Spontaneous Transient Lateral Thoracic Lung Herniation Resulting in Systemic Inflammatory Response Syndrome (SIRS) and Subsequent Contralateral Lung Injury.

Lung herniation is a relatively rare clinical entity that is most commonly either congenital or acquired traumatically. We describe a case of spontaneous lung herniation secondary to acute cough in an obese male smoker complicated by contralateral acute lung injury and systemic inflammatory response syndrome (SIRS). Mechanisms of lung herniation, classification, diagnosis, and management will be discussed.

Case Report

An elderly male patient in his 60’s with a 150 pack year history of smoking, chronic obstructive pulmonary disease, hiatal hernia, gastroesophageal reflux disease, and coronary artery disease presented to the emergency room complaining of a three-week history of incessant forceful cough and right-sided chest pain in the absence of trauma. He required emergent uneventful endotracheal intubation and mechanical ventilation for hypoxic respiratory failure upon arrival to the emergency room. Pertinent medications included oral aspirin 325 mg and clopidogrel 75 mg daily.

Physical examination revealed an obese male with a heart rate of 110 beats per minute and blood pressure 135/80 mmHg. Decreased breath sounds over the right lung with overlying severe right anterior chest wall ecchymosis and subcutaneous edema were noted. No clinical signs of heart failure were present on physical exam.

Laboratory testing included an arterial blood gas with a pH 7.28, PaO2 107 mmHg (100% FiO2), PCO2 43 mmHg, HCO3 20 meq/L, hemoglobin 11.5 g/dL, and white blood cell count 23,100 cm2. Chest X-Ray (CXR) on presentation (Fig. 1) revealed minimal opacity at the right lung base and blunting of the left costophrenic angle. Computed tomography (CT) of the chest (Fig. 2) revealed a dramatic lateral herniation of the right lung at the seventh intercostal space without evidence of any overlying rib fractures. Current radiologic findings were compared to images from a prior CT scan performed five months earlier which demonstrated symmetrically developed thoracic cage muscles without evidence for fracture or herniation.

Figure 1

CXR on presentation.

Figure 2

CT of the chest showing lateral lung hernation of the right lung at the seventh intercostal space.

Initial management in the medical Intensive Care Unit (ICU) included intravenous sedation and low tidal volume ventilation with attention to peak airway pressures and permissive hypercapnea given the high risk for incarceration and potential advancement of the lung herniation. An initial conservative strategy was opted for given the patient’s overall co-morbidities contributing to high surgical risk and having no evidence for impending lung incarceration.

Repeat CT chest in 24 hours revealed multi-lobar infiltrates. The previously identified lung herniation was no longer visualized but an extensive extra pleural collection consistent with a large hematoma remained. Patient remained on intravenous antibiotics during this time but blood and sputum cultures showed no growth of organisms. Repeat chest CT eight days later showed right anterior abdominal intramuscular hemorrhage. Examination showed expanding hematoma (Fig. 3). Radiological studies supported evidence for contralateral acute lung injury, making mechanical ventilation and oxygenation very challenging.

Figure 3

Right anterior abdominal intramuscular hemorrhage resulting in expanding hematoma.

Other ICU complications included persistently high fevers despite broad-spectrum antibiotics, intra-cerebral hemorrhage due to cerebral amyloid angiopathy, and ST segment elevation myocardial infarction. His hospital course was further complicated by anoxic encephalopathy due to inability to maintain adequate gaseous exchange. Aggressive medical care was stopped after several weeks of ICU care. The patient expired soon after.

Discussion

Lung herniation is an uncommon medical problem with only about 300 cases cited to date.1–3 It has been defined in the literature as a displacement of lung tissue outside the thoracic cavity through a defect in the pleura of the chest wall, diaphragm, or mediastinum.4 The Morel-Lavallee system developed in 1845 is used to classify lung hernias on the basis of location and etiology.5 Location is further broken down into cervical, diaphragmatic, and thoracic. The etiology can be either congenital or acquired. If acquired, it may be due to traumatic, spontaneous, pathological, or post-surgical causes.5

Spontaneous lung herniation due to coughing is related to a combination of two processes: weakness of the boundaries of the thoracic cavity and increased intra-thoracic pressure. Weakness in the intercostal muscles may be a consequence of corticosteroid use, congenital abnormalities, or trauma; however, chronic cough, Valsalva maneuver, or playing wind instruments can contribute to increased intra-thoracic pressures.6 Interestingly, there is a report in the literature of a spontaneous lung herniation after a single cough.7

Most patients present clinically with crepitus and a bulging thoracic mass that increases in size with Valsalva maneuver, coughing, or straining. Patients may or may not have pain.8 Diagnosis is usually clinical although CT is helpful in delineating the exact size and location of the hernia.4 Treatment is still debated in asymptomatic patients, especially given the low incidence of this clinical entity. Surgical intervention is considered to be the treatment of choice if the hernia causes extreme pain, incarcerates the pulmonary parenchyma, or results in infection.9–11 A conservative, nonsurgical approach is generally recommended for asymptomatic patients; however this dogma may be changing. Surgery may be the treatment option of choice even for asymptomatic patients to prevent complications or extension of the defect into the abdominal wall.12–14

This case represents a rare fulminant and atraumatic complication of violent and pervasive coughing. Initially, there was evidence of only unilateral lung herniation which we believe may have contributed to a systemic inflammatory response with contralateral lung injury followed by several ICU complications. We believe that lung injury due to extra-thoracic herniation was complicated by ventilator-induced lung injury. The mechanism of this process relates to cyclical stretching of alveoli which leads to an ensuing cascade of inflammatory processes that are associated with cytokine upregulation.15 The subsequent leukocyte attraction and activation of polymorphonuclear neutrophils (PMNs) from elevated levels of proinflammatory cytokines including tumor necrosis factor alpha (TNF)-α, interleukin (IL)-6, IL-8, and IL-1β which are produced by bronchial, bronchiolar, and alveolar epithelial cells may have led to a systemic inflammatory response and multiple organ dysfunction syndrome (MODS).15,16 Furthermore, due to the direct mechanical trauma to the lung parenchyma from herniation, a state of alveolar leakage of proteins may have led to some degree of surfactant dysfunction exaggerating the lung injury.15 Ventilation and oxygenation were very challenging due to development of bilateral lung injury. While surgery is advised in cases of symptomatic lung herniation, given the patient’s multiple co morbidities he was deemed to be a poor surgical candidate.

To the best of our knowledge, this is the first report of unilateral spontaneous lung herniation associated with contralateral acute lung injury. We propose that patients with lung herniation who require mechanical ventilation may benefit from early surgical intervention to reduce the inflammatory response that can predispose to contralateral lung injury, thus minimizing morbidity and mortality.