title: Fractional excretion of sodium in hepatorenal syndrome: Clinical and pathological correlation.
abstract: OBJECTIVE
  To determine the accuracy of fractional excretion of sodium (FeNa) in the diagnosis of hepatorenal syndrome (HRS).
  
  
  METHODS
  Eighty-eight liver transplantation candidates with renal dysfunction and/or proteinuria were included in the study sample. The baseline characteristics of the patients were obtained. All the 88 patients underwent iothalamate glomerular filtration rate testing, 24-h urine collection for urinary sodium and protein excretions, random urine for sodium and creatinine testing, and percutaneous kidney biopsy. FeNa was calculated using the equation [(urine sodium × serum creatinine)/(serum sodium × urine creatinine)] × 100%. Diuretic use was recorded among the participants. Patients on renal replacement therapy were not included in the original sample.
  
  
  RESULTS
  Seventy-seven (87%) of the 88 patients had FeNa < 1%. FeNa < 1% was present in 10/10, 10/12, 11/13, 12/15 and 34/38 in patients with HRS, acute tubular necrosis, membranoproliferative glomerulonephritis, minimal histological findings (≤ 30%) and advanced (≥ 30%-40%) interstitial fibrosis and/or glomerulosclerosis, respectively (P= 0.4). FeNa < 1% was 100% sensitive and 14% specific in diagnosing HRS. Receiver operating characteristic curve confirmed the poor accuracy of FeNa < 1% in diagnosing HRS (area under the curve = 0.58,P= 0.47). Calculated positive predictive value and negative predictive value for FeNa < 1% in HRS diagnosis were 46% and 100%, respectively. When used as a continuous variable, FeNa did not correlate with kidney biopsy findings (P= 0.41).
  
  
  CONCLUSIONS
  FeNa < 1% was common in cirrhotic patients with renal dysfunction and it did not differentiate between HRS and other causes of renal pathologies. HRS diagnosis should be avoided in patients with FeNa > 1%.
authors.affiliation: Ali A Alsaad, Department of Internal Medicine, Mayo Clinic, Jacksonville, FL 32224, United States.
authors.forename: Ali A
authors.initials: AA
authors.lastname: Alsaad
authors.affiliation: Ali A Alsaad, Department of Internal Medicine, Mayo Clinic, Jacksonville, FL 32224, United States.
authors.forename: Hani M
authors.initials: HM
authors.lastname: Wadei
keywords: Accuracy; Fractional excretion of sodium; Hepatorenal syndrome; Liver transplantation; Renal dysfunction; Urinary sodium excretion