Ascites

Diagnosis

• Imaging:
  • Initial: Abdominal Ultrasound (detects as little as 100 mL of fluid, evaluates liver parenchymal echogenicity, screens for portal vein thrombosis).
• Gold Standard/Confirmatory Procedure:
  • Diagnostic Paracentesis (indicated for all patients with new-onset ascites or suspected infection/SBP).
• Key Labs (Ascitic Fluid Analysis):
  • Serum-Ascites Albumin Gradient (SAAG): Serum albumin minus ascitic fluid albumin.
    • SAAG ≥ 1.1 g/dL (indicates portal HTN): Cirrhosis, HF, Budd-Chiari syndrome, portal vein thrombosis.
    • SAAG < 1.1 g/dL (indicates non-portal HTN): Peritoneal carcinomatosis, TB peritonitis, nephrotic syndrome, pancreatitis.
  • Ascitic Fluid Total Protein:
    • < 2.5 g/dL: Cirrhosis, nephrotic syndrome.
    • ≥ 2.5 g/dL: Cardiac ascites (HF), Budd-Chiari, TB peritonitis.
  • Cell Count & Differential: PMN count ≥ 250/mm³ is diagnostic for Spontaneous Bacterial Peritonitis (SBP).
  • Other tests: Cytology (malignancy), Amylase (pancreatic ascites), Acid-fast bacilli stain/culture (TB).

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Management

• First-line (for Portal HTN-related ascites):
  • Dietary sodium restriction (< 2 g/day).
  • Oral diuretics: Combined therapy with Spironolactone and Furosemide (ratio of 100 mg to 40 mg to maintain potassium balance). c
    • Spironolactone (Aldosterone Antagonist):
      • Primary agent: Addresses the root cause of sodium retention by directly blocking mineralocorticoid receptors in the distal tubule/collecting duct.
      • Prevents $N{a}^{+}$ reabsorption and potassium ($K^{+}$) excretion.
      • Limitation: Weak diuretic on its own; slow onset of action (takes 2-4 days to reach full effect).
    • Furosemide (Loop Diuretic):
      • Inhibits $N{a}^{+}-K^{+}-2C{l}^{-}$ cotransporters in the thick ascending limb of the loop of Henle.
      • Potent and fast-acting: Rapidly increases urinary flow and sodium excretion.
      • Limitation: If used alone, the excess $N{a}^{+}$ delivered downstream to the distal tubule is simply reabsorbed due to the hyperaldosteronism state.
• Second-line:
  • Large-Volume Paracentesis (LVP) for refractory ascites or tense ascites causing respiratory compromise.
  • Administer IV Albumin (6-8 g per Liter of fluid removed) if > 5 L of fluid is extracted to prevent post-paracentesis circulatory dysfunction.
• Refractory / Definitive:
  • Transjugular Intrahepatic Portosystemic Shunt (TIPS) (relieves portal HTN; contraindicated in severe hepatic encephalopathy or HF).
  • Liver transplantation.
• Non-Portal HTN ascites (SAAG < 1.1):
  • Diuretics are generally ineffective; must treat the underlying etiology directly (e.g., chemotherapy for malignancy, anti-TB therapy, steroid therapy for nephrotic syndrome).