Ascites diagnosis and management

Pathophysiology - How Fluid Builds Up

• The core driver is portal hypertension, which triggers splanchnic vasodilation via nitric oxide (NO) release. This pooling of blood in the gut circulation ↓ the effective arterial blood volume.
• The kidneys perceive this "underfilling" and activate the Renin-Angiotensin-Aldosterone System (RAAS).
• RAAS drives aggressive sodium and water retention, leading to total body fluid overload that manifests as ascites.

⭐ Splanchnic vasodilation, mediated by nitric oxide, is the primary driver that initiates sodium and water retention by the kidneys.

Diagnosis & SAAG - Tapping the Abdomen

• Physical Exam: Suspect with abdominal distension. Key signs include shifting dullness and a positive fluid wave test. Ultrasound is the most sensitive method to confirm ascites.
• Diagnostic Paracentesis (Abdominal Tap): Essential first step for new-onset ascites.
  • Fluid Analysis:
    • Cell count & differential: PMN > 250/mm³ suggests Spontaneous Bacterial Peritonitis (SBP).
    • Albumin & Total Protein: Crucial for SAAG calculation.
    • Culture: In blood culture bottles to improve yield.
• Serum-Ascites Albumin Gradient (SAAG):
  • $SAAG = (Serum Albumin) - (Ascitic Fluid Albumin)$
  • SAAG > 1.1 g/dL: High gradient, indicates portal hypertension (e.g., cirrhosis, heart failure).
  • SAAG < 1.1 g/dL: Low gradient, suggests other causes (e.g., malignancy, pancreatitis).

⭐ The Serum-Ascites Albumin Gradient (SAAG) is the most useful single test for differentiating ascites caused by portal hypertension from other causes, with an accuracy of about 97%.

Management - Drain and Diurese

• Initial Therapy: First-line management combines sodium restriction (<2 g/day) with diuretics.
• Diuretic Regimen:
  • Start with oral Spironolactone and Furosemide.
  • 📌 Begin with a 100mg Spironolactone to 40mg Furosemide ratio to maintain normokalemia.
• Tense/Refractory Ascites: Perform Large-Volume Paracentesis (LVP).
  • For removal >5L, infuse 6-8 g of IV albumin per liter removed.

⭐ Administering intravenous albumin after large-volume paracentesis (>5L) is crucial to prevent post-paracentesis circulatory dysfunction (PCD), characterized by rapid reaccumulation of ascites and renal impairment.

SBP - A Deadly Complication

• Pathophysiology: Infection of ascitic fluid without an intra-abdominal source.
• Symptoms: Fever, abdominal pain, altered mental status (can be subtle).
• Diagnosis: Requires paracentesis.
  • Ascitic fluid PMN count ≥ 250 cells/mm³.
• Treatment: Empiric 3rd-generation cephalosporins (e.g., Cefotaxime, Ceftriaxone).

⭐ Prophylaxis: Patients with a prior SBP episode, or ascitic fluid protein <1.5 g/dL with advanced liver failure, require long-term prophylaxis with fluoroquinolones (e.g., norfloxacin).

High‑Yield Points - ⚡ Biggest Takeaways

• A SAAG (Serum-Ascites Albumin Gradient) ≥ 1.1 g/dL indicates portal hypertension; < 1.1 suggests other causes.
• First-line treatment is sodium restriction and dual diuretics (spironolactone and furosemide, 100:40 ratio).
• Suspect SBP with fever/pain; diagnose with ascitic fluid PMN count ≥ 250/mm³.
• Treat SBP empirically with a third-generation cephalosporin (e.g., cefotaxime).
• Large-volume paracentesis (>5L) requires IV albumin to prevent circulatory dysfunction.
• Refractory ascites may necessitate TIPS or liver transplantation.