What is the treatment for a pleural effusion with fluid trapped in the space behind the right lung?

Management of Trapped Pleural Fluid

When fluid is trapped behind the lung (trapped lung syndrome), pleurodesis will likely fail, and a pleuroperitoneal shunt or indwelling pleural catheter should be inserted instead of attempting standard chemical pleurodesis. 1

Understanding Trapped Lung

Trapped lung occurs when the lung cannot fully re-expand after fluid removal due to:

• A cortex of malignant tissue or fibrosis covering the visceral pleura 1
• Lack of mediastinal shift on chest radiographs (suggesting the lung is fixed and cannot expand) 1, 2
• Persistent pleural space despite adequate drainage 1

This is a critical distinction because trapped lung is a contraindication to standard pleurodesis—the procedure will fail if the lung cannot fully expand and contact the parietal pleura. 1

Primary Treatment Approach

For Trapped Lung with Inadequate Re-expansion:

Insert a pleuroperitoneal shunt as the definitive treatment. 1 This approach:

• Allows continuous drainage of fluid from pleural space to peritoneal cavity 1
• Provides symptom relief even when lung expansion is impossible 1
• Can be performed via VATS or limited thoracotomy 1

Key management points:

• Have a shunt readily available when undertaking surgical treatment, as trapped lung may only be discovered intraoperatively 1
• Shunt occlusion occurs in 12% of patients and requires shunt replacement 1
• If infection is confirmed, long-term chest tube drainage is indicated instead of shunt replacement 1

Alternative: Indwelling Pleural Catheter

For patients who are not surgical candidates or prefer outpatient management:

• Long-term indwelling catheter drainage is suitable for the outpatient setting 1
• Provides modest success rates with intermittent drainage 1
• Risk of local infection and potential tumor seeding (particularly concerning in mesothelioma) 1

When Partial Pleurodesis May Still Be Attempted

Even with incomplete lung re-expansion, chemical pleurodesis should still be attempted if there is partial pleural apposition, as it may provide symptomatic relief. 2 However, success rates will be lower than with complete lung expansion 2.

Controlled Drainage Protocol:

Before any intervention, drain the effusion in a controlled fashion:

• Limit drainage to 1-1.5 L at one time to prevent re-expansion pulmonary edema 2, 3
• Stop immediately if patient develops chest discomfort, persistent cough, or vasovagal symptoms 2, 3
• Obtain chest radiograph after drainage to assess lung re-expansion 1, 2

Management of Loculated Trapped Fluid

If the trapped fluid is loculated (septated):

Administer intrapleural fibrinolytic therapy before attempting definitive management: 2

• Urokinase 100,000 IU daily for 3 days, OR
• Streptokinase 250,000 IU twice daily for three doses 2
• Results in >67% reduction in effusion size in 72% of patients 2

Surgical Options for Refractory Cases

If the above measures fail and the patient has good performance status:

Decortication with pleurectomy may be considered, but carries significant risks: 1

• The cortex of malignant tissue covering pleural surfaces may be removable by open thoracotomy 1
• Pleurodesis may then become possible after cortex removal 1
• Reported perioperative mortality is 12%, making patient selection critical 1
• Major surgical procedures (parietal pleurectomy, decortication) do not provide superior palliation compared to pleurodesis alone when pleurodesis is feasible 1

Common Pitfalls and How to Avoid Them

Do not attempt standard talc pleurodesis in patients with trapped lung—it will fail. 1 Signs suggesting trapped lung include:

• Absence of mediastinal shift toward the effusion on imaging 1, 2
• Persistent pleural space after adequate drainage 1
• Known mainstem bronchial occlusion 1

Do not rapidly drain large effusions. 2, 3 Re-expansion pulmonary edema is rare but serious, resulting from rapid expansion of collapsed lung—prevent by strict adherence to 1-1.5 L volume limitations 2, 3.

Do not withhold intervention attempts even if complete re-expansion cannot be achieved. 2 Partial pleurodesis or shunt placement still provides symptomatic benefit in most patients 2.