The classification system for pulmonary hypertension was revised at the 4th World Symposium on Pulmonary Hypertension held in Dana Point, California, in 2008 1.
This system is as:
group 1: pulmonary arterial hypertension
1.1: idiopathic pulmonary arterial hypertension
1.2: heritable pulmonar...
Pulmonary hypertension is defined as a resting mean pulmonary arterial pressure of 25 mmHg or greater at right heart catheterisation, which is a haemodynamic feature that is shared by all types of pulmonary hypertension in the Dana Point classification system. A resting mean pulmonary arterial p...
A box-shaped heart is a radiographic description given to the cardiac silhouette in some cases of Ebstein anomaly. The classic appearance of this finding is caused by the combination of the following features:
huge right atrium that may fill the entire right hemithorax
shelved appearance of th...
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:
Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CTs.
tubing, clamps, syringes lying on or under the patient
rubber sheets, foam mattresses, clothing, hair braids, nipple piercings etc may also be visible
These devices ...
Rasmussen aneurysm (not to be confused with Rasmussen encephalitis) is an uncommon complication of pulmonary tuberculosis and represents a pulmonary artery aneurysm adjacent or within a tuberculous cavity.
It can be present in up to 5% of patients with chronic cavitary tuberculos...
Implantable cardiac conduction devices 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 automatic implantable cardioverter-defibrillators (AICD/ICD), and...
The ball of wool sign, also referred to as the yarn sign or congealed water lily sign, is an ultrasound appearance, representing degeneration of hydatid cysts (WHO class CE 4). The inner side of the cyst detaches from the cyst wall and folds on itself, causing a change from anechoic (fluid) to a...
The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph.
The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly th...
Chest x-ray lines and tubes can be easily assessed and should be the first thing that you look at when reviewing a chest x-ray. Assessment of their position is important, but they also give you an idea about how sick the patient is and narrow down the differential diagnosis.
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.
In angioinvasive fungal infection, the no...
Lymphocele of the thoracic duct (thoracic duct cyst) is usually asymptomatic or less commonly may present as left supraclavicular fossa mass 1.
The clinical significance of a thoracic duct cyst lies in its misidentification as a pathological lesion at radiological assessment, whi...
Perivascular epithelioid cells tumours (PEComas) are a group of related mesenchymal tumours and tumour-like conditions found in many locations. This group includes:
clear cell 'sugar' tumour of the lung
clear cell myomelanocytic tumour (CCM...
Clear cell tumour of the lung is a rare benign pulmonary neoplasm that contains an abundant amount of glycogen. It is often classified under the spectrum of perivascular epithelioid cell tumours (PEComas).
Usually seen as a rounded, smooth-walled, and peripheral parenchym...
Pulmonary embolism (PE) refers to embolic occlusion of the pulmonary arterial system. The majority of cases result from thrombotic occlusion and therefore the condition is frequently termed pulmonary thrombo-embolism which is what this article mainly covers.
Other embolic sources include:
Asthma is a relatively common condition that is characterised by at least partially reversible inflammation of the airways and reversible airway obstruction due to airway hyper-reactivity. It can be acute, subacute or chronic.
Asthma is one of the most common chronic diseases in t...
Papillary predominant adenocarcinoma of lung is a subtype of adenocarcinoma of the lung.
It may account for 7-12% of all lung adenocarcinomas. There may be predilection in female non smokers 1.
It this form papillary structures replace the underlying alveolar architect...
Pulmonary oedema is a broad descriptive term and is usually defined as an abnormal accumulation of fluid in the extravascular compartments of the lung 1.
One method of classifying pulmonary oedema is as four main categories on the basis of pathophysiology which include:
Silhouette sign is somewhat of a misnomer and in the true sense actually denotes the loss of a silhouette, thus, it is sometimes also known as loss of silhouette sign or loss of outline sign 4.
The differential attenuation of x-ray photons by two adjacent structures defines the silhouette, e.g...
Radiological manifestations of recreational drug use are not infrequently seen as the use of recreational drugs is widespread.
Interestingly, recent reports have suggested a decreasing incidence of reported drug use in the general population over the past decade, but it remains th...
Haemoptysis refers to coughing out blood. Generally, it appears bright red in colour as opposed to blood from gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying aetiology.
Massive haemoptysis is referred to as expectoration of >...
Pericardial calcification (PC) usually occurs in patients with a history of pericarditis.
previous trauma or prior pericarditis
later sequelae of rheumatic heart disease
malignant pericardial involvement (e.g. mediastinal teratoma)
On chest radiography, location ...
Lymphangitic carcinomatosis, or lymphangitis carcinomatosa, is the term given to tumour spread through the lymphatics of the lung and is most commonly seen secondary to adenocarcinoma.
The demographics will reflect that of the underlying malignancy (see below).
Constrictive pericarditis (or perhaps better termed pericardial constriction) is a type of pericarditis which leads to diastolic dysfunction and potentially symptoms of right heart failure.
No single demographic is affected as there are numerous causes of constrictive pericarditi...
Saddle pulmonary embolism commonly refers to a large pulmonary embolism that straddles the bifurcation of the pulmonary trunk, extending into the left and right pulmonary arteries.
If large enough, it can completely obstruct both left and right pulmonary arteries resulting in right heart failur...
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...
Thoracic outlet syndrome (TOS) refers to a group of clinical syndromes caused by congenital or acquired compression of the brachial plexus or subclavian vessels as they pass through the superior thoracic aperture.
Clinical presentation will depend on the structure compre...
The aortic arch represents the direct continuation of the ascending aorta and represents a key area for a review of normal variant anatomy and a wide range of pathological processes that range from congenital anomalies to traumatic injury.
origin: continuation of the ascending aorta at...
Cavitating pulmonary metastases refer to pulmonary metastases which then tend to cavitation. The term is similar but may not be identical to cystic pulmonary metastases in the wall of the former may be thicker.
Cavitation is thought to occur in around 4% of lung metastases 2.
Thoracic aortic injury is the most common type of traumatic aortic injury and is a critical life-threatening, and often life ending event. It can result from either blunt or penetrating trauma:
blunt trauma (more common)
rapid deceleration (eg. motor vehicle accident, fall from great height)
Osteophyte induced adjacent pulmonary atelectasis and fibrosis are typically seen as focal pulmonary interstitial opacities adjacent to thoracic spinal osteophytes. They can be a relatively common finding in thoracic CT imaging. They are more common in older individuals
They are thou...
Westermark sign is a sign of pulmonary embolus (PE) seen on chest radiographs.
Along with Fleishner sign and Hampton hump, it makes one of the three described signs of pulmonary embolus on chest radiographs.
In one study (PIOPED) this sign was present on ~10% of chest x-rays of pati...
Fleischner sign is a prominent central artery that can be caused either by pulmonary hypertension that develops or by distension of the vessel by a large pulmonary embolus. It can be seen on chest radiographs and CT pulmonary angiography.
It is seen most commonly in the setting of massive pulmo...
The diaphragm is the dome-shaped muscle that separates the thoracic cavity from the abdominal cavity, enclosing the inferior thoracic aperture.
The muscular fibres of the diaphragm originate around the circumference of the inferior thorax and converge to a common insertion point ...
Right middle lobe consolidation refers to consolidation in part (incomplete) or all (complete) of the right middle lobe.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inflammatory), tissue, or other material.
The list of ca...
The lesser diaphragmatic apertures allow the passage of smaller structures from the thoracic cavity to abdominal cavity across the diaphragm. They are very much smaller than the other diaphragmatic apertures:
two in the right crus of the diaphragm: transmit greater and lesser right splanchnic n...
The intercostal spaces are supplied by pairs of anterior and posterior intercostal arteries.
The first two intercostal spaces are supplied by the superior intercostal artery, and the remaining nine are supplied by separate branches from the descending thoracic aorta 1. The right ...
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 ...
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...
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 haemorrahage) 6
If there is calcification associa...
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...
Pulmonary emphysema is defined as the "abnormal permanent enlargement of the airspaces distal to the terminal bronchioles accompanied by destruction of the alveolar wall and without obvious fibrosis". Emphysema is one of the entities grouped together as chronic obstructive pulmonary disease. Emp...
Aortic intramural haematoma (IMH) is an atypical form of aortic dissection due to haemorrhage into the wall from the vasa vasorum without an intimal tear. It is part of the acute aortic syndrome spectrum.
Typically aortic intramural haematomas are seen in older hypertensive patien...
Chronic obstructive pulmonary disease (COPD) represents a spectrum of obstructive airway diseases. It includes two key components which are chronic bronchitis-small airways disease and emphysema.
The most common cause has historically been, and unfortunately continues to be, smok...
Cervical aortic arch is a rare aortic arch anomaly characterised by an elongated, high-lying aortic arch extending at or above the level of the medial ends of the clavicles.
Patients with cervical aortic arch are usually asymptomatic. Symptomatic patients may present with...
Minimal aortic injuries are traumatic aortic lesions that usually involve the intima and are recognised more frequently due to the use of high-resolution imaging.
Minimal aortic injuries account for 10-28% of all blunt traumatic aortic injuries 1,6,7. The proportion of this type o...
Lung abscess is a circumscribed collection of pus within the lung, and potentially life threatening. They are often complicated to manage and difficult to treat.
As a result of the widespread availability of antibiotics, the incidence of lung abscesses has dramatically reduced. Si...
Lung cancer screening with low-dose CT (LDCT) is an imaging strategy that is beginning to be adopted for high-risk patients in some health systems. Lung cancer is the most common cause of cancer death worldwide, and there is accumulating higher level evidence that a mortality benefit exists with...
Pulmonary baritosis (or simply known as baritosis) is type of benign non-fibrotic pneumoconiosis 2 which can be precipitated by aspiration of barium sulfate particles. Inhaled barium particles can lie in the lungs for years without producing symptoms or causing any impairment in lung function 3....
Pulmonary alveolar microlithiasis (PAM) is a rare idiopathic condition characterised by widespread intra-alveolar deposition of spherical calcium phosphate microliths (calcospherites).
A slight female predilection may be present in the familial form 2. Most cases are reported in ...
Pulmonary stannosis is a condition in which tin oxide is deposited in lung tissue after inhalation. Tin oxides i.e. tin oxide, a.k.a. stannous oxide (SnO), and tin dioxide, a.k.a. stannic oxide (SnO2), are radiologically-visible and are extremely dense, although there is no tissue reaction to th...
Round atelectasis, also known as folded lung or Blesovsky syndrome, is an unusual type of lung atelectasis where there is infolding of a redundant pleura. The way the lung collapses can at times give a false mass-like appearance.
Two theories have been put forward. The second theory ...
Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is an extremely rare pulmonary disorder where there is a proliferation of neuroendocrine cells within the lung. It is however recognised with increasing frequency.
There may be an increased female predilection ...
Congestive cardiac failure (CCF) is a form of cardiac failure which is primarily manifested by the heart's inability to pump the volume of blood. It can affect the left (common) or right cardiac chambers or both.
It may be precipitated by intrinsic cardiac or extrinsic factors (which...
A loculated pneumothorax is a form of pneumothorax where a pocket of pleural air is trapped within a localised area. They may occur in a number of situations including in patients with acute respiratory disease treated with mechanical ventilation 1 and status post pleural aspiration in the conte...
Pneumonectomy is the complete surgical removal of the lung. It is most commonly performed for a primary lung malignancy. The lung is removed in its entirety providing the patient has adequate pulmonary reserve from the contralateral lung.
Recognised post-pneumonectomy complications include:
Post-pneumonectomy syndrome is delayed complication of pneumonectomy characterised by respiratory compromise caused by severe mediastinal shift and counterclockwise rotation of the heart and great vessels.
Rare delayed complication of pneumonectomy, which is more common on the rig...
Broncholithiasis is a term given for the presence of calcified or ossified material within the lumen of the bronchus.
A broncholith is usually formed by erosion by and extrusion of a calcified adjacent lymph node into the bronchial lumen and is usually associated with long-standing f...
Progressive massive fibrosis (PMF) refers to the formation of large mass-like conglomerates, predominantly in the upper pulmonary lobes, associated with radiating strands. These classically develop in the context of certain pneumoconioses (especially Coal worker's pneumoconiosis and silicosis) a...
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...
Posteroanterior (PA) chest view is the most common radiological investigation in the emergency department 1. The PA view examines the lungs, bony thoracic cavity, mediastinum and great vessels. The chest X-ray is frequently used to aid diagnosis of acute and chronic conditions.
A tracheo-bronchial stent is a device used in the treatment of symptomatic airway compression.
This device is inserted under bronchoscopic guidance in patients with external compression from mediastinal based malignancy, for example lung or oesophageal cancers. It may also be used in the treat...
Pneumatoceles are intrapulmonary air-filled cystic spaces that can have a variety of sizes and appearances. They may contain air-fluid levels and are usually the result of ventilator-induced lung injury in neonates or post-infectious. They should not be mistaken for a cavitating lung mass.
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...
Pulmonary Langerhans cell histiocytosis (PLCH) can be seen as part of widespread involvement in patients with disseminated LCH or more frequently as a distinct entity in young adult smokers. This article focuses on the latter.
PLCH is usually identified in young adults (20-40 yea...
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 is believed to occur in approximately 1 in 12,000 people 2.
There are two main types of dextr...
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...
The black pleura sign is a feature described in pulmonary alveolar microlithiasis. It is seen as a strip of tangential peripheral lucency underlying the ribs as compared to the adjacent diffusely dense calcified lung.
Although termed black pleura, it actually represents subpleural sparing of pu...
Scimitar syndrome, also known as hypogenetic lung syndrome, is characterised by a hypoplastic lung that is drained by an anomalous vein into the systemic venous system. It is a type of partial anomalous pulmonary venous return and is one of the several findings in congenital pulmonary venolobar ...
Bronchogenic cysts are congenital malformations of the bronchial tree (a type of bronchopulmonary foregut malformation). They can present as a mediastinal mass that may enlarge and cause local compression. It is also considered the commonest of foregut duplication cysts.
Mosaic attenuation is the description given to the appearance at CT where there is a patchwork of regions of differing attenuation. It is a non-specific finding, which may be seen in any of the following:
obstructive small airways disease: low attenuation regions are abnormal and reflect decre...
Mnemonics for a unilateral hyperlucent hemithorax include:
C: contralateral lung increased density, e.g. supine pleural effusion
A: air, e.g. pneumothorax
W: wall, e.g. chest wall mass, mastectomy, polio, Poland syndrome, surgical re...
Unilateral hypertranslucent hemithorax has many potential causes. It may be the result of rotation away from an optimal position or because of pathology.
A unilateral hypertranslucent hemithorax may be caused by the positioning of the patient. Rotation away from the radiation beam alt...
Primary sarcomatoid carcinomas of the lung refer to a heterogeneous group of non-small cell lung carcinomas (NSCLC).
They are thought to account for 0.2 to 1% of all lung cancers 1. A sarcomatoid histology may be present in 0.1-0.4% of non-small cell lung cancers 3.
Hydropneumothorax is a term given to the concurrent presence of a pneumothorax as well as a hydrothorax (i.e. air and fluid) in the pleural space.
It may arise in various situations which include
This mnemonic will help with the sonographic approach to the critically ill patient with dyspnoea:
C: collapsed lung (pneumothorax)
absent anterior lung sliding / anterior B lines
lung point present 1
H: heart failure (acute pulmonary oedema)
diffuse bilateral anterior B ...
RASopathies are a class of developmental disorders caused by germline mutations in genes that encode for components or regulators of the Ras/mitogen activated protein kinase (MAPK) pathway.
As a group, RASopathies represent one of the most common malformation syndromes, with an in...
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...
A useful mnemonic for pulmonary predominantly upper zone involvement (infiltration/shadowing/fibrosis) causes include:
E: extrinsic allergic alveolitis
A: ankylosing spondylitis / aspergillus
Mnemonics for peripheral lung opacities seen on chest x-ray or CT are useful to remember differentials. Examples include:
A: alveolar sarcoidosis
E: eosinophilic pneumonia
O: cryptogenic organizing pneumonia (COP)
U: usual interstitial pneumon...
A particularly helpful mnemonic for causes of pulmonary cavities is:
bronchogenic carcinoma: most frequently squamous cell carcinoma (SCC)
cavitary pulmonary metastasis(es): most frequently SCC
A: autoimmune; granulomas from
Wegener granulomatosis (granulomatos...
A mnemonic to remember the causes of obliterative bronchiolitis is:
C: cryptogenic organising pneumonia (COP)/BOOP
R: rheumatoid arthritis
I: infectious: post-viral/post-atypical infection (e.g. Mycoplasma pneumonia)
T: transplant: heart/lung/haematopoetic stem cell transpl...
The causes of non-cardiogenic pulmonary oedema can be recalled with the following mnemonic:
N: near drowning
O: O2 therapy/post-intubation pulmonary oedema
T: trauma/transfusion (TRALI: transfusion-related acute lung injury)
C: CNS: neurogenic pulmonary o...
The following differentials can be considered when small lung volumes are seen:
prior surgery, e.g. lobectomy, lung volume reduction surgery
skeletal deformities, e.g. kyphosis, scoliosis
systemic lupus erythematosus (SLE)
neuromuscular disorders, e.g. p...
Idiopathic interstitial pneumonias (IIPs) are diffuse interstitial lung diseases of unknown cause. A useful mnemonic for the American Thoracic Society-European Respiratory Society (ATS-ERS) classification of IIPs is:
All Idiopathic Chronic Lung Disease aRe Nonspecifically Patterned
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...
Lung-RADSTM (or lung imaging reporting and data system) is a classification proposed to aid with findings in low dose CT screening exams for lung cancer. The goal of the classification system is to standardize follow-up and management decisions. The system is similar to the Fleischner criteria b...
Lung volume reduction surgery (LVRS) is an emerging promising palliative treatment option for select patients with severe, debilitating pulmonary emphysema. It usually involves bilateral wedge resection of 20-30% of the most diseased lung through a median sternotomy. It has been proposed that L...
Multinodular goitre (MNG) is defined as an enlarged thyroid gland (i.e. goitre) due to multiple nodules which may have normal, decreased or increased (toxic nodule) function. It is a slightly unhelpful term as some multinodular thyroids are not enlarged, resulting in the unwieldy term "multinodu...
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.
Macrocystic honeycombing refers to a morphological sub type of honeycombing. Many publications consider the individual lung cysts to be greater than 4mm to be classified into this category. This form is considered to be more associated with UIP 3.
Silicosis is a fibrotic pneumoconiosis caused by the inhalation of fine particles of crystalline silicon dioxide (silica). Occupations such as mining, quarrying, and tunneling are associated with silicosis.
The disease occurs in two clinical forms that are subdivided by their temporal relations...