The American Association for the Surgery of Trauma (AAST) injury scoring scales are the most widely accepted and used system of classifying and categorizing traumatic injuries. Injury grade reflects severity, guides management, and aids in prognosis. Currently (early 2019), 32 different injury s...
Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterized by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and esophagus to reach the left lung. It may lea...
Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are among the commonest aortic arch anomalies.
The estimated incidence is 0.5-2% 1.
as can be expected from the embryological development of the artery, the right recurrent laryngeal nerve...
Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
a central core consisting of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood...
An absent azygos vein is a very uncommon variant in which the azygos vein fails to develop. In cases of agenesis of the azygos vein, the hemiazygos and accessory hemiazygos veins play an important role in venous drainage, accounting for drainage of both the right and left intercostal veins 1-3.
Absent pulmonary valve syndrome (APVS) also known as congenital absence of pulmonary valve or pulmonary valve agenesis is a rare cardiac outflow tract anomaly.
It is characterized by a completely absent or rudimentary pulmonary valve. It can be associated with aneurysmal dilatation ...
Accessory fissures of the lung usually occur at the borders of bronchopulmonary segments. They are common normal variants but are less commonly seen on imaging.
Some of the more common accessory fissure include 1:
azygos fissure: most commonly seen accessory fissure
inferior accessory fissur...
The accessory (or superior) hemiazygos vein forms part of the azygos system and along with the hemiazygos vein, it is partially analogous to the right-sided azygos vein. It drains the left superior hemithorax.
Spelling it "hemiazygous" when referring to the vein is incorrect, rega...
Accessory muscles of respiration refer to muscles that provide assistance to the main breathing muscles, mainly when additional power is needed, for example during exercise or those with airway pathologies (e.g. COPD) 1,2.
During normal quiet breathing, inspiration is an active process primaril...
The accessory phrenic nerve is an anatomical variant seen in a little over one third of patients (36%). It most commonly arises from the ansa cervicalis, or slightly less commonly, the subclavian nerve. It is unknown as to how much the accessory phrenic nerve contributes to diaphragmatic functio...
Achalasia (primary achalasia) is a failure of organized esophageal peristalsis causing impaired relaxation of the lower esophageal sphincter, and resulting in food stasis and often marked dilatation of the esophagus.
Obstruction of the distal esophagus from other non-functional etiologies, not...
Acinar-predominant adenocarcinoma of the lung is a histological subtype of non-mucinous invasive adenocarcinoma of the lung.
In 2011, the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS), and European Respiratory Society (ERS) 4 introd...
Acinic cell carcinoma of the lung (also known as a Fechner tumor) is a type of lung carcinoma of the salivary gland type. It is extremely rare, especially when it presents in the form of primary acinic cell carcinoma.
Histologically, they are comprised of clear cells with abundant gr...
There are many acquired aortic conditions. These include
aortic rupture / transection
ascending aortic aneurysm
thoracic aortic injury
abdominal aortic aneurysm
inflammatory abdominal aortic aneurysm
An acquired tracheo-esophageal fistula refers to a pathological communication between the trachea and esophagus due to a secondary cause.
Acquired causes of tracheo-esophageal fistulae can be divided into those that are related to malignancy (common) and those from other causes (unco...
Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalized airspace opacification and includes:
post-obstructive causes (usually chronic, but 'new' changes can occur)
primary lung cancer
Acute aspiration pneumonitis occurs when solid or liquid ingested particles enter the airways and lungs, leading to inflammation.
This article will focus on the acute form of aspiration (cf. chronic aspiration pneumonia), mainly concerning its radiographic features; for a broader discussion, p...
Acute bilateral airspace opacification is a subset of the larger differential diagnosis for airspace opacification. An exhaustive list of all possible causes of acute bilateral airspace opacities is long, but a useful way to consider the huge list is via the material within the airways:
Acute bronchitis (plural: bronchitides) refers to acute-onset, short-term bronchial inflammation. It is usually self-limiting and often the result of a viral infection. Chest radiography is rarely necessary.
Acute bronchitis can affect people of all ages, but it is commonest in ch...
Acute coronary syndrome (ACS) is a group of cardiac diagnoses along a spectrum of severity due to the interruption of coronary blood flow to the myocardium, which in decreasing severity are:
ST elevation myocardial infarction (STEMI)
non-ST elevation myocardial infarction (NSTEMI)
Acute eosinophilic pneumonia is a type of eosinophilic lung disease diagnosed when the following combination of clinical and radiographic findings occur 5,7:
febrile illness of less than five days' duration
diffuse alveolar or mixed alveolar-interstitial opacities on chest radiograp...
Acute exacerbation of interstitial lung disease (AE-ILD), which sometimes also encompasses acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF), is an acute, clinically significant deterioration which develops within less than 1 month without an obvious clinical precipitant such as fluid...
Acute exogenous lipoid pneumonia is an uncommon form of exogenous lipoid pneumonia and is typically caused by an episode of aspiration of a large quantity of a petroleum-based products.
Non-specific but may show areas of consolidation and with a lower lo...
Acute hypersensitivity pneumonitis, also known as acute extrinsic allergic alveolitis, is a legacy term not recommended in the most recent guidelines (c. 2020) 9. It refers to the episodic form of this condition usually happening in just a few hours after the antigen exposure and often recurring...
Acute interstitial pneumonitis (AIP), also known as Hamman-Rich syndrome, is a rapidly progressive non-infectious interstitial lung disease of unknown etiology. It is considered the only acute process among the idiopathic interstitial pneumonias.
AIP has a similar clinical present...
Acute lung injury (ALI) refers to a rather broad clinical syndrome defined by a constellation of clinical criteria:
acute onset of bilateral pulmonary infiltrates
without evidence of hydrostatic pulmonary edema
pulmonary wedge pressures of usually 18 mmHg or less
Acute lung transplant rejection is one of the early post lung transplant complications.
It can occur as several episodes and the first episode may occur early as 5 days after transplantation. The incidence is thought to peak at approximately 2 months post-transplantation (with sev...
Acute lupus pneumonitis is one of the presentations of thoracic manifestations of systemic lupus erythematosus.
Acute lupus pneumonitis presents with acute onset of fever, cough, tachypnea, and hypoxia.
Appearances are non-specif...
Acute esophageal necrosis, sometimes known as Black esophagus or esophageal stroke, is a rare entity characterized by patchy or diffuse circumferential black pigmentation of the esophageal mucosa from ischemic necrosis.
It is classically characterized by a striking endoscopic image of diffuse, ...
Acute pulmonary schistosomiasis refers to the acute form of pulmonary schistosomiasis.
The acute form commonly occurs approximately 6 weeks after the infection and is thought to represent an allergic manifestation to the presence of Schistosoma worm or eggs.
Acute respiratory distress syndrome (ARDS) is a form of acute lung injury and occurs as a result of a severe pulmonary injury that causes alveolar damage heterogeneously throughout the lung. It can either result from a direct pulmonary source or as a response to systemic injury.
This is a disti...
Acute right heart syndrome (ARHS) is defined as a sudden deterioration in right ventricular (RV) function and failure of the RV to deliver adequate blood flow to the pulmonary circulation. This can result in systemic hypoperfusion.
ARHS can occur in several settings 1
in the setting...
Acute unilateral airspace opacification is a subset of the differential diagnosis for airspace opacification.
The exhaustive list of all possible causes would be huge, but a useful framework includes:
pus, i.e. pulmonary infection
Adalimumab induced interstitial lung disease is a form of anti-TNF-induced diffuse interstitial lung disease from the broader category of drug induced lung disease. The disease occurs as a response to the disease modifying anti-rheumatic drug adalimumab or HumiraTM.
Exact mechanism o...
Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarcinoma of the lung have replaced the now-defunct term bronchoalveolar carcinoma (BAC).
In 2011 the International Association for the Study of Lung Cancer (IASLC) and several other societies jointly revised the classi...
Adenocarcinomas in situ (AIS) of the lung refer to a relatively new entity which falls under the spectrum of pre-invasive lesions of the lungs. This entity partly replaces the noninvasive end of the previous term bronchoalveolar carcinoma. Adenocarcinoma in situ is defined as a localized adenoca...
Adenocarcinoma of the lung is the most common histologic type of lung cancer. Grouped under the non-small cell carcinomas of the lung, it is a malignant tumor with glandular differentiation or mucin production expressing in different patterns and degrees of differentiation.
This article brings...
Adenoid cystic carcinomas are a rare histological subtype of adenocarcinoma.
Adenoid cystic carcinomas are generally considered low grade 4. The tumors have a notable tendency for perineural spread.
They have a wide distribution and mainly occur in relation to the airways,...
Adenoid cystic carcinoma (ACC) of the lung is a type of non-small cell lung cancer.
They are classified under lung carcinomas of the salivary gland type. Primary occurrence in the lung parenchyma is rare, while in the thorax they occur more commonly as adenoid cystic carcinoma of the...
Adenoid cystic carcinomas of the tracheobronchial tree are a type of low-grade tracheal tumor. They are considered to be the second most common primary tumor of the trachea.
They are usually first recognized in patients in their 4th and 5th decades. There is no recognized gender p...
Adenosquamous carcinoma of the lung is a rare type of non-small cell lung cancer containing both components of lung adenocarcinoma and lung squamous cell carcinoma (SCC).
It is thought to constituting 0.4-4% of cases non-small cell lung cancer.
cigarette smoking 8
Adhesive atelectasis refers to the specific form of lung atelectasis that occurs due to the decrease or absence of pulmonary surfactant produced by type II pneumocytes. Without sufficient surfactant the alveoli collapse due to increased surface tension. It is most commonly seen in neonates with ...
Tuberculous adrenalitis is the result of adrenal mycobacterium tuberculosis (TB) infection. Its incidence has decreased in the western world with the declining incidence of tuberculosis.
As the tuberculous infection causes destruction of the adrenal cortex, primary adrenal insufficie...
Adult chest radiograph common exam pathology is essential to consider in the build up to radiology exams. The list of potential diagnoses is apparently endless, but there are some favorites that seem to appear with more frequency.
When dealing with the adult chest radiograph in the exam setting...
A chest radiograph in the exam setting may contain a vast variety of pathology. However, consider the history and correlate the likely diagnoses that may be demonstrated on film. Furthermore, check your review areas to ensure that the abnormality isn't at the corner of the film.
The adult chest radiograph pathology checklist is just a pathology checklist of things not to miss when reviewing a chest radiograph, especially in the exam setting.
standard review areas
below the diaphragm
right descending pulmonary artery (like a l...
There are a number of adult chest radiograph set-pieces. These are based on common patterns of disease that are seen on chest radiographs. Make sure that you have relevant differentials for these appearances and a quick oral set-piece for them when they come up.
The aerodigestive tract is a non-TA descriptive collective term for the respiratory tract and proximal portion of the digestive tract. As it is a non-standard term, its precise components vary somewhat with the context in which the term is being employed.
Definitions of what precis...
Aerogenous metastases are a rare form of metastases that can occur in the lung due to aerogenous spread along the airways.
It is related to but not considered identical to the term spread through air spaces (STAS) 4.
Aerogenous metastases are usually from primary lung cancer dissemi...
Aflatoxins are naturally-occurring mycotoxins that are produced by Aspergillus species, especially Aspergillus flavus. They are acutely toxic and carcinogenic.
High-level aflatoxin exposure can result in acute aflatoxicosis with acute hepatic necrosis, leading to cirrhosis, and ...
The biological/medical term agenesis (plural: ageneses) refers to failure of an organ to grow or develop during the embryological period.
corpus callosum agenesis
dental agenesis (anodontia)
Agenesis of the diaphragm is a congenital diaphragmatic developmental anomaly where all or part of diaphragm fails to form. It can sometimes be thought of as an extreme form congenital diaphragmatic herniation 1.
The agenesis can either be unilateral or bilateral. Herniation of abdom...
AIDS-defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are:
bacterial infections: multiple or recurrent
AIDS-related pulmonary lymphoma (ARPL) is classified as a distinct form of pulmonary lymphoma. Pulmonary involvement is a common extranodal site in AIDS-related NHL.
ARPL is typically a high-grade B-cell non-Hodgkin's lymphoma and the majority of patients have advanced HIV infection,...
Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
This is a basic article for medical students and other non-radiologists
Air-bronchograms are gas-filled bronchi surrounded by alveoli filled with fluid, pus or other material 1. It is a very useful sign because it is highly sensitive and specific for the presence of lung consolidation rather th...
The air bubble sign is seen in CT of complicated (ruptured or infected) pulmonary hydatid cyst and refers to small bubbles of gas within the periphery of pulmonary mass and is helpful, particularly in endemic areas, in suggesting the diagnosis over other masses (e.g. metastases or primary lung t...
An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis, or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity.
It should not be confused w...
An air space nodule is a small (few millimeters to 1 cm), ill-defined, nodular opacity that is often centrilobular in location and is non-specific, seen in many conditions. Commonly it represents a focal area of consolidation or peribronchiolar inflammation, and can indicate endobronchial spread...
Airspace nodules are irregularly marginated nodular opacities with air bronchograms that tend to measure 8 mm in diameter. They are quite separate from pulmonary nodules that range in size, are homogeneous and well-defined (being surrounded by normal lung).
Air space opacification is a descriptive term that refers to the filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is one of the many patterns of lung opacification and is equivalent to the pathological diagnosis of pulmonary consoli...
This is a basic article for medical students and other non-radiologists
Air-space opacification is a descriptive term that refers to filling of the lung parenchyma with material that attenuates x-rays more than the unaffected surrounding lung tissue. It is the radiological correlate of the path...
The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows:
acute airspace opacities with lymph node enlargement
acute airspace opacities: un...
Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
Airway centered interstitial fibrosis is a rare subtype of pulmonary fibrosis with variable outcomes.
It is characterized by fibrosis of the respiratory bronchioles and the peribronchiolar interstitium. It may be triggered by exogenous agents or endogenous autoimmune conditions such ...
Airway foreign bodies in children are potentially fatal, which is why immediate recognition is important. Unfortunately, delayed diagnosis is common.
Children under the age of four years are at increased risk of foreign body (FB) aspiration, with a slight male predominance 1.
Airway invasive aspergillosis, also known as Aspergillus bronchopneumonia or bronchopneumonic aspergillosis, refers to a form of invasive aspergillosis that affects the airways as the major or only feature.
It usually occurs in immunocompromised neutropenic patients, particularly ...
Airway pressure release ventilation (APRV) is an alternative mode for mechanical ventilation. It can be adopted as an alternative method for difficult-to-oxygenate patients with acute lung injury (ALI) / acute respiratory distress syndrome (ARDS).
It is usually not recommended in patients who ...
An A-line is an ultrasonographic artifact appreciated during the insonation of an aerated lung. 1
The term may be applied to the horizontal, echogenic long path reverberation artifacts that occur beneath the pleural line at multiples of the distance between the ultrasound probe and the visceral...
Allergic bronchopulmonary aspergillosis (ABPA) is at the mild end of the spectrum of disease caused by pulmonary aspergillosis and can be classified as an eosinophilic lung disease 2-4.
This entity is most commonly encountered in patients with longstanding asthma, and only occasi...
All-trans retinoic acid (ATRA) syndrome, more recently known as differentiation syndrome 8, is a condition that can occur with patients with acute promyelocytic leukemia who are on therapeutic all-trans-retinoic acid (ATRA).
All-trans retinoic acid (ATRA) is a normal constituent of plasma that ...
Alpha-1-antitrypsin (A1AT) deficiency is a hereditary metabolic disorder and is the most common genetic cause of emphysema and metabolic liver disease in children. It results in the unopposed action of neutrophil elastase and subsequent severe basal panlobular emphysema and respiratory symptoms....
Alveolar sarcoidosis is an atypical pulmonary manifestation of sarcoidosis.
This appearance may be apparent in approximately 4% of those with pulmonary sarcoidosis on plain film 1 and up to 15% on CT 2.
This appearance is thought to result from the aggregation of a va...
The alveoli (singular: alveolus) are tiny hollow air sacs that comprise the basic unit of respiration.
Alveoli are found within the lung parenchyma and are found at the terminal ends of the respiratory tree, clustered around alveolar sacs and alveolar ducts. Each alveolus is app...
Amiodarone lung is an interstitial lung disease seen in patients being administered the cardiac drug amiodarone and can manifest in a number of histopathologic patterns.
The reported prevalence of pulmonary toxicity in patients receiving amiodarone is ~10% (range 2-18%) 8.
Amniotic fluid embolism is a special type of pulmonary embolism where the embolus is comprised of amniotic fluid. It can be a highly fatal complication of pregnancy, with an 80% maternal mortality rate.
It is thought to complicate 1/8,000-80,000 pregnancies.
Anaphylaxis (also known as anaphylactic shock or reaction) is an acute severe systemic type I hypersensitivity reaction, commonly presenting with urticaria/angioedema, hypotension and bronchial hyperreactivity. It may be fatal.
Anaphylactoid reactions result from non-immune system ...
Anaplastic lymphoma kinase (ALK) fusion oncogene positive non small cell lung cancer refers to a specific set of non small cell lung cancers that contain an inversion in chromosome 2. They are associated with specific clinical features, including never or light smoking history, younger age, and ...
Anaplastic lymphoma kinase (ALK) gene rearrangements are known to occur in association with several tumors. The genes code for an enzyme called anaplastic lymphoma kinase (ALK) or ALK tyrosine kinase receptor (also known as CD246) which is thought to play a role in brain development and exerts i...
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
Anectasis is a term that describes primary atelectasis, as distinct from secondary atelectasis.
Anectasis refers to the failure of the lung to expand fully at birth.
Angioinvasive aspergillosis is the most severe and aggressive form of invasive aspergillosis. It is a life-threatening condition that requires prompt treatment. Fortunately, it is not seen in the general population and only occurs in profoundly immunocompromised patients.
Angiosarcoma involving the lung includes:
metastatic angiosarcoma to lung 1
usual primary sites include the heart and breast 2
primary pulmonary angiosarcoma: very rare
Thoracic manifestations of ankylosing spondylitis can be varied. For a general discussion of the condition refer to the parent article on ankylosing spondylitis.
It can affect the tracheobronchial tree and the lung parenchyma, and the disease spectrum includes:
upper lobe fibrocystic changes -...
Anomalous systemic arterial supply to normal lung is an anatomical variant in which a portion of the lung (usually a basal segment) is supplied by a systemic vessel without a distinct pulmonary sequestration.
It was traditionally (perhaps inappropriately since not a true sequestrat...
Anorexia nervosa is a psychiatric disorder characterized by distorted self-perception of body weight leading to starvation, obsession with remaining underweight, and an excessive fear of gaining weight. One in five patients with anorexia dies due to complications of the disease.
The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph.
The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly the...
The anterior junction (or junctional) line is a feature of frontal chest radiographs and chest CTs. It is a result of the parietal and visceral pleura meeting anteromedially. It normally contains a small amount of fat in between but can form a stripe of variable thickness if there is a lot of fa...
Germ cell tumors are one of the causes of an anterior mediastinal mass, and any of the germ cell histologies may be identified. They can therefore be divided histologically into:
non-seminomatous germ cell tumors (NSGCT)
yolk sac tumo...
Anterior mediastinal masses can be caused by neoplastic and non-neoplastic pathology. These masses arise in the anterior mediastinum, that portion of the mediastinum anterior to the pericardium and below the level of the clavicles.
The prevalence of anterior mediastinal masses on...
Getting a film with an anterior mediastinal mass in the exam is one of the many exam set-pieces that can be prepared for.
The film goes up and after a couple of seconds pause, you need to start talking:
There is a left sided mediastinal mass that makes obtuse angles with the mediastinal c...
The anterior mediastinum is the portion of the mediastinum anterior to the pericardium and below the thoracic plane.
It forms the anterior part of the inferior mediastinum, and contains the thymus, lymph nodes, and may contain the portions of a retrosternal thyroid.
The common causes of an anterosuperior mediastinal mass can be remembered by using the mnemonic:
T: thoracic aorta
T: terrible lymphoma
T: teratoma and germ cell tumors - see mediastinal germ cell tumors
Testicular cancer metastasis can represent a sixt...