Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Extrathoracic lung herniation
- Radiologic Findings
- The patient had a history of traffic accident and was treated for multiple fractures about 10 years ago. A dumbell-shaped lesion was found on chest CT, which straddled across the right anterior chest wall. The lesion showed low attenuation as much as the air in the lung (figure 1). On bone window setting, chest CT demonstrates non-union of old fracture involving anterior arc of right 3rd rib (figure 2). When tracing the lesion up and down, the low attenuated lesion was continuous with lung parenchyma in the thorax and connecting pulmonary vessels were squeezed through the slit of non-union of right 3rd rib. Figure 3 is a 3D reconstructed image with SSD (surface shaded display)-technique. The communication between the herniated lung and intrathoracic lung parenchyma is nicely demonstrated on this 3D volume image.
- Brief Review
- Herniation of the lung and pleural membranes outside of the bony thorax is a rare occurrence. Broadly, the etiology is either congenital (accounting for 18% of cases) or acquired. When congenital, the hernia is caused by rib or intercostal hypoplasia or agenesis. An acquired extrathoracic lung hernia can be either caused by trauma (52% of cases), which is more often penetrating than blunt injury, or spontaneously acquired (30% of cases).These hernias can be asymptomatic and uncomplicated; therefore, presentation can be delayed. Presentation in these individuals occurs with a slowly enlarging fluctuant swelling more conspicuous on Valsalva manoeuvre.
Plain chest radiography may produce only subtle findings. Bony or joint trauma may be seen. Owing to the sharply defined density difference between herniated aerated lung and the surrounding chest wall soft tissues, the hernia itself may be apparent. The absence of contrast within the vessels of a herniated lung on contrast-enhanced CT can be taken as an indication of strangulation and therefore of imminently at-risk lung or already non-viable lung. Management decisions depend on whether the herniated lung is viable, the patient’s condition, and the site, type and size of the thoracic wall defect. Conservative treatment relies upon spontaneous regression of the hernia. Serial clinical and imaging examinations are vital for the conservatively managed patient.
- References
- Clark AJ, Hughes N, Chisti F. Traumatic extrathoracic lung herniation. Br J Radiol 2009; 82:e82-84.
- Keywords
- Lung, Chest wall, Trauma, Postoperative complication,