in the R-, I- and F-classes, respectively. The authors concluded that the RIFLE criteria was more accurate than the measurement of plasma creatinine levels or the rate of urine production.