Differentiating benign from malignant pulmonary nodules is of great importance as it determines the further course of management of the patient.
Benign pulmonary nodule
size: the smaller the size the more likely to be benign
~80% of benign nodules are <2 cm in size.
margin: smooth, regular; ...
Thymic calcifications are rare findings usually associated with thymoma but are also seen in other pathologies.
thymoma - more frequent in invasive thymoma 1
multilocular thymic cyst 2
anterior mediastinal a...
Bilateral hypertranslucent hemithoraces is the presence of decreased density of the hemithoraces bilaterally on a plain chest radiograph. This hypertranslucency, a.k.a. hyperlucency, may be focal or diffuse 1.
Also see unilateral hypertranslucent hemithorax.
Apical chest masses are often important and may be missed, especially when examined with a plain chest radiograph. It is always recommended to perform a targeted assessment of the apices of the lungs during a chest x-ray; they are one of the classic review areas.
Reflux of contrast into inferior vena cava can be common findings seen on CT. It is considered a specific but insensitive sign of right-sided heart disease / right heart dysfunction at low contrast injection rates although the usefulness decreases with high injection rates.
Bilateral pleural effusions can be common in general radiology practice. They may be symmetrical or asymmetrical. They can occur from several varied etiologies although congestive heart failure (CHF), renal or liver failure are generally considered common 1.
Recognized list of causes are many...
Hemithoracic volume loss can occur from a number of situations. These include:
pulmonary hypoplasia (unilateral)
isolated unilateral pulmonary artery agenesis
skeletal deformities - e.g. kyphosis,
Infection in childhood
Giant cell carcinomas of the lung are a rare type of non-small cell lung carcinomas (NSCLC) classified under sarcomatoid carcinomas of the lungs.
They represent less than 0.5% of all NSCLC 2. There is a recognized association with smoking 1.
Symptoms are n...
Bronchial stenosis, or bronchial strictures, are descriptive terms to denote regions of focal narrowing involving the bronchi. They can arise from a wide variety of etiologies.
It can arise from a large range of etiological factors, which include:
Only a small number of pulmonary diseases are known to directly traverse the lung fissures such that the lung pathology extends from one lobe via the interlobar fissure into an adjacent lobe 1. The finding is most commonly due to primary malignancy, however, some infections are also known to do ...
Esophageal wall thickening can be observed in a number of situations and can be either focal or diffuse. It may be physiological, and can also be due to benign or malignant disorders.
diffuse esophageal spasm
forms of esophagitis
diffuse esophageal intramural hemat...
Hyperattenuating pulmonary consolidation refers to a region of lung parenchyma with air space opacification that has higher attenuation on CT than muscle or than expected with typical causes of consolidation such as pneumonia (fluid attenuation) or cancer (soft tissue attenuation).
Diffuse airway narrowing can occur from a number of pathologies; these include:
granulomatosis with polyangiitis
various infections including
Non-cardiogenic pulmonary edema is a classification of pulmonary edema where the underlying etiology is not due to left ventricular dysfunction. Causes include:
pulmonary edema with acute asthma
post-obstructive pulmonary edema/postintubation pulmonary edema/negative pressure ...
A reticulonodular interstitial pattern is an imaging descriptive term that can be used in thoracic radiographs or CT scans when are there is an overlap of reticular shadows with nodular shadows. This may be used to describe a regional pattern or a diffuse pattern throughout the lungs.
Linear atelectasis (plural: atelectases), and also known as discoid, plate or band atelectasis, refers to a focal area of subsegmental atelectasis that has a linear shape. Linear atelectasis may appear to be horizontal, oblique or perpendicular and is very common. It usually occurs as a conseque...
Compressive atelectasis refers to a form of lung atelectasis due to compression by a space-occupying process.
Some authors describe it as a subtype of passive (relaxation) atelectasis where the reduction in lung volume is greater than its normal relaxed state 1. Whereas others describe it as th...
Lobar consolidation is the term used to describe consolidation in one of the lobes of the lung. It infers an alveolar spread of disease and is most commonly due to pneumonia.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inf...
Right upper lobe consolidation refers to consolidation in part (incomplete) or all (complete) of the right upper lobe.
Consolidation refers to the alveolar airspaces being filled with fluid (exudate/transudate/blood), cells (inflammatory), tissue, or other material.
The list of caus...
Peribronchovascular thickening is a broad imaging descriptive term commonly used to describe thickening of any one or more of the below:
peribronchovascular interstitial thickening
bronchial wall thickening: can be differentiated from true peribronchovascular thickening on cross-section...
Secondary organizing pneumonia (SOP) refers to organizing pneumonia that can be attributed to a specific cause, in contrast to cryptogenic organizing pneumonia (COP) in which no cause is present.
Secondary organizing pneumonia can be attributed to the following causes 1:
Chronic suppurative lung disease (CSLD) refers to a group of conditions which includes:
primary ciliary dyskinesia
This term is usually used in the context of pediatric patients.
Intralobular septal thickening is a form of interstitial thickening and should be distinguished from interlobular septal thickening. It is often seen as fine linear or reticular thickening.
It has been described with several conditions of variable etiology which include
The following differential diagnoses can be considered when small lung volumes are seen:
prior surgery, e.g. lobectomy, lung volume reduction surgery
pleural disease, e.g. pleural thickening
skeletal deformities, e.g. kyphosis, scoliosis
systemic lupus erythematosus (SLE)...
Pulmonary calcification has many causes and varying morphology:
calcific pulmonary nodules or masses
healed varicella pneumonia
coal worker's pneumoconiosis
The differential diagnoses for mediastinal widening include:
traumatic aortic injury
thoracic aortic aneurysm
aberrant right subclavian artery
azygos continuation of the IVC
pulmonary masses abutting the m...
The differential diagnosis for a middle mediastinal mass includes 1-3:
aneurysm e.g. aortic, pulmonary artery, bronchial artery
foregut duplication cyst (e.g. esophageal, bronchial)
primary/secondary cardiac tumor
There is a long list of fat containing thoracic lesions. They may involve the mediastinum, lung, pleura or chest wall.
Differential diagnosis includes:
intrapulmonary: fat containing pulmonary lesions
Megaesophagus or diffuse esophageal dilatation can be caused by a variety of conditions.
Some of the more common causes are given below 1-3:
malignant stricture, e.g. esophageal cancer, ca...
There are several pulmonary complications that can arise in the setting of cirrhosis:
hepatopulmonary syndrome (HPS): considered the commonest
portopulmonary hypertension (POPH)
hepatic hydrothorax (HH)
intrathoracic portosystemic collateral vessel formation
acute respiratory distress syndr...
Dynamic tracheal collapse refers to collapse of the trachea during expiration. It is perhaps best assessed on CT in the end expiratory phase. An inspiratory series is also useful for comparative purposes. The term excessive dynamic airway collapse (EDAC) refers to abnormal and exaggerated bulgin...
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...
Resorptive or obstructive atelectasis is a form of lung collapse that is due to obstruction of the airways supplying a lung segment or lobe. It is a term used to distinguish atelectasis identified on imaging based on the underlying pathophysiology to guide diagnosis.
Chronic interstitial pneumonitis is a broad descriptive term where an interstitial pneumonia has a prolonged course. It can arise from a range of etiologies. The term does not usually imply a specific radiographic pattern and includes UIP, NSIP or other patterns. As a general rule, there is litt...
Empyemas are purulent inflammatory collections within a body cavity. Contrast this with abscesses, which arise within parenchymal tissue, rather than occupying a pre-existing anatomical space.
Colloquially, the standalone term empyema is used to refer to thoracic empyemas but there...
Pericardial fat pads are normal structures that lie in the cardiophrenic angle. They are adipose tissues surrounding the heart composed of the epicardial fat, which lies between the myocardium and visceral pericardium, and paracardial fat, which is adherent and external to the parietal pericardi...
Pleural adhesions usually refers to the formation of fibrotic bands that span the pleural space, between the parietal and visceral layers of the pleura.
They may be local or diffuse. The presence of a pleural adhesion is one of the causes for a pneumothorax not to resolve.
Pulmonary arterial calcification is a phenomenon which is usually seen in the setting of advanced pulmonary hypertension. It can however be uncommonly present in those without pulmonary hypertension.
The general mechanism in the vast majority is thought to be from high end pulmonary ...
Pulmonary fungal disease encompasses a broad spectrum of infections related to fungal sources. They can particularly affect immunocompromised individuals.
pulmonary aspergillosis: pulmonary aspergillus infection considered the most important in immunocompromised individuals 5
Mucoid impaction, also referred to as mucus plugging, mucous plugging, bronchial mucocele or bronchocele formation, refers to airway filling by mucoid secretions and can be obstructive or non-obstructive. It is a common pathological finding in chest imaging.
Calcification associated with pulmonary emboli is usually associated with chronic pulmonary embolism. Calcification is occasionally related to prior congenital cardiac repairs 1.
If it is purely high attenuating, consider
polymethylmethacrylate (PMMA) embolism into the ...
Cicatrisation atelectasis is a form of lung atelectasis which occurs as a result of scarring or fibrosis that reduces lung expansion. Cicatrisation atelectasis is classic in tuberculosis. The term is closely related to cicatrisation collapse when an entire lobe is collapsed from the same process...
Mediastinal lymph node enlargement can occur from a wide range of pathologies, either by its own or in association with other lung pathology. Historically, a size cut-off of 10 mm short-axis diameter was used.
Although mediastinal lymphadenopathy is used interchangeably - by some ...
Subpulmonic effusions (also known as subpulmonary effusions) are pleural effusions that can be seen only on an erect projection. Rather than layering laterally and blunting of the costophrenic angle, the pleural fluid lies almost exclusively between the lung base and the diaphragm.
Hemoptysis (plural: hemoptyses) refers to coughing up of blood. Generally, it appears bright red in color as opposed to blood from the gastrointestinal tract which appears dark red. It is considered an alarming sign of a serious underlying etiology.
A variety of clinical classifica...
Pure ground glass lung nodules (pGGN's) are a subtype of ground glass lung nodules where there is no associated solid component.
Apart from inflammatory foci they have been shown to represent various pathologies such as 1,3
adenocarcinoma in situ of lung
A coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present 1,3. Typically but not always the patient is asymptomatic 1.
The differential diagnosis for such lesions i...
Bronchial wall thickening is an imaging descriptor used to describe abnormal thickening of bronchial walls and can arise from a vast number of pathological entities. It is one of the causes of peribronchial cuffing.
The presence of bronchial wall thickening usually (but not always) implies infl...
Elevated diaphragm refers to the symmetrical elevation of both domes of the diaphragm.
There is some overlap with causes of an elevated hemidiaphragm.
poor inspiratory effort
Diffuse pulmonary nodules are usually seen as multiple pulmonary nodular opacifications on a HRCT chest scan. They can signify disease processes affecting either the interstitium or the airspace. They can range from a few millimeters to up to 1 cm and when very small and numerous there can be so...
A number of differentials must be kept in mind while approaching diffuse or multiple pulmonary nodules. Interpretation is easier if nodules are the only abnormality.
These differentials can be narrowed down based on several criteria:
Based on appearance
Granulomatous lung disease refers to a broad group of infectious and non-infectious conditions characterized by the formation of granulomas. The spectrum includes:
pulmonary non-tuberculous mycobacterial infection
Pulmonary ossification is a rare finding and is characterized by the presence of mature bone in alveolar or interstitial spaces, either localized or disseminated throughout the lung parenchyma.
It can be idiopathic (idiopathic pulmonary ossification) or secondary to chronic lung, cardiac or sys...
Diaphragmatic paralysis (also considered very similar to the term diaphragmatic palsy) can be unilateral or bilateral.
Clinical features are highly variable according to underlying etiological factors:
unilateral paralysis: asymptomatic in most of the patients as the oth...
Calcifying pulmonary metastases are rare. These should not be confused with metastatic pulmonary calcification.
Calcification in metastases can arise through a variety of mechanisms: bone formation in tumors of osteoid origin, calcification and ossification of tumor cartilage, dystro...
Localized pulmonary hemorrhage is a descriptive term for a pulmonary hemorrhage restricted to a particular focal region of the lung. It can range from involving a small focus of hemorrhage to a whole lobe.
Focal pulmonary hemorrhage can occur from a number of causes:
A hemopneumothorax (plural: hemopneumothoraces) (or, less commonly, haematopneumothorax or pneumohemothorax) is a term given when there is concurrent presence of a hemothorax and pneumothorax. It is a variant of a hydropneumothorax.
Approximately 5% of patients with pneumothorax ...
A hemothorax (plural: hemothoraces), or rarely hematothorax, literally means blood within the chest, is a term usually used to describe a pleural effusion due to accumulation of blood. If a hemothorax occurs concurrently with a pneumothorax it is then termed a hemopneumothorax.
A tension hemot...
Cavitating pneumonia is a complication that can occur with severe necrotizing pneumonia and in some publications, it is used synonymously with the latter term 2. It is a rare complication in both children and adults.
Cavitation associated with Mycobacterium tuberculosis is separately discussed...
There are several tumors that can involve the pleura which can range from being benign to malignant (see malignancies of the pleura). The list includes:
primary pleural tumors 5
pleural malignant mesothelioma
well-differentiated papillary mesothelioma
adenomatoid tumor of...
Pulmonary or interstitial fibrosis is a descriptive term given when there is an excess of fibrotic tissue in the lung. It can occur in a wide range of clinical settings and can be precipitated by a multitude of causes.
The term should not be confused with idiopathic pulmonary fibro...
Cystic lesions in pediatric patients are usually congenital lesions and, as such, can be seen antenatally and following delivery.
These congenital lesions are predominantly covered by the overarching diagnosis of bronchopulmonary foregut malformation. This is a ...
Pleural thickening is a descriptive term given to describe any form of thickening involving either the parietal or visceral pleura.
It can occur with both benign and malignant pleural disease. According to etiology it may be classified as:
benign pleural thickening
following recurrent inflam...
Diffuse pleural thickening refers to a morphological type of pleural thickening. It can occur from malignant as well as non-malignant causes, which include:
diffuse pleural fibrosis / fibrothorax 6
asbestos-related pleural disease (asbestos related diffuse pleural thickening): typically seen a...
The incomplete border sign is useful to depict an extrapulmonary mass on chest radiograph.
An extrapulmonary mass will often have an inner well-defined border and an ill-defined outer margin 1-3. This can be attributed to the inner margin being tangential to the x-ray beam and having a good inh...
Fatty mediastinal masses are relatively uncommon, and the differential diagnosis is brief, including 1-4:
benign mature teratoma
extravasation of lipid-rich hyperalimentation fluid 3
fibrofatty replacement of the central portion of mediastinal l...
Non-calcified hyperdense pulmonary nodules are predominantly the result of inhalational exposure to substances, although embolization of material may cause dense nodular opacification within the lung.
inhalation disease, e.g. pneumoconioses
pulmonary baritosis (barium dust)
Cavitating pulmonary metastases refer to pulmonary metastases which then tend to cavitate. The term is similar but may not be identical to cystic pulmonary metastases in which the wall of the former may be thicker.
Cavitation is thought to occur in around 4% of lung metastases 2.
Perilymphatic lung nodules follow perilymphatic channels and on imaging are typically subpleural, occur along fissures (perifissural nodules), interlobular septa, and adjacent to the bronchovascular bundles.
Lung nodules in a perilymphatic distribution can be seen in ass...
Centrilobular lung nodules refer to a HRCT chest imaging descriptor for small 5-10 mm lung nodules which are anatomically located centrally within secondary pulmonary lobules. The term is applied on the basis of location of the nodule and not its morphology, that is they may be well-defined or p...
Cystic pulmonary metastases are an atypical morphological form of pulmonary metastases where lesions manifest as distinct cystic lesions. It is slightly different from the term cavitating pulmonary metastases in that the lesions are extremely thin walled.
It has been reported with ma...
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 prefer...
Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients.
In adults, an ascending aortic diameter greater than 4 cm is considered to indicate dilatation 4. Aneurysmal dilatation is considered when the ascending aortic diameter reaches or ex...
Diffuse alveolar hemorrhage (DAH) is a subset of diffuse pulmonary hemorrhage when bleeding is diffuse and directly into the alveolar spaces. It can occur in a vast number of clinical situations and can be life-threatening.
Blood tends to fill alveolar spaces at multiple sites.
Pulmonary hemorrhage is a rather broad term given to describe any form of bleeding into the lung and can arise from a myriad of causes. In a very traditional sense it is described when the following constellation of clinicoradiological features occurs simultaneously 2 (although this is never an ...
Pulmonary vasculitis refers to vasculitides that affect the lung or pulmonary vessels. If this definition is used, a large group of conditions can fall into this category. The respiratory system may be potentially involved in all systemic vasculitides, although to a variable degree.
The cardiophrenic space is usually filled with fat. However, lesions originating above or lower to the diaphragm can present as cardiophrenic angle lesions.
The more common lesions encountered include:
pericardial fat pad
pericardial fat necrosis
Postobstructive pulmonary edema is a type of non-cardiogenic pulmonary edema and is an uncommon but well-described complication of upper airway obstruction.
It occurs in three clinical settings 6:
acute airway obstruction
chronic upper airway obstruction
Diffuse pulmonary hemorrhage (DPH) is a subtype of pulmonary hemorrhage where bleeding into the lung is diffuse (cf. focal pulmonary hemorrhage). If the bleeding is into the alveolar spaces, it can be further subclassified as diffuse alveolar hemorrhage (DAH).
An interstitial lung pattern is a regular descriptive term used when reporting a plain chest radiograph. It is the result of the age-old attempt to make the distinction between an interstitial and airspace (alveolar) process to narrow the differential diagnosis.
A re-read of the timeless work o...
Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CT scans.
tubing, clamps, syringes, scissors, lying on or under the patient
rubber sheets, foam mattresses, clothing, hair braids, nipple piercings, etc. may also be visib...
Pneumatoceles are intrapulmonary gas-filled cystic spaces that can have a variety of sizes and appearances. They may contain gas-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 blebs are small subpleural thin-walled air-containing spaces, not larger than 1 or 2 cm in diameter (with the precise limit varying by source). Their walls are less than 1 mm thick. If they rupture, they allow air to escape into the pleural space resulting in a spontaneous pneumothorax...
Right lower lobe (RLL) collapse has distinctive features, and is usually relatively easily identified. The smaller overlying heart shadow obscures less lung compared with left lower lobe collapse.
Findings of lower lobe collapse can be grouped together as they are almost identical on both side...
Right upper lobe collapse has distinctive features, and is usually easily identified on frontal chest radiographs; much more so than left upper lobe collapse.
For a general discussion please refer to the article on lobar collapse.
Collapse of the right ...
Right middle lobe collapse (or simply termed middle lobe collapse) has distinctive features, but can be subtle on frontal chest radiographs.
For a general discussion please refer to the article on lobar collapse.
It is important to note that of all the lobes, the right middle lobe is the mo...
Enlargement of the cardiac silhouette on a frontal (or PA) chest x-ray can be due to a number of causes 1:
cardiomegaly (most common cause by far)
anterior mediastinal mass
prominent epicardial fat pad
AP projection (e.g supine radiographs taken w...
A narrow fetal thorax on antenatal ultrasound can be present with a number of anomalies which include:
Jeune syndrome - asphyxiating thoracic dysplasia
short rib polydactyly syndro...
Calcified pulmonary nodules are a subset of hyperdense pulmonary nodules and a group of nodules with a relatively narrow differential.
The most common cause of nodule calcification is granuloma formation, usually in the response to healed infection.
A pulmonary mass is any area of pulmonary opacification that measures more than 30 mm, an arbitrary but useful measurement. The commonest cause of a pulmonary mass is primary lung cancer 1-3:
granuloma: most common non-malignant cause
Interstitial lung disease (ILD) is an umbrella term that encompasses a large number of disorders that are characterized by diffuse cellular infiltrates in a periacinar location. The spectrum of conditions included is broad, ranging from occasional self-limited inflammatory processes to severe de...
Echogenic fetal lung lesions on antenatal ultrasound can be detected in a number of situations. They include:
Airway obstructions: lung are often enlarged and echogenic bilaterally
congenital high airways obstruction syndrome (CHAOS)
congenital tracheal stenosis
Cystic retroperitoneal lesions carry a relatively broad differential, which includes:
retroperitoneal lymphatic malformation
retroperitoneal mucinous cystadenoma
retroperitoneal cystic teratoma
retroperitoenal cystic mesothelioma
pseudomyxoma retroperitonei with cystic change