Multidetector CT Detection Characterization and Differential Diagnosis MarieMichele Theriault MD FRCPC Kathleen Eddy MD Joy N Borgaonkar MD FRCPC Judith L Babar MRCP FRCR Daria Manos MD FRCPC ID: 908509
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Slide1
Diseases Involving the Central Bronchi: Multidetector CT Detection, Characterization, and Differential Diagnosis
Marie-Michele
Theriault
, MD, FRCPC, Kathleen Eddy, MD,
Joy N.
Borgaonkar
, MD, FRCPC, Judith L. Babar, MRCP, FRCR, Daria Manos, MD, FRCPC
Department of Diagnostic Radiology,
Université
de
Sherbrooke
,
Sherbrooke
, Canada (M.M.T.); Department of Diagnostic Radiology, Dalhousie University, 1276 S Park St, PO Box 9000, Halifax, NS, Canada B3H 2Y9 (K.E., J.N.B., D.M.); and Department of Radiology,
Addenbrooke’s
Hospital, Cambridge University, Cambridge, England (J.L.B.).
Address correspondence to D.M. (e-mail: daria.manos@nshealth.ca).
Presented as an education exhibit at the 2016 RSNA Annual Meeting (CH007-EB-X).
All authors have disclosed no relevant relationships.
Slide2IntroductionOverview
Radiologists encounter a variety of bronchial diseases. An organized approach to lesions involving the central bronchi can help radiologists formulate an appropriate differential diagnosis. Information obtained from the radiologist is invaluable for directing further investigation and management.
Early disease can be difficult to detect and can be easily missed if the airways are not systematically evaluated as part of every computed tomographic (CT) examination.
This presentation provides a guide to the identification and differential diagnosis of central bronchial lesions, including wall thickening and endoluminal nodules. Diseases limited to small airways and characterized primarily by bronchiectasis are not included.
A
Fig. 1. Axial CT image (A) shows a solitary tiny endobronchial lesion (arrow) in the superior segment of the right lower lobe (RLL). The lesion was missed. CT image obtained 2 years later (B) demonstrates a larger lesion completely obstructing the bronchus (arrow).
B
Slide3Introduction
Learning Objectives
Review the anatomy and function of the bronchial tree.
Discuss the ancillary CT signs that may improve detection and characterization of central bronchial lesions, including the double artery sign, the finger-in-glove sign, and
postobstructive bronchiectasis.Use a pattern-based approach to the differential diagnosis of central bronchial lesions, including focal abnormalities such as debris and tumors, as well as diffuse abnormalities, which usually result from inflammatory, infectious, or infiltrative processes.
Slide4Anatomy
DDx
: Focal lesion
Conclusion
DDx: Diffuse or multifocal processAnatomy and function
Main bronchiUnlike the C-shaped cartilage in the trachea, cartilage rings encircle the entire lumen.
Normal main bronchial wall thickness: ≈1.3 mmWall thickness decreases as the caliber of the bronchial lumen decreases. For main, lobar, and segmental bronchi, wall thickness is normally about one-fifth (20%) of the internal bronchial diameter.
Calcification of cartilage is a normal finding in older patients (occurring more often in women than in men) and is often discontinuous.Lobar and segmental bronchi Cartilage found in incomplete rings
Ancillary CT findingsAssessment of the airwaysSubsegmental bronchi arise from the segmental bronchi and may further branch before dividing into bronchioles. Bronchioles, unlike bronchi, do not contain cartilage or glandular tissue in their walls. On CT images, it may be difficult to distinguish between subsegmental bronchi and bronchioles. The term small airways is used for airways with an internal diameter of 2 mm or less and a normal wall thickness less than 0.5 mm. Small-airways disease generally refers to any condition affecting the bronchioles. Small airways disease is not included in this review.
Fig. 2. Anatomy of the main airways with C-shaped cartilaginous rings in the trachea and circumferential rings in the main bronchi.
Subsegmental
bronchi and bronchioles
Slide5In addition to facilitating gas exchange, the bronchial tree has defense functions.
The respiratory epithelium protects the respiratory system in three ways.
Physical barrier
: protecting the body against inhaled particles
Active barrier: removal of inhaled particles through the mucociliary system. Particles are trapped by mucus and then ejected through the synchronized motion of tiny cilia. Chemical defense: release of mediators involved in the control of inflammatory responseFunctionDDx: Focal lesionConclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Cartilage
Fig. 3. Photomicrograph shows the normal anatomy of the bronchial wall.
Respiratory epithelium
This defense can be compromised by
Obstruction
: the exit of the
mucociliary
system is blocked, and mucus builds up distal to the obstruction.
Ciliary
dysfunction
: either congenital (
eg
, primary ciliary dyskinesia), infectious, or environmental (
eg
, smoking)
Ineffective mucus
: abnormal mucus impedes clearance (
eg
, in cystic fibrosis).
Ancillary CT findings
Assessment of the airways
Serous and mucin-secreting glands
Smooth muscle
Slide6Ancillary CT findings
Assessment of the airways
DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Modalities in the Assessment of the Airways
For basic evaluation,
multidetector
CT acquisition is made at end-inspiration with thin-section axial and orthogonal
multiplanar
reformation images in coronal and sagittal planes.
Intravenous administration of contrast material can be useful to characterize some lesions and for assessing associated mediastinal or lung abnormalities.
Multidetector
CT
Expiratory CT images can be obtained to assess for
Postobstructive
air trapping (see slide 9)
Tracheobronchomalacia
: Anteroposterior luminal diameter reduction of 70% in expiration is suggestive and can be seen as an isolated process, associated with chronic inflammation (
eg
, chronic obstructive pulmonary disease [COPD], relapsing
polychondritis
) or advanced age.
Dynamic expiratory CT is more sensitive than static end-expiratory imaging. Expiratory images can be acquired with low-dose imaging techniques.
A
B
Fig. 4. Bronchomalacia. Inspiratory (A) and expiratory (B) CT images
show collapse of the central bronchi in expiration (arrows).
High-spatial frequency (bone) reconstruction is used to assess bronchial wall thickness. Use a window width of −450 HU and a window mean of 1000–1400 HU.
Mediastinal windows are used to assess tissue density (calcification, fat, mucus, soft tissue) of the bronchial wall and endoluminal tissue.
Slide7Fig. 5. Endobronchial hamartoma (arrows). Axial CT (A), coronal CT (B), virtual
bronchoscopic
(C) images.
Ancillary CT findings
Assessment of the airwaysDDx: Focal lesionConclusion
DDx
: Diffuse or multifocal process
Anatomy and function
More Advanced Multidetector CT Reconstructions
Fig. 6. Volume-rendered CT reformation shows bronchial narrowing in granulomatosis with
polyangiitis (arrow).
C
A
B
Advanced two- and three-dimensional reconstructions may improve diagnostic confidence and can provide more anatomically familiar information to the pulmonologist and surgeon.
CT techniques used in advanced visualization of the central airways include
Nonorthogonal
multiplanar
reformation (
eg
, coronal or sagittal oblique
multiplanar
reformation)
Maximum or minimum intensity projection
Curved planar reconstructions
Volume-rendered CT reformation
External (depicts external surface of airways and lungs)
Internal (virtual bronchoscopy)
Fig. 7. Minimum intensity projection
coronal image (10-mm-thick section) shows normal central airways.
Slide8Fig. 8. Endobronchial hamartoma (arrow). Bronchoscopic images before (A) and after (B) treatment. Note the tip of the bronchoscope (*).
DDx
: Focal lesion
Conclusion
DDx: Diffuse or multifocal processAnatomy and function
*
Other Modalities
Bronchoscopy
Allows dynamic functional evaluation
Extraluminal
extent of disease not evaluated
Limited evaluation of peripheral lesions
Biopsy or washings possible
Treatment (laser) possible
Fig. 10. Endobronchial US image demonstrates a lower right
paratracheal
node just deep to the bronchial wall.
Ancillary CT findings
Assessment of the airways
Node
Bronchial wall
Endobronchial Ultrasonography (US)
Predominantly used for nodal staging in cancer
Radial endobronchial US can also help evaluate endobronchial lesions, including extraluminal extent.
Allows guided biopsy
Fluorine 18
Fluorodeoxyglucose
(FDG) Positron Emission Tomography (PET)/CT
Increased FDG uptake in malignancy
Helps distinguish
postobstructive
atelectasis and consolidation from tumor
A
*
Fig. 9. Axial fused FDG PET/CT image at the level of the right hilum (A) shows FDG uptake centrally within the RLL bronchus (blue arrow) corresponding to endobronchial squamous cell carcinoma. PET/CT image at the level of the lung bases (B) shows no uptake in the
opacified
RLL (*): this is
postobstructive
atelectasis. Yellow arrows outline the major fissure.
B
A
B
Slide9DDx: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Fig. 13. Coronal CT image shows focal tree-in-bud opacities (oval) confined to the posterior segment of the right upper lobe (RUL). Squamous cell carcinoma was found in the segmental bronchus at bronchoscopy.
Impaction and dilatation of bronchioles, often because of infection. However, when focal and isolated, check for a central obstructing lesion.
Tree-in-bud sign
When a
nondilated
bronchus is filled with mucus, the associated pulmonary artery will be accompanied by an apparently identical tubular structure. Look for a central obstructing lesion.
Double artery sign
Ancillary CT Findings
These seven CT signs are found in many different processes. However, all may occur secondary to an obstructing central bronchial process and should prompt the radiologist to review the supplying bronchus.
Ancillary CT findings
Assessment of the airways
Fig. 11. Axial paired inspiratory (A) and low-dose expiratory (B) CT images show
hyperlucent
lung distal to a carcinoid tumor (arrow) in the anteromedial basal segmental bronchus of the left lower lobe (LLL).
Gas may be trapped in lung distal to an obstructing lesion with
hyperlucent
lung on expiratory images. Occasionally,
hyperlucent
lung is visible on inspiratory images when the window width is narrowed.
Air trapping
Fig. 12. Axial CT image shows mucus plugs (yellow arrows) in the RLL bronchi adjacent to similar-appearing arteries. Compare with normal appearance of LLL bronchi (blue arrows).
A
B
Slide10DDx: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Fig. 15. Coronal CT image shows marked volume loss (oval) distal to a squamous cell carcinoma (arrow) in the LLL bronchus. Note elevation of the hemidiaphragm.
Atelectasis distal to an obstructing lesion
Postobstructive atelectais
Fig. 14. Axial CT image shows postobstructive consolidation (pneumonia in circle) in a 25-year-old male patient with a carcinoid tumor (arrow) obstructing the right main bronchus.
Consolidation distal to an obstructing lesion manifesting as alveolar opacities
Postobstructive consolidation
Fig. 16. Sagittal oblique CT image shows bronchiectasis (circle) distal to an endobronchial carcinoid tumor (arrow) in a 69-year-old male patient.
Chronic obstruction may cause distal bronchial wall inflammation, leading to bronchiectasis.
Postobstructive
bronchiectasis usually occurs as a result of a chronic process or a slow-growing tumor.
Postobstructive
bronchiectasis
Ancillary CT Findings
Ancillary CT findings
Assessment of the airways
Finger-in-glove sign
Fig. 17. Coronal CT image demonstrates the finger-in-glove sign (arrow) in a 66-year-old female asthmatic patient with allergic bronchopulmonary aspergillosis (ABPA).
Impaction and dilatation of central bronchi manifesting as branching tubular opacities
Slide11Differential Diagnosis
DDx
: Focal lesion
Conclusion
DDx: Diffuse or multifocal process
Anatomy and function
Focal lesion
Diffuse or multifocal process
NeoplasticNonneoplastic
Malignant tumor
(90%)
Benign tumor
(10%)
Nonneoplastic
Inflammatory and infiltrative
Infection
Mucus*
Blood
Broncholith
Granulomatous lesions
Foreign body
Neoplastic
Endobronchial hamartoma*
Squamous cell papilloma
Endobronchial lipoma
Leiomyoma
Pulmonary pleomorphic adenoma
Lung cancer*
Adenoid cystic carcinoma
Carcinoid
Mucoepidermoid
carcinoma
Metastasis
Viral*
Bacterial*
Tuberculosis
Fungal
COPD*
Aspiration*
Sarcoidosis
Granulomatosis with
polyangiitis
Amyloidosis
Inflammatory bowel disease (IBD)
Tracheobronchopathia
osteochrondroplastica
Relapsing
polychondritis
Mucopolysaccharidosis
Lymphoma
Tracheobronchial papillomatosis
Metastases*
Ancillary CT findings
Assessment of the airways
Most Common*
Slide12Nonneoplastic
DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Malignant tumor
Benign tumor
Common, especially in patients with chronic bronchial inflammation (eg, COPD, asthma, bronchiectasis) and in patients who have difficulty coughingCT findings
Fluid density (mediastinal window)
May see internal gasOften dependent within the bronchusCan also be seen peripheral to obstruction
BEWARE: Solitary plug may be an early sign of endobronchial neoplasm (Fig. 28)
.
A benign cause of persistent focal bronchial plugs includes bronchial atresia. The mucus plug (
mucocele
) forms peripheral to the atretic segment because of inability to clear secretions. The peripheral lung is usually
hyperlucent
because of air trapping.
Ancillary CT findings
Assessment of the airways
Mucus plug
Fig. 19. Bronchial
atresia
. Large branching endobronchial mucus plug (arrow) in the posterior segment of the RUL seen on coronal CT image (A). (B) Coronal minimum intensity projection (30 mm) in the same patient highlights the associated segmental air trapping.
B
A
Fig. 18. Mucus plug (arrow) in the posterior basal segmental LLL bronchus on paired axial enhanced CT images in lung (A) and mediastinal (B) windows. The endobronchial lesion had low opacity (−5 to 5 HU) consistent with fluid. Note the gas bubble.
A
B
Slide13Nonneoplastic
DDx
: Focal lesion
References
DDx
: Diffuse or multifocal process
Anatomy and function
Malignant tumor
Benign tumor
Indistinguishable from other noncalcified
endobronchial material at CTUsually occurs in the setting of hemoptysis
May be aspirated from an upper tract source
Ancillary CT findings
Assessment of the airways
Fig. 20. Axial CT image shows a blood clot (yellow arrow) in the right intermediate bronchus in a 67-year-old man with pulmonary hemorrhage.
Endobronchial blood
Broncholith
Usually caused by
Extrusion of an adjacent calcified lymph node into a bronchus, usually in the setting of prior tuberculosis or histoplasmosis infection OR
In situ calcification of foreign material
Fig. 21.
Broncholith
. Axial CT image shows a peripherally calcified opacity (arrow) in the anterior segmental bronchus of the RUL.
Slide14Nonneoplastic
DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Malignant tumor
Benign tumorForeign body aspiration is most common in the 2nd year of life and in the elderly.
Predisposing factors includeIntubation
Neurologic deficitFacial trauma
Dental procedure
Fig. 22. Axial CT image (A) shows a calcified foreign body (yellow arrow) in the left main stem bronchus. Chest radiograph (B) better demonstrates the cause—a tooth (green arrow).
Ancillary CT findings
Assessment of the airways
B
A
Fig. 23. Aspiration in an 83-year-old man. Coronal oblique (A) and axial (B) CT images show right middle lobe (RML) collapse (blue arrows), obstruction of a 1.5-cm length of the RML bronchus (yellow arrow), and bronchiectasis. Photomicrograph of the transbronchial biopsy (C) in the same patient reveals degenerating exogenous material compatible with either aspirated adipose tissue or vegetable material.
B
A
C
Foreign body
Slide15DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Malignant tumor
Benign tumor
Nonneoplastic
Most common benign lung tumor
A
minority are endobronchial.
Most common benign endobronchial tumor
CT findings
Macroscopic fat (−40 to −120 HU).
Differential diagnosis: Lipoma (lipoma much more rare)
Calcification (>200 HU)
Can be
popcornlike
(cartilaginous)
Differential diagnosis: Carcinoid
Combination of fat and calcification
Considered diagnostic
Hamartoma
Ancillary CT findings
Assessment of the airways
Fig. 24. Endobronchial hamartoma. Axial CT image demonstrates a partially calcified nodule (yellow arrow) within the superior
lingular
bronchus. Note the peripheral mucus plugging (blue arrows).
Fig. 25. Paired axial CT images in lung (A) and mediastinal (B) windows demonstrate a low-attenuating endobronchial lesion in the LLL bronchus (arrows). This was persistent at serial CT examinations and therefore not consistent with mucus plug.
Bronchcoscopic
and endobronchial biopsy findings confirmed an endobronchial hamartoma. (Case courtesy of Joao Ignacio, University of Ottawa.)
Slide16DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Malignant tumor
Benign tumor
Nonneoplastic
Lipoma
Endobronchial location very rare
Arises from adipose tissue in the submucosal layer of bronchial wall
Most commonly appears as a focal endobronchial nodule of fat attenuation
Note: Hamartoma may give an identical appearance and is much more common.
May be asymptomatic or may present with cough, increased sputum production, or other symptoms of obstruction
Fig. 26. Axial CT image of a bronchial lipoma. Focal smoothly
marginated
fat-opacity nodule (arrow) in the left main stem bronchus.
Ancillary CT findings
Assessment of the airways
Slide17DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Malignant tumor
Benign tumor
Nonneoplastic
Other benign neoplasms
These entities are rare with specific diagnosis generally requiring tissue biopsy.
Squamous cell papilloma
Solitary equivalent of tracheal papillomatosis (see slide 36)
Pulmonary pleomorphic adenoma
Slowly growing tumor; involves central airways; has salivary gland features
Airway leiomyoma
Two-thirds in the trachea, one-third in the bronchi
Arises from smooth muscle of bronchial wall
Other benign tumors
Hemangioma
Fibroma
Neurogenic tumors
Inflammatory
myofibroblastic
tumor
(also known as pulmonary inflammatory
pseudotumor
, plasma cell granuloma,
xanthogranuloma
); rare overall, but common pediatric primary lung tumor
Ancillary CT findings
Assessment of the airways
Fig. 27. Schwannoma in the RLL bronchus. Axial CT image (A) shows soft tissue at the origin of the RLL bronchus (yellow arrow). This could be misinterpreted as a lymph node. Coronal CT image (B) more clearly shows the endobronchial nature. Note the associated peripheral mucous plugging (blue arrows). The CT features are not specific, and
bronchoscopic
biopsy was required to make the diagnosis.
A
B
Slide18DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Malignant tumor
Benign tumor
Non neoplastic
Lung cancer
Strongly associated with cigarette smoking
Squamous cell carcinoma is the most common subtype to affect the central bronchi.
When confined to bronchial tree, can be difficult to appreciate
Look for ancillary signs, including focal peripheral
postobstructive
tree-in-bud,
mucus plug, atelectasis, and consolidation.
Ancillary CT findings
Assessment of the airways
Fig. 29. Endobronchial squamous cell carcinoma. Axial CT image (A) shows a nodule in the LLL bronchus (yellow arrow). Coronal CT image (B) shows the same lesion (yellow arrow) causing
postobstructive
atelectasis (blue arrow).
B
A
Fig 28. Axial CT image shows endobronchial adenocarcinoma (arrow). Although mucus plugging is common in smokers, this lesion is isolated, in the upper lobe, and dilates the affected bronchi. These features are rare for the benign mucus plugging common in smokers and should raise concern for neoplasm.
Slide19DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Benign tumor
Nonneoplastic
Fig. 31. Carcinoid. Axial
precontrast (A) and postcontrast (B) CT images demonstrate an enhancing lesion in the LLL bronchus (yellow arrows) with irregular calcification (blue arrow). Neuroendocrine neoplasmRanges from low-grade typical carcinoid to atypical carcinoid (aggressive course)
Not associated with smokingCT findings
80% arise centrally (main, lobar, segmental bronchi).May appear completely or partially endobronchial
Well-defined, round, slightly lobulatedOften strong enhancement due to
hypervasularity
Eccentric calcifications in 30%
A
Ancillary CT findings
Assessment of the airways
Fig. 30. Carcinoid. Axial CT image (A) shows endobronchial lesion in the anteromedial basal LLL bronchus (yellow arrow). Two years later, axial CT image (B) shows the tumor has enlarged and is now associated with
postobstructive
mucus plugging (blue arrow).
A
B
B
Carcinoid tumor
Malignant tumor
Slide20DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Benign tumor
Nonneoplastic
Fig. 32. Carcinoid. Axial CT image (A) shows nodule (blue arrow) in the RML lobar bronchus. Note the associated complete atelectasis of the RML. (B) Photomicrograph from video-assisted
thoracoscopic surgical (VATS) wedge resection in the same patient demonstrates typical submucosal origin of tumor lifting the respiratory epithelium and protruding into the bronchial lumen.Ancillary CT findings
Assessment of the airways
Bronchial lumen
carcinoid
Cartilage in bronchial wall
Respiratory epithelium
B
A
Carcinoid tumor
Malignant tumor
Slide21DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Benign tumor
Nonneoplastic
Adenoid cystic carcinoma
Cancer of salivary gland origin
Tends to be central (trachea more common than main or lobar bronchi)
Tendency toward submucosal extension with circumferential and infiltrative growth
Ancillary CT findings
Assessment of the airways
Mucoepidermoid
carcinoma
Arises from minor salivary glands
Most involve lobar or segmental bronchus (trachea less common)
Intraluminal nodule adapting to the branching features of the airways
Fig. 33. Adenoid cystic carcinoma. Axial (A) and coronal (B) CT images in a 31-year-old man with a solitary endobronchial left main bronchus lesion (yellow arrow) extending through the bronchial wall.
Fig. 34. Mucoepidermoid carcinoma (arrows) in two patients. Curved coronal oblique CT image (A) in an 87-year-old woman shows a lesion in the left main bronchus with
postobstructive
atelectasis. Axial CT image (B) in a 28-year-old man shows a lesion in bronchus intermedius. Note that in both cases there is no evidence of extraluminal extension.
A
B
B
A
Malignant tumor
Slide22DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Benign tumor
Nonneoplastic
Fig. 36. Endobronchial osteosarcoma metastasis. Photomicrograph demonstrates typical pattern of metastasis arising focally in the bronchial wall and then enlarging to fill the lumen. Note portions of the bronchial wall are preserved with intact epithelium
.Endobronchial tumor
Cartilage
Respiratory epithelium
Hematogenous
metastases to the bronchi are usually multifocal but can be solitary. (See also slide 37).
Ancillary CT findings
Assessment of the airways
Even in the presence of known
extrathoracic
malignancy, solitary metastases often require tissue confirmation to exclude primary endobronchial neoplasm.
Malignant tumor
Metastasis
Fig. 35. Axial CT images in two patients with solitary endobronchial metastasis: breast carcinoma (yellow arrow in A) and colorectal adenocarcinoma (orange arrow in B).
B
A
Slide23Differential Diagnosis
DDx
: Focal lesion
Conclusion
DDx: Diffuse or multifocal process
Anatomy and function
Focal lesion
Diffuse or multifocal process
NeoplasticNonneoplastic
Malignant tumor
(90%)
Benign tumor
(10%)
Nonneoplastic
Inflammatory and infiltrative
Infection
Mucus*
Blood
Broncholith
Granulomatous lesions
Foreign body
Neoplastic
Endobronchial hamartoma*
Squamous cell papilloma
Endobronchial lipoma
Leiomyoma
Pulmonary pleomorphic adenoma
Lung cancer*
Adenoid cystic carcinoma
Carcinoid
Mucoepidermoid
carcinoma
Metastasis
Viral*
Bacterial*
Tuberculosis
Fungal
COPD*
Aspiration*
Sarcoidosis
Granulomatosis with
polyangiitis
Amyloidosis
IBD
Tracheobronchopathia
osteochrondroplastica
Relapsing
polychondritis
Mucopolysaccharidosis
Lymphoma
Tracheobronchial papillomatosis
Metastases*
Ancillary CT findings
Assessment of the airways
Most Common*
Slide24DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Neoplastic
Inflammatory or infiltrative
Infection
Bacterial and Viral
Most community-acquired bronchitis is viral (85%–95%).
Smooth wall thickening and luminal narrowing are seen at CT.
Rhinoscleroma
is a unique bacterial infection uncommon in North America.
Chronic granulomatous infection affecting nose and larynx much more commonly than tracheobronchial tree
Caused by
Klebsiella
rhinoscleromatis
Causes wall thickening, nodules, and strictures
Fig. 37. Active bacterial bronchitis. Axial CT image (A) shows central bronchial wall thickening (arrow). Photomicrograph (B) from a VATS resection specimen in a different patient shows bronchial wall inflammation in active bronchitis.
cartilage
B
A
Inflammatory
exudate
(pus) in lumen
Thickened mucosa and
submucosa
Lymphoid follicle
Ancillary CT findings
Assessment of the airways
Slide25DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Neoplastic
Inflammatory or infiltrative
Tuberculosis
Fig. 39. Active tuberculosis. Axial CT image shows RUL bronchial wall thickening (yellow arrow). The
subsegmental bronchial wall measures 1.8 mm and is almost as thick as the bronchial lumen. Note adjacent cavitary lung disease of tuberculosis (green arrow).
Central airway involvement mechanismSpread along peribronchial lymphatics or local extension from lymphadenitis
Less commonly, through spread of infected sputumTubercles in submucosa lead to ulceration, which may heal with or without stenosis.
CT findings of bronchial tuberculosis
Active disease
Irregular circumferential bronchial wall thickening with luminal narrowing
Lymphadenitis (may
cavitate
)
Associated
mediastinitis
possible; associated pulmonary disease typical
Fibrotic disease
Smooth concentric central airway narrowing
Minimal wall thickening
Fig. 38. Fibrotic tuberculosis 61 years after active infection. Coronal CT image shows narrowing of the left upper lobe bronchus (yellow arrow) with
postobstructive
atelectasis (green arrows). The
lingula
(*) is spared.
*
Ancillary CT findings
Assessment of the airways
Infection
Slide26DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Neoplastic
Inflammatory or infiltrative
Fig. 41. ABPA. Unenhanced CT images in mediastinal (A) and lung (B) windows show
hyperattenuating mucus impaction (arrows) with associated complete atelectasis of the RUL (*). Fungal tracheobronchitisUsually in the setting of immunocompromiseMost common: Aspergillus and Candida speciesCT findings
Smooth or nodular tracheobronchial wall thickening with or without focal mucus and/or fungal plugs
APBAAffects patients with asthma or cystic fibrosis
Hypersensitivity reactionCT findingsBilateral central (segmental and subsegmental
) branching mucus plugs within
bronchiectatic
airways (finger-in-glove sign)
Hyperdense
mucus specific but not sensitive, seen in approximately 25% of patients
Fungal
Ancillary CT findings
Assessment of the airways
*
A
B
A
B
Fig. 40. Airway invasive fungal disease. Axial (A) and coronal (B) CT images in a 66-year-old immunosuppressed woman (liver transplant) with diffuse bronchial thickening and narrowing (yellow arrows) and
peribronchovascular
nodules (green arrows).
Infection
Slide27DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Inflammatory or infiltrative
Infection
COPD and Asthma
Ancillary CT findings
Assessment of the airways
Fig. 43. Coronal CT image demonstrates bronchial diverticula (green arrows) in a smoker.
Diffuse airway wall thickening (AWT) is common in COPD and can affect both central bronchi and small airways.
AWT may occur independently of emphysema and reflects the chronic bronchitis COPD phenotype.
AWT in COPD is important to report and may reflect reversible disease.
Asthma typically affects smaller airways but can affect large bronchi.
Patients with asthma and COPD often have mucous plugs that tend to be basal, multifocal, and transient.
Tiny diverticula of the central bronchi are more common in smokers (from hyperplasia of the submucosal glands) but can also be seen in never smokers.
COPD can cause
tracheobronchomalacia
.
Fig. 42. Bronchial wall thickening (green arrows) on axial CT images in a patient who smokes one pack per day. Bronchial wall thickness is 2 mm or greater at the RUL anterior segmental bronchus (A), the LLL lobar and superior segmental bronchi (B), the medial and lateral segmental RML bronchi (C), and the LLL lateral and posterior segmental bronchi (D).
A
B
c
D
Slide28DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Infection
Sarcoidosis
Multisystem inflammatory granulomatous disorder, lung involvement commonLarge airway stenosis underappreciated radiographically, often seen at bronchoscopy
Bronchial involvement more common than involvement of trachea or larynxIrregular or smooth narrowing caused by
Accumulation of granulomas in bronchial wallExtrinsic compression by lymph nodes
Distortion secondary to fibrotic parenchymal disease
Fig. 44. Bronchial wall thickening and luminal narrowing in sarcoid. Axial enhanced CT image (A) demonstrates severe narrowing of the LLL bronchus (yellow arrow) secondary to wall thickening. Coronal reformatted image viewed in bone windows (B) also shows the wall thickening of the LLL bronchus (yellow arrow) and reveals characteristic calcification of adjacent nodes (green arrow).
B
A
Ancillary CT findings
Assessment of the airways
Inflammatory or infiltrative
Slide29DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Infection
Amyloidosis
Deposition of abnormal proteinaceous material (amyloid) in extracellular tissue
Tracheobronchial amyloidosis can be an isolated manifestation of amyloidosis or associated with systemic amyloidosis.
CT findings
Diffuse airway involvement is more common but can be focal (
amyloidoma
) or multifocal.
AWT, frequently calcified (no sparing of the posterior membranous trachea)
Luminal narrowing
Fig. 45. Bronchial amyloid. Coronal oblique CT images (A,B) show bronchial wall thickening with calcifications (yellow arrows) predominantly involving the large airways. Note peripheral atelectasis (green arrow) secondary to bronchial narrowing.
Fig. 46. Bronchial amyloid. Polarized light photomicrograph from a
transbronchial
biopsy shows characteristic apple green birefringence.
A
Ancillary CT findings
Assessment of the airways
B
Inflammatory or infiltrative
Slide30DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Infection
Granulomatosis with Polyangiitis
Fig. 47. Bronchial involvement in granulomatosis with polyangiitis. (A,B) Axial CT images show bronchial narrowing and wall thickening (yellow arrows) and cavitating lung nodules and masses (green arrows). Virtual (C) and conventional (D) bronchoscopic images in the same patient show airway inflammation and narrowing (blue arrows).
Previously: Wegener granulomatosis
Idiopathic multisystem necrotizing granulomatous vasculitis
Subglottic involvement more common than bronchial involvement
CT findings of central airway involvement
Noncalcified
irregular circumferential wall thickening
Ulcerated wall thickening possible
Stenosis, obstruction
Endobronchial
pseudotumors
of inflammatory granulomatous tissue
Ancillary CT findings
Assessment of the airways
A
D
B
C
Inflammatory or infiltrative
Slide31DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Infection
Inflammatory Bowel Disease
IBD only rarely affects the airway and is more common in ulcerative colitis than in Crohn disease.Manifestations include tracheobronchitis, bronchiectasis, and small airways disease.
CT findings of tracheobronchial involvementNoncalcified
tracheobronchial wall thickeningIrregular luminal narrowing and postobstructive findings
Fig. 48. Images in a 57-year-old man with ulcerative colitis. Axial (A) and coronal (B) CT images reveal circumferential thickening of the central airways, including the trachea and left and right main bronchi (yellow arrows). Coronal CT image with lung windowing (C) demonstrates
bibasal
bronchiectasis with bronchial wall thickening and mucus plugging (green arrows). Virtual CT
bronchoscopic
image (D) shows a featureless mucosal surface, with loss of the normal cartilaginous ring indentations.
Ancillary CT findings
Assessment of the airways
D
C
B
A
Inflammatory or infiltrative
Slide32Tracheobronchopathia
Osteochondroplastica
Rare idiopathic process affecting the large airways of middle-aged adults, more often men than women
Multiple nodules, with or without calcification, arise from the cartilaginous rings and protrude into the airway lumen. Posterior trachea is spared as it contains no cartilage.
Involvement of the mid and distal trachea; main and lobar bronchi is typical.
DDx
: Focal lesion
ConclusionDDx: Diffuse or multifocal processAnatomy and function
Neoplastic
Infection
Fig. 49.
Tracheobronchopathia
osteochondroplastica
. Axial CT images (A,B) demonstrate multiple tiny nodules arising from the anterior and lateral walls of the trachea (yellow arrows). Axial CT images (C,D) in another patient demonstrate small endobronchial nodules (green arrows).
Ancillary CT findings
Assessment of the airways
B
D
A
C
Inflammatory or infiltrative
A
B
Slide33DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Infection
Rare autoimmune disease of cartilageRecurrent episodes of cartilaginous inflammation results in destruction and fibrosisPeak prevalence 40–60 years, occurs in women more often than in men Airway involvement = poor prognosis
CT findingsCalcified thickening of cartilaginous portion of trachea and bronchi is specific.
Excessive tracheal and bronchial collapse in expiration (tracheobronchomalacia)More irregular and more thick than senile calcification of cartilage
Clinical diagnosis made when there are three or more of the following:Auricular chondritis
Nonerosive
seronegative polyarthritis
Nasal
chondritis
Ocular inflammation
Respiratory tract
chondritis
Audiovestibular
damage
Relapsing
Polychondritis
Fig. 50. Relapsing
polychondritis
. Axial (A) and coronal (B) CT images at the trachea show calcification and wall thickening (yellow arrows) that spare the posterior membranous (
noncartilaginous
) trachea (green arrow). Axial CT image (C) just below the carina shows similar findings at the main bronchi (yellow arrow). The wall is much thicker than in senile calcification. Technetium 99m–methylene diphosphonate bone scan (D) demonstrates exaggerated activity in cartilaginous structures, including the cartilaginous portion of the anterior ribs and larynx.
Ancillary CT findings
Assessment of the airways
B
D
A
C
Inflammatory or infiltrative
C
Slide34Mucopolysaccharidoses are a group of disorders associated with malfunctioning of lysosomal enzymes leading to accumulation of glycosaminoglycans in tissues and progressive damage.
Hunter syndrome is one of the seven types of
mucopolysaccharidoses
(type 2) and is associated with airway involvement.
Most commonly affects distal trachea and central bronchiSevere airway stenosis possible and may be life threateningDDx: Focal lesionConclusion
DDx
: Diffuse or multifocal process
Anatomy and function
NeoplasticInfection
Mucopolysaccharidoses
Fig. 51. Hunter syndrome. Axial CT images viewed in lung windows (A) and mediastinal windows (B) show diffuse wall thickening of the right and left main bronchi (yellow arrow) resulting in severe luminal stenosis (green arrows). Sagittal CT image (C) demonstrates typical severe tracheal narrowing in the anteroposterior dimension (blue arrows).
C
A
B
Ancillary CT findings
Assessment of the airways
Inflammatory or infiltrative
Slide35DDx: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Neoplastic
Inflammatory or infiltrative
Infection
Lymphoma
Endobronchial involvement in lymphoma is rare.
More common with Hodgkin disease than with non-Hodgkin lymphoma
Typically occurs in the setting of advanced disease elsewhere
May manifest with symptoms of airway narrowing and obstruction
Endobronchial involvement may be nodular (solitary or multiple) or may manifest as diffuse wall thickening.
Fig. 52. Endobronchial involvement in non-Hodgkin lymphoma. Coronal CT image demonstrates a nodule in the right main stem bronchus (arrow). Nodal enlargement and lymphangitic
carcinomatosis
is also present. Multiple additional endobronchial nodules not shown.
Ancillary CT findings
Assessment of the airways
Slide36DDx
: Focal lesion
Conclusion
DDx
: Diffuse or multifocal processAnatomy and function
Inflammatory or infiltrative
Infection
Tracheobronchial
Papillomatosis
Related to human papillomavirus
Multiple endobronchial nodules (squamous cell
papillomas
)
Most frequent in young people (transmission during vaginal birth or through sexual contact)
The larynx is most commonly affected, followed by the trachea and then the central bronchi. Occasionally there is spread to the lung parenchyma (nodules that usually
cavitate
).
Endobronchial obstruction by the nodules may result in:
Postobstructive
pneumonia, atelectasis, mucus plugging, and thin walled cysts
Typically treated with laser. May recur. May spread through airways. May undergo malignant transformation to squamous cell carcinoma.
Fig. 53. Tracheobronchial papillomatosis. Axial CT image (A) demonstrates bilateral endobronchial nodularity (yellow arrow) and
postobstructive
atelectasis (orange arrow). Note
postobstructive
mucus plugging (blue arrow). Another CT image (B) in the same patient demonstrates a cyst (green arrow).
B
A
Ancillary CT findings
Assessment of the airways
Neoplastic
Slide37DDx: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and function
Inflammatory or infiltrative
Infection
Metastases
Fig. 54. Prostate metastases. Coronal minimum intensity projection shows endobronchial nodules (arrows) in the right main stem bronchus and the
interlobar
bronchus.
Transbronchial
biopsy was required to confirm the diagnosis.
Ancillary CT findings
Assessment of the airways
Hematogenous metastases to the bronchi
Most common primary malignancies are
Breast
*
Colorectal
*
Kidney
*
Stomach
Prostate
Melanoma
Thyroid
CT findings: Solitary or multiple nodules or eccentric wall thickening
BEWARE: Endobronchial renal cell carcinoma metastases, like the primary lesions, may grow slowly
.
Neoplastic
Slide38DDx: Focal lesion
Conclusion
DDx
: Diffuse or multifocal process
Anatomy and functionConclusion
Both focal and diffuse central bronchial lesions may be easily overlooked.
CT provides excellent characterization of central bronchial lesions allowing evaluation of tissue density, extent of endobronchial involvement, assessment of the lung distal to the endobronchial abnormality, and evaluation of the surrounding tissues.
Ancillary CT signs improve detection of focal endobronchial lesions. Particularly when isolated and especially when persistent, ancillary signs should prompt careful evaluation of the supplying bronchus. Advanced reconstructions (eg, minimum intensity projection, three-dimensional rendering, virtual bronchoscopy) can improve diagnostic confidence, allow better anatomic assessment, and more clearly define airway compromise.
Functional impairment, symptoms, and uncertainty regarding diagnosis frequently lead to bronchoscopy for further evaluation of lesions demonstrated at CT. With the exception of transient processes such as mucus plugs and infection, most central bronchial lesions require tissue diagnosis. Management depends both on the pathologic finding of the abnormality and on the obstructive potential of the process.Ancillary CT findingsAssessment of the airways
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