Post-traumatic pulmonary pseudocyst (PPP) is an uncommon result of blunt trauma to the chest, presenting as one or more cavitary lesions within the lung parenchyma. We present the case of young man diagnosed with PPP following a motor vehicle accident.
A 20-year-old man was a restrained passenger in a car which struck a tree after the driver fell asleep while traveling approximately 20 mph. The patient walked some distance from the car before collapsing. He was evaluated at the local hospital, where a CT of the abdomen showed a liver laceration with hematoma and cavitary lesions of the lower lungs with air-fluid levels and surrounding ground glass opacity (see figure). He was transferred to a level one trauma center for management of the liver laceration, and pulmonary consultation was requested to evaluate the lesions in the lungs. The differential diagnosis for the cavitary or cystic lesions was organized as follows: 1) lesions unrelated to the trauma: blebs, bullae, congenital cysts, coccidioidomycosis, PCP, tuberculosis, hydatid disease, cavitary pneumonia, and 2) lesions related to the trauma: cavitating hematomas, lung lacerations, traumatic pseudocysts. The young man was a current smoker, with no known pulmonary disease. He had no known contact with tuberculosis, but reported a 2-pound weight loss and occasional cough. PPD had been negative several years before. He had had a normal chest radiograph 1 year earlier, at the time of a clavicular fracture. Physical exam revealed a young man in no distress. Vital signs were normal. The lungs were clear to auscultation. There was mild abdominal tenderness over the lacerated liver. Inpatient studies included induced sputum and bronchial washings negative for acid-fast bacilli but positive for Staphylococcus aureus. Blood cultures were negative. Fungal serology was negative. The diagnosis of PPP was made after granulomatous infection had been excluded. Repeat CT chest several days after admission showed the cavities were smaller, with persistent air-fluid levels. A percutaneous drain was placed into the largest cavity, and approximately 100 mL of hemorrhagic fluid was removed. Culture of the fluid yielded S. aureus. The drain was removed after 2 days, and the patient was discharged home on prolonged antibiotic treatment with amoxicillin/clavulanate. Follow up CT imaging showed resolution of the cavities over a period of 10 weeks.
PPP is a cystic lesion (i.e. no epithelial lining) which forms in the lungs following significant blunt trauma. The mechanism of injury involves both shear forces, as in traumatic deceleration, and burst forces, as in thoracic compression with a closed or narrowed glottis. It is more common in young patients, whose more flexible chest wall may transmit the force of the injury to the lungs more efficiently. PPP generally resolves without specific intervention. The principle complication is infection, as in our patient, which occurs in up to 40% of patients in some series, and often requires percutaneous drainage or surgery.
PPP should be considered in the differential diagnosis of cystic or cavitary lung lesions following significant blunt trauma, particularly in younger patients. No specific intervention is needed, but infectious complications must be ruled out, or treated aggressively if they develop.
R.W. Ashton, None.