As a part of international evidence based guidelines adopted by collaborative effort of American Thoracic Society, the European Respiratory Society, the Japanese Respiratory Society and the Latin American Thoracic association, specific diagnostic HRCT criteria for usual interstitial pneumonia (U...
The American Association for the Surgery of Trauma (AAST) injury scoring scales are the most widely accepted and used system of classifying and categorising traumatic injuries. Injury grade reflects severity, guides management, and aids in prognosis. At the time of writing (mid 2016), 32 differe...
Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterised by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and oesophagus to reach the left lung. It may le...
Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are the commonest of the aortic arch anomalies 2.
The estimated incidence is 0.5-2%.
They are often asymptomatic, but around 10% of people may complain of tracheo-oesophageal symptom...
Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
central core comprised of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessels a...
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.
Origin and course
The accessory hemiazygos vein is formed by the con...
Achalasia (primary achalasia) refers to a failure of organised oesophageal peristalsis with an impaired relaxation of the lower oesophageal sphincter (LOS), resulting in often marked dilatation of the oesophagus and food stasis. Obstruction of the distal oesophagus (often due to tumour) has been...
Acinic cell carcinoma of the lung (also known as a Fechner tumour) is a type of lung carcinoma of the salivary gland type. It is extremely rare especially when it presents in the form of a primary acinic cell carcinoma.
Histologically, they are comprised of clear cells with abundant ...
Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalised airspace opacification and includes:
post-obstructive causes (usually chronic, but 'new' changes can occur)
primary lung cancer
Acute aspiration pneumonitis refer to a form aspiration pneumonia where the time of onset is rapid.
Plain radiograph / CT
Features can be variable and can range from a pulmonary oedema pattern to areas of consolidation. These changes may have a gravity dependant distribu...
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 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 (non-STEMI)
Acute eosinophilic pneumonia (AEP) is a type of eosinophilic lung disease. It is diagnosed when the following combination clinical and radiographic findings occur 5,7:
febrile illness of less than five days duration
diffuse alveolar or mixed alveolar-interstitial opacities on chest...
Acute hypersensitivity pneumonitis (AHP) refers to the acute form of hypersensitivity pneumonitis although this classification system has recently been challenged 4. For a general discussion of the condition, refer to the parent article.
Fever, chills, myalgia, headaches,...
Acute interstitial pneumonitis (AIP), also know as Hamman-Rich syndrome is a rapidly progressive non infectious interstitial lung disease of unknown aetiology. It is considered the only acute process of the idiopathic interstitial pneumonias.
AIP (without an underlying cause) tend...
Acute lung transplant rejection is one of the post lung transplant complications. Histologically, it is defined as perivascular or peribronchiolar mononuclear inflammation and may affect up to 55% of lung transplant recipients within the first year after a transplant 2.
It can oc...
Acute respiratory distress syndrome (ARDS) is a form of acute lung injury (ALI) and occurs as a result of severe pulmonary injury that cause alveolar damage heterogeneously throughout the lung. It can either result from a direct pulmonary source or as a response to systemic injury.
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. infection
Adenocarcinoma in situ (AIS) of lung refers to a relatively new entity for a pre invasive lesion in the lung. This entity partly replaces the non invasive end of the previous term bronchoalveolar carcinoma. AIS is defined as a localised adenocarcinoma of <3 cm, that exhibits a lepidic pattern wi...
Adenocarcinoma in situ, minimally invasive adenocarcinoma and invasive adenocarincoma of lung are relatively new classification entities which now replaces the now defunct term bronchoalveolar carcinoma (BAC).
In 2011 the International Association for the Study of Lung Cancer and other societie...
Adenocarcinoma of the lung is one of the non-small cell carcinomas of the lung and is a malignant tumour with glandular differentiation or mucin production. This tumour exhibits various patterns and degrees of differentiation, including lepidic, acinar, papillary, micropapillary and solid with m...
Adenoid cystic carcinoma (ACC) are a rare histological subtype of adenocarcinoma.
ACCs are generally considered low grade 4. The tumors have notable tendency for perineural spread.
They have wide distribution and mainly occur in relation to the airways, lacrimal glands and...
Adenoid cystic carcinoma (ACC) of lungs are a type of non small cell lung cancer. They are classified under lung carcinomas of the salivary gland type. Primary occurrance in the lung parenchyma is rare and in the thorax, they more commonly occur as adenoid cystic carcinoma of the tracheo-bronchi...
Adenoid cystic carcinomas of the tracheobronchial tree are a type of low-grade tracheal tumour. They are considered to be the second most common primary tumour of the trachea.
They are usually first recognized in patients in their 40s. There is no recognised gender predilection.
Adenosquamous carcinoma (ASC) of the lung is a rare type of non-small cell lung cancer.
It is thought to constituting 0.4-4% of cases non-small cell lung cancer.
The definition of adenosquamous carcinoma indicates a carcinoma showing components of adenocarcinoma and sq...
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 settin...
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 aural set-piece for them when they come up.
Aflatoxins are naturally occuring mycotoxins that are produced by Aspergillus species, especially Aspergillus flavus. They are acutely toxic and carcinogenic.
High-level aflatoxin exposure can result acute aflatoxicosis with acute hepatic necrosis, resulting in cirrhosis, and po...
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 ...
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.
In angioinvasive fungal infection, the no...
Air space disease, or alveolar lung disease, is a process in which there is a filling of the lung's alveoli / acini.
lobar or segmental distribution
tendency to coalesce
bat's wing (butterfly) distribution...
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...
Air space opacification is a descriptive term that refers to 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 consolidat...
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...
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).
Airway foreign bodies in children are potentially fatal and proper recognition is important because 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 refers to a form of invasive aspergillosis that affects the airways as the major or only feature.
It usually occurs in immunocompromised neutropenic patients and patients with AIDS. Aspergillosis affecting the airways as the major or only feature of t...
Airway pressure release ventilation (APRV) is an alternative mode for mechanical ventilation. It can be adopted as a method of alternative method for difficult-to-oxygenate patients with acute lung injury / acute respiratory distress syndrome (ALI/ARDS).
Its is usually not recommended in patien...
All trans retinoic acid (ATRA) syndrome (more recently known as differentiation syndrome (DS)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. ...
Allergic bronchopulmonary aspergillosis (ABPA) is at one end of the spectrum of disease caused by pulmonary aspergillosis and can be classified as an eosinophilic lung disease 2-4.
This entity is seen is almost only encountered in patients with longstanding asthma, and only occasi...
Alpha-1-antitrypsin (AAT) 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 pan lobular emphysema and respiratory symptoms....
Alveolar sarcoidosis is an atypical pulmonary manifestation of sarcoidosis.
This appearance may be present in around 4% 1 of those with pulmonary sarcoidosis on plain film and up to 15% 2 of those on CT.
This appearance is thought to result from aggregation of large n...
Amiodarone lung is an interstitial lung disease seen in patients being administered amiodarone, and can manifest in a number of histopathologic patterns.
The reported prevalence of pulmonary toxicity in the patients receiving amiodarone is ~10% (range 2-18%) 8.
Patients are usual...
Amniotic fluid emboli (AFE) 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 1/8000-80,000 pregnancies.
Amyloidosis is a heterogeneous disease or even considered a constellation of diseases resulting in a deposition relatively similar proteins. It has many causes and can affect essentially any organ system.
There may be male predilection. Typically affects middle aged individuals a...
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge.
Head and neck anatomy
Abdominal and pelvic anatomy
Lower limb anatomy
Upper limb anato...
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
angiosarcoma - general article
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 t...
The anterior junction (junctional) line is a feature of frontal chest x-rays and chest CTs. It is a result of the parietal and visceral pleura meeting anteromedially. It normally contains a small amount of fat but can form a stripe of variable thickness if there is a lot of fat present or by the...
Germ cell tumours are one of the causes of anterior mediastinal mass, and any of the germ cell histologies may be identified. They can therefore be divided histologically into:
non-seminomatous germ cell tumours (NSGCT)
embryonal cell carcinoma
yolk sac tumour
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 that 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 causes of an anterosuperior mediastinal mass can be remembered by using the mnemonic:
T: thymus-see primary tumours of the thymus
T: thyroid-see primary tumours of the thyroid
T: thoracic aorta-see causes of a dilated thoracic aorta
T: terrible lymphoma
T: teratoma and ...
Anti-neutrophil cytoplasmic antibody associated vasculitides refer to a group of heterogeneous autoimmune diseases characterized by necrotising vasculitides and positive anti-neutrophil antibody titres. They are reactive to either proteinase-3 (PR3-ANCA) - cANCA or myeloperoxidase (MPO-ANCA) - p...
Anti-synthetase syndrome (ASS) is a systemic, inflammatory, autoimmune disease that is characterised by inflammatory myositis, polyarthritis associated with interstitial lung disease (ILD) and anti-synthetase autoantibodies.
ASS can result from autoantibodies to eight of the aminoacy...
Antiphospholipid syndrome is a systemic autoimmune disorder. It is usually defined as the clinical complex of vascular occlusion and ischaemic events occurring in patients who have circulating antiphospholipid antibodies.
Patients have circulating antiphospholipid antibodies cross-re...
Pulmonary involvement in antiphospholipid syndrome is one of the most frequent artial complications of antiphopholipid syndrome.
It is essentially related pulmonary arterial microthrombosis although a wide spectrum of conditions can result which include 3-5
The aortic arch represents the direct continuation of the ascending aorta and represents a key area for a review of normal variant anatomy and a wide range of pathological processes that range from congenital anomalies to traumatic injury.
origin: continuation of the ascending aorta at...
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 hiatus is one 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 midline ...
Aortic intramural haematoma (IMH) is an atypical form of aortic dissection due to haemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural haematomas are seen in older hypertensive patien...
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 (the left superior intercostal vein might be a collateral pathway).
The aortic-pulmonary stripe is an uncommon feature of frontal chest x-rays 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 trunk ...
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 is a radiological mediastinal space seen on frontal chest x-rays.
The term "aortopulmonary window" can also refer to a rare form of congenital heart disease, where there is an opening between the aorta and the pulmonary trunk 4. It...
A handy mnemonic to remember common apical lung disease is:
SET CARP or CARPETS
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: often a chronic ischaemic aetiology is...
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.
A solitary pulmonary nodule, according to the Nomenclature Committee of the Fleischner Society, defined as a rounded opacity, well or poorly defined on a conventional radiograph, measuring up to 3 cm in diameter and is not associated with lymphadenopathy, atelectasis, or pneumonia.
A number of differentials must be kept in mind while approaching diffuse pulmonary nodules. Interpretation is easier if nodules are the only abnormality.
These differentials can be narrowed down based on the several criteria:
Based on appearance
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 fibres triggers a fibrogenic response via the release...
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 fibres. They can be divided into benign and malignant changes 1-3.
Benign pleural and parenchymal lung disease
asbestos related benign pleural d...
Asbestosis refers to later development of diffuse interstitial fibrosis secondary to asbestos fibre 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...
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 a...
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 a...
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 tumour (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 tumour, 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.
Although the term mycetoma is frequently used to describe these fungal balls, it is an incorrect term to use 5-6.
Aspergillus is a fungal genus consisting of approximately 180 species. It is a ubiquitous fungus found frequently 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...