Medical Treatment of Malignant Ascites
Therapeutic paracentesis is the first-line treatment for malignant ascites, providing rapid symptom relief in up to 90% of patients, followed by sodium restriction and diuretic therapy to prevent reaccumulation. 1, 2, 3
Initial Management: Therapeutic Paracentesis
Perform large-volume paracentesis as the primary intervention to achieve immediate symptom relief within minutes to hours. 1, 4
Volume and Albumin Replacement
- For paracentesis >5 liters: Administer intravenous albumin at 8g per liter of ascites removed to prevent circulatory dysfunction. 1, 4
- For paracentesis ≤5 liters: Synthetic plasma expanders (150-200 ml of gelofusine or haemaccel) can be used instead of albumin, though albumin remains preferred. 5
- The volume of fluid removed does not correlate with symptom improvement; even small-volume paracentesis (1500-2500 mL) effectively alleviates abdominal distension without shortening the paracentesis-free interval. 6, 7
Post-Paracentesis Management
- Immediately initiate sodium restriction to 88 mmol/day (2000 mg/day) after paracentesis. 1, 4
- Start diuretic therapy within 1-2 days of paracentesis to prevent rapid reaccumulation (ascites recurs in 93% without diuretics versus only 18% with spironolactone). 5
Diuretic Therapy
Begin with spironolactone as monotherapy, as it is the first-line diuretic for malignant ascites. 1, 8
Dosing Algorithm
- Initial dose: Spironolactone 100 mg once daily (or 50-100 mg/day). 5, 1, 4
- Titration: Increase by 100 mg every 3-5 days if inadequate response, up to maximum 400 mg/day. 5, 1, 4
- Add furosemide 40 mg once daily if spironolactone 400 mg alone is ineffective. 1, 4
- Maintain 100:40 ratio of spironolactone to furosemide when titrating both drugs. 1
- Maximum doses: Spironolactone 400 mg/day and furosemide 160 mg/day. 5, 1, 4
Important Considerations
- Diuretics are effective in approximately one-third of patients with malignant ascites, with efficacy potentially determined by plasma renin/aldosterone concentrations. 2
- Take spironolactone consistently with or without food (food increases bioavailability by 95%), establishing a routine pattern. 8
- Target weight loss should not exceed 0.5 kg/day in patients without peripheral edema to avoid rapid fluid shifts. 4
Monitoring Requirements
Monitor serum electrolytes, creatinine, and weight within 1 week of initiation or dose titration, then regularly thereafter. 1, 8
Critical Parameters to Track
- Hyperkalemia risk: Spironolactone can cause dangerous hyperkalemia, especially with impaired renal function or concomitant ACE inhibitors, ARBs, or potassium supplementation. 8
- Hyponatremia: If serum sodium falls to 120-125 mmol/L, consider fluid restriction; if <120 mmol/L, stop diuretics. 5, 1
- Renal function: Monitor for worsening creatinine, particularly with excessive diuresis or nephrotoxic drugs. 8
- Other electrolyte abnormalities: Watch for hypomagnesemia, hypocalcemia, hypochloremic alkalosis, and hyperglycemia. 8
Follow-up Frequency
- Every 2-4 weeks initially, then adjust based on response and stability. 1
- More frequent monitoring when combining spironolactone with other potassium-increasing drugs or in patients with renal impairment. 8
Management of Refractory Ascites
If ascites recurs rapidly or remains unresponsive to maximum diuretic therapy (spironolactone 400 mg + furosemide 160 mg), it is considered refractory. 1, 4
Treatment Options
- Serial therapeutic paracenteses every 2-3 weeks as the primary approach for refractory malignant ascites. 1
- Permanent percutaneous drains or tunneled catheters may prevent repeated paracenteses, though infection risk exists. 2, 3
- Peritoneovenous shunts maintain normal serum albumin but have 25% blockage rate and are contraindicated with heavily bloodstained ascites. 2
Critical Precautions and Pitfalls
Medications to Avoid
- Strictly avoid NSAIDs: They reduce urinary sodium excretion, induce azotemia, and can convert diuretic-sensitive patients to refractory status. 1, 4, 8
- Avoid nephrotoxic drugs (aminoglycosides, cisplatin) that worsen renal function. 8
Common Complications
- Gynecomastia: Occurs in approximately 9% of male patients on spironolactone (dose-dependent, usually reversible). 8
- Hepatic encephalopathy: Can occur in 26% with over-diuresis. 5
- Post-paracentesis circulatory dysfunction: Prevented by appropriate albumin replacement. 5, 1
Compliance Issues
- Verify dietary sodium compliance by measuring urinary sodium excretion; if urinary sodium exceeds intake despite treatment failure, assume non-compliance. 5
- Ensure patients are not consuming sodium-rich medications or salt substitutes. 5
Symptom Assessment
Paracentesis provides symptom relief measurable by validated questionnaires, with major improvements in abdominal bloating (42-54%), dyspnea (33-43%), anorexia (20-37%), and fatigue (14-17%). 6