Archived case 173 · January 14-January 21, 2015
You are shown a contrast-enhanced chest CT image of a bicyclist struck by a car.
Which one of the following options BEST characterizes the type of pulmonary laceration seen in the left upper lobe?
Radiologic Findings Contrast-enhanced chest CT (lung window) shows a Type I left upper lobe pulmonary laceration (arrow). Note the surrounding ground glass consistent with hemorrhage and the lower lobe consolidation and volume loss. Pneumomediastinum and a left pneumothorax are also present. Answer Diagnosis: Type 1 Pulmonary Laceration
Type 1 Pulmonary Laceration
Differential Diagnosis
None
Discussion
Pulmonary laceration represents serious sequelae of chest trauma and may be caused by perforation of the lung parenchyma or pleura (e.g., stab wounds, gunshot wounds, and rib fractures) or by inertial deceleration. These lacerations may be inconspicuous or difficult to appreciate on initial chest radiography, often obscured by surrounding lung contusion, consolidation, and not infrequently, an ipsilateral hemothorax. CT more readily reveals lacerations as localized air collections of varying shapes and morphologies within areas of lung consolidation. Pulmonary lacerations are classified into four categories based upon the nature of the applied force and the CT appearance. Multiple laceration types may coexist in the same patient, lung or even lobe. Type I laceration (compression rupture) is the most common, results from chest wall compression causing an area of lung parenchyma to rupture, and is located centrally. Type II laceration (compression shear) is the result of a lateral compression force between the lung and the thoracic spine and is most often seen as a paravertebral tubular lesion in the lung bases. Type III laceration (rib penetration tear) is usually small, rounded, peripherally located and often associated with rib fractures and a pneumothorax. Type IV laceration (adhesion tear) results from the shearing of peripheral lung from previously formed pleuropulmonary adhesions and are only diagnosed at surgery or on pathologic specimens.
Prognosis
· Pulmonary lacerations usually resolve over 3-5 weeks.
· Complicated lacerations may persist for as long as one year.
· Pulmonary lacerations may be complicated by bronchopleural fistula; which can be further complicated by pneumothorax or tension pneumothorax.
· Post traumatic pneumatocele(s) may progressively enlarge in patients on mechanical ventilation.
Caveat:
· A pneumatocele forms if the space created by the laceration fills with air from the tracheobronchial tree.
· A pulmonary hematoma forms if this space instead fills with blood originating from a disrupted lung vessel.
· Pneumatocele and hematoma may coexist (i.e., hematopneumocele) and is characterized by an air-fluid level.
Selected Readings
1. Costantino M, Gosselin MV, Primack SL. The ABC’s of Thoracic Trauma Imaging. Semin Roentgenol 2006 Jul; 41(3): 209-25.
2. Gavelli G, Canini R, Bertaccini P, et al. Traumatic injuries: imaging of thoracic injuries. Eur Radiol 2002; 12: 1273-1294.
3. Parker MS, Rosado de Christenson ML, Abbott GF. Thoracic Trauma: Pulmonary Lacerations in: Chest Imaging Case Atlas 2nd edition 2012, Thieme New York. Pp 438-440.
4. Sangster GP, González-Beicos A, Carbo AI, Heldmann MG, Ibrahim H. Blunt traumatic injuries of the lung parenchyma, pleura, thoracic wall, and intrathoracic airways: multidetector computer tomography imaging findings: Pictorial Essay. Emerg Radiol 2007; 14: 297-310.
(Click for a larger image.)
Original case written by its authors at Virginia Commonwealth University and published at this address as part of a weekly teaching collection. Reproduced here as an archive.