Imaging of the trachea

Abstract

Numerous benign and malignant tracheal diseases may affect the trachea primarily and secondarily. While the posterior anterior (PA) and lateral chest radiograph is the conventional study for initial evaluation of the trachea and central airways, findings may not always be apparent on conventional radiographs, and further evaluation with cross sectional imaging is usually necessary. Computed tomography (CT) is the imaging modality of choice for imaging the trachea and bronchi. Familiarity with the imaging appearances of the normal and diseased trachea will enhance diagnostic evaluation.

Keywords: Trachea; tracheal stenosis; tracheal tumor; tracheomalacia.

Figure 1

Normal trachea. Paired inspiratory (A) and expiratory (B) axial CT images in lung windows demonstrate a thin smooth tracheal wall. On inspiration, the trachea has a normal circular configuration, but on expiration the posterior membranous wall becomes concave in configuration. Normally the tracheal lumen may decrease by 30% on expiration. Note that on expiration, the lung density also increases. A virtual bronchoscopic image (C) of the normal trachea at the level of the carina depicts the trachea from the perspective of bronchoscopy. The right main bronchus is seen on the right side of the image and the left main bronchus is seen on the left side of the image. The anterior trachea wall is seen at the top of the image and the posterior tracheal wall is seen at the bottom of the image. Note the slight indentation of the posterior membranous wall and the cartilaginous rings of the trachea. A 3D surface rendering of the trachea (D) demonstrates the normal trachea, main and lobar bronchi.

Figure 2

Tracheal “pig” bronchus. Axial CT (A) and coronal CT (B) images in lung windows demonstrate a tracheal bronchus arising from the right lateral wall of the distal trachea proximal to the take off the right upper lobe bronchus. In this case, a displaced bronchus supplies a portion of the right upper lobe.

Figure 3

Tracheal diverticulum and tracheobronchomegaly, Mounier-Kuhn syndrome. In a patient with a tracheal diverticulum, an axial CT image (A) of the trachea just below the thoracic inlet demonstrates an air-filled cystic structure arising from the right lateral wall of the trachea. In a patient with Mounier-Kuhn syndrome (B-D), a coronal CT image (B) reveals diffuse tracheobronchomegaly with typical scalloped appearance of the tracheal and main bronchial walls. A virtual bronchoscopic image (C) shows the dilated trachea and the out-pouchings of the wall manifesting as “diverticula”. An axial CT image in lung windows (D) demonstrates varicose and cystic bronchiectasis of the central subsegmental bronchi following multiple respiratory infections.

Figure 4

Tracheal stenosis. In a patient with post intubation “cuff stenosis” (A-D), an axial CT image (A) demonstrates circumferential thickening of the tracheal wall and narrowing of the lumen. A virtual bronchoscopic image (B) shows the circumferential stenosis. Coronal (C) and sagittal (D) CT images reveal the typical “hour glass” stenosis in the trachea at the level of the endotracheal tube cuff. In a patient with post traumatic tracheal stenosis (E), an axial CT image (E) of the proximal thoracic trachea reveals a circumferential stenosis of the trachea with diffuse irregular soft tissue thickening due to fibrosis. The enhancing right innominate artery forms the anterior wall of the trachea in this patient who presented with a delayed tracheal stenosis following a missed tracheal laceration resulting from trauma. In a patient with a “saber sheath trachea” (F-H), a posterior anterior (PA) (F) and lateral (G) chest radiographs and axial CT images (H) demonstrate diffuse narrowing the intrathoracic trachea. Note that the trachea is narrowed transversely and elongated in the sagittal plane and that the tracheal narrowing begins in the proximal thoracic trachea below the thoracic inlet.

Figure 5

Diffuse tracheal stenosis. In a patient with relapsing polychondritis (A-D), axial CT images of the thoracic trachea (A) and main bronchi (B) and coronal (C) and sagittal (D) images of the trachea demonstrate diffuse thickening of the cartilaginous portions of the trachea, sparing the posterior membranous wall. There are scattered calcifications within the abnormally thickened tracheal wall. In a patient with tracheopathia osteochondroplastica (E,F), axial CT of the trachea (E) and main bronchi (F) show smooth nodular thickening of the anterior and lateral walls of the trachea and main bronchi in which cartilaginous calcification is seen. The posterior membranous wall is spared. In a patient with amyloidosis (G,H), axial (G) and sagittal (H) CT images in soft tissue window reveal a circumferential stenosis of the thoracic trachea that involves the cartilaginous and membranous wall of the trachea. In two additional patients with amyloidosis (I,J), axial CT images demonstrate calcification within tracheal amyloid. In image (I) the tracheal wall is diffusely thickened and calcified involving the membranous and cartilaginous walls. In a different patient with tracheal amyloid (J), there is a large calcified soft tissue mass that nearly obstructs the cervical trachea.

Figure 6

Inflammatory and infectious tracheal lesions. In a patient with granulomatous polyangiitis (GPA) (A-D), axial CT images of the proximal trachea (A) and mid thoracic trachea (B), and coronal image of the trachea (C) demonstrate smooth circumferential soft tissue thickening of the trachea with stenosis of the lumen. A CT image of the sinuses (D) reveals diffuse thickening of the maxillary antrum. In a patient with fibrosing mediastinitis (E,F), axial CT images in soft tissue windows of the carina (E) and main bronchi (F) demonstrate narrowing and distortion of the carina and main bronchi by surrounding calcified soft tissue representing fibrosis. There is also narrowing of the right interlobar pulmonary artery by the fibrosis (F). In a patient with tuberculous tracheobronchial stenosis, hyperplastic phase (G-J), axial CT images of the distal cervical trachea (G), mid thoracic trachea (H) and main bronchi (I) in soft tissue windows reveals diffuse irregular thickening of the tracheal wall and diffuse stenosis of the trachea and left main bronchus in this patient with a chronic history of active post-primary tuberculosis. An axial CT image in lung window (J) reveals tree-in-bud opacities, bronchiectasis and bronchial wall thickening consistent with active tuberculosis. In a patient with a tuberculous tracheobronchial stenosis, fibrotic phase (K,L), a coronal CT (K) in lung windows and a virtual bronchoscopic image (L) demonstrate a smooth fibrotic stenosis of the left main bronchus from healed tuberculosis. In a patient with tracheobronchial papillomatosis (M-O), axial CT images of the proximal (M) and mid (N) thoracic trachea reveals multiple nodular soft tissue filling defects without evidence for invasion. A 3D-rendering of the trachea and main bronchi (O) demonstrates multiple nodules in the trachea and left main bronchus. In a separate patient with tracheobronchial papillomatosis (P,Q), axial CT images through the lower lobes in lung windows (P) and (Q) reveals multiple thin-walled pulmonary cysts in the lower lungs. There is a spiculated right lower lobe mass representing a squamous cell carcinoma that nearly occludes the bronchus intermedius (P) and right lower lobe bronchus (Q).

Figure 7

Tracheal tumors. In a patient with a chondroma of the cricoid cartilage (A), axial CT image (A) demonstrates a nodular tumor arising from the right aspect of the cricoid cartilage that contains dense calcification typical of a cartilaginous tumor. In a patient with a tracheal metastasis from melanoma (B), an axial CT image (B) at the thoracic inlet reveals a soft tissue mass arising from the anterior tracheal wall causing significant narrowing of the tracheal lumen. In a patient with squamous cell carcinoma of the trachea (C-F), an axial CT image (C) and virtual bronchoscopic image (D) of the mid trachea reveals a spiculated and nodular broad-based tumor arising from the left lateral wall of the trachea with associated thickening of the tracheal wall. There is an adjacent prominent lymph node is the left paratracheal region (C). A coronal CT image (E) and 3D surface rendering (F) of the trachea demonstrate the focal mass along the left lateral wall of the trachea. In a patient with adenoid cystic carcinoma of the trachea (G), an axial CT (G) in soft tissue window shows a soft tissue nodule arising from the left lateral tracheal wall that protrudes into the tracheal lumen. Notice the thickening of the left anterolateral tracheal wall by the tumor. In a different patient with adenoid cystic carcinoma of the trachea (H,I), axial (H) and coronal (I) soft tissue images of the trachea reveal diffuse smooth thickening of the trachea extending from the subglottic region to the thoracic inlet typical of diffuse submucosal spread of the tumor. In another patient with adenoid cystic carcinoma (J,K), coronal CT image in lung window demonstrates the pre-operative appearance (J) of an adenoid cystic carcinoma of the distal trachea and right main bronchus with distal atelectasis in the right lower lobe. A coronal CT image reveals the expected post-operative appearance following a carinal resection (K) in which the distal trachea and proximal main bronchi were resected. The right upper lobe bronchus was anastomosed to the trachea (end-to-side), the distal trachea was anastomosed to the left main bronchus (end-to-end) and the bronchus intermedius was anastomosed to the left main bronchus (end-to-side). In a patient with mucoepidermoid tumor at the carina (L-N), axial CT (L), coronal CT (M) in soft tissue windows and virtual bronchoscopic (N) image reveal a nodular soft tissue tumor obstructing the proximal right main bronchus extending to the carina.

Figure 8

Tracheomalacia. In a patient with tracheomalacia (A-D), axial CT images through the proximal intrathoracic trachea on inspiration (A) and expiration (B) demonstrates >70% narrowing of the tracheal lumen on expiration. Note that on expiration (B) there is marked anterior deviation of the posterior membranous wall of the trachea demonstrating the “frown sign”. Sagittal CT images through the trachea on inspiration (C) and expiration (D) reveals marked collapse of the intrathoracic trachea on expiration. In another patient with tracheomalacia (E-H), axial CT on inspiration (E) and expiration (F) reveal an elongated posterior membranous wall of the trachea and >70% collapse on expiration (F). Virtual bronchoscopic images on inspiration (G) and expiration (H) demonstrate significant collapse of the trachea consistent with tracheomalacia.

Video

Imaging of the trachea.