Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
a central core consisting of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessel...
Acute airspace opacification with lymphadenopathy is a subset of the differential diagnosis for generalized airspace opacification and includes:
post-obstructive causes (usually chronic, but 'new' changes can occur)
primary lung cancer
Acute bilateral airspace opacification is a subset of the larger differential diagnosis for airspace opacification. An exhaustive list of all possible causes of acute bilateral airspace opacities is long, but a useful way to consider the huge list is via the material within the airways:
Acute unilateral airspace opacification is a subset of the differential diagnosis for airspace opacification.
The exhaustive list of all possible causes would be huge, but a useful framework includes:
pus, i.e. infection
Adhesive atelectasis refers to the specific form of lung atelectasis that occurs due to the decrease or absence of pulmonary surfactant produced by type II pneumocytes. Without sufficient surfactant the alveoli collapse due to increased surface tension. It is most commonly seen in the neonate wi...
Tuberculous adrenalitis is the result of adrenal mycobacterium tuberculosis (TB) infection. Its incidence has decreased in the western world with the declining incidence of tuberculosis.
As the tuberculous infection causes destruction of the adrenal cortex, primary adrenal insufficie...
AIDS-defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS, and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are:
bacterial infections: multiple or recurrent
An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity.
It should not be confused wi...
Air space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is one of the many patterns of lung opacification and is equivalent to the pathological diagnosis of pulmonary consolidati...
The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows:
acute airspace opacities with lymph node enlargement
acute airspace opacities: un...
Airway foreign bodies in children are potentially fatal, which is why immediate recognition is important. Unfortunately, delayed diagnosis is common.
Children under the age of four years are at increased risk of foreign body (FB) aspiration, with a slight male predominance 1.
An aortic nipple is seen in about 10% of PA chest x-rays on the lateral surface of the aortic arch/aortic knob. It represents the left superior intercostal vein.
When prominent, superior vena cava obstruction should be considered as the left superior intercostal vein serves as a collateral path...
The aortopulmonary (aortic-pulmonary or AP) window (also known as APW, but see 'Terminology' below) is a radiological mediastinal space seen on frontal chest radiographs.
The term "aortopulmonary window" (also called an aortopulmonary septal defect) can also refer to a rare form of...
Apical pleural cap refers to a curved density at the lung apex seen on chest radiograph.
The frequency of apical pleural thickening increases with age 3.
It arises from a number of causes:
idiopathic: chronic ischemic etiology is favored f...
Asbestos related disease, in particular affecting the lung, comprise of a broad spectrum of entities related to the inhalational exposure to asbestos fibers. They can be divided into benign and malignant changes 1-3.
Benign pleural and parenchymal lung disease
asbestos related benign pleural d...
Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients.
In adults, an ascending aortic diameter greater than 4 cm is considered to indicate dilatation 4. Aneurysmal dilatation is considered when the ascending aortic diameter reaches or ex...
Aspiration pneumonia is caused by a direct chemical insult due to the entry of a foreign substance, solid or liquid, into the respiratory tract.
Aspiration may be clinically silent, or it may present with dyspnea, cough, or fever. The clinical and radiographic features de...
Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4.
Bat's wing pulmonary opacities can be caused by:
Benign esophageal lesions are less symptomatic than malignant esophageal lesions, making up for only 1% of clinically apparent esophageal lesions.
esophageal leiomyoma (>50%)
esophageal fibrovascular polyp (~12.5%)
may contain fat
esophageal duplication cyst (10%)
Bentall procedure is performed for the repair of ascending aortic root lesions. Typically the native aortic root and aortic valve are replaced with a composite graft that comprises both ascending aortic and aortic valve grafts, to which the coronary arteries are anastomosed.
History and etymolo...
Bilateral axillary lymphadenopathy can result from a number of causes and generally implies a systemic process. They include:
autoimmune diseases, e.g.:
systemic lupus erythematosus (SLE)
Bird fancier lung refers to a type of hypersensitivity pneumonitis occurring as a response to avian antigens (usually inhaled proteins in the dust of bird feathers and droppings). It can have acute, subacute and chronic clinical presentations.
For a broad discussion on this entity, please refer...
Bleomycin lung toxicity is an uncommon but recognized complication that can occur with the chemotherapeutic drug bleomycin.
Bleomycin is an antitumour antibiotic which was initially isolated from a strain of Streptomyces verticillus in 1966. It is commonly used (either alo...
Bronchial atresia is a developmental anomaly characterized by focal obliteration of the proximal segment of a bronchus associated with hyperinflation of the distal lung.
On imaging, it commonly presents as a proximal focal tubular shaped opacity radiating from the hilum associated with a dista...
Bronchiolectasis is a descriptive term which is given to dilatation of bronchioles, which are of smaller caliber than bronchi. It can arise of a number of pathologies.
bronchiectasis: dilatation of larger aiways
Bronchiolitis is a broad term that refers to any form of inflammation of the bronchioles. It is often used in situations where there inflammation primarily occurs in airways smaller than 2 mm 6. It can carry variable clinical, functional and morphological expression. Bronchiolar disease may be ...
Broncho-esophageal fistula (BOF) refers to abnormal communication between a bronchus and the esophagus.
For congenital fistulas, please refer to the article on congenital tracheo-esophageal fistula.
A small proportion of patient with congenital forms may present in adult...
Following are the main differentiating features of bronchopleural fistula and lung abscess on plain radiographs and CT 1:
bronchopleural fistulas have mostly lenticular shape of space
length of air fluid level in bronchopleural fistula in different projections is unequ...
There are numerous causes of calcified mediastinal lymph nodes.
Common causes include:
infectious granulomatous diseases
Uncommon causes include:
Pneumocystis jiroveci (PCP) pneumonia
thyroid carcinoma: papi...
Calcified pulmonary (lung parenchymal) densities can occur in a number of conditions.
healed varicella pneumonia 1
pulmonary alveolar microlithiasis
occupational lung diseases
coal workers pneumoconiosis
Large nodules or masses
Calcification associated with pulmonary emboli is usually associated with chronic pulmonary embolism. Calcification is occasionally related to prior congenital cardiac repairs 1.
If it is purely high attenuating, consider
polymethylmethacrylate (PMMA) embolism into the ...
Calcified pulmonary nodules are a subset of hyperdense pulmonary nodules and a group of nodules with a relatively narrow differential.
The most common cause of nodule calcification is granuloma formation, usually in the response to healed infection.
Calcifying pulmonary metastases are rare. These should not be confused with metastatic pulmonary calcification.
Calcification in metastases can arise through a variety of mechanisms: bone formation in tumors osteoid origin, calcification and ossification of tumor cartilage, dystrophi...
Carcinoid tumors of the lung are a subgroup of neuroendocrine tumors of the lung, of lower grade than small cell carcinoma of the lung and large cell neuroendocrine carcinoma of the lung.
For a general discussion, please refer to the article on carcinoid tumors.
Implantable cardiac conduction devices (also known as cardiac implantable electronic devices or CIEDs) are a very common medical device of the thorax, with over one million implanted in the United States of America alone.
There are two major types of cardiac conduction devices: pacemakers and a...
The cardiophrenic space is usually filled with fat. However, lesions originating above or lower to the diaphragm can present as cardiophrenic angle lesions.
The more common lesions encountered include:
pericardial fat pad
pericardial fat necrosis
There are relatively few causes of calcification of the ascending aorta 1-3:
atherosclerosis (this usually spares the ascending aorta)
Cavitating pneumonia is a complication that can occur with a severe necrotizing pneumonia and in some publications it is used synonymously with the latter term 2. It is a rare complication in both children and adults.
Cavitation associated with Mycobacterium tuberculosis is separately discusse...
Cavitating pulmonary metastases refer to pulmonary metastases which then tend to cavitate. The term is similar but may not be identical to cystic pulmonary metastases in which the wall of the former may be thicker.
Cavitation is thought to occur in around 4% of lung metastases 2.
Distribution of bronchiectasis can help in narrowing the differential diagnosis. Central bronchiectasis is typically seen in:
allergic bronchopulmonary aspergillosis (ABPA)
congenital tracheobronchomegaly (a.k.a. Mounier Kuhn syndrome)
Williams Campbell syndrome (rare)
Centrilobular lung nodules refer to an HRCT chest imaging descriptor for small 5-10 mm lung nodules which are anatomically located centrally within secondary pulmonary lobules. The term is applied on the basis of location of the nodule and not its morphology that is they may be well defined or p...
There are many signs in radiology that are related to Christmas:
snowcap sign in avascular necrosis
in total anomalous pulmonary venous return
in pituitary macroadenomas
snowstorm appearance in complete hydatidiform and testicular microlithiasis
holly leaf sign in calcified pl...
Chronic bilateral airspace opacification is a subset of the differential diagnosis for airspace opacification. An exhaustive list of all possible causes of chronic bilateral airspace opacities is long, but a useful framework is as follows:
granulomatosis with polyangi...
Chronic interstitial pneumonitis is a broad descriptive term where an interstitial pneumonia has a prolonged course. It can arise of a range of etiologies. The term does not usually imply a specific radiographic pattern and includes UIP, NSIP or other pattern. As a general rule there is little o...
Chronic suppurative lung disease (CSLD) refers to a group of conditions which includes:
primary ciliary dyskinesia
This term is usually used in the context of pediatric patients.
Chronic unilateral airspace opacification is a subset of the differential diagnoses for airspace opacification. An exhaustive list of all possible causes of chronic unilateral airspace opacities is long, but a useful framework is as follows:
Cicatrisation atelectasis is a form of lung atelectasis which occurs as a result of scarring or fibrosis that reduces lung expansion. Cicatrisation atelectasis is classic in tuberculosis. The term is closely related to cicatrisation collapse when an entire lobe is collapsed from the same process...
Coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present 1,3. Typically but not always the patient is asymptomatic 1.
The differential diagnosis for such lesions is ...
Compressive atelectasis refers to a form of lung atelectasis due to compression by by a space-occupying process.
Some authors describe it as a subtype of compressive (relaxation) atelectasis where the reduction in lung volume is greater than its normal relaxed state 1. Where as others describe ...
Crazy paving refers to the appearance of ground-glass opacity with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT. It is a non-specific finding that can be seen in a number of conditions.
A number of entities can present as cyanotic congenital heart disease. These can be divided into those with increased or decreased pulmonary vascularity (pulmonary plethora):
increased pulmonary vascularity
total anomalous pulmonary venous return (TAPVR) (types I and II)
transposition of the ...
Cystic lung disease is an umbrella term used to group the conditions coursing with multiple lung cysts.
The clinical presentation is an important clue to the differential diagnosis of cystic lung diseases 12.
Diseases that present with insidious dyspnea or spontaneous p...
Cystic lesions in pediatric patients are usually congenital lesions and, as such, can be seen antenatally and following delivery.
These congenital lesions are predominantly covered by the overarching diagnosis of bronchopulmonary foregut malformation. This is a ...
The differential diagnosis for cystic masses of the mediastinum include:
esophageal duplication cyst
cystic teratoma of mediastinum
cystic degeneration of an intrathoracic tumor
Cystic or necrotic appearing lymph nodes can be caused by a number of infectious, inflammatory or malignant conditions:
squamous cell carcinoma metastases
plasmacytoid T-cell leukemia
acute myeloid leukemia
herpes simplex lymphadenit...
Cystic pulmonary metastases are atypical morphological form on pulmonary metastases where lesions manifest as distinct cystic lesions. It is slightly different from the term cavitating pulmonary metastases in that the lesions are extremely thin walled.
It has been reported with many ...
A cystic retroperitoneal lesion can carry a relatively broad differenital which includes:
retroperitoneal cystic lymphangioma
retroperitoneal mucinous cystadenoma
retroperitoneal cystic teratoma
retroperitoenal cystic mesothelioma
pseudomyxoma retroperitonei with cystic change
Dextrocardia is a congenital cardiac malrotation in which the heart is situated on the right side of the body (dextroversion) with the apex pointing to the right.
Dextrocardia merely refers to the laterality of the heart, it says nothing about the orientation of the patient's other...
Diaphragmatic paralysis (also considered very similar to the term diaphragmatic palsy) can be unilateral or bilateral.
Clinical features are highly variable according to underlying etiological factor:
unilateral paralysis: asymptomatic in most of the patients as the othe...
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
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 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.
Blood tends to fill alveolar spaces at multiple sites.
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 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).
While the exact presentation can vary is ha...
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...
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...
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 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...
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 term for painful swallowing.
Fluoroscopy is the mainstay of imaging assessment but manometry can help evaluate the e...
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
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...
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. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space.
Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
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...
Endobronchial metastases 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
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 ...
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
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...
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
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
Gravity dependent atelectasis refers to a form of lung atelectasis which occurs in the dependent portions of the lungs due to a combination of reduced alveolar volume and increased perfusion. Being due to gravity, it usually has a dependent and subpleural distribution. It is very commonly seen i...
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...
Hemopneumothorax (or, less commonly, pneumohemothorax) 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 .
Hemoptysis (plural: hemoptyses) refers to coughing up of 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 t...
Hemothorax (plural hemothoraces), or rarely hematothorax, 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 hemothor...
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.
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...
High attenuation lymphadenopathy has been described with:
Kaposi sarcoma 1,6
angioimmunoblastic lymphadenopathy (AILD)
Kimura disease (due to nodal hemorrhage) 6
metastatic hypernephroma (presumed due to nodal hemorrhage) 6
If there is calcification associated...
HIV-associated neoplasms are numerous and can be broadly divided into two groups:
associated but not AIDS defining malignancies
The development of these malignancies in HIV affected individuals generally implies progression to AIDS 4: