Apical pleural cap refers to a curved density at the lung apex seen on chest radiograph.
The frequency of apical pleural thickening increases with age 3.
It arises from a number of causes:
idiopathic: chronic ischemic etiology is favoured ...
The apical zone is one of the four chest radiograph zones and an important location for missed diagnoses when reporting a frontal chest radiograph and makes up one of the "check areas". It is sometimes thought of as a subdivision of the upper zone.
Asbestos is a set of six naturally occurring silicate minerals from mixture of calcium magnesium, iron, and sodium exploited commercially for their desirable physical properties, particularly their resistance to heat and burning. They all form thin elongated fibrous crystals, and can be manufact...
An asbestos body is a histological finding in interstitial lung disease that is suggestive of significant occupational asbestos exposure. They are usually identified following a parenchymal lung biopsy 3.
Macrophage ingestion of the asbestos fibers triggers a fibrogenic response via the release...
Asbestosis refers to later development of diffuse interstitial fibrosis secondary to asbestos fiber inhalation and should not be confused with other asbestos related diseases.
Asbestosis typically occurs 10-15 years following the commencement of exposure to asbestos and is dose re...
Asbestos related benign pleural disease forms a large part of asbestos related lung changes.
The spectrum comprises of:
pleural effusions: benign-asbestos induced pleural effusions
can be associated with functional impairment
usually occur within 10 years of exposure but can also develop muc...
Asbestos related disease, in particular affecting the lung, comprise of a broad spectrum of entities related to the inhalational exposure to asbestos fibers. They can be divided into benign and malignant changes 1-3.
Benign pleural and parenchymal lung disease
asbestos related benign pleural d...
Ascariasis is due to infection with the Ascaris lumbricoides adult worm and typically presents with gastrointestinal or pulmonary symptoms, depending on the stage of development.
Ascaris lumbricoides is widely distributed in tropical and subtropical regions and in other humid ar...
Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients.
In adults, an ascending aortic diameter greater than 4 cm is considered to indicate dilatation 4. Aneurysmal dilatation is considered when the ascending aortic diameter reaches or ex...
Ascending aortic aneurysms are the most common subtype of thoracic aortic aneurysms and may be true or false injuries.
Ascending aortic aneurysms represent 60% of thoracic aortic aneurysms.
Typically ascending aortic aneurysms are an incidental finding an...
The ascending cervical artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It is a small artery that ascends medial to the phrenic nerve on the prevertebral fascia. It contributes many small spinal branches into the intervertebral foramina of ...
The original description of the Askin tumor (by Askin and Rosai in 1979 1), and many studies following it have led to a great deal of confusion. Until recently it has been considered a separate entity or as a type of peripheral primitive neuroectodermal tumor, usually of the chest wall.
Aspergillomas are mass-like fungus balls that are typically composed of Aspergillus fumigatus and are a non-invasive form of pulmonary aspergillosis. It usually falls under the subgroup chronic pulmonary aspergillosis.
Although the term mycetoma is frequently used to describe these...
Aspergillus is a fungal genus consisting of approximately 180 species. It is a ubiquitous fungus frequently found in urban areas especially in decomposing organic matter or water damaged walls and ceilings. Only a few Aspergillus species are associated with human disease.
Aspergillus clavatus is one of the species of Aspergillus that can cause pathology in humans. It is allergenic and causes a hypersensitivity pneumonitis called malt-workers lung.
Aspergillus flavus is a fungus and one of the species of Aspergillus that is common in the environment and responsible for pathology in humans.
It is the second most common cause of pulmonary aspergillosis (after Aspergillus fumigatus) and can additionally cause corneal, otomycotic, and nasoorb...
Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in immuno-compromised individuals.
A. fumigatus is a saprotroph (an organism that gets its energy from non-living organic matter) that is widespread in nature, typicall...
Aspiration bronchiolitis, or diffuse aspiration bronchiolitis, is a condition characterized by a chronic inflammation of bronchioles caused by recurrent aspiration of foreign particles.
The onset of aspiration bronchiolitis can be more insidious than aspiration pneumonia,...
Aspiration pneumonia is caused by a direct chemical insult due to the entry of a foreign substance, solid or liquid, into the respiratory tract.
Aspiration may be clinically silent, or it may present with dyspnea, cough, or fever. The clinical and radiographic features de...
Described below are points to consider on assessment of bones and soft tissue on chest x-ray.
lesions (most commonly metastases): may appear as lucent and/or sclerotic; inverting contrast may help in identification
previous surgery, e.g. thoracotomy with rib resection
Described below is one approach to systematic assessment and associated pathology of the cardiomediastinal contours on chest x-ray.
size: widened mediastinum can be seen in aortic dissection, traumatic aortic injuries
abnormal contour, e.g. lymphadenopathy, anterior mediastinal m...
Described below are some points on an approach to the assessment of the chest x-ray technical adequacy. Rarely, a technically inadequate chest x-ray will prohibit diagnostic interpretation but knowledge of the limitations will impact on diagnostic confidence.
Described below is one approach to the assessment of airways, lungs and pleura on chest x-ray. Start by assessing the tracheal air column, followed by the lungs and finally the pleural spaces.
assess position, should be central and deviation can be due to
positive mass ...
Described here are points to consider when approaching the assessment of the pulmonary hila on chest x-ray:
normally appear as gentle C-shapes on either side
contents: pulmonary arteries and veins, bronchi, lymph nodes
left hilum is normally 1-2 cm higher than the right
Asthma is a relatively common condition that is characterized by at least partially reversible inflammation of the airways and reversible airway obstruction due to airway hyperreactivity. It can be acute, subacute or chronic.
Asthma is one of the most common chronic diseases in th...
This is a basic article for medical students and other non-radiologists
Asthma is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. It is defined by two main features 1:
a history of respiratory symptoms such as wheeze, shortness of breat...
Asthmatic pulmonary eosinophilia is a form of pulmonary eosinophilia which is commonly attributed to Aspergillus fumigatus. Although many cases have not shown any allergen.
Plain radiograph - patterns
hyperinflation (in acute attacks or chronic severe asthma)
This is a basic article for medical students and other non-radiologists
Atelectasis describes loss of lung volume secondary to collapse. It has many causes, the root of which is bronchial obstruction with absorption of distal gas. Atelectasis may be subsegmental, segmental, lobar, or involve th...
The atoll sign in radiology can refer to:
reverse halo sign (atoll in thoracic CT)
atoll sign in liver MRI: suggestive of an inflammatory hepatic adenoma
Atrio-esophageal fistulas are rare pathological connections between the left atrium and the esophagus.
The presentation is non-specific. Patients may complain of fever, malaise, and/or dysphagia, or present with neurological symptoms 3.
The chief cause of at...
Atypical adenomatous hyperplasia (AAH) of the lung is a putative precursor lesion of adenocarcinoma of the lung. This entity replaces part of a spectrum of the former bronchoalveolar carcinoma (BAC).
AAHs are localised small cell proliferation, usually measuring ≤0.5 cm, of mildly to...
Atypical pneumonia refers to the radiological pattern associated with patchy inflammatory changes, often confined to the pulmonary interstitium, most commonly associated with atypical bacterial etiologies such as Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophilia. Viral ...
Owing to their features, the first, eleventh and twelfth ribs are considered atypical ribs.
Of all ribs, the first is the strongest, broadest and most curved. Ribs eleven and twelve are unique, among other reasons, by not being attached to the sternum.
The azygo-esophageal recess (also known as the line/interface) (AER) is a prevertebral space formed by the interface of the posteromedial segments of the right lower lobe and the azygos vein and esophagus 1-3. The AER extends from the azygos arch to the aortic hiatus and has the following border...
The azygoesophageal recess (AER) is formed by the interface between the right lung and the mediastinal reflection of the azygos vein and oesphagus. The line has a variable appearance:
in its upper third, it deviates to the right, where it may either be straight or concave relative to the right ...
An azygos lobe is created when a laterally displaced azygos vein creates a deep pleural fissure into the apical segment of the right upper lobe during embryological development. It is a normal anatomic variant of the right upper lobe due to invagination of the azygos vein and pleura during devel...
The azygos vein is a unilateral vessel that ascends in the thorax to the right side of the vertebral column, carrying deoxygenated blood from the posterior chest and abdominal walls. It forms part of the azygos venous system.
The azygos vein is formed by the union of the...
The azygos (venous) system is a collective term given to the H-shaped configuration of the azygos, hemiazygos, accessory hemiazygos veins and left superior intercostal vein.
It is responsible for draining the thoracic wall and upper lumbar region via the lumbar veins and posterior intercostal v...
Bacillary angiomatosis is an infective complication in those with the acquired immunodeficiency syndrome (AIDS) 3. Amongst other widespread multi-organ manifestations, the infection causes skin lesions which can be similar to those of Kaposi sarcoma.
Characterized by a non-neoplastic...
Exudative tracheitis, also known as bacterial tracheitis, membranous croup or membranous laryngotracheobronchitis, is a rare, but potentially life-threatening cause of upper airway obstruction.
Typical age ranges from 6 to 10 years of age.
Clinically it pre...
The ball of wool sign, also referred to as the yarn sign or congealed water lily sign, is an ultrasound appearance, representing degeneration of hydatid cysts (WHO class CE 4). The inner side of the cyst detaches from the cyst wall and folds on itself, causing a change from anechoic (fluid) to a...
BALT lymphoma is an abbreviated term for bronchus-associated lymphoid tissue lymphoma. These neoplasms fall under the broader umbrella of mucosa associated lymphoid tissue (MALT) lymphomas. It is sometimes considered a type of primary pulmonary lymphoma.
Up to half of pat...
Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4.
Bat's wing pulmonary opacities can be caused by:
BCGosis is a rare granulomatous disease following intravesical Bacillus Calmette-Guerin immunotherapy used in the treatment of superficial transitional cell carcinoma of the urinary bladder.
It manifests as a miliary pattern best seen in the lungs.
Bedside lung ultrasound in emergency (BLUE) is a basic point-of-care ultrasound (POCUS) examination performed for undifferentiated respiratory failure at the bedside, immediately after the physical examination, and before echocardiography.
It has been designed as a fast (<3 minute), three-point...
Behçet disease is a multisystemic and chronic inflammatory vasculitis of unknown etiology.
The mean age at which Behçet disease occurs is 20-30 years. The disease is most prevalent in the Mediterranean region, Middle East and East Asia. The highest incidence has been reported in T...
Thoracic manifestations in Behçet disease have a wide spectrum of appearances.
The reported prevalence of thoracic involvement of Behçet disease is thought to range around 1-8% 2.
Chest HRCT can demonstrate the entire spectrum of thoracic manifestation...
Benign metastasising leiomyomas are a rare metastatic phenomenon that is observed when a pelvic leiomyoma is present.
Women who have undergone hysterectomy for leiomyomas are most commonly affected.
Patients are usually asymptomatic at presentation. A histo...
Benign esophageal lesions are less symptomatic than malignant esophageal lesions, making up for only 1% of clinically apparent esophageal lesions.
esophageal leiomyoma (>50%)
esophageal fibrovascular polyp (~12.5%)
may contain fat
esophageal duplication cyst (10%)
Benjamin "Benny" Felson (1913-1988) was a renowned Cincinnati chest radiologist who coined or popularised several of the most commonly-used terms in the everyday parlance of the English-speaking radiology community.
Benjamin Felson was born in Newport, Kentucky on 21st October 191...
Bentall procedure is performed for the repair of ascending aortic root lesions. Typically the native aortic root and aortic valve are replaced with a composite graft that comprises both ascending aortic and aortic valve grafts, to which the coronary arteries are anastomosed.
History and etymolo...
Beryllium sensitisation (BeS) is a process whereby individuals exposed to beryllium dust develop a hypersensitivity reaction to it. A sizeable proportion of these individuals can progress to chronic beryllium lung disease with ongoing exposure.
Bifid or forked ribs are uncommon. They are thought to occur in ~0.2% of the population and there may be a female as well as right-sided predilection 2.
Usually asymptomatic, they may cause musculoskeletal pain or intercostal nerve entrapment. A bifid first rib is an unco...
The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.
It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.
Bilateral axillary lymphadenopathy can result from a number of causes and generally implies a systemic process. They include:
autoimmune diseases, e.g.:
systemic lupus erythematosus (SLE)
Bilateral hilar lymph node enlargement can arise from many causes, which include:
lymphoma: more common in Hodgkin lymphoma than non-Hodgkin lymphoma.
inorganic dust disease
Bird fancier lung refers to a type of hypersensitivity pneumonitis occurring as a response to avian antigens (usually inhaled proteins in the dust of bird feathers and droppings). It can have acute, subacute and chronic clinical presentations.
For a broad discussion on this entity, please refer...
The black pleura sign is a feature described in pulmonary alveolar microlithiasis. It is seen as a strip of tangential peripheral lucency underlying the ribs as compared to the adjacent diffusely dense calcified lung.
Although termed black pleura, it actually represents subpleural sparing of pu...
Bleomycin lung toxicity is an uncommon but recognised complication that can occur with the chemotherapeutic drug bleomycin.
Bleomycin is an antitumour antibiotic which was initially isolated from a strain of Streptomyces verticillus in 1966. It is commonly used (either alo...
The B-line is an artifact relevant in lung ultrasonography. As originally described, it has seven defining features 1:
a hydroaeric comet-tail artifact
arising from the pleural line
moving in concert with lung sliding, if lung...
A Bochdalek hernia is a form of congenital diaphragmatic hernia. They occur posteriorly and are due to a defect in the posterior attachment of the diaphragm when there is a failure of pleuroperitoneal membrane closure in utero. Retroperitoneal structures may prolapse through the defect, e.g. ret...
A helpful mnemonic for remembering the features of a Bochdalek hernia is:
B: back and medial, usually on the left side
B: bad (associated with pulmonary hypoplasia)
Bornholm disease, also known as epidemic pleurodynia, is a virally-mediated condition presenting as recurrent episodes of acute severe pleuritic pain. It is usually self-limiting, and serious morbidity is rare.
Its true incidence is unknown and it is thought that it is underdiagno...
Bovine arch is the most common variant of the aortic arch and occurs when the brachiocephalic (innominate) artery shares a common origin with the left common carotid artery.
A bovine arch is apparent in ~15% (range 8-25%) of the population and is more common in individuals of African descent. ...
A box-shaped heart is a radiographic description given to the cardiac silhouette in some cases of Ebstein anomaly. The classic appearance of this finding is caused by the combination of the following features:
huge right atrium that may fill the entire right hemithorax
shelved appearance of th...
The Boyden classification of bronchi refers to the standard nomenclature used to describe bronchopulmonary segmental anatomy.
Each lung has 10 segments, however on the left, the first two segments share a common trunk and are hence B1/2. Also given the shared trunk on the left of the lower lobe...
Brachiocephalic veins (BCV), previously the innominate veins are large paired valveless asymmetric veins that drain the head, neck, upper limbs and part of the thorax and mediastinum.
In the root of the neck, the internal jugular and subclavian veins unite to form the bra...
Brachytherapy seed migration to the lung is a known complication of radioactive seed therapy. These seeds are used for localised treatment of malignancies, most commonly prostate cancer.
Regarding staging, nearly 79% of the cases are localized, 12% are regional and 5% present with distant disea...
Useful mnemonics to remember the four branches of the thoracoacromial artery are:
CAlifornia Police Department
Cadavers Are Dead People
B: breast (pectoral)
CAlifornia Police Department
The Brasfield scoring system is a scoring system for patients with cystic fibrosis. The score is based on conventional chest radiographic findings and has been reported to have good correlation with pulmonary function. There can be intra- and interobserver variability between radiologists.
A bridging bronchus is a rare congenital bronchial anomaly where there is an anomalous bronchus to the right lung arising from the left main bronchus. It has a high association with right upper lobe bronchus (pig bronchus) and congenital cardiac and vascular malformations, particularly a left pu...
British Thoracic Society guidelines for pulmonary nodules were published in August 2015 for the management of pulmonary nodules seen on CT. In the United Kingdom, they supersede the Fleischner Society guidelines.
They are based initially on identifying whether the nodule is solid or subsolid an...
The Brock model, also known as the PanCan model, is a multivariable model that estimates the risk that a pulmonary nodule on CT scan is a lung cancer.
The model was developed from participants enrolled in the Pan-Canadian Early Detection of Lung Cancer Study 1, has been validated in lung cancer...
Bronchial anthracofibrosis has been defined as luminal bronchial narrowing associated with anthracotic pigmentation on bronchoscopy without a relevant history of pneumoconiosis or smoking.
However, there is a potential relationship between bronchial anthracofibrosis and tuberculosis (TB) 1. Co-...
Bronchial arterial aneurysm refers to any form of aneurysmal dilatation involving any segment of the bronchial artery. The term is sometimes used synonymously with a bronchial arterial pseudoaneurysm 2.
They are a rare entity and are reported in <1% of those who undergo selective ...
Bronchial arterial enlargement usually occurs as a result of bronchial pulmonary shunting. This can result from a number of situations:
underlying parenchymal pathology
bronchiectasis: especially in those with pulmonary manifestations of cystic fibrosis
those with certain forms of pulmonary h...
The bronchial arteries are the major supply of high-pressure oxygenated blood to the supporting structures of the lung, including the pulmonary arteries, yet they are responsible for only 1% of the lung blood flow overall.
Bronchial artery anatomy is variable, most commonly classified according...
Bronchial atresia is a developmental anomaly characterized by focal obliteration of the proximal segment of a bronchus associated with hyperinflation of the distal lung.
On imaging, it commonly presents as a proximal focal tubular shaped opacity radiating from the hilum associated with a dista...
Bronchial carcinoid tumors are carcinoid tumors primarily occurring in relation to a bronchus. They were previously incorrectly termed as bronchial adenomas. They usually occur in association with a segmental or larger bronchus.
Typically affects patients from 3rd to 7th decades w...
The bronchial cut-off sign refers to the abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucus plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse.
A bronchial diverticulum refers to a blind-ended outpouching arising from the bronchial tree.
They are relatively common on CT studies. They are more common and more widespread in smokers 2 but can also present in non-smokers. There may be a slightly increased male predilection ...
A mnemonic for the features of a bronchial fracture on a chest radiograph is:
P: progressive or
P: persistent pneumothorax or
A bronchial hamartoma falls under the same spectrum of pathology as a pulmonary hamartoma (except for their location), but a hamartoma in an bronchial location is less common than a peripheral pulmonary location. Bronchial hamartoma accounts for only around 1.4-10% of all intrathoracic hamartoma...
The bronchial veins are counterparts to the bronchial arteries and drain the bronchi, hilar structures and the mid-portion of the esophagus.
There is typically a single bronchial vein at each hilum, formed from the superficial bronchial veins with deep bronchial veins draining in...
Bronchial wall thickening is an imaging descriptor used to describe abnormal thickening of bronchial walls and can arise from a vast number of pathological entities. It is one of the causes of peribronchial cuffing.
The presence of bronchial wall thickening usually (but not always) implies infl...
Bronchiectasis is defined as irreversible abnormal dilatation of the bronchial tree. It has a variety of underlying causes, with a common etiology of chronic inflammation. High resolution CT is the most accurate modality for diagnosis.
As there are many causes of bronchiectasis, w...
A mnemonic to remember the common causes of bronchiectasis is:
CAPT Kangaroo has Mounier Kuhn
C: cystic fibrosis or congenital cystic bronchiectasis (Williams-Campbell syndrome)
A: allergic bronchopulmonary aspergillosis (ABPA)
P: post-infectious (most common)
T: tuberculosis (gra...
This is a basic article for medical students and other non-radiologists
Bronchiectasis refers to permanent dilatation of the airways secondary to chronic inflammation or infection. It is the common pathological response of bronchi to a variety of congenital and acquired conditions.
Bronchiolectasis is a descriptive term which is given to dilatation of bronchioles, which are of smaller caliber than bronchi. It can arise of a number of pathologies.
bronchiectasis: dilatation of larger aiways
Bronchioles are the branches of the tracheobronchial tree that by definition, are lacking in submucosal hyaline cartilage.
The bronchioles typically begin beyond the tertiary segmental bronchi and are described as conducting, terminal or respiratory bronchioles. Following the te...
Bronchiolitis is a broad term that refers to any form of inflammation of the bronchioles. It is often used in situations where there inflammation primarily occurs in airways smaller than 2 mm 6. It can carry variable clinical, functional and morphological expression. Bronchiolar disease may be ...
Bronchitis refers to inflammation of large airways (i.e. bronchi). This may be acute or chronic and can be precipitated by a variety of conditions.
bronchiolitis - inflammation of small airways
small airways disease
The broncho-arterial (BA) ratio is a descriptive parameter used in thoracic CT imaging. It is defined as the diameter of the bronchial lumen divided by the diameter of its accompanying artery 1. It is usually measured in the segmental to subsegmental artery level.
In healthy humans, the broncho...