CASE CONFERENCES The Expert Clinician Section Editors: Peter Clardy, M.D., and Jess Mandel, M.D.

No Gravity in This Cavity Yu Kuang Lai, Chitra Punjabi, and Glenn Eiger Department of Internal Medicine, Einstein Medical Center Philadelphia, Philadelphia, Pennsylvania

Keywords: cyst; lung; pseudocyst; trauma; traumatic pneumatocele

In Brief Cavitary lung lesions can be seen in a wide array of both infectious and noninfectious diseases. A detailed history and physical examination are pivotal for generating a rational differential diagnosis and an appropriate diagnostic evaluation. We present a case in which an unusual etiology of adult cystic lung disease was appropriately diagnosed and managed using sound clinical reasoning.

Case Vignette A 65-year-old female was brought to the emergency department after a motor vehicle accident. The patient lost consciousness before the event and could not recall the details, but witnesses reported her car crossing the center line and hitting a parked car, with extensive damage to both vehicles. She was an unrestrained driver of the vehicle. The vehicle’s airbags deployed at the time of the collision. Her past medical history included asthma, non–insulin-dependent diabetes mellitus, hypertension, and hypothyroidism. Her medications included montelukast, inhaled albuterol, insulin, chlorthalidone, lisinopril, and levothyroxine. She did not smoke and denied illicit drug use. She was in a good general state of health with a negative review of symptoms before the event. On examination, her blood pressure was 122/80 mm Hg, with a heart rate of

91 beats/minute, respiratory rate of 18 breaths/minute, and oxygen saturation of 99% on 2 L of oxygen via nasal cannula; her temperature was 378 C. Her only complaint was chest and knee pain. Her chest was clear to auscultation but tender to palpation on the right; abrasions were noted on the left knee; otherwise physical examination was unremarkable. Laboratory results showed a white cell count of 9000 cells/ml, hemoglobin of 13.7 g/dl, blood glucose of 133 mg/dl, and a normal metabolic panel. Liver function tests were remarkable for alanine transaminase (395 IU/L) and aspartate transaminase (315 IU/L). Standard trauma evaluation included chest computed tomography, which revealed nondisplaced fractures of the right anterior fifth to eighth ribs, findings of hepatic contusion, and a 1.8 3 1.5 3 1.3 cm right middle lobe cavitary lesion with air–fluid level and surrounding ring of ground glass opacities (Figure 1). She had no prior chest imaging for comparison.

Questions What is the differential diagnosis for the abnormal findings on the chest computed tomography study? What is the most appropriate management strategy for this patient? What is the natural history and likely prognosis for the most likely etiology in this case?

Clinical Reasoning Many diseases present as cavitary lung lesions, including both infectious and noninfectious entities. Differential diagnosis of this radiographic abnormality includes infectious disorders such as tuberculosis, cryptococcal cavitary lesion, septic embolism, and pulmonary abscess, and noninfectious disorders including cavitating carcinoma; traumatic pneumatocele; and congenital disorders such as bronchogenic cyst, cystic pulmonary adenomatoid malformation, or pulmonary sequestration. To narrow the differential diagnosis, and proceed with an appropriate diagnostic evaluation, a detailed history and physical examination are critical. It may be difficult to differentiate many of the possible etiologies from traumatic pneumatocele, based solely on radiographic appearance, and therefore traumatic pneumatocele is a diagnosis of exclusion. However, a history of blunt trauma, absence of lesions on previous radiographs, and rapid regression of the lesions are all compatible with the diagnosis of traumatic pneumatocele. In this case, given the antecedent history of trauma and lack of any constitutional symptoms in our patient, and lack of additional lesions, traumatic pneumatocele was considered the most likely diagnosis.

(Received in original form November 22, 2013; accepted in final form February 26, 2014 ) Correspondence and requests for reprints should be addressed to Yu Kuang Lai, M.D., Department of Internal Medicine, Einstein Medical Center Philadelphia, Philadelphia, PA 19141. E-mail: [email protected] Ann Am Thorac Soc Vol 11, No 5, pp 841–843, Jun 2014 Copyright © 2014 by the American Thoracic Society DOI: 10.1513/AnnalsATS.201311-411CC Internet address: www.atsjournals.org

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Figure 1. Lateral (left), coronal (top right), and axial (bottom right) slices of chest computed tomography scan showing a 1.8 3 1.5 3 1.3 cm right middle lobe cavitary lesion with air–fluid level and surrounding ring of ground glass opacities.

Discussion A traumatic pneumatocele, or traumatic pulmonary pseudocyst, is a rare benign lesion found in the lung parenchyma that usually occurs after blunt or penetrating trauma to the chest. It is estimated to occur in 1–3% of chest injuries (1, 2) and is more commonly described in children and adults less than 30 years of age (1, 3, 4). Males are predominantly affected (1, 3, 5). In adults, traumatic force to the chest is more evenly distributed to the bony structures, protecting the underlying lung. In contrast, the increased compliance of the chest wall in children and young adults allows transmission of the impact force directly to the underlying lung parenchyma, accounting for the predilection in this age group. The kinetic energy transmitted causes a rapid compression and decompression of the lung, lacerating alveoli and the interstitium. The negative pressure created by the retraction of the elastic lung facilitates formation of an air-filled cavity (6). Concurrent tachypnea and respiratory distress can further increase the negative pressure transmitted from the pleura and result in rapid growth of the lesion. The growth of the lesion will stop once the pressure between the cavity and surrounding tissues reaches equilibrium (4). 842

Patients can be asymptomatic or present with fever, cough, chest pain, dyspnea, hypoxemia, hemoptysis, or rarely, mental status change (3). Hemoptysis may persist up to 2 weeks (3). Laboratory findings include leukocytosis and elevation of liver enzymes from coexisting liver injury (3, 4). Traumatic pneumatocele is often identified incidentally by chest computed tomography during radiographic evaluation of trauma patients. Plain radiography is insensitive and may be negative in up to 50% of cases, as the cystic lesion may be obscured by the underlying pulmonary contusion or the small size of the cyst (3, 6). Once the contusion focus resolves, the traumatic pneumatocele may become apparent on an upright chest radiograph. Through computed tomography imaging, the lesion may be seen as early as 2–3 hours post-trauma, but may also become apparent a few days after the traumatic event (3, 5, 7, 8). The most common finding on computed tomography is a uniloculated or multiloculated, round or oval cystic structure with or without an air–fluid level. The lesion is usually found at the periphery, predominantly in the lower lobes, surrounded by ground glass opacity or consolidation from pulmonary contusion (1, 3, 6).

It may rarely occur bilaterally (4). Associated findings on computed tomography can include pneumothorax, hemopneumothorax, rib fracture, or pneumomediastinum (6, 9). Treatment is primarily supportive, as the clinical course is usually benign. However, complications that require intervention may occur such as superinfection (7, 10), abscess formation, hemothorax, and secondary pneumothorax (2, 8). Follow-up imaging is therefore recommended. Spontaneous resolution is expected within weeks or months if the size is less than 2 cm3. Antibiotics are not required in uncomplicated cases despite the presence of fever and leukocytosis, unless superimposed infection is suspected.

Final Diagnosis Traumatic pneumatocele.

Follow-Up To secure the diagnosis of traumatic pneumatocele, acid-fast smears and sputum culture were sent and all were negative. Computed tomography of the

AnnalsATS Volume 11 Number 5 | June 2014

CASE CONFERENCES abdomen and pelvis did not show any evidence of malignancy. Her alanine transaminase and aspartate transaminase trended down. On Day 2 of her hospital stay, a small right-sided pneumothorax was identified on chest radiograph. She was closely monitored with additional radiographs as she remained clinically stable. Repeat images eventually showed resolution of the pneumothorax with interval decrease in the surrounding contusion of the pneumatocele.

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Traumatic pneumatoceles are pseudocysts that can rarely occur after blunt trauma to the chest. The compliance of the chest wall plays a major role in the formation of traumatic pneumatocele; thus, the majority of cases have been described in children or young adults.

References 1 Melloni G, Cremona G, Ciriaco P, Pansera M, Carretta A, Negri G, Zannini P. Diagnosis and treatment of traumatic pulmonary pseudocysts. J Trauma 2003;54:737–743. 2 Kato R, Horinouchi H, Maenaka Y. Traumatic pulmonary pseudocyst: report of twelve cases. J Thorac Cardiovasc Surg 1989;97:309–312. 3 Chon SH, Lee CB, Kim H, Chung WS, Kim YH. Diagnosis and prognosis of traumatic pulmonary pseudocysts: a review of 12 cases. Eur J Cardiothorac Surg 2006;29:819–823. 4 Stathopoulos G, Chrysikopoulou E, Kalogeromitros A, Papakonstantinou K, Poulakis N, Polyzogopoulos D, Karabinis A. Bilateral traumatic pulmonary pseudocysts: case report and literature review. J Trauma 2002;53:993–996.

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Traumatic pneumatocele is the likely diagnosis in the appropriate clinical setting of antecedent trauma, absence of lesions on prior radiographs, and rapid regression of the lesion. The clinical course is almost always benign and the abnormal radiographic findings typically resolve spontaneously. n

Author disclosures are available with the text of this article at www.atsjournals.org.

5 Shirakusa T, Araki Y, Tsutsui M, Motonaga R, Iwanaga M, Ogami H, Matsuba K. Traumatic lung pseudocyst. Thorax 1987;42:516–519. 6 Tsitouridis I, Tsinoglou K, Tsandiridis C, Papastergiou C, Bintoudi A. Traumatic pulmonary pseudocysts: CT findings. J Thorac Imaging 2007;22:247–251. 7 Barbick B, Cothren CC, Zimmerman MA, Moore EE. Posttraumatic pneumatocele. J Am Coll Surg 2005;200:306–307. 8 Yazkan R, Ozpolat B, Sahinalp S. Diagnosis and management of posttraumatic pulmonary pseudocyst. Respir Care 2009;54:538–541. 9 Kaira K, Ishizuka T, Yanagitani N, Sunaga N, Hisada T, Mori M. Pulmonary traumatic pneumatocele and hematoma. Jpn J Radiol 2009;27:100–102. 10 Gincherman Y, Luketich JD, Kaiser LR. Successful nonoperative management of secondarily infected pulmonary pseudocyst: case report. J Trauma 1995;38:960–963.

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