Pulmonary Pseudocyst: A Rare Presentation of Blunt Chest Wall Trauma

CASE PRESENTATION

A20-year-old man with no past medical history was admitted to the trauma intensive care unit after a motor vehicle collision. He was intubated on scene and saturating well on the ventilator. Initial chest x-ray (CXR) showed left sided opacity with a small hemopneumothorax and non-displaced left rib fractures (Figure 1, A). Computerized tomography (CT) of the chest demonstrated large, bilateral consolidations compatible with pulmonary contusion (Figure 1, B). A left surgical thoracostomy tube was placed for the hemopneumothorax, which quickly resolved. He self-extubated on day two and remained on room air. CXR showed persistent left-sided opacities, which was concerning for malignancy or infection. Pulmonology was consulted for potential lung biopsy. Repeat chest CT 7 days after trauma showed improving consolidations with residual blood-filled pneumatoceles suggestive of post-traumatic pulmonary pseudocysts (TPP) (Figure 2). Given his overall clinical appearance, we did not treat with antibiotics and did not perform biopsy. The patient was discharged without complications. On follow up, he was asymptomatic and back to baseline. Repeat chest CT at 13 weeks showed complete resolution of the pseudocysts (Figure 3).

FIGURE 1.

FIGURE 2.

FIGURE 3.

Post-traumatic pulmonary pseudocysts (TPP) are cystic, cavitary lung lesions without a true epithelial lining that typically develop after blunt chest trauma. First described in children, the incidence among adults after chest trauma is 1–3%¹ and is more common adults under 30.² The compressive force of blunt trauma is transmitted to the lung parenchyma, leading to a rapid compression and decompression injury to the alveoli and interstitium (i.e. barotrauma).³ Concomitantly, the retraction of normal elastic lung tissue leads to cavitary formation that can be filled with either air or fluid.^1–3 The injury is exacerbated by entrapment of air in the injured area of lung against a closed glottis or obstructed bronchus.² Younger adults develop TPP more commonly because they tend to have higher chest wall compliance and elasticity.¹ The most common symptoms include cough, chest pain, dyspnea, and hypoxemia.²

TPP are often missed on initial imaging and recognized 8–10 days after injury as contusions may obscure visualization and positive pressure ventilation can transform parenchymal lacerations into cavitary lesions.^1–3 Uncomplicated TPP generally self-resolves within weeks to months from the initial injury with usual care. The most common complication is secondary infection, for which antibiotics are indicated.^2,3 Other complications are rare but can be severe, and include rupture leading to secondary pneumothorax with tension physiology, worsening respiratory failure and hypoxemia, and bleeding into the pseudocyst.² In cases of severe infection, increasing size, or bleeding, surgical intervention including drainage and/or resection is required.³ Differential diagnosis includes congenital lesions (e.g. bronchial cysts), infection, and malignancy.²

This case is a classic presentation of a traumatic pulmonary pseudocyst occurring with blunt chest wall trauma in a young, otherwise healthy man. It remains under-recognized among many internists. Knowledge of TPP is important to prevent over-treatment with antibiotics and to protect against unnecessary invasive procedures like bronchoscopies, CT guided drainage, biopsies and even repeated CT scans, as this condition resolves for most patients with routine care.