What are the typical urine study changes in patients with Hepatorenal Syndrome (HRS)?

From the Guidelines

Patients with Hepatorenal Syndrome (HRS) typically exhibit urine study changes characterized by very low sodium concentration (usually <10 mEq/L), low urine output, high urine osmolality, and a high urine-to-plasma creatinine ratio, with a fractional excretion of sodium (FENa) <1% and fractional excretion of urea (FEUrea) <28.16%. These findings are indicative of functional kidney impairment without structural damage, reflecting intense sodium retention and reduced glomerular filtration rate in response to splanchnic vasodilation and reduced effective arterial blood volume in advanced liver disease 1. The urinalysis is typically benign with minimal proteinuria (<500 mg/day), absence of significant hematuria, and few to no cellular casts.

The diagnosis of HRS is based on the presence of advanced liver disease, serum creatinine >1.5 mg/dL, and absence of shock, bacterial infection, or nephrotoxic drug use, with no improvement in renal function after diuretic withdrawal and plasma volume expansion 1. The urinary parameters, including FENa and FEUrea, are important diagnostic criteria for HRS and help guide appropriate management strategies.

Some key points to consider in the diagnosis and management of HRS include:

• Low FENa (<1%) suggests prerenal causes, including HRS, while high FENa (>1%) suggests structural causes of acute kidney injury (AKI) like acute tubular necrosis (ATN) 1
• FEUrea may better discriminate HRS from prerenal azotemia or ATN, with a cutoff value of <28.16% having a sensitivity of 75% and specificity of 83% in separating HRS from non-HRS 1
• The use of vasoconstrictor drugs, such as terlipressin, in combination with albumin, has been shown to improve renal function in patients with HRS-AKI, with a response rate of 20-80% 1
• The diagnosis and management of HRS should be guided by the most recent and highest-quality evidence, taking into account the patient's individual clinical context and the potential risks and benefits of different treatment strategies 1.

From the Research

Urine Study Changes in Hepatorenal Syndrome

• The typical urine study changes in patients with Hepatorenal Syndrome (HRS) include low sodium urine concentration 2
• Low urinary sodium before treatment is associated with poor survival in patients with HRS 2
• High baseline urinary sodium levels are of prognostic value for survival in patients with HRS 2
• Improvement in renal function, as evidenced by increased renal sodium excretion and glomerular filtration rate, can be achieved with treatment, such as midodrine, octreotide, and albumin, or terlipressin and albumin 3, 4, 5
• Normalization of plasma renin and aldosterone levels, and elimination of ascites, can also occur with effective treatment, such as TIPS insertion in selected patients 4

Predictors of Treatment Response

• High age is a predictor of non-response to treatment in patients with HRS 2
• Low urinary sodium before treatment is associated with poor survival in patients with HRS 2
• Improvement in renal function and lower baseline Model for End-Stage Liver Disease score are associated with better survival in patients with HRS 5

Treatment-Related Changes

• Medical therapy with midodrine, octreotide, and albumin can improve renal function and renal sodium excretion in patients with HRS 4
• TIPS insertion can further improve renal function and sodium excretion in selected patients with HRS 4
• Terlipressin plus albumin is significantly more effective than midodrine and octreotide plus albumin in improving renal function in patients with HRS 5