Exogenous lipoid pneumonia is a form of lipoid pneumonia. Please refer to the main article for a broad discussion.
In terms of the onset of the presentation, it can be divided into two different forms:
acute exogenous lipoid pneumonia
uncommon and typically is caused by an episode of aspirat...
Expiratory HRCT is an useful method for detecting small airway obstructive disease in which the air remain trapped in the small airways even after the expiration and appear as mosaic attenuation.
Ideally, an expiratory HRCT scan should be performed in all obstructive airway diseases...
The external (or outermost) intercostal muscles are important muscles of respiration. They number eleven on each side and are located in the intercostal space, expanding the transverse dimension of the thoracic cavity during inspiration.
The external intercostal muscles are the o...
Extracorporeal membrane oxygenation (ECMO) is used as a modified pulmonary or cardiopulmonary bypass technique in those with severe cardiac and/or respiratory failure refractory to conventional ventilatory support and medical intervention 1,3. There are two access paths for extracorporeal life s...
Extramedullary hematopoiesis is a response to the failure of erythropoiesis in the bone marrow.
This article aims to a general approach on the condition, for a dedicated discussion for a particularly involved organ, please refer to the specific articles on:
extramedullary hematopoiesis in the...
The extrapleural air sign is one of the many signs of pneumomediastinum, and was first described by Lillard and Allen in 1965. It is defined as the presence of gas between the parietal pleura and the diaphragm. On a lateral projection the gas forms a radiolucent pocket of gas posterior to the do...
Extrapleural fat is benign condition and refers to relaitve diffuse deposition of fat outside the parietal pleura. It can occur in various locations but typically occurs along the chest wall. It is a component of the loose connective tissue of the endothoracic fascia and is most abundant along t...
The extrapleural fat sign is an imaging feature which can be seen on CT under certain circumstances. It occurs from the inward displacement of extrapleural fat by an extrapleural fluid collection, extrapleural hematoma or extrapleural mass. The presence of the extrapleural fat sign is indicative...
Extrapleural hematomas are uncommon and usually seen in the context of rib fracture, subclavian venous catheter traumatic insertion, and blunt chest injury.
Extrapleural hematomas result from the accumulation of blood in the extrapleural space where the overlying extrapleural fat is ...
The extrapleural sign, described by Ben Felson in 1973 1, refers to the appearance of a pulmonary opacity with oblique margins that taper slowly to the chest wall when the lesion is viewed tangentially to the x-ray beam. This appearance suggests that the lesion is pleural or extrapleural in natu...
An exudate is a collection that has a relatively high specific gravity and protein concentration. They occur as the result of an inflammatory process that either increases the permeability of the surrounding membrane or disrupts the ability of resorption of fluid. They may be secondary to:
The fallen lung sign (also known as CT fallen lung sign) describes the appearance of collapsed lung away from the mediastinum encountered with tracheobronchial injury (in particular those >2 cm away from the carina). It is helpful to look for this rare but specific sign, in cases of unexplained ...
The differential of a fat containing solitary pulmonary nodule is very narrow.
In a well circumscribed smooth or lobulated mass (especially if it has been largely stable in size over time) presence of fat is essentially pathognomonic of a pulmonary hamartoma, and usually not further assessment ...
There is a long list of fat containing thoracic lesions. They may involve the mediastinum, lung, pleura or chest wall.
Differential diagnosis includes:
intrapulmonary: fat containing pulmonary lesions
Fat embolism syndrome (FES) is a rare clinical condition caused by circulating fat emboli leading to a multisystemic dysfunction. The classical clinical triad consists of:
It occurs in ~2.5% (range 0.5-4%) of tho...
Fat stranding is a common sign seen on CT wherever fat can be found. It is most commonly seen in abdomen/pelvis, but can also be seen in retroperitoneum, thorax and subcutaneous tissues. It can be helpful in localising both acute and chronic pathology.
Fat stranding c...
Fatty mediastinal masses are relatively uncommon, and the differential diagnosis is brief, including 1-4:
benign mature teratoma
extravasation of lipid-rich hyperalimentation fluid 3
fibrofatty replacement of the central portion of mediastinal l...
Feeding vessel sign consists of a distinct vessel leading directly to a nodule or a mass. This sign indicates either that the lesion has a haematogenous origin or that the disease process occurs near small pulmonary vessels.
A number of vessel-related non-neoplastic disorders of the lung produ...
Feingold syndrome is characterized by the combination of:
alimentary tract atresias especially esophageal atresia
Feline esophagus also known as esophageal shiver, refers to the transient transverse bands seen in the mid and lower esophagus on a double contrast barium swallow.
The appearance is almost always associated with active gastro-esophageal reflux 2,3 and is thought to be due to contract...
A ferruginous body is a histological finding in interstitial lung disease that is a result inorganic dust inhalation.
Macrophage ingestion of the inorganic fiber results in a fibrotic reaction with encasement of the fiber in iron-rich material that is derived from proteins such as ferritin and ...
The FEV1/FVC ratio (FEV1%), also known as the Tiffeneau-Pinelli index, is a spirometric parameter and refers to a calculated ratio which represents the proportion of a patients vital capacity that they are able to expire in the first second of forced expiration.
FEV1% is used in the diagnosis a...
Fibrinous pericarditis results from fine granular roughening of the pericardium.
Pericardial friction rub may be heard.
acute rheumatic fever
myocardial infarction: Dressler syndrome
chronic renal fail...
Fibrobullous disease is an observational finding where there are bullous spaces interspersed by areas of scarring (fibrosis). In general, there may be an apical predilection. This has been described in association with conditions such as:
ankylosing spondylitis 1
rheumatoid arthritis 2
Fibrosarcoma of the chest wall refers to a malignant tumor arising from the chest wall.
It typically presents in adults, although the age range of presentation is wide. It rarely occurs as a congenital form in infants and children 2.
In the thorax, fibrosarcomas usuall...
Fibrosing mediastinitis is a rare non-malignant acellular collagen and fibrous tissue proliferative condition occurring within the mediastinum. On imaging, the condition can sometimes mimic malignancy.
Although it can potentially present at any age, it typically presents in young ...
Fibrothorax is defined as fibrosis within the pleural space, and occurs secondary to the inflammatory response to one of the following events:
tuberculosis / tuberculous pleuritis / tuberculous empyema: mainly as a late sequela 3
asbestos-related pleural disease
The term fibrotic idiopathic intersitial pneumonia (FIIP) is refers to a morphological subset of idiopathic interstitial pneumonia where there is great then 5% of honeycombing present on HRCT 1.
fibrotic non specific interstitial pneumonitis
Fibrotic non-specific interstitial pneumonitis is a histological subtype of non-specific interstitial pneumonitis (NSIP). It is considered the more common form 1. This pattern manifests as chronic interstitial inflammation obscured by interstitial fibrosis (with dense collagen), a temporal homog...
The figure 3 sign is seen in aortic coarctation and is formed by prestenotic dilatation of the aortic arch and left subclavian artery, indentation at the coarctation site (also known as the "tuck"), and post-stenotic dilatation of the descending aorta.
On barium studies of the esophagus in pati...
Finger clubbing, also called "drumstick fingers", is a common clinical sign in patients with heart or lung disease. The term is used to describe an enlargement of the distal phalanges of the fingers, giving them a drumstick or club-like appearance.
Finger clubbing presen...
The finger in glove sign can be seen on either a chest radiograph or CT chest and refers to the characteristic sign of a bronchocoele. The same appearance has also been referred to as:
rabbit ear appearance
mickey mouse appearance
The first rib is the most superior of the twelve ribs. It is an atypical rib and is an important anatomical landmark and is one of the borders of the superior thoracic aperture.
Compared to a typical rib, the first rib is short and thick and it has a single articular f...
Flail chest or flail thoracic segment occurs when three or more contiguous ribs are fractured in two or more places. Clinically, a segment of only one or two ribs can act as a flail segment, hence there is some controversy between the clinical and radiological definitions.
Flattening of the diaphragm is the most sensitive sign on chest radiographs for the presence of hyperinflation of the lungs, usually due to emphysema 1-2.
The normal dome of each hemidiaphragm should rise at least 1.5 cm above a line connecting the costophrenic angle posteriorly and sternophren...
The flat waist sign refers to flattening of the contours of the aortic arch and adjacent pulmonary trunk. It is seen in severe left lower lobe collapse and is caused by leftward displacement and rotation of the heart.
Fleischner sign can refer to two distinctly separate signs:
Fleischner sign (enlarged pulmonary artery)
Fleischner sign (tuberculosis of ileocecal junction)
The Fleischner sign refers to a prominent central pulmonary artery that can be commonly caused either by pulmonary hypertension or by distension of the vessel by a large pulmonary embolus. It can be seen on chest radiographs, CT pulmonary angiography, and MR pulmonary angiography.
It is seen mo...
The Fleischner Society is a interdisciplinary learned society with the key aim to advance the study of pathologies of the chest by the use of thoracic imaging.
Eight radiologists congregated in November 1969 to found a new society to advance the knowledge of diseases of the chest, pred...
The Fleischner Society pulmonary nodule recommendations are for the follow-up and management of pulmonary nodules detected incidentally on imaging. The guideline does not apply to patients <35 years or with a history of cancer or immunosuppression. The initial guideline was released in 2005 1; s...
The fluid bronchogram sign can be seen on chest CT or ultrasound as the presence of fluid attenuation material within respiratory bronchioles with surrounding collapsed or consolidated lung.
The presence of this sign suggests endobronchial obstruction as a precipitating cause for consolidation/...
The fluid color sign is a diagnostic sign to differentiate a pleural effusion from pleural thickening by means of color Doppler ultrasound. In the case of pleural effusion a color signal is seen in the pleural fluid during respiratory and cardiac movement, whereas this color signal is not seen i...
Fluoroscopic evaluation of esophagectomy is an important study, given the high rate of complication following esophagectomy (~10-20% rate of leak). Although the approach will differ slightly depending on the type of esophagectomy performed, the principles are similar.
Focal interstitial pulmonary fibrosis refers to a manifestation of pulmonary fibrosis where changes are confined and localised to a small region of the lung, they can arise of range of etiologies with one rather common example being osteophyte induced adjacent pulmonary atelectasis and fibrosis....
Focal lymphoid hyperplasia of the lung refers to an abnormal accumulation of non-malignant lymphocytic aggregates within the lung.
Previously known as pulmonary pseudolymphoma.
Clinical features can vary from being asymptomatic to various symptoms such as w...
Causes of focal pulmonary opacities on a chest radiograph can be remembered using the rather crude mnemonic:
F: 'fection (pulmonary infection)
F: 'farction (pulmonary infarction)
F: fluid (pulmonary edema)
F: f***ed (lung cancer)
Follicular bronchiolitis (FB) is a nonneoplastic primary polyclonal B cell hyperplasia of the bronchus-associated lymphoid tissue (BALT) due to chronic exposure to antigens in those with underlying collagen vascular or immune deficiency diseases which usually manifested as small centrilobular gr...
Folliculin gene-associated syndrome (FLCN-S) or Birt-Hogg-Dubé (BHD) 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 foramina of Morgagni, also known as the sternocostal triangles, are small defects in the posterior aspect of the anterior thoracic wall between the sternal and costal attachments of the diaphragm. The internal thoracic vessels descend through these foramina to become the superior epigastric ...
Foregut duplication cysts are a type of congenital duplication cyst. They are sometimes classified under bronchopulmonary foregut malformations.
Entities classified as foregut duplication cysts include:
other enteric cysts
esophageal duplication cysts
Funnel trachea is a colloquialism for a congenital long-segment intrathoracic tracheal stenosis.
The diameter of the trachea immediately below the cricoid is normal, and becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or completel...
The so-called galaxy sign, initially described as the sarcoid galaxy, represents a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis 1. The same appearance can be seen in tuberculosis 2,3. In other words, it represents a mass-like region composed of numerous smaller ...
Ganglioneuromas are fully differentiated neuronal tumors that do not contain immature elements and potentially occur anywhere along the peripheral autonomic ganglion sites.
On imaging, usually, they present as well-defined solid masses and can be quite large at presentation. Generally, they ar...
Garland triad, also known as the 1-2-3 sign or Pawnbrokers sign, is a lymph node enlargement pattern on chest radiographs which has been described in sarcoidosis:
right paratracheal nodes
right hilar nodes
left hilar nodes
Hilar lymphadenopathy is symmetrical and usually massive. These so-ca...
A gastro-pleural fistula is a very rare situation characterized by a pathological communication between the stomach and the pleural cavity.
They can occur in number of situations:
trauma (stab injuries 3)
iatrogenic (following bariatric, pulmonary or esophageal surgery 1)
GATA2 deficiency is a germ-line disease expressed as a wide spectrum of phenotypes, including monocytopenia, myelodysplasia, myeloid leukaemias, and lymphoedema. It is a rare cause of pulmonary alveolar proteinosis.
GATA2 deficiency has considerably variable clinical mani...
The Geneva score, similarly to the Wells score, is a clinical stratifying system to estimate the probability of pulmonary embolism (PE) in patients in which this diagnosis was considered. The criteria were originally published by the clinical team of the Geneva University Hospital in 2001 1, and...
A Ghon lesion (sometimes called Ghon focus) represents a calcified tuberculous caseating granuloma (tuberculoma) and represents the sequelae of primary pulmonary tuberculosis infection.
When associated with a calcified ipsilateral hilar node it is known as a Ranke complex.
History and etymolog...
Giant cell interstitial pneumonia is a rare form of pulmonary fibrosis. It is currently considered form of pneumoconiosis and in many situations is caused by exposure to metal compounds such as cobalt or tungsten carbide.
While some authors consider this term to be synonymous with or being almo...
The ginkgo leaf sign of the chest, also referred as the ginkgo leaf sign of subcutaneous emphysema, is a radiograph appearance which is seen with extensive subcutaneous emphysema of the chest wall. Gas outlines the fibers of the pectoralis major muscle and creates a branching pattern that resemb...
The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden.
Although typically seen with right upper lobe collapse, the S-sign can also be seen with the...
Goodpasture syndrome, also referred as antiglomerular basement membrane (anti-GBM) antibody disease, is an autoimmune disease characterized by damage to the alveolar and renal glomerular basement membranes by a cytotoxic antibody. It is a type of pulmonary-renal syndrome.
Goodpasture syndrome i...
Good syndrome is a rare paraneoplastic syndrome in which a thymoma causes hypogammaglobulinemia and humoral immunodeficiency. It has been estimated to occur in 0.2%–2% of thymomas 2.
low to absent B-cells
T-cell mediated defects
CD4 T-cell lymphopenia
inverted CD4/CD8+ T-cell ratio
Pulmonary graft versus host disease (GvHD) is one of the thoracic manifestations that can complicate hematopoietic stem cell transplantation. Pulmonary GvHD can be broadly divided into acute and chronic disease 1-4:
acute pulmonary GvHD
pulmonary involvement is rare
the median time of onset o...
Granulomatosis with polyangiitis (GPA), previously known as Wegener granulomatosis, is a multisystem necrotizing non-caseating granulomatous c-ANCA positive vasculitis affecting small to medium sized arteries, capillaries and veins, with a predilection for the respiratory system and kidneys 3.
This article discusses the pulmonary manifestations of granulomatosis with polyangiitis (previously known as Wegener granulomatosis). It is classified as a type of pulmonary angiitis and granulomatosis.
For a general discussion of the condition, please refer to the main article on granulomatosi...
Granulomatous bronchiolitis is a pathological type of bronchiolitis (not an imaging classification) characterized by an underling granulomatous reaction involving the small airways (bronchioles).
It is grouped as form of cellular bronchiolitis 1
It can be associated with a ...
Granulomatous lung disease refers to a broad group of infectious and non-infections conditions characterized by the formation of granulomas.
The spectrum includes
pulmonary non-tuberculous mycobacterial infection
Granulomatous-lymphocytic interstitial lung disease (GLILD) is a relatively recent term given to describe non-infectious, diffuse lung disease complications that develop in common variable immunodeficiency (CVID) patients.
They exhibit both granulomatous and lymphoproliferative histo...
Ground-glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide etiology including infection, chronic interstitial disease an...
H1N1 influenza is a strain of influenza that notably resulted in a pandemic in 2009.
It is caused by a type of influenza A virus of swine origin.
There can be a wide spectrum of clinical syndromes ranging from being asymptomatic to fulminant viral pneumonia, r...
Hemopneumothorax is a term given when there is concurrent presence of a hemothorax and well as a pneumothorax. It is a variant of a hydropneumothorax.
Approximately 5% of patients with pneumothorax will have concomitant hemothorax 6 .
It is typically seen in the setti...
Hemoptysis refers to coughing out blood. Generally, it appears bright red in color as opposed to blood from the gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying etiology.
Massive hemoptysis is referred to as expectoration of >...
A mnemonic for primary malignancies responsible for hemorrhagic metastases is:
MR CT BB
M: melanoma: metastatic melanoma to brain
R: renal cell carcinoma
T: thyroid carcinoma, teratoma
B: bronchogenic carcinoma
B: breast carcinoma
Hemorrhagic pneumonia refers to a descriptive term for pneumonia (infective - inflammatory consolidation of the lung) when is complicated by pulmonary hemorrhage. It can be localised or diffuse to varying degrees dependent on the extent of involvement +/- aetiological agent.
Hemorrhagic pulmonary metastases are those which tend to be complicated by pulmonary hemorrhage within them, resulting in characteristic imaging appearances. Metastases of some tumor histologies are more likely to hemorrhage -- knowledge of this can help refine the differential diagnoses.
Hemothorax literally means blood within the chest, is a term usually used to describe a pleural effusion due to accumulation of blood. If a hemothorax occurs concurrently with a pneumothorax it is then termed a hemopneumothorax.
A tension hemothorax refers to hemothorax that results from massi...
Hairy pleural plaques are a manifestation of asbestos-related disease. They arise from the visceral pleura, typically from an interlobar fissure. The hairiness stems from short radially-oriented linear regions of fibrosis extending from the plaque into the adjacent lung parenchyma.
Compared to ...
The Haller index (HI), also known as the pectus index, is a simple mathematical way to assess and describe the chest cage on CT of the thorax and is used in the detection of pectus excavatum, as well as preoperative and postoperative assessment 1,5.
The Haller index is calculated by ...
The halo sign in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents hemorrhage. It is typically seen in angioinvasive aspergillosis.
Histopathologically, it represents a focus of pulmona...
Hamman syndrome, also known as Macklin syndrome, refers to spontaneous pneumomediastinum along with subcutaneous emphysema.
It is a rare entity most often encountered in young adults. It is a known entity peri- and postpartum 3.
The condition is most common...
Hampton hump refers to a dome-shaped, pleural-based opacification in the lung most commonly due to pulmonary embolism and lung infarction (it can also result from other causes of pulmonary infarction (e.g. vascular occlusion due to angioinvasive aspergillosis). While a pulmonary embolism is expe...
A hard metal pneumoconiosis is usually classified as a type of fibrotic pneumoconiosis where the precipitating agent consists of a hard metal (not a heavy metal) such as.
tungsten/tungsten carbide alloys
or a mixture
A broader term used is hard metal lung disease (HMLD) w...
The haystack sign on chest x-rays in pediatric patients is indicative of pneumomediastinum. The pediatric heart is surrounded above and below with gas, giving it an appearance of a haystack from Monet's paintings.
The head cheese sign refers to a juxtaposition of regions with three different densities:
ground glass opacities (high attenuation)
mosaic attenuation pattern (low attenuation)
normal lung tissue (normal attenuation)
A mixed infiltrative (ground glass opacity) and obstructive (mosaic attenua...
The heart is a hollow, muscular organ of the middle mediastinum, designed to pump oxygenated blood around the systemic circulation and de-oxygenated blood around the pulmonary circulation
The heart has a somewhat conical form and is enclosed by pericardium. It is positioned poste...
There are four heart chambers, the right atrium, left atrium, right ventricle and left ventricle. These receive blood from the body and lungs and contract to transmit blood to the lungs for oxygenation and to the body for use in metabolism.
It is best to list the four chambers in order of the s...
This is a basic article for medical students and other non-radiologists
Heart failure is a syndrome of cardiac ventricular dysfunction, where the heart is unable to pump sufficiently to meet the body's blood flow requirements.
Although it is useful to divide the signs an...
The Heimlich valve, also known as the flutter valve, is a unidirectional valve to ensure that gas/fluid drained from the pleural space cannot flow back in.
The Heimlich valve is cheap, easy to use, and does not require clamping unlike 'traditional' thoracostomy drainage tubes. Suction can stil...
The Heiner syndrome is a rare form of primary pulmonary hemosiderosis associated with an allergy to cow's milk. The syndrome includes:
rectal blood loss with hypochromic microcytic anemia
pulmonary infiltrates (often recurrent)
There are many thoracic complications that can occur following hematopoietic stem cell transplantation. These can precipitate during various stages following transplantation and can be either infectious or noninfectious.
The hemiazygos vein is the asymmetric counterpart to the azygos vein and forms part of the azygos venous system.
The hemiazygos vein is formed by the confluence of the left ascending lumbar and left subcostal veins.
The hemiazygos vein enters the thorax either ...
Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation: the position of the trachea. Is it central, pulled or pushed from the side of opacification? Is there pulmonary volume loss or vo...