This is a basic article for medical students and other non-radiologists
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 art...
The Swiss cheese sign has been used for the appearance on CT of fluid-containing pneumatoceles, that typically occur following pulmonary lacerations 1. They have also been described on CT appearances where there is pulmonary infection superimposed on emphysema 2.
The pneumatocoeles appear as 'h...
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...
This is a basic article for medical students and other non-radiologists
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 i...
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 ...
The syndrome of inappropriate antidiuretic hormone secretion (SIADH or SIAD) (also known as Schwartz-Bartter syndrome) was initially described in patients with lung cancer who developed hyponatremia associated with continued urinary sodium loss. The result is often dilutional hyponatremia in whi...
One approach to a systematic chest radiograph assessment is as follows:
assessment of the technical adequacy
tubes and lines
airways, lungs and pleura
bones and soft tissue
Following a systematic approach on every chest radiograph ...
Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multisystem involvement. Although abnormalities in almost every aspect of the immune system have been found, the key defect is thought to result from a loss of self-tolerance to autoantigens.
There is a strong...
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 exposure to the mineral talc (hydrated magnesium silicate).
Four types of pulmonary disease secondary to talc exposure have been defined, these are:
talcosilicosis - associated with occupational exposure
Talcosis is a type of pneumoconiosis and can be prevalent in intravenous drug users. It is one of the four recognized types of 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. ...
Talc pleurodesis is one of the chemical methods of pleurodesis which is a procedure performed to prevent recurrence of a pneumothorax or recurrent pleural effusion in benign or malignant conditions. It involves achieving an area of adhesion between the parietal and visceral layers of the pleura....
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 (macroaggregated 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
Technetium agents based on the technetium-99m (Tc-99m) radioisotope are frequently used agents in medical imaging. A radiopharmaceutical labeled with 99mTc constitutes a coordination complex in which ligands bond to a central atom of 99mTc by coordinate covalent bonds 4 .
The radioactive techne...
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 ...
A tension hemothorax refers to hemothorax that exert considerable mass effect. It often results from massive intrathoracic hemorrhage and often causing ipsilateral lung compression and mediastinal displacement.
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 both rapid recognition and prompt treatment to avoid a cardiorespiratory arrest.
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 are not the final branches but rather the distal bronchioles that do not bear alveoli. The first 19 divisions fr...
Thalassemia is an autosomal recessive hemoglobinopathy 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 hemoglobin molecules. The resultant microcytic anemia is the characteristic prese...
Thalidomide-induced pneumonitis is a rare from of drug-induced lung disease. It could be suspected in patients who develop dyspnea, cough, and fever after taking thalidomide, without a definite cause, with chest radiographs +/- CT shows supportive findings. Many publications suggest this is reve...
Thickening of bronchovascular bundles is a chest CT imaging feature that can be observed in a number of entities. It has some overlap with the terms peribronchovascular interstitial thickening and peribronchovascular thickening.
Conditions that can result in bronchovascular b...
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 tap 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 thor...
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 constitutes ∼15% of the total burden of...
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 amyloidosis can have different manifestations depending on the specific anatomic site:
nodular parenchymal amyloidosis
diffuse parenchymal amyloidosis
Thoracic anatomy encompasses the anatomy of all structures of the thorax.
This anatomy section promotes the use of the Terminologia Anatomica, the international standard of anatomical nomenclature.
Thoracic aortic aneurysms are relatively uncommon compared to abdominal aortic aneurysms. There is a wide range of causes, and the ascending aorta is the segment most commonly affected. Both CTA and MRA are the modalities of choice to image this condition.
The normal aortic diamete...
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.
Approximately 80% of patients with thoracic aortic injury die at the scene of the trauma. In those who make it to hospital, clinical...
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 vessel for the return of chyle/lymph to the systemic 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 supe...
Thoracic duct embolization (TDE) is a safe, efficacious treatment for chylothorax 1. Chylothoraces with a low drain output (<1L/day) are traditionally managed conservatively with dietary change, while high output (>1L/d) are managed with surgical thoracic duct (TD) ligation 2.Thoracic duct embo...
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 hemoptysis: when...
Thoracic (or pulmonary) histoplasmosis refers to pulmonary manifestations from infection with the organism Histoplasma capsulatum which is an organism endemic to the Central American state of El Salvador but can be found widely in other parts of both North and South America. It can have variable...
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 defined by the International Association for the Study of Lung Cancer (IASLC) 1, principally in the context of oncologic staging. For the purpose of prognostication, the stations may be grouped into 7 zones. The IASLC definitions leave some a...
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)
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...
Thoracic pleomorphic adenoma can include
pleomorphic adenoma which has metastased to the lungs
primary pulmonary pleomorphic adenoma - extremely rare 1
primary pleomorphic adenoma of bronchial/tracheal origin - extremely rare 4,5
Thoracic sarcoidosis can be staged on a chest radiograph with implications for prognosis although HRCT and FDG-PET provide more information to help guide treatment.
Chest radiographs have been the mainstay of staging thoracic sarcoidosis for many decades with fair interobserver concord...
The thoracic spine sign, or spine sign, on lung ultrasound is an indirect indicator of the presence of a pleural effusion or hemothorax. It represents the visualization of the vertebral bodies in the thoracic cavity above the diaphragm which are usually not seen unless there is a fluid collectio...
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...
The thoracoepigastric vein provides a communication between the superficial epigastric vein and the lateral thoracic vein as it ascends superficially on the anterolateral chest and abdominal wall. It, therefore, drains into both the superior vena cava via the axillary vein and the inferior vena ...
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 etiology 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 . It involved resection of multiple ribs, allowed the apposition of parietal to the visceral or mediastinal pleura. Until...
Thymic carcinoid tumor refers to a carcinoid tumor arising in the thymus. It is the most common histologic type for a neuroendocrine tumor of the thymus.
Affected patients are typically in the fourth or fifth decades of life. There is a recognized male predominance with M:F ratios...
Thymic carcinoma is part of the malignant end of thymic epithelial tumors.
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. T...
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. They are however reported to be the second most common type of primary mediastinal cyst 7....
Thymic epithelial tumors are rare tumors arising from thymus in anterior mediastinum of middle age patients. However, they are still the most common primary neoplasm of the thymus and 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
lymphoid thymic hyperplasia
Both true thymic hyperplasia and lymphoid hyperplasia manifest as diffuse symmetric enlarge...
The thymic notch sign represents the normal thymus in a newborn on a frontal chest radiograph. Interruption of the cardiac silhouette forms a notch, which may be seen on either side, but more frequently is seen on the left side.
thymic sail sign
thymic wave sign
The thymic sail sign represents a triangular-shaped inferior margin of the normal thymus seen on a neonatal frontal chest radiograph. It is more commonly seen on the right side, but can also be bilateral. It is seen in 3-15% of all cases. This sign should not be confused with the spinnaker sail ...
Thymic wave sign refers to the indentation of the normal thymus in young children by the ribs, resulting in a wavy border on chest radiograph.
There are at least 3 described signs relating to a normal thymus in infants; thymic sail sign, thymic notch sign and thymic wave sign. Being able to id...
Thymolipoma is a rare, benign anterior mediastinal mass of thymic origin, containing both thymic and mature adipose tissue.
Thymolipomas comprise ~5% (range 2-9%) of all thymic neoplasms, but are less common than a mediastinal lipoma of non-thymic origin. There is no recognized s...
The thymus (plural: thymi) is a T-cell producing lymphoid organ in the anterior mediastinum that plays a role in the development of the immune system, particular the maturation of T-cells. It typically has a retrosternal location and hence can mimic retrosternal pathology.
It is ...
Thyroid transcription factor 1 (TTF1) refers to a homeodomain-containing nuclear transcription factor which belongs to the Nkx2 gene family encoded by a gene located on chromosome 14q13.
It is expressed in the forebrain, thyroid and lung tissues. The presence of TTF-1 protein on a tissue sample...
Thyroid transcription factor 1 deficiency is a situation characterized by mutations in the gene encoding thyroid transcription factor, NKX2-1.
It can result in neurological, thyroid, and pulmonary dysfunction (including neonatal respiratory distress). Children can have a range of mil...
Tietze syndrome is a benign condition characterized by a self-limiting inflammation of the costal cartilages often with hypertrophy. Although often described as such, it is not a costochondritis 9.
The exact incidence of occurrence is not known. It is seen most commonly in the 2nd...
Tissue tropism is a phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens. This concept is central to the radiological evaluation of infectious disease.
As infections that display tissue tropism will thrive in certain tissue locati...
Total repair of tetralogy of Fallot is a corrective surgical procedure that involves closure of the ventricular septal defect (VSD) and relief of right ventricular outflow tract (RVOT) obstruction.
Most patients with tetralogy of Fallot (TOF) undergo elective surgical repair between ...
The trachea, known colloquially as the windpipe, connects the upper respiratory tract to the lungs via the tracheobronchial tree, enabling gas exchange.
The trachea is a tube-shaped structure consisting of 15-to-20 D-shaped cartilage rings anterolaterally bridged by annular ligam...
Primary tracheal and endobronchial lesions are generally rare and can be either malignant or benign. The majority of these lesions are malignant.
primary malignant endobronchial lesions
squamous cell carcinoma: commonest malignant lesion in th...
Tracheal atresia (TA) is an extremely rare anomaly and refers to a congenital absence of the trachea.
There may be a greater male predilection 5.
Tracheal atresia falls under the spectrum of laryngeal-tracheo-bronchial atresia which in turn results either from an obstr...
The tracheal bifurcation angle can have a wide range of normal values in patients and can vary significantly in serial radiographs. It is of poor diagnostic value due to the lack of sensitivity and specificity in identifying the underlying pathology.
The interbronchial angle is th...
A tracheal bronchus (with some variations also known as a pig bronchus) is an anatomical variant where an accessory bronchus originates directly from the supracarinal trachea. The latter term (pig bronchus or bronchus suis) is often given when the entire upper lobe (usually right side) is suppli...
Tracheal buckling is a normal finding in young infants when it is more flexible. There is typically deviation of the trachea anteriorly and to the right (up to 90°) and any other configuration (i.e. to the left or posteriorly) should raise the possibility of underlying pathology.
Tracheal calcification, or tracheobronchial calcification, is a benign radiological finding of the middle aged and elderly and is usually of no clinical significance.
Patients are generally asymptomatic.
Long-term warfarin therapy may be associated with trache...
Tracheal diverticula, also known as tracheoceles, are usually an incidental finding. Occasionally it may mimic pneumomediastinum, so-called pseudopneumomediastinum.
There is an overlap in the use and description of the terms paratracheal air cyst and a tracheal diverticulum in the ...
Tracheal leiomyoma is a form of a benign tracheal tumor.
They are thought to account for around 1% of all tracheal tumors.
Presentation depends on tumor location and size with some reports suggesting patients becoming symptomatic when tumor obstructs more ...
The differential for tracheal masses can be rather wide.
For a single mass consider:
direct invasion from adjacent organ (lung, thyroid, esophagus and larynx)
distant metastasis (e.g. melanoma, breast, renal, and colon cancer)
squamous cell carcinoma: commone...
Tracheal stenosis is usually acquired following intubation or tracheostomy. It can also arise as part of the spectrum of tracheobronchial stenosis.
Inflammation and pressure necrosis of the tracheal mucosa most commonly occur at either the tracheostomy stoma or at the level of the tube balloon....
Tracheal wall thickening may have several causes. For diagnostic purposes, tracheal thickening may be categorized by length of airway involvement in order to narrow the differential diagnoses. Note that some etiologies may be associated with either focal or diffuse pattern of involvement.
Tracheal webs occur as a thin layer of tissue that narrows the tracheal lumen. They do not completely obstruct the trachea.
The incidence of congenital tracheal is 1:10,000 births.
Some patients will be asymptomatic. Symptomatic patients can present with a ...
Tracheobronchial amyloidosis refers to tracheal and/or bronchial involvement in amyloidosis. It is sometimes classified as a subtype of pulmonary amyloidosis.
It is a rare manifestation with some reports suggesting less than 100 published cases around the time of writing 5.
Tracheobronchial branching anomalies can be seen as an isolated finding or accompanying heterotaxy syndromes, pulmonary sling, and conditions associated with pulmonary underdevelopment (agenesis and aplasia), including the scimitar syndrome.
Abnormal branching patterns include:
right sided iso...
Tracheobronchial injury is a serious but uncommon manifestation of chest trauma. It is usually a fatal injury with only a small percentage of patients making it to hospital. Given the magnitude of force required to injure the major airways, there are often multiple chest injuries and other body ...
A tracheobronchial 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 esophageal cancers. It may also be used in the treatme...
The tracheobronchial tree is the branching tree of airways beginning at the larynx and extending inferiorly and peripherally into the lungs as bronchioles. The luminal diameter decreases as the branching increases more peripherally into the lungs. The walls of the airway down to the level of the...
Tracheobronchopathia osteochondroplastica (TO) is a very rare idiopathic non-neoplastic tracheobronchial abnormality.
The estimated prevalence on routine bronchoscopy can be up to 0.7%. It typically affects those in the 5th to 6th decades and there may be a male predilection 4.
Tracheomalacia, or sometimes described as tracheobronchomalacia, is a common incidental finding on imaging of the chest of older patients and manifests as an increase in tracheal diameter as well as a tendency to collapse on expiration.
Tracheomalacia can be broadly considered as being congenit...
A dilated trachea has numerous causes, and in almost all cases represents tracheomalacia (increased size and increased compliance).
As is almost always the case, various diameters have been used. Typical figures include >26 mm in men, >23 mm in women or >3 cm for both genders.
Although many of...
Tracheo-esophageal fistula is a pathological communication between the trachea and esophagus.
It can be broadly classified into two types:
congenital tracheo-esophageal fistula
acquired tracheo-esophageal fistula: from malignancy/tuberculosis