Discussion
Diagnosis With Brief Discussion
- Diagnosis
- Pulmonary sequestration
- Radiologic Findings
- Fig 1. Unremarkable finding in the chest radiography.
Fig 2. Serial low-dose non-contrast chest CT scans shows increasing irregular shape consolidation in left lower lobe.
Fig 3. Enhanced chest CT scan shows persistent irregular shape consolidation in left lower lobe with suspicious feeding vessel from the descending thoracic aorta.
- Brief Review
- The patient, with no notable medical history, was admitted after an incidental finding of consolidation on a low-dose chest CT during a screening. The patient had no presenting symptoms, and blood tests showed no abnormalities. Her chest radiography appeared normal, and the consolidation seen on the CT was not definitely observed on the chest radiography. A follow-up with low-dose chest CT was conducted to rule out malignancy. Over approximately three years of follow-up, the extent of the consolidation gradually increased. In two transbronchial lung biopsy (TBLB) instances, findings indicated chronic nonspecific inflammation, and the PET-CT showed equivocal FDG uptake, leading the medical team to plan surgery to exclude malignancy definitively. On the Enhanced CT taken a day before the surgery, the extent of the consolidation in the left lower lobe slightly increased. A systemic artery branching from the descending thoracic aorta and supplying the affected lung parenchyma was also identified. The surgical pathology results showed chronic inflammation associated with pulmonary sequestration, which had a feeding vessel.
Pulmonary sequestration (PS) is a malformation of the lower respiratory tract, consisting of a nonfunctioning mass of the lung tissue that lacks normal communication with the tracheobronchial tree and receives its blood supply from one or more aberrant systemic arteries. Despite being a relatively rare condition (accounting for 0.15% to 6.4% of all congenital pulmonary malformations), it is the second most common congenital lung malformation. Based upon the pleural investment of the sequestered lung parenchyma, PS can be classified as either intralobar or extralobar. Intralobar sequestration is characterized by sharing the same visceral pleura lining of the native lung and has a venous drainage into the pulmonary veins. Conversely, extralobar sequestration has its own viscerl pleural investment outside the normal lung and drains into a systemic vein, forming an accessory lobe.
In 1.5% of intralobar sequestration may also be seen as an irregular lesion mimicking a malignant tumor. Pleural effusion may rarely occur, and other findings such as focal bronchiectasis, subsegmental atelectasis, decreased lung volume have also been described. CT and MRI play a pivotal role in the diagnosis of PS, owing to their ability to accurately depict its anatomical location and structure and to identify its arterial supply and venous drainage.
Surgical resection with isolation and division of anomalous systemic feeding arteries is the treatment of choice for PS, and is recommended because of the likelihood of recurrent infection, the need for larger resection if the sequestration becomes chronically infected, the risk of hemorrhage and the reported development of malignancy, but also in asymptomatic patients to avoid infection.
Low-dose, non-contrast scans are widely used for screening and follow-up purposes. However, if there is suspicion of malignancy or surgery is being planned, an enhanced CT scan is necessary. Additionally, if persistent consolidation is observed in the left lower lobe, it is essential to consider the possibility of pulmonary sequestration and carefully check for the presence of a feeding vessel.
- References
- 1. Frazier, Aletta Ann, M. L. Rosado de Christenson, J. Thomas Stocker, and Philip A. Templeton. "Intralobar sequestration: radiologic-pathologic correlation." Radiographics 17, no. 3 (1997): 725-745.
2. Gabelloni, Michela, Lorenzo Faggioni, Sandra Accogli, Giacomo Aringhieri, and Emanuele Neri. "Pulmonary sequestration: what the radiologist should know." Clinical imaging 73 (2021): 61-72.
- Keywords