Case Control Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Hepatol. Dec 8, 2016; 8(34): 1497-1501
Published online Dec 8, 2016. doi: 10.4254/wjh.v8.i34.1497
Fractional excretion of sodium in hepatorenal syndrome: Clinical and pathological correlation
Ali A Alsaad, Hani M Wadei
Ali A Alsaad, Department of Internal Medicine, Mayo Clinic, Jacksonville, FL 32224, United States
Hani M Wadei, Department of Transplant, Mayo Clinic, Jacksonville, FL 32224, United States
Author contributions: Alsaad AA and Wadei HM contributed to the design of the study, acquisition, analysis and interpretation of the data, writing and reviewing the manuscript, and approved the final version of the manuscript for submission.
Institutional review board statement: We obtained approval from the Mayo Clinic Institutional Review Board (IRB) to conduct this study.
Informed consent statement: Exempted, demonstrated as minimal risk study.
Conflict-of-interest statement: No potential conflicts of interest relevant to this article were reported.
Data sharing statement: Consent was not obtained but the presented data are anonymized and risk of identification is low.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Hani M Wadei, MD, Department of Transplant, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, United States. wadei.hani@mayo.edu
Telephone: +1-904-9536259 Fax: +1-904-9533220
Received: July 1, 2016
Peer-review started: July 4, 2016
First decision: August 10, 2016
Revised: September 2, 2016
Accepted: October 22, 2016
Article in press: October 24, 2016
Published online: December 8, 2016
Processing time: 157 Days and 9.3 Hours
Abstract
AIM

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).

CONCLUSION

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%.

Keywords: Fractional excretion of sodium; Hepatorenal syndrome; Renal dysfunction; Liver transplantation; Urinary sodium excretion; Accuracy

Core tip: In this retrospective analysis of patients with advanced end-stage liver disease, we describe three main concepts. First, our data indicates that fractional excretion of sodium (FeNa) < 1% is a common finding in this group of patients irrespective of the etiology of their renal dysfunction. Second, our study suggests that FeNa < 1% cannot differentiate hepatorenal syndrome (HRS) from other causes of renal pathology. And third, we statistically measured the performance of FeNa < 1% in patients with HRS using kidney biopsy findings as golden diagnostic standard.