Fractional excretion of sodium in hepatorenal syndrome: Clinical and pathological correlation

Abstract

AIMTo determine the accuracy of fractional excretion of sodium (FeNa) in the diagnosis of hepatorenal syndrome (HRS).METHODSEighty-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.RESULTSSeventy-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).CONCLUSIONFeNa < 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%.

Hepatorenal syndrome: pathophysiology, diagnosis, and management

“…Some experts have used urinary sodium (>40 mEq/L), fractional excretion of sodium (FeNa >2%), and low urine osmolality (<400 mOsm/L) as suggestive of ATN; however, urinary sodium can be elevated secondary to diuretics, frequently used in this group of patients with large volume ascites. 55 Conversely, low FeNa has also been observed in patients with biopsy proven ATN, 56 so urinary sodium and FeNa are no longer part of the diagnostic criteria of AKIHRS. Studies in patients without liver disease have found that fractional excretion of urea is superior to FeNa in differentiating AKIHRS from ATN in patients taking diuretics.…”

The Current Management of Hepatorenal Syndrome–Acute Kidney Injury in the United States and the Potential of Terlipressin

“…Error! Bookmark not defined., 25 Additional factors decrease the utility of sCr measurements in HRS-AKI. Creatine is synthesized in the liver prior to storage in muscles, where it is phosphorylated to creatinine (Cr).…”

Clinical Practice of Hepatorenal Syndrome: A Brief Review on Diagnosis and Management

“…Alsaad and colleagues mentioned that FeNa <1% in HRS was not accurate. But the test had high sensitivity and high negative predictive value, indicating that HRS diagnosis can be excluded in patients with negative test results (if FeNa more than 1%) [23].…”