• Urine Sodium NaU mEq per L Urine Creatinine CrU mg per dL Plasma Creatinine CrP mg per dL Calculate

• Renal Failure Index Explanation and Clinical Context
  Renal Failure Index is a calculated parameter used to differentiate prerenal azotemia from intrinsic renal tubular injury. It incorporates urine sodium urine creatinine and plasma creatinine into a single ratio that reflects tubular sodium handling. A low value reflects preserved tubular sodium conservation which often indicates prerenal physiology. A higher value reflects impaired tubular reabsorption which suggests intrinsic renal damage most commonly acute tubular injury.
  
  Normal Value
  An index less than one indicates prerenal origin where renal perfusion is reduced but tubular function is intact. An index greater than one supports intrinsic renal injury where tubular sodium reabsorption becomes impaired.
  
  Clinical Significance
  This index assists clinicians in early evaluation of acute kidney dysfunction. It helps determine the appropriate management strategy by distinguishing disorders of perfusion from parenchymal injury. Accurate classification improves treatment selection and prevents further renal deterioration.
  
  Clinical Interpretation Summary
  A value less than one suggests a prerenal state with intact tubular sodium retention. A value greater than one suggests intrinsic tubular damage most frequently associated with acute tubular injury due to ischemia or nephrotoxins. Interpretation should always integrate clinical presentation volume status and laboratory findings.
  
  Reference
  Espinel CH. The FeNa test usefulness and limitations in the differential diagnosis of acute renal failure. Nephron. 1976 17 172 to 178.
  

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