Emphysema refers to any disease process involving an abnormal accumulation of air/gas in the tissues. When used alone, it is usually taken to mean the lung disease, pulmonary emphysema, which forms part of the spectrum of chronic obstructive pulmonary disease (COPD).
gastric emphysema: include...
Pleural silicone granulomas result from an extremely rare situation where there is leakage of silicone from an implant rupture into the thorax.
It is thought that scars from remote thoracotomy may provide a potential pathway for ruptured silicone to fistulise into the pleural space....
Carbon monoxide transfer coefficient (often abbreviated as KCO) is a parameter often performed as part of pulmonary function tests. It is also often written as DLCO/VA (diffusing capacity per liter of lung volume) and is an index of the efficiency of alveolar transfer of carbon monoxide.
Cannonball metastases refer to multiple large, well-circumscribed, round pulmonary metastases. Numerous primary tumors have been described presenting with cannonball metastases, however, some primary tumors have a predilection for this presentation.
It should be noted that it is difficult to f...
Thymic MRI is a targeted mediastinal imaging protocol performed mainly to distinguish surgical from nonsurgical thymic lesions (eg. thymic hyperplasia, thymic cysts, and lymphoma).
Note: This article is intended to outline some general principles of protocol design. The specifics will vary depe...
Hypomyopathic dermatomyositis is a rare systemic autoimmune disorder of the skin with little to no muscle involvement. It makes up <5% of all dermatomyositis diagnoses.
The incidence is 2 in 1,000,000 ref and it typically affects women more than man at a 2:1 1.
Ring shadows on chest x-ray are classically associated with cystic bronchiectasis 1,2 but the term has also been used to describe a normal bronchus imaged end-on 3.
A mnemonic to remember the diagnostic criteria of lymphangioleiomyomatosis (LAM) is:
T: tuberous sclerosis
H: HRCT characteristic or compatible lung findings of LAM
RA: renal angiomyolipoma
L: lymphatic malformations
L: lung biopsy-proven LAM
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.
Coal mine dust lung disease encompasses a number of occupational lung diseases 1,2:
coal workers' pneumoconiosis (CWP)
mixed dust pneumoconiosis
dust-related diffuse fibrosis
chronic obstructive pulmonary disease (COPD)
The skinfold artifact can mimic a pneumothorax on chest radiography and is caused by the added density of a skin fold against the image. It appears as a broad opacity laterally, outlined by a lucent line (Mach band effect) 2.
The following features may h...
Giant cell carcinomas of the lung are a rare type of non-small cell lung carcinomas (NSCLC) classified under sarcomatoid carcinomas of the lungs.
They represent less than 0.5% of all NSCLC 2. There is a recognized association with smoking 1.
Symptoms are n...
Bronchial stenosis, or bronchial strictures, are descriptive terms to denote regions of focal narrowing involving the bronchi. They can arise from a wide variety of etiologies.
It can arise from a large range of etiological factors, which include:
Antineutrophil cytoplasmic antibodies (ANCAs) are a heterogenous class of IgG autoantibodies raised against the cellular contents of neutrophils, monocytes and endothelial cells 1. Under indirect immunofluorescence (IIF) microscopy, three ANCA staining patterns are observed, based on the varying...
Pembrolizumab-induced sarcoid-like reaction is a recently (c.2019) reported phenomenon which has been associated with the use of the programmed cell death protein 1 (PD1) inhibitor pembrolizumab. It could be mistaken for metastatic disease in some situations.
drug induced lung diseas...
Diffuse or widespread ground-glass opacification/opacity can either manifest as diffuse ground-glass nodules or amorphous areas of diffuse ground glass.
They can carry a wide differential diagnosis 1-3:
diffuse alveolar disease
hydrostatic pulmonary edema
acute respiratory dist...
Mushroom worker’s disease is a hypersensitivity pneumonitis caused by the occupational exposure of allergenic fungal spores and compost associated with the inhalation of organic dust from mushroom composting and spawning.
It presents as an acute pulmonary illness with cou...
Tracheal leiomyoma is a form of a benign tracheal tumor.
They are thought to account for around 1% of all tracheal tumors.
Presentation depends on tumor location and size with some reports suggesting patients becoming symptomatic when tumor obstructs more ...
Tuberculous pleuritis is a form of pleural tuberculosis and refers to inflammation of the pleura due to infection by Mycobacterium tuberculosis. It is considered the second most common form of extra-pulmonary tuberculosis 1. It may progress into a tuberculous empyema.
It may be co...
Maple bark disease, also known as maple bark stripper’s disease, is a rare hypersensitivity pneumonitis caused by the allergenic fungal spores of Cryptostroma corticale. The fungus causes sooty bark disease under the bark of maples and sycamore trees.
The first formal clinical accounts of the d...
Cheese workers' lung is a rare hypersensitivity pneumonitis due to the exposure of certain Penicillium species seen in people who work with mouldy cheese.
It can present as an acute pulmonary illness with fever and dyspnea. Clinical features are consistent with other form...
Interstitial pneumonia with autoimmune features (IPAF) is a term given for patients with interstitial lung disease (ILD) who show some features related to autoimmunity but without meeting full criteria for a defined connective tissue disease.
The term is based on the 2015 European Respiratory S...
Only a small number of pulmonary diseases are known to directly traverse the lung fissures such that the lung pathology extends from one lobe via the interlobar fissure into an adjacent lobe 1. The finding is most commonly due to primary malignancy, however, some infections are also known to do ...
Mediastinitis refers to inflammation of any of the soft tissues within the mediastinum.
In clinical practice, mediastinitis is generally used to refer to acute mediastinitis, resulting from bacterial infection within the mediastinum. This is considered a serious and potentially li...
Sternal dehiscence of the median sternotomy closure is an infrequent post sternotomy complication. It may be latent or difficult to detect clinically, or it may be sudden and very obvious. It may lead to sternal non-union. It may or may not be complicated by infection.
It may occu...
British Thoracic Society (BTS) guidelines for pulmonary nodules1 recommend the application of the Herder risk model in predicting malignancy in pulmonary nodules.
The Herder model 2 predicts the risk of malignancy in solid pulmonary nodules using patient characteristics, nodules characteristics...
HIV associated pulmonary arterial hypertension (HIV-PAH) is a specific form of pulmonary arterial hypertension associated with HIV.
It is thought that approximately 0.5% of patients with HIV infection can develop moderate to severe pulmonary arterial hypertension. This is consider...
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.
Lepidic growth is a pathological term referring to a pattern of cell proliferation along the lining of the alveolar structures of the lung as is seen in a subset of lung tumors 1.
History and etymology
‘lepidic’ was coined by the English pathologist John George Adam (1862-1926) whilst at McGil...
A mnemonic to remember differentials causing lower lobe fibrosis or predominant lower lobe fibrosis.
S: systemic sclerosis and other connective tissue diseases (e.g. rheumatoid arthritis)
A: aspiration, alpha-1 antitrypsin deficiency, asbestosis
The ring around artery sign refers to a (semi-) circular radiolucency surrounding the right pulmonary artery caused by mediastinal air in the case of pneumomediastinum 1-3.
The sign was originally described on lateral chest radiographs 1-4 but can be equally appreciated on sagittal multiplanar ...
Pulmonary gangrene can be a complication of necrotizing pneumonia and often represents a final stage in a continuum of progressive devitalisation of pulmonary parenchyma and is characterized by sloughing of a pulmonary segment or lobe.
In most instances, it occurs as a complication o...
Transient arterial phase respiratory motion-related artifact refers to common self-limited dyspnea observed immediately after the administration of gadoxetate disodium during liver MRI studies. The pathophysiology behind this phenomenon is poorly understood and its incidence varies among differe...
The sandwich sign is used for two different imaging appearances:
sandwich sign (Marchiafava-Bignami disease)
sandwich sign (mesentery)
Sandwich sign has also been coined for the appearance of:
primary pleural lymphoma 1,2
mediastinal lymphoma 3
marrow edema and hemorrhage on MRI of flexion...
The evocative appearance of a mosaic is used for two different entities:
mosaic attenuation of the lungs
mosaic pattern of Paget disease of the bone
Radiation recall pneumonitis is a rare reaction occurring in previously irradiated areas of pulmonary tissue after the application of triggering agents (e.g. chemotherapeutic agents, immunomodulators). It is not thought to be due to the direct effect of radiation. Classically this has been descr...
Immune checkpoint inhibitor therapy-related pneumonitis is one of the complications that can occur in the setting of immune checkpoint inhibitor therapy.
Immune checkpoint inhibitor therapy-related pneumonitis is considered a rare complication with a reported incidence of <5% in m...
Pulmonary vein obstructive syndrome (PVOS) is a form of pulmonary venous stenosis which can occur as a result of pulmonary venous infiltration by a tumor or compression by affected lymph nodes with resultant venous stasis +/- subsequent thrombosis. It can occur to a variable extent.
Melphalan-associated pulmonary toxicity is a rare form of drug induced lung disease. It is an alkylating agent and toxicity has usually been described with high dose. Typically a diffuse interstitial pneumonitis has been described.
A mnemonic to remember the lung carcinoma doubling time, in order of increasing time, is:
SM: small cell lung cancer - 30 days
S: squamous cell carcinoma (lung) - 90 days
L: large cell cancer of lung - 120 days
A: adenocarcinoma in situ of the lung - 150-180 days
Silico-asbestosis refers to a rare form of pneumoconiosis where there are features of silicosis and asbestosis. It is thought to due to the combined sclerosing effect of crystalline silica and asbestos fibers 2.
Interventricular septal bulge (also known as a sigmoid septum) is a common finding in imaging studies in the elderly population and refers to an isolated thickened basal septum resulting in a sigmoid configuration.
Although it is currently unclear whether this entity is part of the normal agin...
Oxygen masks are commonly visible on chest imaging, as they are generally not removed before the examination is performed.
Oxygen masks are of soft-tissue density and may mimic lung lesions. A nebuliser mask with liquid in its cup causing an air-fluid l...
Percutaneous lung tumor ablation techniques are an alternative to surgery or stereotactic body radiotherapy (SBRT) for the treatment of certain malignancies. They have specific indications and contraindications, but are mostly limited to small oligonodular and favourably located lesions.
A filling defect is a general term used to refer to any abnormality on an imaging study which disrupts the normal opacification (filling) of a cavity or lumen. The opacification maybe physiological, for example, bile in the gallbladder or blood in a dural venous sinus, or maybe due to the instal...
This summary article is intended to be used as a quick reference guide. Please see our complete COVID-19 article for more detail.
COVID-19 (coronavirus disease 2019) is a viral infectious disease caused by SARS-CoV-2 and is currently a World Health Organizatiοn (WHO) declared pandemic. As of m...
The CT chest (non-contrast) protocol serves as an outline for the acquisition of a chest CT without the use of an intravenous contrast medium.
Note: This article aims to frame a general concept of a CT protocol for the assessment of the chest. Protocol specifics will vary depending on CT scanne...
Lung carcinosarcomas are uncommon malignant biphasic tumors classified as a subtype of sarcomatoid tumors of the lung.
It is rare and thought to account for <1% of all lung cancers. There may be a greater male predilection with tumor generally occurring in heavy smokers with peak...
Excipient lung disease refers to a granulomatous angiocentric pulmonary response to the intravenous injection of fillers in crushed oral tablets or particulate agents in recreational drugs.
Excipients are insoluble inert fillers used to protect the active components of drugs in ora...
Hyperacute lung transplant rejection is a rare, rapid and often fatal form of early post lung transplant complications.
Hyperacute rejection occurs in the first few hours after reperfusion of the allograft lungs.
Following recommencement of blood flow into the allogra...
Pulmonary tumor thrombotic microangiopathy occurs when there are non-occlusive tumor cell microemboli with fibrointimal remodeling in small pulmonary arteries, veins and lymphatics. It rarely causes pulmonary hypertension.
At autopsy, approximately 25% patients with ...
Lateral intercostal artery perforator (LICAP) flap is a technique performed in breast reconstruction. It is considered suitable for some patients who have breast cancer in the outer part of the breast. It aims to replace lost breast tissue, fat and occasionally skin that is removed at the time o...
Fluoroscopy is an imaging modality that allows real-time x-ray viewing of a patient with high temporal resolution. It is based on an x-ray image intensifier coupled to a still/video camera. In recent years flat panel detectors (which are similar to the digital radiography used in projection radi...
The Cheerio sign has been described in two different scenarios:
Cheerio sign (pulmonary nodule)
Cheerio sign (shoulder)
Primary pulmonary chondrosarcoma is an extremely rare form of chondrosarcoma, in terms of location. The majority of intrathoracic chondrosarcomas occur in relation to the chest wall.
While the exact incidence is unknown, only a handful of cases have been reported in the literature...
Stridor is a term to describe an abnormal, high-pitched breath sound produced by abnormal, turbulent air flow with respiration 1. It usually represents narrowing of the large, extrathoracic airways 2.
Stridor can be caused by numerous conditions, but its presence may indica...
Rheumatoid factor (RF) is an immunoglobulin initially described in association with rheumatoid arthritis. It is an IgM antibody against the FC portion of the IgG antibodies. Ongoing research has identified a group of related immunoglobulins, classed as rheumatoid factors (RFs) and despite extens...
The inferior cavoatrial junction (ICAJ) is the term given to the point at which the inferior vena cava (IVC) enters the right atrium. It is less commonly used/seen, in contradistinction to the superior cavoatrial junction.
Accurate localization of the inferior cavoatrial junction is of practic...
The interchondral joints are small articulations between the apposed costal cartilages of the ribs 7-10.
On each side are three diminutive synovial joints between the surfaces of the 6th and 7th costal cartilages, 7th and 8th costal cartilages and 8th and 9th costal cartilages. The 9th and 10th...
Costochondritis (rare plural: costochondritides) is a common, usually self-limiting, painful inflammation of one or multiple costochondral junctions and/or the costosternal articulation. There is usually a distinct absence of swelling and chest wall palpation usually reproduces the pain.
The head and neck manifestations of cystic fibrosis are common compared to the well-known respiratory manifestations.
For general discussion of cystic fibrosis, and a discussion of its other manifestations, please refer to:
cystic fibrosis (parent article)
pulmonary manifestations of cystic ...
Neuroendocrine cell hyperplasia of infancy (NEHI) is a rare interstitial lung disease of childhood that typically presents in the first year of life.
Neuroendocrine cell hyperplasia of infancy was previously reported as persistent tachypnea of infancy until the disease was found to...
Esophageal wall thickening can be observed in a number of situations and can be either focal or diffuse. It may be physiological, and can also be due to benign or malignant disorders.
diffuse esophageal spasm
forms of esophagitis
diffuse esophageal intramural hemat...
The human coronaviruses (hCoVs), members of the family Coronaviridae, are enveloped RNA viruses that affect humans, mammals and birds, causing both acute and chronic illnesses.
Four of the seven known human coronaviruses usually cause a mild coryzal illness only, these are HKU1, NL63, OC43, and...
The severe acute respiratory syndrome (SARS) is a zoonotic illness caused by severe acute respiratory syndrome-related coronavirus (SARS-CoV-1), a coronavirus. The disease was first seen in the city of Foshan in Guangdong Province in China in 2002 and was traced back to the Himalayan (masked) p...
The penetration-aspiration scale (PAS) is a means of grading the severity of penetration or aspiration observed in a videofluoroscopic swallow study and is widely used 2.
The term aspiration is used for material that passes inferior to the level of the vocal folds. If material enters the larynx...
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 penetrati...
For a quick reference guide, please see our COVID-19 summary article.
COVID-19 (coronavirus disease-2019) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a strain of coronavirus. The first cases were seen in Wuhan, China, in December 2019 before ...
Hyperattenuating pulmonary consolidation refers to a region of lung parenchyma with air space opacification that has higher attenuation on CT than muscle or than expected with typical causes of consolidation such as pneumonia (fluid attenuation) or cancer (soft tissue attenuation).
Histoplasmoma is the name for a specific kind of nodule secondary to granulomatous reaction to histoplasmosis infection. It is often described as having a pathognomonic target lesion appearance, describing a well-defined nodule with a central core of calcification 5.
Histoplasmomas can appear ...
Pneumococcal pneumonia is a common lung infection caused by the organism Streptococcus pneumoniae (a.k.a. pneumococcus).
Pneumococcal pneumonia is one of the most common community-acquired pneumonias, and the most common in many areas. The pathogen afflicts all age groups worldwid...
A lobectomy (plural: lobectomies) is the complete resection of one lobe of the lung and is the commonest lung surgery performed for bronchogenic carcinoma.
A posterolateral thoracotomy is the commonest approach for the resection of lung malignancies. For other surgical approaches for...
The small heart sign represents a rarely encountered but critical sign on chest caused by a sudden reduction of heart size caused by cardiac tamponade due to either tension pneumopericardium or pneumomediastinum.
A sudden, >2 cm reduction in the transverse cardiac diameter is considered highly...
Paragonimiasis is a disease caused by several species of the trematode genus Paragonimus.
More than 50 different species of Paragonimus have been described in Asia, Africa, and the Americas and of those nine species infecting humans. The most important species is Paragonimus Westermani, which ...
Thalidomide-induced pneumonitis is a rare form of drug-induced lung disease. It could be suspected in patients who develop dyspnea, cough, and fever after taking thalidomide, without a definite cause, with chest radiographs +/- CT shows supportive findings. Many publications suggest this is reve...
Lung (or pulmonary) surgery is most frequently performed for lung carcinoma, and encompasses a broad spectrum of procedures:
lobectomy: commonest surgery for bronchogenic carcinoma
includes sleeve lobectomy and bilobectomy
Chen sign on chest radiography is the prominence of the left basal pulmonary vasculature, compared to the right, seen in valvular pulmonary stenosis. It is due to the asymmetric increase in pulmonary blood flow to the left lung due to preferential blood flow into the left pulmonary artery after ...
The term scimitar, referring to the characteristic shape of the Middle Eastern sword, may refer to the following:
scimitar syndrome (lungs)
scimitar sign (cystic adventitial disease)
scimitar sacrum (bones)
Pleomorphic adenomas, also known by the misnomer benign mixed tumors (BMTs), are benign epithelial neoplasms related to glandular tissue. They have a small but real risk of malignant transformation.
For a discussion of specific sites of pleomorphic adenoma, please refer to
A crus (plural: crura) is an anatomical term used for a structure which resembles a leg.
crus (internal capsule)
crus (semicircular duct)
Pulmonary interstitial edema represents a form of pulmonary edema resulting from pathological fluid buildup in the interstitial spaces due to increased hydrostatic driving pressure.
Interstitial lung edema arises almost exclusively due to an increase of the pulmonary capillary hydros...
Airway-centered interstitial fibrosis is a type of interstitial lung disease first proposed in 2004 2. It is still unclear (c.2015) whether it represents a variant of preexisting interstitial lung disease (such as hypersensitivity pneumonitis or organizing pneumonia) or constitutes a separate en...
The retrocardiac sail sign represents the characteristic and highly specific appearance of left lower lobe collapse on a frontal chest x-ray.
The collapsed, medially displaced left lower lobe is represented by a triangular area of increased density with sharp margins, s...
Obstructive sleep apnea (OSA), also known as obstructive sleep apnea syndrome (OSAS), is a disorder characterized by repetitive episodes of total (i.e. apnoeas) or reduction (i.e. hypopnoeas) in ventilation due to total or partial collapse of the upper airway during sleep.
This condition is dis...
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)
Diffuse airway narrowing can occur from a number of pathologies; these include:
granulomatosis with polyangiitis
various infections including
The xiphisternal joint (or more rarely, the sternoxiphoid joint) is a symphysis between the inferior margin of the body of the sternum and the superior margin of the xiphoid process. In most people it ossifies with age, usually becoming fully fused by the age of 40 years, forming a synostosis.
Non-cardiogenic pulmonary edema is a classification of pulmonary edema where the underlying etiology is not due to left ventricular dysfunction. Causes include:
pulmonary edema with acute asthma
post-obstructive pulmonary edema/postintubation pulmonary edema/negative pressure ...
Cardiogenic pulmonary edema is a subtype of pulmonary edema where the underlying etiology is due to left ventricular dysfunction.
left heart failure
congestive cardiac failure
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...
Spontaneous rib fractures are rib fractures that occur in the absence of a definitive precipitant. According to one study, they were most frequently between the 4th and 9th ribs and multiple in around 40% of cases. Some were associated with factors such as 1
chronic obstructive pulmonary diseas...
The double density sign can refer to several radiological signs:
double density sign (left atrial enlargement)
double density sign (berry aneurysm)
double density sign (osteoid osteoma)
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...