Imaging features of relapsing polychondritis
In late stages of the disease, the pathological process involves the airways, which is clearly visualized by diagnostic imaging modalities. The main target is the cartilaginous framework.
- Axial CT (at the aortic arch level): marked thickening of the anterior and lateral walls of the trachea is identified. Due to this, the airway lumen narrows pathologically and acquires an atypical round shape.
- Coronal reformation (minimum intensity projection): allows assessing the extent of the process. Thickening of the lateral walls (tracheolateral walls) is observed, and the luminal narrowing itself extends from the cervical trachea down to its bifurcation (carina).
Diffuse tracheal inflammation in relapsing polychondritis leads to cartilage weakening, which is a direct factor in the development of tracheobronchomalacia.
Tracheobronchomalacia as a consequence of polychondritis
Loss of structural integrity and cartilage destruction in polychondritis increase airway wall compliance (compliance). This condition is called tracheobronchomalacia (aside from polychondritis, it is associated with trauma, COPD, and Mounier-Kuhn syndrome).
- CT diagnostic criterion: reduction in luminal diameter by more than 70% on expiration (compared to inspiration).
- Radiography: demonstrates a significant decrease in sagittal diameter on expiration (a specific indicator is a decrease of nearly 300%).
- Lumen morphology: the frontal (coronal) diameter becomes significantly greater than the sagittal diameter. The trachea acquires a lunate shape (lunate configuration).
Flaccidity (flaccidity) of the trachea and bronchi is best detected during coughing or forced expiration.
Differential diagnosis: inflammatory bowel disease (IBD)
Airway symptoms may manifest even earlier than the intestinal manifestations of IBD (more commonly in ulcerative colitis than in Crohn's disease). A rare complication develops — ulcerative tracheitis and tracheobronchitis.
Unlike polychondritis, where cartilage is affected, IBD histologically reveals chronic inflammation and concentric fibrosis of the mucosa and submucosa with ulceration. The main difference: cartilage plates are not destroyed.
CT findings in IBD:
- Thickening of the tracheobronchial walls and uneven luminal narrowing.
- Thickening of the bronchial walls and bronchiectasis.
- Bronchial obstruction by mucous plugs (mucoïd impaction).
Differential diagnosis: nodular and deforming lesions
Aside from polychondritis, tracheal narrowing or deformation is caused by other rare syndromes that have their own specific imaging patterns.
Osteochondroplastic tracheobronchopathy Characteristic of men over 50 years old. Multiple broad-based nodules form in the submucosal layer, containing heterotopic bone, cartilage tissue, and calcified acellular matrix. The overlying mucosa is unchanged. Specific CT sign: calcified nodules protrude from the anterior and lateral walls into the lumen, while the posterior (membranous) tracheal wall is completely intact since it lacks cartilage.
Sabre-Sheath Trachea (Sabre-Sheath Trachea) Diffuse narrowing of the intrathoracic segment, almost always associated with COPD (due to abnormal intrathoracic pressure). CT and radiography: the internal frontal (side-to-side) diameter is reduced by 2 times or more compared to the sagittal diameter. The narrowing terminates at the level of the thoracic inlet (thoracic inlet). The contour is smooth or nodular, and the cartilages are often calcified.
Tracheobronchomegaly (Mounier-Kuhn Syndrome) Atrophy of elastic and muscular elements (in both the cartilaginous and membranous parts) leads to marked dilatation. The subglottic region remains normal. The mucosa prolapses between the rings, creating a corrugated contour (corrugated outline) and diverticula. CT criteria (diameter): trachea > 3 cm (2 cm above the aortic arch), right main bronchus > 2.4 cm, left > 2.3 cm.
Briefly: answers to topical questions
Which organs and cartilaginous structures, besides the airways, are affected in relapsing polychondritis?
In relapsing polychondritis (Relapsing Polychondritis), in addition to the tracheobronchial tree, the following structures are affected:
- Ears — involvement of cartilage tissue.
- Nose — involvement of cartilages.
- Joints — systemic involvement of cartilage tissue.
The pathogenesis is based on an acute inflammatory infiltrate in the cartilages and perichondral tissue, leading to progressive dissolution, cartilage fragmentation, and fibrosis.
What is the mechanism of deformation development in sabre-sheath trachea?
The mechanism of deformation in sabre-sheath trachea (Sabre-Sheath Trachea) lies in an acquired shape change associated with an abnormal pattern and magnitude of intrathoracic pressure. This pathology is almost always associated with chronic obstructive pulmonary disease (COPD).
Deformation characteristics:
- Frontal diameter — reduced by two times or more compared to the sagittal diameter.
- Extent — diffuse narrowing involves the entire intrathoracic segment of the trachea.
- Upper boundary — sharp return to normal caliber at the level of the thoracic inlet.
In polychondritis and osteochondroplastic tracheopathy, the pathology "hugs" the trachea anteriorly and laterally (following the shape of the cartilages), while the posterior wall remains intact. In IBD, fibrosis is concentric (circular).
Class and exam questions
How to confirm the diagnosis of tracheobronchomalacia on CT?
Key CT criterion — reduction of tracheal lumen diameter by more than 70% on expiration compared to the inspiration phase.
Is cartilage tissue affected in tracheitis associated with ulcerative colitis?
No, in inflammatory bowel disease, the cartilage plates are not destroyed. Concentric fibrosis of the mucosa and submucosa occurs.
What is the main feature of sabre-sheath trachea?
In sabre-sheath trachea, the frontal diameter is reduced by at least half compared to the sagittal diameter, and the narrowing is strictly limited to the intrathoracic segment (up to the thoracic inlet).
What else to study on this topic
- Pathogenesis of sabre-sheath tracheal deformation in COPD
- Histological appearance of nodules in osteochondroplastic tracheobronchopathy
- Association of tracheobronchomegaly with recurrent infections and diverticulosis
- Dynamic CT tests for assessing expiratory collapse (wall compliance)
- Extraintestinal manifestations of IBD affecting the respiratory system
Master the entire topic in the "Diagnostic Radiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Relapsing Polychondritis" and 2,199 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 10 video lessons on the subject
Other topics in the «Chest Radiology» section
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.