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 th...
Fat stranding is a common sign on CT seen anywhere fat can be found but is most commonly seen in the abdomen/pelvis, but also in the retroperitoneum, thorax and subcutaneous tissues. It can be helpful in localising both acute and chronic pathology.
Fat stranding can a...
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 characterised by the combination of:
alimentary tract atresias especially oesophageal atresia
Feline oesophagus also known as oesophageal shiver, refers to the transient transverse bands seen in the mid and lower oesophagus on a double contrast barium swallow.
The appearance is almost always associated with active gastro-oesophageal reflux 2,3 and is thought to be due to cont...
A ferruginous body is a histological finding in interstitial lung disease that is a result inorganic dust inhalation.
Macrophage ingestion of the inorganic fibre results in a fibrotic reaction with encasement of the fibre in iron-rich material that is derived from proteins such as ferritin and ...
The FEV1/FVC ratio (or 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.
Is used in the diagnosis and assessment of obstructive ...
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 tumour 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 usual...
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 oesophagus in pat...
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.
The underlying pathogenesis of fin...
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 ileocaecal 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 colour sign is a diagnostic sign to differentiate a pleural effusion from pleural thickening by means of colour Doppler ultrasound. In the case of pleural effusion a colour signal is seen in the pleural fluid during respiratory and cardiac movement, whereas this colour signal is not se...
Fluoroscopic evaluation of oesophagectomy is an important study, given the high rate of complication following oesophagectomy (~10-20% rate of leak). Although the approach will differ slightly depending on the type of oesophagectomy 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 aetiologies 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 oedema)
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 characterised by:
multiple lung cysts and secondary spontaneous pneumothoraces
multiple bilateral renal tumours (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
oesophageal 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 tumours 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 a...
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...
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 fibres 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 characterised 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 haematopoietic 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 ...
Granulomatosis with polyangiitis (GPA), previously known as Wegener granulomatosis, is a multisystem necrotising 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) characterised 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 characterised by the formation of granulomas.
The spectrum includes
pulmonary non-tuberculous mycobacterial infection
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 aetiology including infection, chronic interstitial disease a...
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...
Haemopneumothorax is a term given when there is concurrent presence of a haemothorax and well as a pneumothorax. It is a variant of a hydropneumothorax.
Approximately 5% of patients with pneumothorax will have concomitant haemothorax 6 .
It is typically seen in the se...
Haemoptysis refers to coughing out blood. Generally, it appears bright red in colour as opposed to blood from the gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying aetiology.
Massive haemoptysis is referred to as expectoration ...
A mnemonic for primary malignancies responsible for haemorrhagic 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
Haemorrhagic pneumonia refers to a descriptive term for pneumonia (infective - inflammatory consolidation of the lung) when is complicated by pulmonary haemorrhage. It can be localised or diffuse to varying degrees dependant on the extent of involvement +/- aetiological agent.
Haemorrhagic pulmonary metastases are those which tend to be complicated by pulmonary haemorrhage within them, resulting in characteristic imaging appearances. Metastases of some tumour histologies are more likely to haemorrhage -- knowledge of this can help refine the differential diagnoses.
Haemothorax literally means blood within the chest, is a term usually used to describe a pleural effusion due to accumulation of blood. If a haemothorax occurs concurrently with a pneumothorax it is then termed a haemopneumothorax.
A tension haemothorax refers to haemothorax that results from ...
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 haemorrhage. It is typically seen in angioinvasive aspergillosis.
Histopathologically, it represents a focus of pulmon...
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 paediatric patients is indicative of pneumomediastinum. The paediatric 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 Heiner syndrome is a rare form of primary pulmonary haemosiderosis associated with an allergy to cow's milk. The syndrome includes:
rectal blood loss with hypochromic microcytic anaemia
pulmonary infiltrates (often recurrent)
There are many thoracic complications that can occur following haematopoietic 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...
Hepatic hydrothorax (HH) is an uncommon manifestation of cirrhosis with ascites. It is one of the pulmonary complications of cirrhosis with portal hypertension.
It is characterised by formation of pleural effusions usually greater than 500 mL, in patients with portal hypertension without any o...
Pulmonary hepatisation refers to the alteration of lung tissue such that it resembles liver tissue. It is a stage of lobar pneumonic consolidation.
In the early stage, haemorrhagic fluid accumulates within the alveoli and gets organised resulting in a pathological appearance called "...
Hepatopulmonary syndrome (HPS) refers to the combination of
hepatic dysfunction (cirrhosis)
hypoxaemia (alveolar-arterial O2 gradient of >15 mmHg; >20 mmHg in >64 years old patients)
peripheral pulmonary arterial dilatation (due to right to left micro-shunts)
It is estimated to...
Hereditary connective tissue diseases are a group of connective tissue disease that have a degree of inheritance risk. They include :
Marfan syndrome - genetic disease causing abnormal fibrillin
Ehlers-Danlos syndrome - progressive deterioration of collagen and affects joints, heart v...
Hereditary haemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is a rare inherited disorder characterised by abnormal blood vessel formation in the skin, mucous membranes, and organs including the lungs, liver, and central nervous system.
Hermansky-Pudlak syndrome (HPS) is a rare syndrome which consists of:
oculocutaneous hypopigmentation (albinism)
abnormal storage of autofluorescent pigment (ceroid or lipofuscin)
typically occurs within lysosomal organelles of the cells of multiple organs and the reti...
Heroin-induced pulmonary oedema is an aetiological subtype of non-cardiogenic pulmonary oedema. It may be prevalent in up to 40% of patients admitted with a heroin overdose 2.
It is defined by some authors as a syndrome in which a patient develops significant hypoxia (room air saturation< 90% w...
Hiatus hernias occur when there is herniation of abdominal contents through the oesophageal hiatus of the diaphragm into the thoracic cavity.
The prevalence of hiatus hernia increases with age, with a slight female predilection.
Many patients with hiatus he...
High altitude pulmonary oedema is a subtype of pulmonary oedema and is caused by prolonged exposure to an environment with a lower partial oxygen atmospheric pressure.
It occurs most frequently in young males and ~24-48 hours after they have made a rapid ascent to heights greater ...
High attenuation lymphadenopathy has been described with:
Kaposi sarcoma 1,6
angioimmunoblastic lymphadenopathy (AILD)
Kimura disease (due to nodal haemorrhage) 6
metastatic hypernephroma (presumed due to nodal haemorrhage) 6
If there is calcification associat...
The hilar point on chest radiographs is formed by the outer margins of the superior pulmonary vein and the descending pulmonary artery as they cross past each other.
The hilum convergence sign is a useful chest radiograph sign to help distinguish a bulky hilum due to pulmonary artery dilatation from a mass/nodal enlargement. In the former, pulmonary vessels can be seen to converge and join a dilated pulmonary artery.
History and etymology
Dr Benjamin Fels...
The hilum overlay sign refers to the appearance of an abnormally dense hilum on frontal chest radiographs.
If a mass arises from the hilum, the normal pulmonary vessels (interlobar artery, upper lobe arteries, and left descending artery) 2 are in contact with the mass and their silhouette is ob...