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 characterised 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 dyspnoea, cough, or fever. The clinical and radiographic features d...
Asthma is a relatively common condition that is characterised 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...
Asthma is a heterogeneous disease, usually characterised 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 breath, chest tightness and cough that vary over time and in intensity, AND
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)
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 the entire lung.
This is a summary article; read more ...
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-oesophageal fistulas are rare pathological connections between the left atrium and the oesophagus.
The presentation is non-specific. Patients may complain of fever, malaise, and/or dysphagia, or present with neurological symptoms 3.
The chief cause of ...
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 previous bronchoalveolar carcinoma. It is defined as a peripheral focal proliferation of atypical cuboidal or columnar epithelial cells ...
Atypical pneumonia refers to the radiological pattern associated with patchy inflammatory changes, often confined to the pulmonary interstitium, most commonly associated with atypical bacterial aetiologies 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-oesophageal recess (AER) is a prevertebral space formed by the interface of the posteromedial segments of the right lower lobe and the azygos vein and oesophagus 1-3. The AER extends from the azygos arch to the aortic hiatus and has the following borders 1, 2:
The azygoesophageal recess (AER) is formed by the interface between the right lung and the mediastinal reflection of the azygos vein 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 in th...
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.
Characterised 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.
Behçet disease is a multisystemic and chronic inflammatory vasculitis of unknown aetiology.
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 ...
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.
CT - HRCT chest
CT can demonstrate the entire spectrum of thoracic manifest...
Benign metastasising leiomyoma (BML) is 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 h...
Benign oesophageal lesions are less symptomatic than malignant oesophageal lesions, making up for only 1% of clinically apparent oesophageal lesions.
oesophageal leiomyoma (>50%)
oesophageal fibrovascular polyp (~12.5%)
may contain fat
oesophageal duplication cyst (10...
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 where individuals exposed to beryllium dust form 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...
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)
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) 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 brachiocephalic veins posterior to the medial ends of the clavicles.
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.
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 sub-solid a...
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 responsible for only 1% of the lung blood flow but they are the major high-pressure oxygenated blood supplier to the supporting structures of the lung parenchyma including pulmonary arteries. The classic pattern described below of two bronchial arteries on the left and...
Bronchial atresia is a developmental anomaly characterised 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 tumours are carcinoid tumours 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...
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). An endobronchial location is less common than a peripheral pulmonary location where thay only account for around 1.4-10% of all intrathoracic hamartomas.
The bronchial veins are counterparts to the bronchial arteries and drain the bronchi, hilar structures and the mid-portion of the oesophagus.
There is typically a single bronchial vein at each hilum, formed from the superficial bronchial veins with deep bronchial veins draining i...
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 refers to abnormal dilatation of the bronchial tree and is seen in a variety of clinical settings. CT is the most accurate modality for diagnosis. It is largely considered irreversible.
As there are many causes of bronchiectasis, which may occur at essentially any a...
A mnemonic to remember the common causes of bronchiectasis is:
CAPT Kangaroo has Mounier Kuhn
C: cystic fibrosis or congenital cystic bronchiectasis
A: allergic bronchopulmonary aspergillosis (ABPA)
P: post-infectious (most common)
T: tuberculosis (granulomatous disease)
Bronchiolectasis is a descriptive term which is given to dilatation of bronchioles, which are of smaller calibre 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 can carry variable clinical, functional and morphological expression. Bronchiolar disease may be a primary or a secondary condition.
According to some authors, there is some overlap with the term small ...
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...
Bronchocentric granulomatosis (BG) is a rare chronic condition involving the lung and is sometimes included in the spectrum of eosinophilic lung disease 7.
It can affect a wide age spectrum of patients but is thought to peak between the 4th to 7th decades 6.
Bronchogenic cysts are congenital malformations of the bronchial tree (a type of bronchopulmonary foregut malformation). They can present as a mediastinal mass that may enlarge and cause local compression. It is also considered the commonest of foregut duplication cysts.
Bronchogenic cysts and oesophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnoses for a cystic mediastinal mass.
asymptomatic bronchogenic cyst
symptomatic oesophageal cyst in the case of peptic ulceration
Broncholithiasis is a term given for the presence of calcified or ossified material within the lumen of the bronchus.
A broncholith is usually formed by erosion by and extrusion of a calcified adjacent lymph node into the bronchial lumen and is usually associated with long-standing f...
Broncho-oesophageal fistula (BOF) refers to an abnormal communication between a bronchus and the oesophagus.
A small proportion of patient with congenital forms may present in adulthood. A common presenting feature is with recurrent pulmonary infections with other uncommo...
Bronchopleural fistula refers to a communication between the pleural space and the bronchial tree.
post-operative complication of pulmonary resection: considered by far the most common cause, with a reported incidence from 1.5 to 28% after pulmonary resection1
Following are the main differentiating features of bronchopleural fistula and lung abscess on plain radiographs and CT 1:
bronchopleural fistulas have mostly lenticular shape of space
length of air fluid level in bronchopleural fistula in different projections is unequ...
Bronchopneumonia, also sometimes known as lobular pneumonia, is a radiological pattern associated with suppurative peribronchiolar inflammation and subsequent patchy consolidation of one or more secondary lobules of a lung in response to bacterial pneumonia.
Pneumonia is the most...
Bronchopulmonary dysplasia (BPD) refers to late pathological lung changes that develop several weeks later in infants on prolonged ventilation.
BPD and chronic lung disease of prematurity (CLDP) have often been used interchangeably to describe the condition post-treatment of premat...
Bronchopulmonary foregut malformation (BPFM) is a term that encompases:
congenital pulmonary airways malformation (CPAM)
foregut duplication cysts
They result from anomalous budding of the ...
Bronchopulmonary segmental anatomy describes the division of the lungs into segments based on the tertiary or segmental bronchi.
The trachea divides at the carina forming the left and right main stem bronchi which enter the lung substance to divide further. This initial division ...
Mnemonics to remember the bronchopulmonary segments are:
A PALM Seed Makes Another Little Palm (right lung)
ASIA ALPS (left lung)
'A PALM Seed Makes Another Little Palm'
right upper lobe
A: apical segment
P: posterior segment
A: anterior segment
L: lateral segment
Bronchorrhoea is the expectoration of copious amounts of mucus from the lungs. It has been defined as production of more than 100 mL of mucus in 24 hours, which is more than is usually seen in chronic lung disease (e.g. chronic bronchitis typically produces 25 mL/24 hrs) 2. It may be a feature o...
Bronchospasm refers to a sudden constriction of the bronchial wall muscles.
It is caused by the release (degranulation) of substances from mast cells or basophils under the influence of anaphylatoxins.
It can be precipitated in many situations
certain formed of pulmonary oedema
A mnemonic to remember diseases that undergo bronchovascular spread is:
K: Kaposi sarcoma
I: infection: pneumocystis pneumonia/tuberculosis
L: lymphangitis carcinomatosis
The bronchus intermedius is one of the two bronchi which the right main bronchus bifurcates into, the other being the right upper lobe bronchus.
The bronchus intermedius runs distal to the right upper lobe bifurcation and follows the trajectory of the right main bronchus 1. Its m...
Bubbly consolidation describes internal or central lucencies which represent normal aerated lung lobule within infarcted, consolidated, lung parenchyma. It is one of the highly specific imaging appearances of focal pulmonary haemorrhage or possibly pulmonary infarct secondary to pulmonary emboli...
The bulging fissure sign refers to lobar consolidation where the affected portion of the lung is expanded. It is now rarely seen due to the widespread use of antibiotics.
The most common infective causative agents are 1:
Klebsiella pneumoniae: Klebsiella pneumonia
Streptococcus pneumoniae: pn...
Bunch of grapes sign refers to the ultrasound appearance of multiple cystic spaces or lesions and it has been described in a number of settings:
within the uterus as a result of hydropic swelling of trophoblastic villi within a hydatidiform mole
in bronchiectasis, where on a chest radiograph, ...
Byssinosis is a type of hypersensitivity pneumonitis which can result from exposure to cotton fibres 1. Other similiar textiles fibres such as jute, hemp and flax are also thought to cause similar lung pathology 2.
The Cabrol shunt or Cabrol fistula, also known as a perigraft-to-right atrial shunt, is a technique used for uncontrolled bleeding following aortic root operations.
The Cabrol shunt is applied when bleeding from an aortic root reconstruction cannot be controlled by traditional means ...
Calcification associated with pulmonary emboli is usually associated with chronic pulmonary embolism. They are occasionally be related to prior congenital cardiac repairs 1.
If it is purely high attenuating, consider:
polymethylmethacrylate (PMMA) embolism into lungs
There are numerous causes of calcified mediastinal lymph nodes.
Common causes include:
infectious granulomatous diseases
Uncommon causes include:
Pneumocystis jiroveci (PCP) pneumonia
thyroid carcinoma: papi...
Calcified pulmonary (lung parenchymal) densities can occur in a number of conditions.
healed varicella pneumonia 1
pulmonary alveolar microlithiasis
occupational lung diseases
coal workers pneumoconiosis
Large nodules or masses
Calcified pulmonary nodules are a subset of hyperdense pulmonary nodules and a group of nodules with a relatively narrow differential.
The most common cause of nodule calcification is granuloma formation, usually in the response to healed infection.
Calcifying fibrous pseudotumours (CFPT) of the lung are very rare, benign lesions of the lung.
They are composed of hyalinised collagen with psammomatous-dystrophic calcification and a typical pattern of lymphocytic inflammation.
CFPTs usually occur within soft tissues but have be...
Calcifying pulmonary metastases are rare. These should not be confused with metastatic pulmonary calcification.
Calcification in metastases can arise through a variety of mechanisms: bone formation in tumours osteoid origin, calcification and ossification of tumour cartilage, dystrop...