Common pathologies of the trachea and bronchi

Learn what signs to look for on a chest x-ray to determine whether something's wrong.

Julian Dobranowski, MD FRCPC FCAR
Julian Dobranowski, MD FRCPC FCAR
30th Jan 2018 • 4m read

Pathologies in the trachea and bronchi can be easy to spot on a chest x-ray if you know what to look for. In this lesson, Dr Dobranowski will show you what signs to look for on a chest x-ray to determine whether something's wrong, and how to confidently identify common pathologies involving the trachea and bronchi.

Join our Chest X-ray Essentials course now!

Want to master chest x-ray interpretation? Take our Chest X-ray Essentials course and learn how to interpret chest x-rays like a pro. Your instructor, Dr Julian Dobranowski—an award-winning author and Professor of Diagnostic Imaging at McMaster University in Ontario, Canada—will guide you through the essentials of chest X-rays. Give your medical career a boost with this Medmastery course!

Start the first chapter of our Chest X-ray Essentials course for free

Video Transcript

[00:00:00] What will I gain from this video? At the end of the video, you will know how to identify common pathology that involves the trachea and bronchi. The trachea and bronchi will be abnormal when the position of the trachea or the bronchi is shifted, or the shape of the trachea and bronchi is altered. The trachea can be displaced by pathology involving the mediastinum or the hila. In this example, there is an anterior mediastinal mass, that is

[00:00:30] displacing the trachea to the left and is narrowing the caliber of the trachea. The trachea is also displaced posteriorly and this posterior displacement is best seen on the lateral x-ray conversely. Middle and posterior mediastinal masses, if large enough, will displace the trachea anteriorly. Tracheal displacement is commonly seen following lung surgery such as pneumonectomy. As the remaining lung hyperinflates, it pushes the trachea to the side of the surgery.

[00:01:00] Diffused diseases, involving the trachea and bronchi, whether focal or diffuse, can also affect the carina. The subcarinal angle will increase from extrinsic influences that cause lifting of the proximal bronchi. This includes enlargement of the left atrium, generalized cardiomegaly, pericardial effusion or subcarinal mass or adenopathy. Often, with aging or with chronic obstructive pulmonary disease, the lateral dimensions of the trachea can decrease, with an increase in the

[00:01:30] anterior-posterior dimension. The analogy to this is pinching a tube between your thumb and index finger. This would cause narrowing in one dimension and expansion in the other dimension. This appearance of the trachea is called the saber sheath trachea and should not be mistaken for tracheal stenosis. Chronic infection can also lead to diffuse enlargement of the proximal bronchi. More commonly, common infections can lead to enlargement of the

[00:02:00] more peripheral bronchi, a condition called bronchiectasis. Depending on the shape of the enlarged bronchi, they are described as cylindrical or cystic. In this case, we see multiple cystic areas, within both lungs, that contain small air fluid levels. These are infected bronchiectatic cysts, within the left lung, predominantly but are also present on the right. Tracheal or bronchial

[00:02:30] narrowing can be focal or diffuse. The narrowing sometimes can lead to complete obstruction of the affected bronchus. When this occurs, the air within the bronchus will be completely lost or cutoff. In this example, we can follow the trachea inferiorly. We can identify the left main stem bronchus. We can only see the more proximal portion of the right mainstem bronchus, as there's complete and abrupt cutoff of the air, within the bronchus, by an

[00:03:00] underlying endobronchial tumor. Normally, the peripheral bronchi, within the lungs, are not identified past the low bar branches. However, if there is airspace disease, if there is fluid, water, blood or tumor within the airspaces, within the lungs, the lungs will look white. If however, the airways are patent, we will identify the patent airways through the opacity of the

[00:03:30] abnormal lung. This is called the air bronchogram and depending on the clinical situation, air bronchograms can be caused by pneumonia, pulmonary contusion and bleeding, pulmonary edema or occasionally bronchioloalveolar carcinoma or lymphoma. This is an example of an air bronchogram. We see the opacity within the right lung. Within the opacity, we can identify these branching tubular black structures, which represent

[00:04:00] the patent bronchi, within the right lung, in this patient with a right upper lobe pneumonia. Occasionally, the bronchi can be dilated and thickened. These bronchi can then be seen as parallel linear shadows on an x-ray. These are similar to train tracks and when present are called the tram track sign. These are associated with cylindrical bronchiectasis. In this example,

[00:04:30] within the right lower lobe, we can identify parallel linear lines, which represent the dilated and thickened bronchi related to bronchiectasis. In this case, we identify the normal caliber of the upper trachea and the normal caliber of the left main stem bronchus. However, the mid and lower trachea shows diffuse, smooth narrowing. The smooth narrowing has occurred as a complication of a previous

[00:05:00] prolonged endotracheal intubation. In this case, we can follow the trachea inferiorly. The trachea is of normal caliber but it's deviated to the right. We can identify the normal right mainstem bronchus but when we follow the left main stem bronchus, we see that the left main stem bronchus airway column is abruptly cutoff. This is because there is a large left hilar tumor, that was causing obstruction on the left mainstem bronchus and complete collapse of the left lung.

[00:05:30] There was also a large left pleural effusion. So, in conclusion, the trachea can be narrowed both focally or diffusely. The trachea can be displaced by adjacent pathology. An abnormal carinal angle can indicate adjacent cardiac or mediastinal pathology.