From the Guidelines
Fractional excretion of urea (FEUrea) can be used to help diagnose hepatorenal syndrome (HRS), with a cutoff of <28.16% having a sensitivity of 75% and specificity of 83% in separating HRS from non-HRS, as reported in a recent study 1. When evaluating patients with suspected HRS, it is essential to consider the limitations and potential benefits of using FEUrea as a diagnostic tool. The calculation of FEUrea is based on the measurements of urea in both urine and serum, along with creatinine values from both sources. Key points to consider when using FEUrea in the diagnosis of HRS include:
- FEUrea may better discriminate HRS from prerenal azotemia or acute tubular necrosis (ATN) compared to fractional excretion of sodium (FENa) 1
- A FEUrea cutoff of <28.16% has been suggested as a potential diagnostic threshold for HRS, with a sensitivity of 75% and specificity of 83% 1
- FEUrea should be interpreted alongside other diagnostic criteria for HRS, including cirrhosis with ascites, serum creatinine >1.5 mg/dL, no improvement after albumin challenge, absence of shock, no recent nephrotoxic drugs, and exclusion of parenchymal kidney disease 1 The use of FEUrea in the diagnosis of HRS is supported by recent evidence, which suggests that it may be a valuable tool in distinguishing HRS from other causes of acute kidney injury (AKI) 1.
From the Research
Fractional Excretion of Urea in Diagnosing Hepatorenal Syndrome
- The use of fractional excretion of urea (FEUrea) as a diagnostic tool for hepatorenal syndrome (HRS) has been explored in several studies 2, 3, 4.
- A study published in 2018 found that FEUrea was a promising tool for the differential diagnosis of acute kidney injury (AKI) in patients with cirrhosis, with an area under the curve (AUC) of 0.87 for HRS versus non-HRS 2.
- However, another study published in 2022 found that FEUrea could not differentiate HRS-AKI vs. non-HRS-AKI satisfactorily, with an AUC of 60.4% 3.
- The comparative benefits of FEUrea and fractional excretion of sodium (FENa) in various azotemic oliguric states were also studied, with FEUrea found to be more accurate in detecting pre-renal azotemia, especially in patients taking diuretics 4.
- The pathophysiology, diagnosis, and management of hepatorenal syndrome were reviewed in a 2020 study, which highlighted the importance of diagnosing HRS accurately, but did not specifically discuss the use of FEUrea as a diagnostic tool 5.
- Overall, the evidence suggests that while FEUrea may be useful in certain contexts, its utility in diagnosing hepatorenal syndrome is limited, and other diagnostic tools, such as FENa, may be more effective 2, 3, 4.