Diaphragmatic eventration refers to an abnormal contour of the diaphragmatic dome. It typically affects only a segment of the hemidiaphragm, compared to paralysis/weakness where the entire hemidiaphragm is typically affected.
Diaphragmatic eventration is congenital in nature and due...
Diaphragmatic hernias are defined as either congenital or acquired defects in the diaphragm.
Demographics and aetiology
There are two main types of congenital diaphragmatic hernia (CDH)s which are uncommon yet distinct entities that usually occur on the left side (80%) of the diaph...
Diaphragmatic paralysis can be unilateral or bilateral.
Clinical features are highly variable according to underlying aetiological factor:
unilateral paralysis: asymptomatic in most of the patients as the other lung compensates
may have dyspnoea, headaches, fatigue, ins...
Diaphragmatic rupture often results from blunt abdominal trauma. The mechanism of injury is typically a motor-vehicle collision.
Given that the most common mechanism is motor vehicle collisions, it is perhaps unsurprising that young men are most frequently affected. The estimated ...
A small cardiothoracic ratio (CTR) as defined as <42%/0.42 when assessed on a PA chest radiograph, and can be due to number of entities:
adrenal insufficiency, e.g. Addison disease
asthmatic paroxysm ...
An anterosuperior mediastinal mass can be caused by neoplastic and non-neoplastic pathology. As their name suggests, they are confined to the anterior mediastinum, that portion of the mediastinum anterior to the pericardium and below the level of the clavicles.
The differential diagnosis for a...
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.
Affected patients present with dyspnoea, cough, and occasionally fever. Diffusing capacity of the lung for...
Diffuse alveolar haemorrhage (DAH) is a subset of diffuse pulmonary haemorrhage 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.
Blood tends to fill alveolar spaces at multiple sites.
Diffuse ground glass nodules can arise from many causes. These include:
atypical infections (especially in immunosuppressed patients) 1,3
pneumocystis jirovecii pneumonia
pulmonary herpes simplex infection
pulmonary respiratory syncytial viral infection
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 c...
Diffuse panbronchiolitis (DPB) or Asian panbronchiolitis is an idiopathic progressive inflammatory small airway obstructive lung disease.
There is striking predilection in East Asia (e.g. Japan, Korea, China). It tends to present in middle-aged (~ 30-60-year-old) adults, often non...
Diffuse pleural thickening refers to a morphological type of pleural thickening. It can occur from malignant as well as nonmalignant causes, which include:
diffuse pleural fibrosis / fibrothorax 6
asbestos related pleural disease: typically seen a continuous sheet of pleural thickening often i...
Diffuse pulmonary haemorrhage (DPH) is a subtype of pulmonary haemorrhage where bleeding into the lung is diffuse. If the bleeding is into the alveolar spaces this can be further subclassified as diffuse alveolar haemorrhage (DAH).
While the exact presentation can vary is...
Diffuse pulmonary lymphangiomatosis (DPL) is a rare condition characterised by diffuse proliferation of anastomosing lymphatic channels (lymphangiomas).
There is no recognised gender predilection. It typically manifests in children and young adults.
Diffuse pulmonary meningotheliomatosis a rare condition manifested by minute pulmonary meningothelial nodules (MPMNs) scattered throughout the lungs.
There may be an increased female predilection and they tend to peak around the 5th to 7th decades of life at time of detection.
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 millimetres to up to 1 cm and when very small and numerous there can be so...
A number of differentials must be kept in mind while approaching diffuse pulmonary nodules. Interpretation is easier if nodules are the only abnormality.
These differentials can be narrowed down based on the several criteria:
Based on appearance
Diffuse pulmonary parenchymal amyloidosis is considered the least common form of pulmonary amyloidosis 6.
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...
Conditions associated with diffuse tracheal narrowing or collapse include (in alphabetical order):
chronic obstructive pulmonary disease (COPD): saber sheath trachea
granulomatosis with polyangiitis
tracheobronchial tuberculosis 3
tracheomalacia/tracheobronchomalacia (due to col...
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
Diverticula are outpouchings of a hollow viscus and can be either true or false.
Diverticula is the correct Latin plural form. 'Diverticuli' and 'diverticulae' are erroneous and should not be used.
contains all layers of the wall of the parent organ (typically mucosa, muscul...
Doege-Potter syndrome is a non-islet cell tumour hypoglycemia, secondary to a solitary fibrous tumour (SFT). It is rare, and more associated with malignant SFTs.
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.
Typically women who present with symptoms of a pneumoconiosis without the history of occupational exposure 2,3...
A "dot in box" appearance is a pattern that has been described with pulmonary lymphangitis carcinomatosis. The interlobular septal thickening from lympangitis forms polygonal arcades accounting for the box while the prominence of the centrilobular bronchovascular bundle is thought to represent ...
Double aortic arch is the most common symptomatic type of the aortic arch variant. It may account for up to 50-60% of vascular rings.
Double aortic arch is mostly diagnosed in childhood due to of symptoms related to oesophageal and/or tracheal obstruction. Respiratory sym...
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.
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...
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...
A double lumen endotracheal tube is a type of ETT where there are two lumens.
It is designed to isolate the lungs from one another anatomically and/or physiologically:
anatomical lung separation: isolatation of diseased lung from contaminating the non-diseased lung
The double lung point sign refers to a sharp boundary found between relatively aerated superior lung fields and coalescent "B‐lines" (representing interstitial oedema) 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...
Drowning is one of the most prevalent causes of non-natural death. According to the World Health Organisation (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...
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.
A wide range of difference drugs have been associated with developing pulmonary hyper...
Drug-induced lung disease can result from a number of agents and can have a myriad of presentations, ranging from 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 appearances ...
Drug rash with eosinophilia and systemic symptoms (DRESS) is a syndrome reflecting a marked hypersensitivity reaction to drugs or medications.
Clinical presentation can be variable and symptoms may arise from 2 to 8 weeks after initiating the offending drug. Typical cli...
The ductus arteriosum (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 the ao...
Aortic ductus diverticulum is a developmental outpouching of the thoracic aorta.
It is usually seen at the anteromedial aspect of the aorta at site of the ligamentum arteriosum, at the aortic isthmus. This is also the site of 90% of post-traumatic aortic injuries as the ligamentu...
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...
Dysphagia refers to subjective awareness of difficulty or obstruction during swallowing. It is a relatively common and increasingly prevalent clinical problem. Odynophagia is the medial term for painful swallowing.
Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluat...
Dysphagia lusoria is an impairment of swallowing due to compression from an aberrant right subclavian artery (arteria lusoria).
Most patients with aberrant right subclavian arteries do not have symptoms. Some present with mild dysphagia, while a small minority have a seve...
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)
congenital tracheal stenosis
A helpful mnemonic for major causes of eggshell calcification in the thorax and mediastinum is:
A Silly Cool Sergeant Likes His Tubercular Blast
C: coal workers' pneumoconiosis (CWP)
L: lymphoma: (postirradiation Hodgkin disease)
Eggshell calcification refers to fine calcification seen at the periphery of a mass and usually relates to 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 the incide...
Ehlers-Danlos syndrome comprises a heterogeneous group of collagen disorders (hereditary connective tissue disease).
There is a recognised male predominance.
Clinically manifests by skin hyperelasticity and fragility, joint hypermobility and blood vessel fr...
Eisenmenger syndrome is a complication of an uncorrected high-flow, high-pressure congenital heart anomaly leading to chronic pulmonary arterial hypertension and shunt reversal.
In general, the shunts that lead to Eisenmenger syndrome share are high pressure and high flow 3. As su...
Elastofibroma dorsi is a benign soft-tissue tumour with a characteristic location and imaging appearance.
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.
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...
Elevated diaphragm refers to the symmetrical elevation of both domes of the diaphragm.
There is some overlap with causes of an elevated hemidiaphragm.
poor inspiratory effort
Elevated hemidiaphragms can result from many causes:
above the diaphragm 1
decreased lung volume
phrenic nerve palsy
contralateral stroke: usually middle cerebral artery distribut...
The atypical 11th rib is one of two floating ribs.
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...
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...
Empyemas are purulent inflammatory collections within a body cavity. They are similar to abscesses, which arise within parenchymal tissue rather than occupying a pre-existing anatomical space.
Colloquially, the term empyema is used to refer to thoracic empyemas but there are variou...
Empyema necessitans (also sometimes spelt as empyema necessitasis) refers to extension of a pleural infection out of the thorax and into the neighbouring chest wall and surrounding soft tissues, e.g. extension of an empyema outwith the pleural cavity.
It may either occur due the viru...
An empyema can resemble a pleural effusion and can mimic a peripheral pulmonary abscess, although a number of features usually enable distinction between the two (see empyema vs. lung abscess). Features that help distinguish a pleural effusion from an empyema include:
Shape and location
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.
Endobronchial intubation is not infrequent 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 intubation.
The main issue with intub...
Endobronchial metastases (EBMs) are an uncommon form of intrathoracic metastases. They are much less common than intrapulmonary metastases.
The clinical presentation varies and includes:
post-obstructive pneumonitis from distal obstruction
Primary neoplasms which may result in endobronchial metastases may be memorized by utilizing the following mnemonic:
Kiss My RBC 1
Kiss: Kaposi sarcoma
R: renal cell carcinoma
B: breast cancer
C: colorectal carcinoma, cervical carcinoma, carcinoid
Endogenous lipoid pneumonia, also known as idiopathic lipoid pneumonia, is of the of the two types of lipoid pneumonias. It is also sometimes known as “cholesterol pneumonia” or “golden pneumonia”
Please refer to the main article for a broad discussion, including clinical presentation, radiogra...
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)
anterior mediastinal mass
prominent epicardial fat pad
AP projection (from supine radiographs taken ...
Eosinophilic granulomatosis with polyangiitis (EGPA), previously known as the Churg-Strauss syndrome (CSS), is a small to medium vessel necrotising pulmonary vasculitis. It is also classified under the spectrum of eosinophilic lung disease and as a type of pulmonary angiitis and granulomatosis.
Eosinophilic lung diseases are heterogenous group of disorders that are characterised by excess infiltration of the eosinophils within the lung interstitium and alveoli and are broadly divided into three main groups 1:
idiopathic: unknown causes
secondary: known causes
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...
Epicardial (pericardial) fat pads are normal structures that lie in the cardiophrenic angle, more so on the right. Unsurprisingly, they are more prominent in obese patients.
They can be affected by fat necrosis (see: epipericardial fat necrosis).
Epipericardial fat necrosis is a rare self-limiting cause of acute chest pain in an otherwise healthy individual. It occurs within the mediastinum outside the pericardium.
The patient presents with an acute chest pain that may mimic other cardiopulmonary causes. It is a s...
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.
Episternal ossicles are usually located posterior or superior to the superior bor...
Epithelial-myoepithelial carcinoma of lung is a very rare type of lung carcinomas of the salivary gland type.
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...
Erdheim-Chester disease (ECD) is a rare non-Langerhans cell, non-familial multisystemic granulomatosis, with widespread manifestations and of highly variable severity. The most common presenting symptom is bone pain.
Erdheim-Chester disease is a rare, non-inherited disease of midd...
Pulmonary manifestations of Erdheim-Chester disease are uncommon.
The lungs are affected in ~25% (range 20-35%) of cases 5.
Described findings include 1
symmetric reticular interstitial opacities
smooth interlobular septal thickening and fiss...
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).
This is a summary article; we do not have a m...
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 ...
Ewing sarcoma family of tumours (ESFT), also referred as Ewing sarcomas of the chest wall, are malignant tumours affecting children and young adults, originating either from the osseous structures or the soft tissues of the chest wall.
On imaging, they are usually characterised as a large extr...
Exogenous lipoid pneumonia is a form of lipoid pneumonia.
In terms of onset of presentation, it can divided into two different forms
acute exogenous lipoid pneumonia
uncommon and typically is caused by an episode of aspiration of a large quantity of a petroleum-based product.
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 haematopoiesis 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 to a particularly involved organ, please refer to the specific articles on:
extramedullary haematopoiesis in th...
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 haematoma or extrapleural mass. The presence of the extrapleural fat sign is indicativ...
Extrapleural haematomas are uncommon and usually seen in the context of rib fracture, subclavian venous catheter traumatic insertion, and blunt chest injury.
Extrapleural haematomas result from the accumulation of blood in the extrapleural space where the overlying extrapleural fat i...
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 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 contraction of ...
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 ...