A solitary pulmonary nodule, according to the Nomenclature Committee of the Fleischner Society, defined as a rounded opacity, well or poorly defined on a conventional radiograph, measuring up to 3 cm in diameter and is not associated with lymphadenopathy, atelectasis, or pneumonia.
Solitary pulmonary nodule (SPN) is defined as a relatively well defined round or oval pulmonary parenchymal lesion equal or smaller than 30 mm in diameter. It is surrounded by pulmonary parenchyma and/or visceral pleura and is not associated with lymphadenopathy, atelectasis, or pneumonia 9.
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 ...
Spindle cell carcinoma of the lung a very rare primary pulmonary malignancy. It is sometimes classified as a sarcomatoid carcinoma of the lung. Some authors also use the term synonymously with pleomorphic carcinomas of the lung, while the WHO 1999 classification system places the latter as a sep...
The spinnaker sign (also known as the angel wing sign) is a sign of pneumomediastinum seen on neonatal chest radiographs. It refers to the thymus being outlined by air with each lobe displaced laterally and appearing like spinnaker sails. This is distinct from the sail sign appearance of the nor...
The split pleura sign is seen with pleural empyemas and is considered the most reliable CT sign helping to distinguish an empyema from a peripheral pulmonary abscess (see empyema vs pulmonary abscess) 1,2.
The sign results from fibrin coating both the parietal and visceral surfaces of the pleu...
Spontaneous haemopneumothorax is a subtype of a haemopneumothorax where there is accumulation of blood and air within the pleural space in the abscence of trauma or other definitive cause.
The source of bleeding is uncertain but in many cases can result from shearing of the adhesions...
Squamous cell carcinoma in situ (CIS) of the lung is a considered a preinvasive type of non-small cell lung cancer.
In some situations, this histology can also be found around the bronchial stump margin after resection of bronchial cancer, when there is presence of CIS on histology in a bronch...
Squamous cell carcinoma (SCC) is one of the non-small cell carcinomas of the lung, overtaken by adenocarcinoma of the lung as the most commonly encountered lung cancer.
Squamous cell carcinoma accounts for ~30-35% of all lung cancers and in most instances are due to heavy smoking...
Squamous dysplasia (SD) of lung is a type of preinvasive lung lesion and is considered a precursor to bronchogenic squamous cell carcinoma. It is sometimes considered a low end of the spectrum of carcinoma in situ (CIS) of lung 2.
The stag's antler sign refers to upper lobe pulmonary venous diversion (cephalisation) in pulmonary venous hypertension or pulmonary oedema as seen on frontal chest radiograph.
The prominence of upper lobe pulmonary veins resemble a stag's antlers. It is the earliest sign of pulmonary venous hy...
The standard uptake value (SUV) is a simple way of determining activity in PET imaging, most commonly used in fluorodeoxyglucose (FDG) imaging. It is also known as the dose uptake ratio (DUR). As the name suggests it is a mathematically derived ratio of tissue radioactivity concentration at a po...
Along with the DeBakey classification, the Stanford classification is used to separate aortic dissections into those that need surgical repair, and those that usually require only medical management. The Stanford classification divides dissections by the most proximal involvement:
type A: A aff...
The sternal body or gladiolus is the middle and largest of the three parts of the sternum. It is formed by the fusion of four sternebrae which finish ossifying after puberty.
The sternal body is the longest of the three parts of the sternum and is widest near its lower end. It i...
Sternal foramen (or perforated sternum) is a developmental variant of the sternum and results from incomplete fusion of the sternal ossification centres. They are common occurring in approximately 5% of the population (range 4.3-6.7%). They are most commonly found in the inferior aspect of the s...
Sternal fractures occur in ~5% of blunt chest trauma with the manubrium being the most commonly injured part.
Acute, severe sternal pain that is worse with respiration with localised tenderness.
Mechanism of injury
Fractures of the sternum can result from bot...
The sternalis muscle is an uncommon anatomic variant of the chest wall musculature and is of uncertain aetiology and function. Its importance lies in that it should not be mistaken for a pathological lesion.
Cadaveric studies have shown that the muscle is present in ~5% (range 1-...
The sternum completes the anterior chest wall as the ventral breastplate.
The sternum is composed of a manubrium, a body and the inferior xiphisternum or xiphoid process. These articulations are via hyaline cartilage with a fibrocartilaginous intervening disc:
the manubrium is ...
The lateral sternum view a radiographic investigation of the entire length of the sternum in profile. The view is used to query fractures or infection 1.
patient is erect with the left or right side of the thorax adjacent to the image receptor
patient's hands are behind their...
Straight back syndrome refers to loss of the normal thoracic kyphosis. Individuals with this condition can present with a cardiac murmur due to compression of the right ventricular outflow tract (RVOT) 2.
There is questionable association with mitral valve prolapse 1.
Subacute hypersensitivity pneumonitis develops when hypersensitivity pneumonitis continues beyond the acute phase (i.e. continues for weeks to months). While some publications suggest the disease to needs to prevail for between 1-4 months to fall into this category 6, it is important to realise ...
Subacute invasive pulmonary aspergillosis (previously known as chronic necrotising aspergillosis (CNA) or semi-invasive aspergillosis is a subacute to chronic localised and indolent form of invasive aspergillosis. It is also sometimes grouped under the term chronic pulmonary aspergillosis.
Subcarinal air cysts refer to small air cyst that can be detected on a CT scan. They are thought to represent small main bronchial diverticula although the former term is preferred 2. They may be associated with chronic airflow limitation.
Patients are asymptomatic and the...
The subclavian arteries are asymmetric paired arteries that supply blood to the posterior cerebral circulation, cerebellum, posterior neck, upper limbs and the superior and anterior chest wall.
Right and left subclavian arteries classically have different origins:
The subclavian vein (SCV) is the major venous channel that drains the upper limb.
Origin and course
The subclavian vein starts at the crossing of the lateral border of the 1st rib. It then arches cephalad, posterior to the medial clavicle before curving caudally and receiving it...
The subcostal muscle has variable anatomy and forms part of the intercostal muscle group. It lies on the deep surface of the innermost intercostal muscle in the posterior chest, near the angles of the ribs, usually running over 2-3 intercostal spaces. It is most common in the upper (1-4) and low...
The subcostal nerve can also be considered as the twelfth intercostal nerve. Some authors describe it as the first branch of the lumbar plexus.
The anterior division of the twelfth thoracic nerve, called the subcostal nerve, is larger than the other intercostal nerves. It runs al...
Subcutaneous or surgical emphysema, strictly speaking, refers to air in the subcutaneous tissues. But the term is generally used to describe any soft tissue emphysema of the body wall or limbs since the air often dissects into the deeper soft tissues and musculature along fascial planes.
Subpleural line refers to a thin curvilinear opacity, 1-3 mm in thickness, lying less than 1 cm from and parallel to the pleural surface. It corresponds to:
atelectasis of normal lung if seen in the dependent posteroinferior portion of lung of a patient in the supine position (disappears if pro...
Subpleural pulmonary bullae are a location specific descriptive term to describe pulmonary bullae occuring in subpleural locations. Many are considered to represent regions of paraseptal emphysema where the emphysematous spaces are greater than 1cm in diameter 1. They may or may not contain sept...
Subpleural sparing in thoracic radiology is a imaging descriptor usually used on cross sectional imaging (mainly CT) where the pathology that affects the lungs spares the extreme peripheral lung margin abutting the pleura - chest wall.
It can be seen in a number of situations
non specific inte...
Subpulmonic effusions are a pleural effusion that can be seen only on an erect projection. Rather than layering laterally and blunting the costophrenic angle, the pleural fluid lies almost exclusively between the lung base and the diaphragm.
The fluid ca...
A superficial endobronchial lung cancer may be defined as a bronchogenic tumour of any size with its invasive component limited to the bronchial wall. It may extend into the proximal bronchus and is often classified as T1 at TNM staging. It is one of the causes of more focal bronchial wall thick...
The superior accessory fissure is present in around 5% of individuals examined with CT 4.
The superior accessory fissure of the right lower lobe is located in the same plane and posterior to the right minor fissure. It separates the right lower lobe into superior and basal segme...
Superior mediastinum is an artificially divided wedge-shaped compartment of the mediastinum located between the thoracic plane inferiorly and the thoracic inlet superiorly. The inferior mediastinum, comprising of the anterior, middle and posterior parts, lies inferiorly.
The superior pulmonary sulcus (or just the superior sulcus) refers to an apical pleuro-pulmonary groove formed by the subclavian artery as it curves in front of the pleura runs upward and lateral immediately below the apex. It is a typical location for Pancoast tumours (also known as superior su...
The superior thoracic aperture, also known as the thoracic inlet or outlet, connects the root of the neck with the thorax.
The superior thoracic aperture is kidney-shaped and lies in an oblique transverse plane, tilted anteroinferiorly to posterosuperiorly.
The superior vena cava (SVC) is a large valveless venous channel formed by the union of the brachiocephalic veins. It receives blood from the upper half of the body (except the heart) and returns it to the right atrium.
The SVC begins behind the lower border of the first right co...
Superior vena caval duplication is the most common form of a left sided SVC, where the normal right sided SVC remains. The right SVC however can be smaller in ~2/3rds of such cases 3.
Results from failure of the embryonic left anterior cardiac vein to regress. Drainage is variable an...
Superior vena cava (SVC) obstruction can occur from extrinsic compression, intrinsic stenosis or thrombosis. Malignancies are the main cause and are considered an oncologic emergency. Superior vena cava syndrome (SVCS) refers to the clinical syndrome with symptoms that results from this obstruct...
The suprapleural membrane, also known as Sibson fascia, is a dense fascial layer that is attached to the inner border of the first rib and costal cartilage anteriorly, C7 transverse process posteriorly and to the mediastinal pleura medially.
It is flat and lies in the oblique plane of the thora...
The suprascapular artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It traverses inferiorly and laterally in the lower anterior neck superficial to the anterior scalene muscle and phrenic nerve before crossing the third part of the subclavia...
The supreme intercostal arteries, or superior intercostal arteries, are formed as a direct result of the embryological development of the intersegmental arteries. These arteries are paired structures of the upper thorax which normally form to provide blood flow to the first and second intercosta...
Surgical emphysema (or subcutaneous emphysema) occurs when air/gas is located in the subcutaneous tissues (the layer under the skin). This usually occurs in the chest, face or neck.
This is a summary article; read more in our article on surgical emphysema.
The Swiss cheese sign has been used for the appearance on CT of fluid-containing pneumatocoeles, that typically occur following pulmonary lacerations 1.
The pneumatocoeles appear as 'holes' in the lung parenchyma and hence the description with respect to Swiss-style cheeses (e.g. Emmental), whi...
Swyer-James syndrome (SJS), also known as Swyer-James-MacLeod syndrome and Bret syndrome, is a rare lung condition that manifests as unilateral hemithorax lucency as a result of postinfectious obliterative bronchiolitis.
The condition typically follows a viral respiratory infecti...
Pneumothoraces (singular: pneumothorax) are collections of gas within the pleural space. If the pneumothorax is under pressure, it is called a tension pneumothorax.
This is a summary article; read more in our article on pneumothorax.
Synchronous primary lung carcinoma (SPLC) is a term given to the occurrence of two or more primary lung carcinomas within different portions of the lung in the same time period.
They are thought to the carry the same pathophysiological mechanism as metachronous lung carcinoma (i.e. two or more ...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. It is also sometimes classified as a vasculitis.
There is an overall increased female predilection. In adults, women are affected 9-13 times more than males. In children, this ratio i...
Thoracic manifestations of systemic lupus erythematosus can be variable.
For a general discussion, and for links to other system specific manifestations, please refer to the article on systemic lupus erythematosus.
pleuritis: considered one of the c...
Takayasu arteritis (TA), also known as idiopathic medial aortopathy or pulseless disease, is a granulomatous large vessel vasculitis that predominantly affects the aorta and its major branches. It may also affect the pulmonary arteries. The exact cause is not well known but the pathology is thou...
The Takeuchi procedure refers to a direct anastomosis of the anomalous left coronary artery from the pulmonary artery directly to the aorta was described in the 1970s and currently remains the procedure of choice.
An intrapulmonary aortocoronary tunnel or baffle was performed by Takeuchi prior ...
Talc induced lung disease comprises of a group of pathologies that can occur related to talc (Magnesium silicate)
Four types of pulmonary disease secondary to talc exposure have been defined these include:
talco-silicosis - associated with occupational exposure
talco-asbestosis - associated w...
Talcosis is a type of pneumoconiosis and can be prevalent in intravenous drug users. It is one of the four recognised types talc induced lung disease.
Talc (magnesium silicate) is used in the preparation of tablets intended for oral use, where it acts as a 'filler' and lubricant. Whe...
Talc (magnesium trisilicate) pulmonary embolism is a rare cause of non thrombotic pulmonary embolism. It tends to be more prevalent in patients with narcotic abuse.
Most patients are asymptomatic although dyspnea and persistent cough occur with severe talc exposure. Clini...
Tc-99m DTPA (diethylenetriamine-pentaacetic acid) (aerosol) is one of the technetium agents and is used in VQ imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 1 hour
normal distribution: lungs
aerosol deposited in bronhoal...
Tc-99m MAA (microaggregated albumin) is one of the technetium radiopharmaceuticals used in lung perfusion imaging.
photon energy: 140 KeV
physical half life: 6 hours
biological half life: 2-3 hours
normal distribution: lungs, liver, spleen, kidneys
Tension gastrothorax describes a rare life-threatening condition caused by mediastinal shift due to a distended stomach herniating into the thorax through a diaphragmatic defect.
Presentation is generally with acute and severe respiratory failure, with clinical features ...
Tension pneumothoraces occur when intrapleural air accumulates progressively in such a way as to exert positive pressure on mediastinal and intrathoracic structures. It is a life-threatening occurrence requiring rapid recognition and treatment is required if a cardiorespiratory arrest is to be a...
This is a basic article for medical students and other non-radiologists
Tension pneumothoraces are pneumothoraces under pressure. If the pressure gets high enough, the pneumothorax can compress the heart and great vessels, and even cause cardiac arrest.
Presentation is u...
The terminal bronchioles are a continuation of the bronchi and are the last divisions of the conducting airways.
Terminal bronchioles, are confusingly named, as they not the final branches but rather the distal bronchioles that do not bear alveoli. The first 19 divisions from ...
Thalassaemia is an autosomal recessive haemoglobinopathy that originated in the Mediterranean region. The genetic defect causes a reduction in the rate of globin chain synthesis which causes the formation of abnormal haemoglobin molecules. The resultant microcytic anaemia is the characteristic p...
The Macklin effect describes one of the pathophysiological processes of pneumomediastinum in blunt chest trauma. The Macklin effect accounts for ~40% of severe blunt traumatic pneumomediastinum. Exclusion of tracheobronchial and oesophageal causes of pneumomediastinum is mandatory to exclude con...
Thickening of bronchovascular bundles is a chest CT imaging feature that can be observed in a number of entities.
Conditions that can result in bronchovascular bundle thickening include:
sarcoidosis - see pulmonary manifestations of sarcoidosis 1
classical condition to giv...
The third mogul sign can be seen on frontal chest radiograph in the presence of left atrial enlargement. It refers to an extra mogul or bump along the upper left cardiac silhouette just below the left main bronchus.
The third mogul sign commonly represents the enlarged left atrial appendage, pa...
Thoracentesis, commonly known as a pleural or chest tap, is a procedure where excess pleural fluid is drained from the pleural space for diagnostic and/or therapeutic reasons. Ultrasound-guided thoracentesis performed by radiologists has been shown to have fewer complications than blind thoracen...
Thoracic actinomycosis refers to an uncommon indolent infection caused principally by the genus Actinomyces (higher prokaryotic bacteria belonging to the family Actinomyceataceae).
While it is rare in general, the thoracic form actinomycosis may constitutes ∼15% of the total burde...
Thoracic air leak syndrome (TALS) is an uncommon late complication in haematopoetic stem cell transplant recipients with chronic graft verses host disease. These patient led to develop features of thoracic air-leakage (i.e. spontaneous pneumomediastinum, spontaneous pneumothorax, pneumopericardi...
Thoracic aortic aneurysms are relatively uncommon compared to abdominal aortic aneurysms. There is a wide range of causes, and the ascending aorta is most commonly affected. CTA and MRA are the modalities of choice to image this condition.
The term aneurysm is used when the axial d...
There are a number of causes and mimics of thoracic aortic dilatation.
post-stenotic dilatation, e.g. bicuspid aortic valve
thoracic aortic aneurysm
atherosclerosis (usually descending thoracic aorta)
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)
The differential for thoracic aortic stenosis includes:
aortitis (especially Takayasu arteritis)
Williams syndrome: supravalvular aortic stenosis
congenital rubella syndrome: supravalvular aortic stenosis
The thoracic cage refers to the skeleton of the thorax:
thoracic vertebral column
12 pairs of ribs
The thoracic duct is the main lymphatic channel for the return of chyle to the venous system. It drains lymph from both lower limbs, abdomen (except the convex area of the liver), left hemithorax, left upper limb and left face and neck.
The thoracic duct is the superior continua...
Pleural-thoracic empyema (commonly referred simply as an empyema) or pyothorax refers to an infected purulent and often loculated pleural effusion, and is a cause of a large unilateral pleural collection. It is a potentially life-threatening condition requiring prompt diagnosis and treatment.
Thoracic endometriosis is an uncommon location for endometriosis and the main cause of catamenial pneumothorax.
Most often occurs in the third and fourth decades of life 3.
Symptoms may include:
catamenial pleuritic chest pain
catamenial haemoptysis: whe...
Thoracic (or pulmonary) histoplasmosis refers to pulmonary manifestations from infection with the organism Histoplasma capsulatum which is an organism endemic to El Salvador but can be found widely in other parts of North, Central and South America. It can have variable clinical and radiographic...
High resolution CT (HRCT) of the lungs has specific terminology relating to pulmonary anatomy with which one needs to be comfortable.
secondary pulmonary lobule
interlobular septal thickening
Thoracic lymph nodes are divided into 14 stations as proposed by the International Association for the Study of Lung Cancer (IASLC) 1, principally in the context of oncologic staging.
highest mediastinal nodes: low cervical, supraclavicular, and sternal notch nodes
Thoracic myelolipomas are extremely rare entities; only ~3% of myelolipomas are thought to occur in the thorax. When do occur in the thorax they can manifest as
mediastinal myelolipoma: most occur in the posterior mediastinum
intrapulmonary myelolipoma (much less common)
As with my...
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 thoracic plane, also known as the transthoracic plane or the plane of Ludwig is an artificial horizontal plane used to divide the mediastinum into the superior mediastinum and the inferior mediastinum.
It is defined as a horizontal line that runs from the manubriosternal joint (sternal angl...
A handy mnemonic to remember the structures found at the level of the thoracic plane (also known as the plane of Ludwig) is:
C: cardiac plexus
L: ligamentum arteriosum
A: aortic arch (inner concavity)
P: pulmonary trunk
T: tracheal bifurcation (carin...
The thoracic spine sign on lung ultrasound is an indirect indicator of the presence of a pleural effusion or haemothorax. It represents the visualisation of the vertebral bodies in the thoracic cavity above the diaphragm which are usually not seen unless there is a fluid collection.
Thoracic splenosis refers to autotransplantation of splenic tissue into the pleural space which typically occurs after trauma. It may occur in approximately 18% of patients with combined diaphragmatic and splenic injuries and is more common after penetrating injuries.
Splenic tissue ...
Thoracoabdominal sign, a variation of the silhouette sign, is a frontal chest radiograph sign which helps to localize a thoracic lesion.
Since the posterior costophrenic sulcus is more caudal than the anterior lung, a thoracic lesion must be posterior if its caudal end is visible below the dome...
Thoracoliths are rare, calcified pleural-based nodules that are almost always incidental findings. They are usually considered mobile, and more common on the left.
The exact aetiology is unknown and theories include 1,2:
calcified fibrin body
degenerated pleural lipoma
Thoracoplasty is a surgical procedure that was originally designed to permanently collapse the cavities of pulmonary tuberculosis by removing the ribs from the chest wall 1-3 . The resection of multiple ribs, allows the apposition of parietal to the visceral or mediastinal pleura. Until supplant...
Thymic carcinoid tumour refers to a carcinoid tumour arising in the thymus. It is the most common histologic type for a neuroendocrine tumour of the thymus.
Affected patients are typically in the fourth or fifth decades of life. There is a recognised male predominance with M:F ra...
Thymic carcinoma is part of the malignant end of thymic epithelial tumours.
Patients are typically 50 to 70 years of age at presentation 9.
The incidence of paraneoplastic syndromes is thought to be low. At least 10 different histologic variants have been described 4. ...
Thymic cysts are cysts that occur within, or arise from, the thymus.
Thymic cysts are uncommon lesions and are estimated to account for approximately 1-3% of all anterior mediastinal masses 4. Approximately 50% of congenital thymic cysts are incidentally discovered during the firs...
Thymic epithelial tumours are rare tumours arising from thymus in anterior mediastinum of middle age patients. However, they are still the most common primary neoplasm of the thymus and of the anterosuperior mediastinum. This article discusses thymomas, invasive thymomas and thymic carcinoma.
Thymic hyperplasia is a disorder whereby there is hyperplasia of the thymus gland.
Thymus hyperplasia can be subdivided into two forms:
true thymic hyperplasia
Both true thymic hyperplasia and lymphoid hyperplasia manifest as diffuse symmetric enlargement of...