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 tu...
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 ...
Tracheobronchial stenosis is a descriptive term given a spectrum of disorders which can result is focal or diffuse narrowings of the trachea and bronchi. The term can encompass.
MinIP images are often helpful for better appreci...
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
Traction bronchiectasis refers to an etiological subtype of bronchiectasis where there is irreversible dilatation of bronchi and bronchioles within areas of pulmonary fibrosis or distorted lung parenchymal architecture.
It can arise from a number of underlying causes which result in ...
Tram-track sign may be used in chest radiography or CT to denote the thickened non-tapering (parallel) walls of cylindrical bronchiectasis.
It should not be confused with other tram-track signs elsewhere in the body.
Transfusion-related acute lung injury (TRALI) is defined as non-cardiogenic pulmonary edema temporally-related to transfusion therapy.
It tends to occur within 6 hours after a blood transfusion and requires exclusion of other alternative diagnoses such as sepsis or volume overload.
Transient tachypnea of the newborn, also known as retained fetal fluid or wet lung disease, presents in the neonate as tachypnea for the first few hours of life, lasting up to one day. The tachypnea usually resolves within 48 hours.
Transient tachypnea is one of the commonest cau...
A transudate is a collection of fluid that has a relatively low specific gravity and protein concentration. They occur secondary to increased hydrostatic pressure or reduced colloid oncotic pressure:
left ventricular failure (increased hydrostatic pressure)
hypoalbuminemia (decreased colloid o...
The transverse cervical artery, also known as the cervicodorsal trunk, is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery).
It is a short artery that bifurcates into the superficial and deep branches, both which course superficially and laterally acro...
The transversus thoracis muscle is the innermost muscle of the anterior thoracic wall (deep to external intercostal and internal intercostal muscles).
The transversus thoracis is a thin band of muscle and tendon arising from the lower posterior surface of the sternum, posterior...
Trapped lung, also known as unexpandable/unexpanded lung, is a term used where there is non-expandable lung after fluid removal, often thoracentesis. It is similar to but not entirely synonymous with the term lung entrapment, which is a similar condition caused by active pleural disease rather t...
Trauma CT thorax review areas are useful to reduce the potential for error, which is higher than usual given the larger number of images requiring review, and the often present time pressures and the potential presence of numerous concurrent injuries (see CT polytrauma).
Using some standard re...
Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern. Although initially described in patients with endobronchial tuberculosis, it is now recognized in a large number of conditions.
The triangle of safety is an anatomical region in the axilla that forms a guide as to the safe position for intercostal catheter (ICC) placement. With the arm abducted, the apex is the axilla, and the triangle is formed by the:
lateral border of the pectoralis major anteriorly
lateral border o...
Trichoptysis (rare plural: trichoptyses) is an extremely rare symptom, whereby patients cough up hair. It is highly specific for rupture of a mediastinal teratoma into the tracheobronchial tree, however it is not pathognomonic as several articles claim (see below) 1,2. Nevertheless it remains a ...
Triple-rule-out CT (TRO CT) angiography may be ordered in the setting of acute chest pain to examine the thoracic aorta and the coronary and pulmonary arteries. The protocol helps exclude life-threatening causes of acute chest pain, especially if atypical, or if alternative causes to acute coron...
True thymic hyperplasia is a form of thymic hyperplasia where there is enlargement of the thymus but with its normal structure being retained.
The underlying pathogenesis of true thymic hyperplasia is largely unknown.
There is an increase of both size and weight of the gland but w...
Tuberculomas or tuberculous granulomas are well defined focal masses that result from Mycobacterium tuberculosis infection and are one of the more severe morphological forms of tuberculosis. Tuberculomas most commonly occur in the brain (see: CNS tuberculosis) and the lung (see: pulmonary tuberc...
Tuberculosis (commonly abbreviated to TB, short for tubercle bacillus) encompasses an enormously wide disease spectrum affecting multiple organs and body systems predominantly caused by the organism Mycobacterium tuberculosis. A small proportion can also be caused by Mycobacterium bovis.
Pulmonary manifestations of tuberculosis are varied and depend in part whether the infection is primary or post-primary. The lungs are the most common site of primary infection by tuberculosis and are a major source of spread of the disease and of individual morbidity and mortality.
A general d...
This is a basic article for medical students and other non-radiologists
Tuberculosis (TB) is a non-bacterial multisystem infection that often affects the lungs. It may be a primary tuberculous infection, secondary infection or appear as chronic scarring. TB may also be seen on a chest x-ray as ...
Tuberculous empyema is a chronic, active infection of the pleural space characterized by a thick rind of pleura with dense and irregular calcification of both the parietal and visceral pleura usually surrounding a loculated pleural fluid which contains a large number of tubercle bacilli 1. This ...
Tuberculous pleuritis refers from inflammation of pleura due to infection by Mycobacterium tuberculosis. It is considered second most common form of extra-pulmonary tuberculosis 1. It may progress into a tuberculous empyema.
It may be commoner in young males 2.
Tuberous sclerosis, also known as tuberous sclerosis complex or Bourneville disease, is a neurocutaneous disorder (phakomatosis) characterized by the development of multiple benign tumors of the embryonic ectoderm (e.g. skin, eyes, and nervous system).
Tuberous sclerosis has an in...
Tulip bulb sign refers to the characteristic appearance of annuloaortic ectasia as seen on CT angiography.
There is symmetric dilatation of the three sinuses of Valsalva, with extension into the ascending aorta and effacement of the sinotubular junction.
It is seen especially in Marfan syndro...
There are many tumor-like conditions of the pleura. These are non-malignant entities that on imaging may mimic a pleural tumor.
Tumors of the chest wall are varied, some of which are found most often in this region. They can be divided into benign and malignant tumors and into those which arise in the ribcage and those of soft tissue density.
Benign tumors include 1,3,4:
Tumor spread through air spaces (STAS) is a relatively recently recognized pattern of invasion in lung adenocarcinoma. According to the 2015 WHO classification, STAS is defined as “micropapillary clusters, solid nests, or single cells spreading within air spaces beyond the edge of the main tumor...
A tumor-to-tumor metastasis, also known as a collision tumor, is a rare metastatic process in which a primary malignant tumor ('donor') metastasizes to another tumor ('recipient'), most commonly a benign tumor such as a meningioma.
Tumor-to-tumor metastasis is considered very rare...
The twelfth rib is an atypical rib. It is the shortest rib, and one of two floating ribs.
The 12th rib has a single facet on its head for articulation with the T12 vertebra. It has a short neck and no tubercle. It also lacks a costal groove and angle. internal surface ...
Type IV endoleaks are a type of endoleak which usually occurs secondary to graft porosity and are typically seen in the immediate post operative angiogram following an endovascular aneurysm repair.
Type IV endoleaks are extremely rare and studies report a prevalence of 0.3%. This ...
Typical pulmonary carcinoid tumors are considered the more common and more benign low grade form of peripheral pulmonary carcinoid tumors. There is little or no known association between typical carcinoid tumors and tobacco use or exposure to other carcinogens which contrasts to atypical carcino...
Typical ribs are those numbered 2 to 10 with ribs 1, 11 and 12 considered atypical. Some authors however include ribs 2 and 10 also atypical.
A typical rib is long and flat. They contain a:
Ribs have a rounded, smooth superior border. The infe...
The term unfolded aorta refers to the widened and 'opened up' appearance of the aortic arch on a frontal chest radiograph. It is one of the more common causes for apparent mediastinal widening and is seen with increasing age.
It occurs due to the discrepancy in the growth of the ascending aorta...
A unifocalisation procedure is a corrective surgical technique used in patients with complete pulmonary artery atresia with major aortopulmonary collateral arteries (MAPCAs). In this technique, the collateral vessels supplying blood from the aorta directly to the lungs are brought into continuit...
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...
Unilateral pulmonary artery atresia (UPAA), also known as unilateral absence of the pulmonary artery (UAPA) or proximal interruption of the pulmonary artery, is a variant of pulmonary artery atresia.
The term interruption is preferred by some to absence or atresia because the anom...
Unilateral pulmonary edema represents only 2% of cardiogenic pulmonary edema with predilection for the right upper lobe and is strongly associated with severe mitral regurgitation 1, 2. It is hypothesized that the regurgitation jet is directed towards the right superior pulmonary vein thus prefe...
Unilateral pulmonary vein atresia is a type of pulmonary vein atresia.
The condition usually present in infancy or childhood with recurrent episodes of pneumonia and/or hemoptysis. Presentation in adulthood does occur but is uncommon.
It results from failure o...
The upper and lower lobe distribution of certain bilateral pulmonary pathologies can be recalled using the following mnemonics:
upper lobe or apical predominance: CASSET HPP or SET CAP
lower lobe or bibasilar predominance: BAD RASH
C: cystic fibrosis
A: ankylosing spo...
Distribution of bronchiectasis can help in narrowing the differential diagnosis. Upper lobe bronchiectasis is typically seen in:
Rarely it may be seen with non-tuberculous mycobacterial infection (e.g. MAC infection 2). Traction bronchiectasis in the upper lobes c...
Upper lobe predominant pulmonary fibrosis can be associated with a number of pathologies. These include
cystic fibrosis: see pulmonary manifestations of cystic fibrosis
Langerhans cell histiocytosis
Upper lobe pulmonary venous diversion (cephalisation) reflects elevation of left atrial pressure and can occur with pulmonary edema. It produces stag-antler's sign on a frontal chest x-ray.
The normal left atrial pressure is 5-10 mmHg. An elevation of left atrial pressure to 10-15 mmHg will res...
The upper zone is one of the four chest radiograph zones. Sometimes the upper zone includes the apical zone.
on frontal chest radiographs, the upper zone extends from the inferior margin of the clavicles to the superior aspect of the hilum
Urinothorax (plural: urinothoraces), also known as urothorax, is a rare cause of pleural effusion due to the accumulation of urine within the pleural space.
Patients present with varying degrees of respiratory distress depending on the amount of fluid that has accumulated...
The ubiquitous USB flash drive (or USB stick) may be an odd article on a radiology website, but those who report a lot of chest radiographs will be aware that it can be often be confused for an implantable loop recorder device or leadless pacemaker.
Whilst USB drives com...
Usual interstitial pneumonia (UIP) is a histopathologic and radiologic pattern of interstitial lung disease, which is the hallmark pattern for idiopathic pulmonary fibrosis (IPF).
On imaging, usual interstitial pneumonia usually presents with a lung volume loss and a craniocaudal gradient of p...
American Thoracic Society (ATS) criteria for the histopathological diagnosis of usual interstitial pneumonia (UIP) are as follows:
advanced subpleural or paraseptal fibrosis +/- honeycombing
patchy temporally heterogeneous fibrosis
the absence of features against UIP
The Valsalva maneuver is the forced expiration of air against a closed airway, resulting in increased intra-abdominal, intrathoracic, and pharyngeal pressure. It can be performed against a closed glottis or by one closing the mouth and pinching the nose while forcibly exhaling.
It is commonly u...
Vaping-associated lung disease, or EVALI (E-cigarette or Vaping product use-Associated Lung Injury), consists of patterns of inhalational pulmonary injury induced by electronic cigarettes (also known as e-cigarettes, e-vaporizers, e-hookahs, vapes, vape pens). These products heat up a liquid con...
Varicella pneumonia is a type of viral pneumonia. It is a common cause of multiple small round calcific lung lesions. Varicella-zoster virus most commonly causes self-limited benign disease (chickenpox) in children. However, in adults it tends to cause significant complications including varicel...
Varicose bronchiectasis refers to an uncommon morphological subtype of bronchiectasis. According to one study, this type as a pure form accounted for ~10% of all bronchiectasis 1.
For a general discussion, please refer to the article on bronchiectasis.
There are intermit...
Vascular invasion in lung cancer is one of the invasive patterns that can occur in lung cancer. Dependent on the publication, this could mean:
intratumoral vascular invasion (IVI)
microscopic vascular invasion (MVI)
lymphovascular invasion (LVI)
Vascular pedicle is bordered on the right by venous structures (right brachiocephalic vein above and superior vena cava) and on the left by an arterial structure (the left subclavian artery origin). The azygos vein (black oval) is seen en face above the right main bronchus.
The vascular pedicle...
Vascular rings and slings refer to the congenital vascular encirclement of the esophagus and/or trachea by anomalous/aberrant vessels.
Vascular rings are rare, occurring in <1% of patients 1. No gender or ethnic predispositions have been identified 3.
The vena caval foramen is one of the three major apertures in the diaphragm. It is the highest of the three and situated at the level of T8-9. It is quadrilateral and placed at the junction of the right and middle leaflets of the central tendon.
It transmits several structures between the thora...
The venous drainage of the thoracic wall drains deoxygenated venous blood from the peripheries of the thoracic cage back into systemic circulation.
Anterior thoracic wall
Anterior intercostal veins
The anterior intercostal veins originate from the intercostal space just inferio...
The venous thoracic outlet syndrome is the second commonest form of thoracic outlet syndrome (with neurogenic thoracic outlet syndrome being the commonest and the arterial thoracic outlet syndrome being the least common).
It may develop suddenly, often after unusual and t...
Ventilator-associated pneumonia (VAP) is a form of hospital-acquired pneumonia (considered the commonest form 3).
Ventilator-associated pneumonia is defined as pneumonia occurring more than 48 hours after patients have been intubated and started on mechanical ventilation 5.
Ventriculopleural shunting is an alternative option for the diversion of CSF and relief of hydrocephalus. In this technique, the distal catheter is placed in the pleural space. It is an alternative to a ventriculoperitoneal shunt (often considered a next most used alternative).
The vertical fissure line commences in or near the costodiaphragmatic recess and heads superomedially towards the hilum and terminates before or at the horizontal fissure. More commonly occurs on the right and may indicate partial volume loss of the lower lobe 1.
Viral bronchiolitis refers to a bronchiolitis secondary to viral etiology.
Viral infection of airways resulting in inflammation and peribronchial edema. Can then result in small airways occlusion which is the basis of hyperinflation and subsegmental atelectasis. Children more suscept...
Viral respiratory tract infection is a broad term given to pulmonary infection caused by viruses.
They can be caused by any of a large number of viral agents, including but not limited to:
H1N1 pneumonia (swine influenza)
Visceral pleural invasion is a feature that can be seen in lung cancers. It is defined as tumor extension beyond the elastic layer of the visceral pleura. It is considered an aggressive sign and one of the most important adverse prognostic factors in non-small cell lung cancers 1.
Vital capacity (commonly termed VC) is a spirometric parameter giving maximum amount of air that can be expelled from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
Vital capacity increases with
Vitamin E (the tocopherols) are a group of fat-soluble vitamins that act as antioxidants.
hypovitaminosis E is rarely seen outside premature infants
hypervitaminosis E is extremely rare as the toxicity of vitamin E is low except in chronic (usually >1 year) high doses. The commonest sequela is...
V/Q (ventilation/perfusion) scan is a scintigraphic examination of the lung that evaluates pulmonary vasculature perfusion and segmental bronchoalveolar tree ventilation.
diagnosis of suspected pulmonary embolism
monitor pulmonary function following lung transplant
The water bottle sign or configuration refers to the shape of the cardiac silhouette on erect frontal chest x-rays in patients who have a very large pericardial effusion. Typically the effusion has accumulated over many weeks to months (e.g. in patients with malignancy) and the pericardium has g...
The water-lily sign, also known as the camalote sign, is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily.
It is classically described on plain radiographs (mainly chest...
A well-differentiated fetal adenocarcinoma (WDFA) of lung is a rare low grade lung tumor. Some consider this as a variant of adenocarcinoma with others considering this under the group of pulmonary blastomas 5.
According to classification by the World Health Organization in 1999, it was remove...
The Wells criteria for pulmonary embolism is a risk stratification score and clinical decision rule to estimate the probability for acute pulmonary embolism (PE) in patients in which history and examination suggests acute PE is a diagnostic possibility. It provides a pre-test probability which, ...
Westermark sign is a sign of pulmonary embolus seen on chest radiographs. It is one of several described signs of pulmonary embolus on chest radiographs.
The theory behind the sign is either obstruction of the pulmonary artery or distal vasoconstriction in hypoxic lung 3.
In one stu...
Thoraco-pulmonary manifestations of Whipple disease are uncommon and present in the late stages of the disease.
Lung involvement is seen in 35-60% of patients with gastrointestinal whipple disease.
Majority of patients present with non-specific pulmonary an...
The WHO classification scheme for thymic epithelial tumors is one of many classifications systems for thymoma and related tumors, and classifies them according to histology:
spindle cell thymoma
type ab: mixed thymoma
type b1: lymphocyte rich
Williams-Campbell syndrome (WCS) is a rare form of congenital cystic bronchiectasis, in which distal bronchial cartilage is defective.
Williams-Campbell syndrome may present with recurrent pneumonia, wheezing, barrel-chest deformity, and Harrison sulcus 8.