Introduction: We are presenting a case of Lung entrapment, a potential complication of malignant mesothelioma. A study published in the American thoracic society journal reported, out of 229 patients diagnosed with mesothelioma, 192 were found to have pleural effusion at presentation. It also reported that 64 out of the 192 (33.3%) patients developed Lung entrapment.

Case: A 75-year-old male with a past medical history of diabetes mellitus type 2, hypertension, and stage 3 mesothelioma, currently on maintenance therapy with Pemetrexed and radiation. He presented to the ED with worsening dyspnea from baseline, generalized weakness, fatigue, and multiple falls. He was tachypneic on admission and pertinent labs included a hemoglobin of 6.7 g/dL and severe leukocytosis. Chest x-ray showed increased pulmonary vascular congestion, a loculated right sided pleural effusion and density in the left lung base, possibly due to atelectasis vs infiltrate. CT chest without contrast was significant for bilateral pleural effusions. The initial working diagnosis included congestive heart failure versus pneumonia, with a possible empyema.

Management: Patient was started on IV diuretics and broad spectrum antibiotics. In addition, an upper extremity venous doppler study revealed a deep venous thrombosis in the right internal jugular vein, therefore, treatment with therapeutic enoxaparin was initiated. A transesophageal echocardiography showed an ejection fraction of 55- 60% along with grade 1 diastolic dysfunction. During this time, serum creatinine worsened to 3.4 (1.9 on admission), subsequently diuretics were discontinued. The acute kidney injury was due to a combination of pre-renal and post-renal (BPH) etiologies, and the patient was managed with IV fluids and insertion of a foley catheter. Infectious Disease recommended discontinuing antibiotics due to no clear source of infection. Patient underwent bilateral thoracentesis which yielded more than 2L of exudative yellow colored fluid, negative for malignant cells. Repeat chest x-ray showed incomplete expansion of the right lung, compatible with “Lung Entrapment”. Cardiothoracic surgery recommended that the patient was not a candidate for decortication and a right sided tunneled pleural catheter was placed.

Final diagnosis: Exudative pleural effusion due to malignant mesothelioma complicated by right sided lung entrapment.

Discussion: An unexpandable lung can be due to either lung entrapment or a trapped lung. Lung entrapment is usually due to an inflammatory process that hinders the lung and/or the pleura from fully expanding, revealing an exudative effusion by light’s criteria. The common causes include pleural malignancies, empyema, and autoimmune pathologies including rheumatoid pleurisy, etc. Trapped lung is a result of a fibrotic process affecting the visceral pleura preventing the lung expansion and a net-negative pressure in the pleural space leading to effusion formation. Trapped lung is usually a consequence of lung entrapment with incomplete resolution of the inflammatory trigger.

Malignant pleural mesothelioma may result in tumor development on the visceral pleural surface, provoking an inflammatory process leading to lung entrapment. Mainstay in management is to address the underlying pathology. Entrapment due to malignancies are not usually responsive to chemotherapy and patients with symptomatic improvement with pleural fluid removal are managed by placement of an indwelling pleural catheter. Pleuroperitoneal shunts may be an option if a chronic transcutaneous drain is not preferred. Pleurectomy or decortications can be performed, which were not viable options in our patient. Despite receiving chemotherapy and radiation therapy for his malignancy, our patient developed lung entrapment, making this a unique finding.

Figure 1