Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

1,794 results found
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Diffuse airway narrowing

Diffuse airway narrowing can occur from a number of pathologies; these include: relapsing polychondritis ulcerative colitis amyloidosis: tracheobronchial sarcoidosis granulomatosis with polyangiitis tracheopathia osteochondroplastica various infections including tracheobronchial papillom...
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Diffuse alveolar damage

Diffuse alveolar damage (DAD) is a common manifestation of drug-induced lung injury that results from necrosis of type II pneumocytes and alveolar endothelial cells. Clinical presentation Affected patients present with dyspnea, cough, and occasionally fever. Diffusion capacity of the lung for ...
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Diffuse alveolar hemorrhage

Diffuse alveolar hemorrhage (DAH) is a subset of diffuse pulmonary hemorrhage when bleeding is diffuse and directly into the alveolar spaces. It can occur in a vast number of clinical situations and can be life-threatening. Pathology Blood tends to fill alveolar spaces at multiple sites. Etio...
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Diffuse ground-glass nodules

Diffuse ground-glass nodules can arise from many causes. These include: infection atypical infections (especially in immunosuppressed patients) 1,3 pneumocystis jirovecii pneumonia cytomegalovirus pneumonia pulmonary herpes simplex infection pulmonary respiratory syncytial viral infection ...
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Diffuse ground-glass opacification

Diffuse or widespread ground-glass opacification/opacity carries a wide differential diagnosis 1-3: diffuse alveolar disease hydrostatic pulmonary edema acute respiratory distress syndrome (ARDS) diffuse alveolar hemorrhage interstitial lung disease hypersensitivity pneumonitis connective...
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Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an extremely rare pulmonary disorder at the benign end of the neuroendocrine cells proliferation spectrum. It is mainly seen in non-smoker middle-age females with a history of chronic cough or asthma. On imaging, it is cha...
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Diffuse panbronchiolitis

Diffuse panbronchiolitis, also referred as diffuse Asian panbronchiolitis, is a form of bronchiolitis and is an idiopathic progressive inflammatory small airways obstructive lung disease. Epidemiology There is a striking predilection in the population from East Asia (e.g. Japan, Korea, China)....
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Diffuse pleural thickening

Diffuse pleural thickening refers to a morphological type of pleural thickening. It can occur from malignant as well as non-malignant causes, which include: diffuse pleural fibrosis / fibrothorax 6 asbestos-related pleural disease: typically seen as a continuous sheet of pleural thickening oft...
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Diffuse pulmonary hemorrhage

Diffuse pulmonary hemorrhage (DPH) is a subtype of pulmonary hemorrhage where bleeding into the lung is diffuse. If the bleeding is into the alveolar spaces this can be further subclassified as diffuse alveolar hemorrhage (DAH). Clinical presentation While the exact presentation can vary is ha...
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Diffuse pulmonary lymphangiomatosis

Diffuse pulmonary lymphangiomatosis (DPL) is a rare condition characterized by diffuse proliferation of anastomosing lymphatic channels (lymphangiomas). Epidemiology There is no recognized gender predilection. It typically manifests in children and young adults. Radiographic features CT ches...
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Diffuse pulmonary meningotheliomatosis

Diffuse pulmonary meningotheliomatosis is a rare condition manifested by multiple minute pulmonary meningothelial nodules (MPMNs) scattered throughout the lungs. Epidemiology There may be an increased female predilection and they tend to peak around the 5th to 7th decades of life at the time o...
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Diffuse pulmonary nodules

Diffuse pulmonary nodules are usually seen as multiple pulmonary nodular opacifications on a HRCT chest scan. They can signify disease processes affecting either the interstitium or the airspace. They can range from a few millimeters to up to 1 cm and when very small and numerous there can be so...
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Diffuse pulmonary nodules (differential diagnosis)

A number of differentials must be kept in mind while approaching diffuse or multiple pulmonary nodules. Interpretation is easier if nodules are the only abnormality. Differential diagnosis These differentials can be narrowed down based on several criteria: Based on appearance  miliary nodule...
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Diffuse pulmonary parenchymal amyloidosis

Diffuse pulmonary parenchymal amyloidosis is considered the least common form of pulmonary amyloidosis 6.  Clinical presentation Unlike the nodular form, patients tend to be more symptomatic and often have symptoms of cough and shortness of breath. The most common presentation in this form ten...
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Diffuse tracheal narrowing

Conditions associated with diffuse tracheal narrowing or collapse include (in alphabetical order): amyloidosis chronic obstructive pulmonary disease (COPD): saber sheath trachea granulomatosis with polyangiitis tracheobronchial tuberculosis 3 tracheomalacia/tracheobronchomalacia (due to col...
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Diffusing capacity of the lungs for carbon monoxide

Diffusing capacity of the lungs for carbon monoxide (often abbreviated as DLCO) is a measure that determines how much oxygen travels from the alveoli of the lungs to the bloodstream. It is an index of the surface area available for gas exchange. It becomes decreased in situations such as emphy...
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Ditzel

A ditzel is an informal term widely used by radiologists to refer to indeterminate small pulmonary nodules 1.  History and etymology The etymology of the term ditzel is disputed. It might be derived from the American term 'ditzy' meaning silly or inane, but there is a lack of good evidence for...
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Diverticulum

Diverticula are outpouchings of a hollow viscus and can be either true or false. Occasionally a diverticulum is used in a more general sense to mean the outpouching of other anatomical structures, e.g. frontal intersinus septal cells are hypothesized to form as diverticula from the frontal sinu...
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Doege-Potter syndrome

Doege-Potter syndrome is a non-islet cell tumor hypoglycemia, secondary to a solitary fibrous tumor (SFT). It is rare, and more associated with malignant SFTs.
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Domestically acquired particulate lung disease

Domestically acquired particulate lung disease (DAPLD) or hut lung is a pneumoconiosis due to exposure from smoke from biomass fuel used in cooking in an enclosed space.  Epidemiology Typically women who present with symptoms of a pneumoconiosis without the history of occupational exposure 2,3...
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Dot in box appearance

A "dot in box" appearance is a pattern that has been described with pulmonary lymphangitis carcinomatosis.  The interlobular septal thickening from lymphangitis forms polygonal arcades accounting for the box while the prominence of the centrilobular bronchovascular bundle is thought to represent...
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Double aortic arch

Double aortic arches are the most common symptomatic type of the aortic arch variant. It may account for up to 50-60% of vascular rings. Clinical presentation Double aortic arch is mostly diagnosed in childhood due to symptoms related to esophageal and/or tracheal obstruction. Respiratory symp...
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Double artery sign

The double artery sign refers to the appearance of a non-dilated mucus-filled bronchus adjacent to a pulmonary artery producing the appearance of a "double artery" on CT chest. This sign is considered a feature of a central endobronchial lesion such as a mucus plug or neoplasm.
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Double density sign (disambiguation)

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)
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Double diaphragm sign

The double diaphragm sign is one of several radiological signs seen with a pneumothorax in a supine patient. Supine films are commonly performed in unwell patients, particularly in the ICU. In a supine patient with a pneumothorax, air may outline the anterior portions of the hemidiaphragm and c...
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Double lumen cannula for VV ECMO

The double lumen cannula enables veno-venous extracorporeal membrane oxygenation (VV ECMO) to patients with severe respiratory failure. It is often used as a bridge to lung transplant.  The cannulation is usually performed via the right jugular vein. This position allows the patients to stay aw...
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Double lumen endotracheal tube

A double lumen endotracheal tube is a type of intubation device where there are two lumens. Indications It is designed to isolate the lungs from one another anatomically and/or physiologically: anatomical lung separation: isolation of diseased lung from contaminating the non-diseased lung ma...
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Double lung point sign (Ultrasound)

The double lung point sign refers to a sharp boundary found between relatively aerated superior lung fields and coalescent "B‐lines" (representing interstitial edema) in the basal lung fields, with a reported sensitivity of 45.6%-76.7% and a specificity of 94.8%-100% 1,3 in diagnosing transient ...
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Doughnut sign (chest)

The doughnut sign can be appreciated on the lateral chest radiograph of patients with mediastinal adenopathy, most commonly seen in pediatric patients with pulmonary tuberculosis infection1. The sign is made up of precarinal, subcarinal and retrocarinal lymph nodes which surround the radiolucen...
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Doughnut sign (disambiguation)

The doughnut sign can refer to a variety of different signs: doughnut sign (bone scan) doughnut sign (bowel) crescent in a doughnut sign (bowel) doughnut sign (chest) doughnut sign (orbit)
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Drowning (postmortem findings)

Drowning is one of the most prevalent causes of non-natural death. According to the World Health Organization (WHO), an estimated 360,000 annual deaths occur due to drowning. This article concerns itself with postmortem appearances in fatalities from drowning. For non-fatal pulmonary changes pl...
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Drug and toxin induced pulmonary hypertension

Drug and toxin induced pulmonary hypertension is one of the causes of pulmonary arterial hypertension. It falls under group 1.3 under the Dana point classification system of pulmonary hypertension.  Pathology A wide range of difference drugs have been associated with developing pulmonary hyper...
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Drug-induced lung disease

Drug-induced lung disease can result from a number of agents and may have a myriad of presentations, ranging from an adult respiratory distress syndrome type picture to established pulmonary fibrosis. Due to this, it can be extremely difficult to pinpoint the offending agent on imaging appearan...
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Drug rash with eosinophilia and systemic symptoms syndrome

The drug rash with eosinophilia and systemic symptoms (DRESS) syndrome typically manifests as a skin rash, fever, lymph nodal enlargement with variable internal organ involvement, and represents a hypersensitivity reaction to medication. Clinical presentation  Clinical presentation can be vari...
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Ductus arteriosus

The ductus arteriosum (DA) (or arteriosus) is the thick short conduit for blood to bypass the non-ventilated lungs in the fetus. It is located between and connects the proximal left pulmonary artery and the undersurface of the aortic arch distal to the origin of the last branch of the arch, at t...
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Ductus diverticulum

Aortic ductus diverticulum is a developmental outpouching of the thoracic aorta which may be mistaken for an acute aortic injury. Gross anatomy It is usually seen at the anteromedial aspect of the aorta at site of the aortic isthmus, where the ligamentum arteriosum attaches. It is also the sit...
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Dynamic tracheal collapse

Dynamic tracheal collapse refers to collapse of the trachea during expiration. It is perhaps best assessed on CT in the end expiratory phase. An inspiratory series is also useful for comparative purposes. The term excessive dynamic airway collapse (EDAC) refers to abnormal and exaggerated bulgin...
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Dysphagia

Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem. Odynophagia is the term for painful swallowing. Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the e...
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Dysphagia lusoria

Dysphagia lusoria is an impairment of swallowing due to compression from an aberrant right subclavian artery (arteria lusoria). Clinical presentation Most patients with aberrant right subclavian arteries do not have symptoms. Some present with mild dysphagia, while a small minority have a seve...
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Echogenic fetal lung lesions

Echogenic fetal lung lesions on antenatal ultrasound can be detected in a number of situations. They include: Airway obstructions: lung are often enlarged and echogenic bilaterally congenital high airways obstruction syndrome (CHAOS) tracheal atresia congenital tracheal stenosis laryngeal a...
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Ectopic meningioma

An ectopic meningioma (or primary ectopic meningioma) refers to rare situations where a meningioma arises outside the dura. These can occur at various sites but usually occur in the head and neck region. Reported sites include scalp skin ear and temporal bone sinonasal tract mandible 1 or...
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EGFR mutation

Epidermal growth factor receptor (EGFR) mutation can be expressed in a large proportion of non-small cell lung carcinomas (NSCLC). However, certain subtypes such as invasive mucinous adenocarcinoma of the lung can have very low expression. The presence of this mutation can be assessed on biopsy...
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Egg and banana sign (pulmonary hypertension)

The egg and banana sign is a sign for the diagnosis of pulmonary arterial hypertension (PAH) on axial CT/MR images. It refers to the appearance of the aortic arch (banana) next to a distorted main pulmonary artery (egg). Like an egg, the main pulmonary artery is preferentially dilated in the PA ...
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Eggshell calcification in thorax and mediastinum (mnemonic)

Helpful mnemonics to remember the major causes of eggshell calcification of the nodes in the thorax and mediastinum are:  A Silly Cool Sergeant Likes His Tubercular Blast Sally Smith Likes Her Smart ABC Mnemonic Mnemonics A Silly Cool Sergeant Likes His Tubercular Blast A: amyloidosis S: s...
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Eggshell calcification (lymph nodes)

Eggshell calcification refers to fine calcification seen at the periphery of a mass and usually relates to lamellar lymph node calcification. For similar appearance in the breast see eggshell calcification (breast). In 1967 Jacobsen and Felson published criteria to help "avoid over-reading of t...
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Ehlers-Danlos syndrome

Ehlers-Danlos syndrome comprises a heterogeneous group of collagen disorders (hereditary connective tissue disease). Epidemiology There is a recognized male predominance. Clinical presentation Ehlers-Danlos syndrome clinically manifests with skin hyperelasticity and fragility joint hypermo...
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Eisenmenger syndrome

The Eisenmenger syndrome is a complication of an uncorrected high-flow, high-pressure congenital heart anomaly leading to chronic pulmonary arterial hypertension and shunt reversal. Epidemiology In general, the shunts that lead to Eisenmenger syndrome share high pressure and high flow 3. As su...
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Elastofibroma dorsi

Elastofibroma dorsi is a benign soft-tissue tumor with a characteristic location and imaging appearance. Epidemiology It is more frequently seen in older women, with a reported female predilection of 5-13:1. The estimated mean age at diagnosis is around 65-70 years. Clinical presentation Ela...
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Elephant trunk repair

An elephant trunk repair is a type of open repair procedure devised to address combined aneurysms, it  is often a two staged procedure wherein the arch repair is facilitated by sternotomy and a second staged procedure is performed via left thoracotomy for the descending or thoracoabdominal aorta...
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Elevated diaphragm

Elevated diaphragm refers to the symmetrical elevation of both domes of the diaphragm. Pathology Etiology There is some overlap with causes of an elevated hemidiaphragm.  Technical  supine position poor inspiratory effort Patient factors obesity pregnancy Diaphragmatic pathology paral...
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Elevated hemidiaphragm

An elevated hemidiaphragm may result from direct and indirect causes which include: above the diaphragm 1 decreased lung volume atelectasis/collapse prior lobectomy or pneumonectomy pulmonary hypoplasia diaphragm 3-7 phrenic nerve palsy diaphragmatic eventration contralateral stroke: ...
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Eleventh rib

The atypical 11th rib is one of two floating ribs. Gross anatomy Osteology The 11th rib has a single facet on its head for articulation with the T11 vertebra. It has a short neck and no tubercle. The angle is slight. Its costal groove is shallow. The internal surface of this rib faces slightl...
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Eloesser flap

Eloesser flap is a single-stage procedure for the treatment of severe pleural empyema, and involves a U-shaped incision and the resection of a number of subjacent posterolateral ribs. The U-shaped flap is then folded into the pleural space creating a permanent communication.  Unlike the Clagett...
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Emphysema (disambiguation)

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...
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Empty cyst sign

The empty cyst sign is described in hydatid disease. After rupture of the cyst and complete evacuation of its content, the pericyst becomes empty as an air-filled cyst on x-ray or CT 1,2. With superadded infection, an air-fluid level may appear within the cyst, mimicking a lung abscess 2.
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Empyema

Empyemas are purulent inflammatory collections within a body cavity. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space. Terminology Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
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Empyema necessitans

Empyema necessitans (also sometimes spelled as empyema necessitasis) refers to extension of an empyema out of the pleural space and into the neighboring chest wall and surrounding soft tissues. Pathology It may either occur due the virulence of the organism or may be facilitated by previous th...
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Empyema vs pleural effusion

An empyema can resemble a pleural effusion and can mimic a peripheral pulmonary abscess. Features that help distinguish a pleural effusion from an empyema include: Shape and location Empyemas usually: form an obtuse angle with the chest wall unilateral or markedly asymmetric whereas pleural ...
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Empyema vs pulmonary abscess

Distinguishing between an empyema and a peripherally located pulmonary abscess is essential. Lung abscesses are usually managed with prolonged antibiotics and physiotherapy with postural drainage whereas an empyema usually requires percutaneous or surgical drainage. Radiographic features Plai...
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Endobronchial hemangioma

An endobronchial hemangioma is a rare benign lesion which can occur in the tracheobronchial tree. Clinical presentation Patients may present with hemoptysis and cough. Radiographic features Maybe be occult on chest radiographs. On CT usually seen as circumscribed lesions protruding into the ...
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Endobronchial intubation

Endobronchial intubation is the not infrequent finding of the endotracheal tube located in a bronchus and is a trivial diagnosis to make in most instances provided an adequately penetrated chest radiograph is obtained. The incidence of endobronchial intubation is greatest following emergency int...
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Endobronchial lipoma

Endobronchial lipomas are rare benign lesions arising from the adipose tissue in the submucosal layer of the bronchial wall. Epidemiology Rare benign tumor with a possible male predilection.  Clinical presentation Presenting symptoms include a cough, sputum, hemoptysis and dyspnea; however, ...
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Endobronchial lipomatous hamartoma

Endobronchial lipomatous hamartoma is a type of hamartoma, found in the conducting airways, that can be considered as a variant of endobronchial hamartoma, with a predominant lipomatous component.  In general endobronchial hamartomas are thought to contain more fat than parenchymal pulmonary ham...
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Endobronchial metastases

Endobronchial metastases are an uncommon form of intrathoracic metastases. They are much less common than intrapulmonary metastases. Clinical presentation The clinical presentation varies and includes: hemoptysis cough post-obstructive pneumonitis from distal obstruction Pathology Frequen...
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Endobronchial metastases (mnemonic)

Primary neoplasms which may result in endobronchial metastases may be memorized by utilizing the following mnemonic: Kiss My RBC 1  Mnemonic K: Kaposi sarcoma M: melanoma R: renal cell carcinoma B: breast cancer C: colorectal carcinoma, cervical carcinoma, carcinoid See also endobronchi...
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Endobronchial valve

Endobronchial valves are one-way valves that restrict airflow to a particular lung segment. The devices are inserted via bronchoscopy. They permit the drainage of airway secretions during the expiratory phase but restrict incoming airflow during inspiration 1. They were originally designed as a...
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Endogenous lipoid pneumonia

Endogenous lipoid pneumonia, also known as idiopathic lipoid pneumonia, is one of the two types of lipoid pneumonias. It is also known as “cholesterol pneumonia” or “golden pneumonia” Please refer to the main article for a broad discussion, including clinical presentation, radiographic features...
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Enlargement of the cardiac silhouette

Enlargement of the cardiac silhouette on a frontal (or PA) chest x-ray can be due to a number of causes 1: cardiomegaly (most common cause by far) pericardial effusion anterior mediastinal mass prominent epicardial fat pad expiratory radiograph AP projection (e.g supine radiographs taken w...
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Eosinophilic granulomatosis with polyangiitis

Eosinophilic granulomatosis with polyangiitis (EGPA), previously known as the Churg-Strauss syndrome (CSS), refers to a small to medium vessel necrotizing pulmonary vasculitis. It is also classified under the spectrum of eosinophilic lung disease and as a type of pulmonary angiitis and granuloma...
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Eosinophilic lung disease

Eosinophilic lung diseases are a heterogenous group of disorders that are characterized by excess infiltration of eosinophils within the lung interstitium and alveoli and are broadly divided into three main groups 1: idiopathic: unknown causes secondary: known causes eosinophilic vasculitis: ...
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Eparterial bronchus

The eparterial bronchus is a synonymous term for the right superior lobar bronchus. Its name is derived from the bronchus being the only one originating superior to the level of the pulmonary artery. Conversely, all other bronchi can be referred to by their anatomical relationship to the pulmona...
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Episternal ossicles

Episternal (or suprasternal) ossicles are accessory bones and a normal variant of the sternum. They result from supernumerary ossification centers and are seen in ~4% (range 1-7%) of the population. Gross anatomy Episternal ossicles are usually located posterior or superior to the superior bor...
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Epithelial-myoepithelial carcinoma of lung

Epithelial-myoepithelial carcinoma of lung is a very rare type of lung carcinomas of the salivary gland type. Pathology Diagnosis is based on the identification of myoepithelial cells, with spindle cells, clear cells, or plasmacytoid differentiation or a mixture of phenotypes, along with a var...
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Erdheim-Chester disease

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell, non-familial multisystemic histiocytosis, with widespread manifestations and of highly variable severity. The most common presenting symptom is bone pain. Epidemiology Erdheim-Chester disease is a rare, non-inherited disease of middl...
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Erdheim-Chester disease (pulmonary manifestations)

Pulmonary manifestations of Erdheim-Chester disease are uncommon. Epidemiology The lungs are affected in ~25% (range 20-35%) of cases 5.  Radiographic features HRCT chest Described findings include 1 symmetric reticular interstitial opacities smooth interlobular septal thickening and fiss...
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Erect chest x-ray (summary)

This is a basic article for medical students and other non-radiologists Erect chest x-rays are standard positioning but are also a specific examination performed for the assessment of subdiaphragmatic free gas (pneumoperitoneum). Reference article This is a summary article; we do not have a m...
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Esophageal and esophagogastric junction adenocarcinoma (staging)

Esophageal and esophagogastric junction adenocarcinoma staging refers to TNM staging of adenocarcinoma originating in the esophagus or esophagogastric junction (including tumors whose center is within the proximal 2 cm of the gastric cardia). Related histologies included in this system are high...
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Esophageal and esophagogastric junction squamous cell carcinoma (staging)

Esophageal and esophagogastric junction squamous cell carcinoma staging refers to TNM staging of squamous cell carcinoma originating in the esophagus or esophagogastric junction (including tumors whose center is within the proximal 2 cm of the gastric cardia). Related histologies included in th...
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Evaluation of endotracheal tube position

Endotracheal tubes (ETT) are wide-bore plastic tubes that are inserted into the trachea to allow artificial ventilation. Tubes come in a variety of sizes and have a balloon at the tip to ensure that gastric contents are not aspirated into the lungs. Adult tubes are usually approximately 1 cm in ...
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Ewing sarcoma (chest wall)

Ewing sarcoma family of tumors (ESFT), also referred as Ewing sarcomas of the chest wall, are malignant tumors affecting children and young adults, originating either from the osseous structures or the soft tissues of the chest wall.  On imaging, they are usually characterized as a large extrap...
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Excessive dynamic airway collapse

Excessive dynamic airway collapse (EDAC) refers to a dynamic form of central airway obstruction characterized by a decrease of ≥50% (more recent publications suggest >70%) in the cross-sectional area of the tracheobronchial lumen. Diagnosis is usually confirmed by dynamic cross-sectional imaging...
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Excipient lung disease

Excipient lung disease (ELD) refers to a granulomatous angiocentric pulmonary response to the intravenous injection of fillers in crushed oral tablets or particulate agents in illicit street drugs. Terminology Excipients are insoluble inert fillers used to protect the active components of drug...
Article

Exogenous lipoid pneumonia

Exogenous lipoid pneumonia is a form of lipoid pneumonia. Please refer to the main article for a broader 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 aspir...
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External intercostal muscle

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. Gross anatomy The external intercostal muscles are the o...
Article

Extracorporeal membrane oxygenation

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...
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Extramedullary hematopoiesis

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...
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Extrapleural air sign (pneumomediastinum)

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 d...
Article

Extrapleural fat

Extrapleural fat is a benign condition and refers to relative 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...
Article

Extrapleural fat sign

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...
Article

Extrapleural hematoma

Extrapleural hematomas are uncommon and usually seen in the context of rib fracture, subclavian venous catheter traumatic insertion, and blunt chest injury. Pathology Extrapleural hematomas result from the accumulation of blood in the extrapleural space where the overlying extrapleural fat is ...
Article

Extrapleural sign

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...
Article

Exudate

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: infe...
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F-18 fluorodeoxyglucose (FDG) embolism

F-18 fluorodeoxyglucose (FDG) embolism is a condition which results in a uniform intense FDG-avid pulmonary focus without any underlying structural CT correlate with an unremarkable follow-up PET-CT scan 1. It is thought to occur as a result of clumping of FDG with blood when the blood is withdr...

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