Hypervolemic Hyponatremia
In a patient with hepatorenal syndrome presenting with low albumin and hyponatremia, this represents hypervolemic (dilutional) hyponatremia.
Pathophysiology in Hepatorenal Syndrome
Hepatorenal syndrome occurs in the context of advanced liver cirrhosis with portal hypertension, which creates a specific pattern of fluid and sodium dysregulation 1, 2:
- Systemic vasodilation from portal hypertension leads to decreased effective plasma volume despite total body fluid overload 3
- Non-osmotic hypersecretion of vasopressin causes excessive water retention disproportionate to sodium retention 4, 3
- Enhanced proximal nephron sodium reabsorption and activation of the renin-angiotensin-aldosterone system further compound the problem 3
- Hypoalbuminemia reduces oncotic pressure, promoting third-spacing of fluid into the peritoneum as ascites 3
Clinical Classification
The hyponatremia in hepatorenal syndrome is hypervolemic because 1, 2:
- Total body sodium is actually increased (manifesting as ascites and edema)
- Total body water is increased even more than sodium, creating dilutional hyponatremia
- The patient demonstrates signs of volume overload: ascites, peripheral edema, and jugular venous distention 1
- This occurs in approximately 60% of cirrhotic patients 1
Why Not the Other Options
Not euvolemic (Option A): Euvolemic hyponatremia (SIADH) presents without clinical signs of volume depletion or overload—no edema, no ascites, normal skin turgor 1. Hepatorenal syndrome patients have obvious ascites and fluid overload 2, 3.
Not hypovolemic (Option C): While effective arterial blood volume may be reduced, total body sodium and water are markedly increased 4. Physical examination reveals volume overload, not depletion 1.
Not pseudohyponatremia (Option D): Pseudohyponatremia occurs with severe hyperlipidemia or hyperproteinemia causing laboratory artifact, or with hyperglycemia (corrected by adding 1.6 mEq/L for each 100 mg/dL glucose >100) 1. In hepatorenal syndrome, the hyponatremia is real and hypotonic, not artifactual 2.
Clinical Significance
Hyponatremia in cirrhosis (typically defined as <130 mmol/L) significantly increases risk of 1, 3:
- Spontaneous bacterial peritonitis (OR 3.40)
- Hepatorenal syndrome (OR 3.45)
- Hepatic encephalopathy (OR 2.36)
- Increased mortality (60-fold increase when <130 mmol/L)
Management Approach
For hypervolemic hyponatremia in hepatorenal syndrome 1, 2:
- Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L
- Albumin infusion to improve oncotic pressure
- Discontinue diuretics temporarily if sodium <125 mmol/L
- Avoid hypertonic saline unless life-threatening symptoms present, as it worsens ascites and edema 1
- Correction rate must not exceed 4-6 mmol/L per day (maximum 8 mmol/L in 24 hours) due to high risk of osmotic demyelination syndrome in cirrhotic patients 1, 2
Answer: B - Hypervolemia