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:
Ps (or written as PPP or PPPP)
Ps: progressive or persistent pneumothorax or pneumomediastinum
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...
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 in 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 bronchioles. Following the tertiary segmental bronchi,...
Bronchiolitis (plural: bronchiolitides) 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. B...
Bronchitis (plural bronchitides) 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 ...
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 esophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnoses for a cystic mediastinal mass.
asymptomatic bronchogenic cyst
symptomatic esophageal 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.
fever, chest pain, rigors: due to obstructive pneumonia
lithoptysis: coughing up of broncholith(s)
A bronch-esophageal fistula (BOF) refers to an abnormal communication between a bronchus and the esophagus.
For congenital fistulas, please refer to the article on congenital tracheo-esophageal fistula.
A small proportion of patient with congenital forms may present in a...
Bronchopleural fistulas are communications between the bronchial tree and the pleural space.
They are usually divided as:
central: when the fistula involves the trachea or a lobar bronchus
peripheral: when a distal airway, either segmental bronchi or the lung parenchyma, communic...
Following are the main differentiating features of bronchopleural fistula versus lung abscess on plain radiographs and CT 1:
bronchopleural fistulas have mostly lenticular shape of space
length of gas-fluid level in bronchopleural fistula in different projections is un...
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 in infants after several weeks 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...
Bronchorrhea 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 of...
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 forms of pulmonary edema
A mnemonic to remember diseases that undergo bronchovascular spread is:
K: Kaposi sarcoma
I: infection (e.g. 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 hemorrhage or possibly pulmonary infarct secondary to pulmonary embolis...
A buffalo pneumothorax (or buffalo chest) refers to the rare occurrence of bilateral pneumothoraces caused by an abnormal physical communication between the two pleural spaces. The pleuropleural communication is postulated to be in the anterior median chest where there is a loss of the normal an...
The bulging fissure sign refers to lobar consolidation where the affected portion of the lung is expanded causing displacement of the adjacent fissure. Any type of pneumonia or space-occupying process can lead to bulging (sagging) fissure sign. Classically, it has been described in right upper l...
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 fibers 1. Other similiar textiles fibers 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 ...
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
See the main article on calcified pulmon...
Calcification associated with pulmonary emboli is usually associated with chronic pulmonary embolism. Calcification is occasionally related to prior congenital cardiac repairs 1.
If it is purely high attenuating, consider
polymethylmethacrylate (PMMA) embolism into the ...
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 pseudotumors (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 bee...
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 tumors osteoid origin, calcification and ossification of tumor cartilage, dystrophi...
A useful mnemonic to remember the causes of calcifying pulmonary metastases is:
B: bone (chondrosarcoma, osteosarcoma)
A: any primary post-chemotherapy
The canals of Lambert are microscopic collateral airways between the distal bronchiolar tree and adjacent alveoli. They are poorly formed in children, and along with poorly formed pores of Kohn, are thought to be responsible for the high frequency of round pneumonia in that age group.
Candida pneumonia is form of pulmonary candidiasis where there is air space opacification due opportunistic infection by the fungus Candida albicans. It typically occurs in immunocompromised patients. Due to the organism normally being present as part of oro-pharyngeal flora the diagnosis is oft...
Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance.
Metastases with such an appearance are classically...
Caplan syndrome, also known as rheumatoid pneumoconiosis, is the combination of seropositive rheumatoid arthritis and a characteristic pattern of fibrosis.
Although first described in coal miners (coal workers' pneumoconiosis), it has subsequently been found in patients with a variety of pneumo...
A capnothorax, sometimes referred to as a carbon dioxide (CO2) pneumothorax, has been reported as a potential complication with laparoscopic surgeries.
It has been reported with almost all laparoscopic surgeries and is more likely to occur with high CO2 pressures and prolonged sur...
Carcinoid tumors are a type of neuroendocrine tumor that can occur in a number of locations. Carcinoid tumors arise from endocrine amine precursor uptake and decarboxylation (APUD) cells that can be found throughout the gastrointestinal tract as well as other organs (e.g. lung). In general, they...
Carcinoid tumors of the lung are a subgroup of neuroendocrine tumors of the lung, of lower grade than small cell carcinoma of the lung and large cell neuroendocrine carcinoma of the lung.
For a general discussion, please refer to the article on carcinoid tumors.
Carcinosarcomas are highly malignant biphasic tumors with both carcinomatous (epithelial) and sarcomatous (bone, cartilage, or skeletal muscle) components.
It can arise in many organs:
lung 5: pulmonary carcinosarcoma
esophagus 1: esophageal carcinosarcoma
genitourinary tract 2
A cardiac bronchus (or sometimes termed accessory cardiac bronchus (ACB)) is a rare anatomic variant of the tracheobronchial tree, arising from the medial aspect of the bronchus intermedius.
This anomaly is rare and is reported in ~0.3% (range 0.09-0.5%) of individuals 3-5. There ...
Implantable cardiac conduction devices (also known as cardiac implantable electronic devices or CIEDs) are a very common medical device of the thorax, with over one million implanted in the United States of America alone.
There are two major types of cardiac conduction devices: pacemakers and a...
Cardiac MRI consists of using MRI to study heart anatomy, physiology, and pathology.
In comparison to other techniques, cardiac MRI offers:
improved soft tissue definition
protocol can be tailored to likely differential diagnoses
a large number of sequences are available
The cardiac plexus is a plexus of nerves situated at the base of the heart. It is formed by cardiac branches derived from both the sympathetic and parasympathetic nervous systems.
Sympathetic cardiac nerves are derived from T1 to T4 segments and partly from the T5 segment of the ...
Cardiac silhouette refers to the outline of the heart as seen on frontal and lateral chest radiographs and forms part of the cardiomediastinal contour. The size and shape of the cardiac silhouette provide useful clues for underlying disease.
From the frontal projection, t...
Cardiogenic pulmonary edema is a classification of pulmonary edema where the underlying etiology is due to left ventricular dysfunction. Causes include:
left heart failure
congestive cardiac failure
The cardiophrenic space is usually filled with fat. However, lesions originating above or lower to the diaphragm can present as cardiophrenic angle lesions.
The more common lesions encountered include:
pericardial fat pad
pericardial fat necrosis
A useful mnemonic to remember the differential diagnoses of a cardiophrenic angle mass is:
P: pericardial cyst
A: aneurysm, adenopathy
D: diaphragmatic hernia
The cardiothoracic ratio (CTR) aids in the detection of enlargement of the cardiac silhouette, which is most commonly from cardiomegaly but can be due to other processes such as a pericardial effusion.
Some report cardiothoracic ratio as a percentage, however this is incorrect, as...
The carina is the sagittally-oriented cartilaginous ridge at the bifurcation of the trachea and is an important reference point in chest imaging.
The carina represents the inferior termination of the trachea into the right and left main bronchi.
The carina usually sits at the le...
Carney complex (not to be confused with the Carney triad) is a rare multiple endocrine neoplasia syndrome characterized by 1-4:
seen in two-thirds of patients with Carney complex
skin pigmentation (blue nevi): especially of the face, trunk, lips, and sclera
Carney triad is a rare syndrome defined by the coexistence of three tumors:
extra-adrenal paraganglioma (e.g. spinal paraganglioma)
initially, only functioning extra-adrenal paragangliomas were included, but subsequent work includes non-functioning extra-adrenal paragangliomas 1
Castleman disease, also known as angiofollicular lymph node hyperplasia or giant lymph node hyperplasia, is an uncommon benign B-cell lymphoproliferative condition. It can affect several regions of the body although commonly described as a solitary mediastinal mass.
There are two distinct subty...
A catamenial hemothorax is one of the potential manifestations of thoracic endometriosis. It is essentially a terms of cyclical hemorrhage into the lungs. It is considered less common than a catamenial pneumothorax and a proportion of patients may present with hemoptysis 3.
Catamenial pneumothorax is a rare type of pneumothorax and is characterized by the recurrent accumulation of air in the thoracic space related to menstruation.
It may represent up to one-third of women with spontaneous pneumothoraces 1. Patient history may or may not be positive f...
Mnemonics to remember the causes of air trapping on HRCT chest are:
Once with HSBC, you are "trapped" with HSBC
H: hypersensitivity pneumonitis
B: bronchiolitis obliterans
C: cystic fibrosis/bronchiectasis
There are relatively few causes of calcification of the ascending aorta 1-3:
atherosclerosis (this usually spares the ascending aorta)
There are several causes leading to a perfusion defect on a VQ scan with an acute pulmonary embolus being only one of them:
acute pulmonary embolus
previous pulmonary embolus (including fat embolism, thromboembolism, air embolism, tumor)
vasculitides affecting the pulmonary v...
Cavitation associated with pulmonary infarction is a rare event. According to autopsy series, the reported cavitation rates are around 4-5% pulmonary infarcts 2-3. They can represent either aseptic pulmonary cavitation or superimposed infection following cavitation. There may be an upper lobe pr...
Cavitating pneumonia is a complication that can occur with severe necrotizing pneumonia and in some publications, it is used synonymously with the latter term 2. It is a rare complication in both children and adults.
Cavitation associated with Mycobacterium tuberculosis is separately discussed...
Cavitating pulmonary metastases refer to pulmonary metastases which then tend to cavitate. The term is similar but may not be identical to cystic pulmonary metastases in which the wall of the former may be thicker.
Cavitation is thought to occur in around 4% of lung metastases 2.
Cavitatory pulmonary sarcoidosis is a very uncommon pulmonary manifestation of sarcoidosis. It is usually reported in those with severe and active disease and its published prevalence is around 2% of all pulmonary sarcoidosis 2.
Imaging differential considerations inclu...
Cellular non-specific interstitial pneumonia is one of the two histological subtypes of non-specific interstitial pneumonia (NSIP). It is less common compared with fibrotic NSIP but carries a much better prognosis.
Symptoms are non-specific and include insidious onset of...
Distribution of bronchiectasis can help in narrowing the differential diagnosis. Central bronchiectasis is typically seen in:
allergic bronchopulmonary aspergillosis (ABPA)
congenital tracheobronchomegaly (a.k.a. Mounier Kuhn syndrome)
Williams Campbell syndrome (rare)
A number of cell groups in the reticular formation of the pons and medulla are responsible for the central control of the respiratory cycle:
inspiratory center (a.k.a. dorsal respiratory group) - bilateral groups of cells in the region of the nucleus of the tractus solitarius in the dorsum of t...
The muscle fibers of the diaphragm converge and attach to the central tendon of the diaphragm. It is a thin but strong layer of aponeurosis which forms an intergral part of respiration.
The central tendon of the diaphragm is located near the center of the diaphragmatic muscle bu...
Centrilobular lung nodules refer to an HRCT chest imaging descriptor for small 5-10 mm lung nodules which are anatomically located centrally within secondary pulmonary lobules. The term is applied on the basis of location of the nodule and not its morphology that is they may be well defined or p...
Centrilobular pulmonary emphysema is the most common morphological subtype of pulmonary emphysema.
It may be found in up to one-half of adult smokers at autopsy 1.
The pathological process of centrilobular emphysema typically begins near the center of the secondary pul...
The centrilobular region, in context of the lungs and HRCT, refers to the central portion of the secondary pulmonary lobule, around the central pulmonary artery and bronchiole.
Cervical aortic arches are a rare aortic arch anomaly characterized by an elongated, high-lying aortic arch extending at or above the level of the medial ends of the clavicles.
Patients with cervical aortic arch are usually asymptomatic. Symptomatic patients may present w...
Cervical ribs are supernumerary or accessory ribs arising from the seventh cervical vertebra. They occur in ~0.5% of the population, are usually bilateral, but often asymmetric 2, and are more common in females.
Although cervical ribs are usually asymptomatic, they are the mo...
The cervicothoracic sign, a variation of the silhouette sign, refers to visualization of a lesion above the level of the clavicle, indicating the abnormality is located posteriorly.
The anterior mediastinum ends at the level of the clavicles. Thus, the upper border of an anterior mediastinal le...
The Chang sign refers to the dilatation and abrupt change in caliber of the main pulmonary artery due to pulmonary embolism 1. It is one of several described signs of pulmonary embolus on chest radiographs.
History and etymology
It is named after C H Joseph Chang, (July 7 1929 - November 15 20...
Charcot-Leyden crystals consist of collections of bipyramidal crystalloid made up of eosinophilic membrane proteins, which occur in:
other eosinophilic lung disease 2
certain cases of sinusitis (e.g. allergic fungal sinusitis)
They may be detected in the sputum or sinus secretions wi...
The Cheerio sign has been described in two different scenarios:
Cheerio sign (pulmonary nodule)
Cheerio sign (shoulder)