Aortic dissection is the most common form of the acute aortic syndromes and a type of arterial dissection. It occurs when blood enters the medial layer of the aortic wall through a tear or penetrating ulcer in the intima and tracks along the media, forming a second blood-filled channel within th...
The aortic dissection detection risk score (ADD-RS) is a clinical decision tool that aids in grading the pretest probability of an acute aortic dissection. Scores range from 0-3, where 0 is classed as low risk, 1 is moderate risk and 2-3 is high risk 1.
The three domains in which pati...
The use of the aortic dissection detection risk score plus D-dimer is a proposed standardized strategy of safely ruling out the diagnosis of an acute aortic syndrome. Similar to how the pulmonary embolism rule-out criteria (PERC) negates the need for further workup of a pulmonary embolism.
The aortic hiatus is one of the three major apertures through the diaphragm and lies at the level of T12. Strictly speaking, it is not a real aperture in the diaphragm, but an osseoaponeurotic opening between it and the vertebral column.
The hiatus is situated slightly to the left of the midli...
Aortic intramural hematoma (IMH) is an atypical form of aortic dissection due to hemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural hematomas are seen in older hypertensive patients....
The aortic knob or knuckle refers to the frontal chest x-ray appearance of the distal aortic arch as it curves posterolaterally to continue as the descending thoracic aorta. It appears as a laterally-projecting bulge, as the medial aspect of the aorta cannot be seen separate from the mediastinum...
An aortic nipple is seen in about 10% of PA chest x-rays on the lateral surface of the aortic arch/aortic knob. It represents the left superior intercostal vein.
When prominent, superior vena cava obstruction should be considered as the left superior intercostal vein serves as a collateral path...
Differentiation of aortic pseudoaneurysm from ductus diverticulum is critical, particularly in the trauma setting. A traumatic aortic pseudoaneurysm is a surgical emergency whereas a ductus diverticulum is a normal anatomic variant.
The following are differentiating features:
The aortic-pulmonary stripe is an uncommon feature of frontal chest radiographs and was first described by Keats in 1972 1.
It is formed by the interface of the pleural surface of the anterior segment of the left upper lobe contacting the mediastinal fat that is anterolateral to the pulmonary t...
An aortic transection, also known as a traumatic aortic rupture, is a type of traumatic aortic injury. It is considered the second most common cause of death associated with motor vehicle accidents.
It occurs from a near-complete tear through "all the layers" of the aorta due to trau...
Aortic valve calcification can be an important incidental observation thoracic radiography or CT imaging. It is considered a marker for clinically significant aortic stenosis.
According to some reports aortic valve calcification may be prevalent as an incidental finding up to 18% of...
Aortopulmonary septal defect (APSD), also known as aortopulmonary window (APW), is a congenital anomaly where there is an abnormal communication between the proximal aorta and the pulmonary trunk in the presence of separate aortic and pulmonary valves.
APSD should not be confused w...
The aortopulmonary (aortic-pulmonary or AP) window (also known as APW, but see 'Terminology' below) is a radiological mediastinal space seen on frontal chest radiographs.
The term should also not be confused with an aortopulmonary septal defect, which is occasionally also called an...
Handy mnemonics to remember common apical lung diseases are:
CARPETS (anagram of SET CARP)
E: eosinophilic pneumonia
C: cystic fibrosis
A: ankylosing spondylitis
R: radiation pneumonitis
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 favored f...
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 processes 1-3.
Benign pleural and parenchymal lung disease
asbestos-related benign pleural...
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...
Asphyxiating thoracic dysplasia, also known as Jeune syndrome, is a type of rare short limb skeletal dysplasia, which is primarily characterized by a constricted long narrow thoracic cavity, cystic renal dysplasia and characteristic skeletal features. It is also sometimes classified as one of th...
Aspiration occurs if liquid or solid material enters the subglottic lower respiratory tract.
The term aspiration is used if material passes below the level of the vocal folds, i.e. subglottic. If material enters the larynx but remains above the vocal folds this is called penetratio...
Aspiration bronchiolitis, or diffuse aspiration bronchiolitis, is a condition characterized by a chronic inflammation of bronchioles caused by recurrent aspiration of foreign particles.
neurologic disorders: ~ 50% 3
dementia: ~50% 3
Patients with esop...
Aspiration pneumonia is caused by a direct chemical insult due to the entry of a foreign substance, solid or liquid, into the respiratory tract.
loss of consciousness
structural abnormalities of the pharynx and esophagus
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.
assessed by ...
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 ...
The assessment of the pulmonary hila on chest x-ray is important for detecting potential mediastinal and lung pathology.
Several features of the hilum and hilar point can be assessed:
normally appear as K or C-shapes on either side
contents: pulmonary arteries and veins, bronchi, lymph...
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 sign in thoracic CT
atoll sign in liver MRI: suggestive of an inflammatory hepatic adenoma
Atresia (plural: atresias) refers to a situation where there is absence, underdevelopment or abnormal closure, of a normal anatomical tubular structure or opening.
Contrast this with agenesis which refers to the complete absence of any anatomical structure including its primordial precursors.
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 represented by localized small cell proliferation, usually measuring ≤0.5 c...
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 ...
An atypical pulmonary carcinoid tumor is a more aggressive variant of a peripheral pulmonary carcinoid tumor. They are considered intermediate grade neoplasms and have the same “carcinoid morphology,” but with mitotic rates increased (at 2–10 mitoses per 2 mm2) where the tumor might also be pun...
Owing to their features, the first, eleventh and twelfth ribs are considered atypical ribs. Some authors however describe the second, tenth and eleventh ribs as atypical ribs also.
Of all ribs, the first is the strongest, broadest and most curved. Ribs eleven and twelve are unique, among other ...
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 the invagination of the azygos vein and pleura during d...
The azygos vein is a unilateral vessel that ascends in the thorax to the right of the vertebral column, carrying deoxygenated blood from the posterior chest and abdominal walls. It forms part of the azygos venous system.
The spelling azygous when referring to the vein is incorrect,...
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...
The bacillus Calmette–Guérin (BCG) vaccine is the only vaccine available for Mycobacterium tuberculosis and despite its global use for 90 years, with proven efficacy and a good safety record, has well-known limitations. It provides only limited protection against pulmonary tuberculosis.
Bacterial (pyogenic) pneumonia is common and is a major cause of morbidity and mortality globally.
Bacterial pneumonia has symptoms similar to other pneumonia. When a productive cough is present, purulent or blood-stained sputum may indicate bacterial pneumonia ref.
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...
Bagassosis refers to a form of hypersensitivity pneumonitis related to a mouldy molasse usually related to sugar cane dry pulpy fibrous residue called bagasse (Thermoactinomyces sacchari). It is considered to reflect a reaction to organic dust and is becoming rarer in recent years.
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...
Barium aspiration occurs occasionally during upper GI fluoroscopic studies using barium sulfate contrast, and usually only small amounts pass into the airways.
When only tiny quantities of barium pass into the airways (so-called microaspiration) the patient may remain asy...
Barium sulfate (BaSO4), often just called barium in radiology parlance, is an ionic salt of barium (Ba), a metallic chemical element with atomic number 56. Barium sulfate forms the basis for a range of contrast media used in fluoroscopic examinations of the gastrointestinal tract. Unlike barium ...
Bat 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 wing pulmonary opacities can be caused by:
pulmonary edema (es...
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.
The protocol is simple and dichotomous, and takes fewer...
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 asbestos-induced pleural effusions are considered part of asbestos related benign pleural disease.
Patients may be asymptomatic or present with dyspnea or chest pain.
They develop after an extended latency period post-asbestos exposure, with a median du...
Benign metastasizing leiomyomas (or leiomyomata) are a rare non-malignant metastatic phenomenon that may be observed with a pelvic leiomyoma.
Women who have undergone hysterectomy for leiomyomas are most commonly affected.
Patients are usually asymptomatic ...
Benjamin "Benny" Felson (1913-1988) was a renowned Cincinnati chest radiologist who coined or popularized 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 21 October 1913 ...
Beryllium (chemical symbol Be) is an alkaline earth metallic element, that has no known function in any organism. Unfortunately beryllium is very poisonous, manifesting as chronic beryllium lung disease, which causes premature mortality in one third 1.
Beryllium is a...
Beryllium sensitization (BeS) is a process whereby individuals exposed to beryllium dust develop a hypersensitivity reaction to it. A sizable proportion of these individuals can progress to chronic beryllium lung disease with ongoing exposure.
Bifid or forked or bifurcated rib is a congenital skeletal abnormality of the rib cage with the cleaved sternal end into two. They are thought to occur in ~0.2% of the population and there may be a female as well as right-sided predilection 2.
Bifid ribs can be seen ...
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
Bilateral pleural effusions can be common in general radiology practice. The may be symmetrical or asymmetrical. they can occur from a number of varied etiologies although congestive heart failure (CHF), renal or liver failure generally considered common 1.
Recognized list of causes are many ...
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).
For a broad discussion on this entity, please refer to the main article on hypersensitivity pneumonitis.
Birt-Hogg-Dubé syndrome or folliculin gene-associated syndrome is a genetic multisystemic disease mainly characterized by:
multiple lung cysts and secondary spontaneous pneumothoraces
multiple bilateral renal tumors (particularly chromophobe renal cell cancer and oncocytoma)
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 recognized 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...
Bochdalek hernias , also known as pleuroperitoneal hernias, (alternative plural: herniae) are the commonest type 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 cl...
A helpful mnemonic for remembering the features of a Bochdalek hernia is:
B: back and lateral, usually on the left side
B: bad (associated with pulmonary hypoplasia)
To remember the side in which a Bochdalek hernia more commonly occurs (and to co...
Body imaging is the term assigned to cross-sectional imaging of the body, which radiologically refers to the chest, abdomen and pelvis. It is often used by radiologists who report this region (sometimes known as body imagers/radiologists) to differentiate their primary area of interest from othe...
Bornholm disease, also known as epidemic pleurodynia, is a virally-mediated myositis 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 underdiagnos...
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...
The brachiocephalic trunk (BCT) (also known as the brachiocephalic artery, and previously as the innominate artery) is a major vessel that supplies the head, neck and right arm.
The brachiocephalic trunk is the first of the three main branches of the aortic arch, which originates...