Yes, ultrafiltration during hemodialysis can effectively remove fluid from bilateral pleural effusions, but the fluid must first redistribute from the pleural space into the intravascular compartment.
In dialysis patients with bilateral pleural effusions, increasing ultrafiltration (UF) during HD sessions is an appropriate and often effective strategy to remove excess fluid, including fluid contributing to pleural effusions, provided the underlying cause is hypervolemia. 1, 2
Mechanism and Evidence
The physiologic principle is straightforward: ultrafiltration removes fluid from the intravascular space, which creates a pressure gradient that draws fluid from the interstitial and pleural spaces back into the circulation. This process depends on adequate "capillary refill rate"—the ability of fluid to redistribute from tissue compartments into plasma 2.
Recent research directly demonstrates that UF volume during HD correlates with improvements in pulmonary function. A 2026 study showed that the volume of ultrafiltration was positively correlated with improvements in FEV1/FVC ratio and FEV1, with respiratory muscle strength significantly improving after HD sessions 3. This provides direct evidence that fluid removal during dialysis impacts pulmonary fluid status.
Clinical Approach
When Hypervolemia is the Cause (Most Common)
- Hypervolemia accounts for 61.5% of pleural effusions in HD patients and is typically bilateral (68.8% of cases) 4
- These effusions are transudative in nature (64.3% of thoracenteses) 4
- Aggressive UF is the appropriate treatment, as the effusions will resolve with achievement of true dry weight
Practical Prescription Guidance
According to KDOQI guidelines, consider the following approach 1:
- Extend treatment time or add additional sessions rather than simply increasing UF rate
- Keep UF rates below 13 mL/kg/h when possible (higher rates associated with increased cardiovascular mortality)
- For patients with large fluid gains or difficulty achieving dry weight, prescribe longer sessions or additional weekly treatments 1
The 2025 European ICM guideline emphasizes that active fluid removal should only occur in patients who are not fluid-responsive and do not need resuscitation 2. However, this applies more to acute critical illness than chronic HD patients with established hypervolemia.
Monitoring During Aggressive UF
Recent evidence supports using point-of-care ultrasound to guide fluid removal 5, 6:
- LVOT VTI (left ventricular outflow tract velocity-time integral) can guide UF even when blood pressure drops—if LVOT VTI improves with fluid removal despite hypotension, continued UF may be safe 5
- Lung ultrasound (B-lines) and IVC diameter can assess volume status 6, 7
- Portal vein pulsatility combined with preload responsiveness testing helps determine safe UF rates 6
Critical Caveats
When UF Won't Work
Not all pleural effusions in dialysis patients are from hypervolemia. Other causes include 4:
- Uremic pleuritis (40% of exudative effusions)—requires different management
- Parapneumonic effusion/infection
- Heart failure with preserved ejection fraction
- Malignancy (though less common in this population)
If effusion is unilateral, strongly consider thoracentesis for diagnosis 4. Unilateral effusions are less likely to be purely from volume overload (only 36% from hypervolemia).
Hemodynamic Limitations
The major limitation is hemodynamic tolerance:
- Patients may develop intradialytic hypotension before adequate fluid is removed
- This is especially problematic with severe tricuspid regurgitation, pulmonary hypertension, or poor cardiac function 5
- The solution is slower UF over longer or more frequent sessions, not abandoning the goal 1
Plasma Refill Rate Variability
Fluid removal from the pleural space is not instantaneous—it depends on adequate redistribution from the pleural space to the intravascular compartment 2. This refill rate may be impaired in conditions with:
- Endothelial dysfunction
- Low oncotic pressure (severe hypoalbuminemia)
- Increased capillary permeability
In such cases, aggressive UF may cause intravascular depletion before pleural fluid is mobilized, requiring a more gradual approach over multiple sessions.
Practical Algorithm
- Confirm hypervolemia as the cause: Bilateral effusions in HD patient = hypervolemia until proven otherwise
- If unilateral or atypical features: Perform diagnostic thoracentesis
- For hypervolemic effusions: Progressively reduce dry weight through increased UF
- Adjust prescription: Extend session time (aim for ≥4 hours) or add sessions rather than just increasing UF rate 1
- Monitor tolerance: Use clinical assessment ± POCUS (LVOT VTI, lung ultrasound) to guide safe UF rates 5, 6
- Reassess regularly: Effusions from hypervolemia should improve over 2-4 weeks of adequate UF 5
The key principle: pleural effusions from volume overload will resolve with achievement of true euvolemia through dialysis, but this requires adequate time, appropriate UF rates, and hemodynamic monitoring.