Lobar collapse is relatively common and occurs following obstruction of a bronchus. Gas is resorbed from the lung parenchyma distal to the obstruction resulting in the collapse of the lung, with volume reduction and negative mass effect.
This is a summary article; read more i...
Lobar collapse refers to the collapse of an entire lobe of the lung. As such it is a subtype of atelectasis (although collapse is not entirely synonymous is atelectasis), which is a more generic term for 'incomplete expansion'. Individual lobes of the lung may collapse due to obstruction of the ...
Lobar pneumonia (also known as non-segmental pneumonia or focal non-segmental pneumonia 7) is a radiological pattern associated with homogenous, fibrinosupparative consolidation of one or more lobes of a lung in response to bacterial pneumonia.
The radiological appearance of lobar pneumonia is...
A localised (solitary) mediastinal malignant mesothelioma is a rare variant of malignant pleural mesothelioma and is thought to arise from mesothelial cells of the pericardium.
There are too few report cases to be dogmatic in regards to epidemiological or radiographic features.
Localised pulmonary emphysema is not a commonly used term but generally given the to describe pulmonary emphysema confined to a particular location with the lung (may involve a lobe,segment or subsegment). It has also been used to describe focal areas of enlargement or destruction of air spaces ...
Localised pulmonary haemorrhage is a descriptive term for a pulmonary haemorrhage restricted to a particular focal region of the lung. It can range from involving a small focus of haemorrhage to a whole lobe.
A focal pulmonary haemorrhage can occur from a number of causes
A loculated pneumothorax is a form of pneumothorax where a pocket of pleural air is trapped within a localised area. They may occur in a number of situations including in patients with acute respiratory disease treated with mechanical ventilation 1 and status post pleural aspiration in the conte...
Simple pulmonary eosinophilia (also known as Löffler syndrome) is a type of pulmonary eosinophilia that typically presents with transient radiographic infiltrates, minimal constitutional upset, and an elevated eosinophil count in peripheral blood.
The cause is not usually ...
Löfgren syndrome is a specific acute clinical presentation of systemic sarcoidosis, consisting of:
hilar adenopathy: see thoracic manifestations of sarcoidosis
arthritis: see musculoskeletal manifestations of sarcoidosis
Low attenuation lymphadenopathy suggests underlying necrosis and can be seen in:
metastatic carcinoma (or lymphoma)
infections (tuberculous or fungal)
low attenuation lymphadenopathy
high attenuation lymphadenoapthy
The distribution of bronchiectasis can help in narrowing the differential diagnosis. Lower lobe bronchiectasis is the commonest zonal predilection in bronchiectasis 2. It is mostly idiopathic but can be typically seen in
post infective bronchiectasis
recurrent childhood infections
A lower respiratory tract infection (LRTI) is a very broad term which can mean inflammation of the respiratory tract below the level of the larynx. This term may include a pneumonia (which is often given to described more organised consolidation within the lungs). There is also overlap with the ...
The lower zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends inferiorly from the inferior aspect of the hilum to the hemidiaphragm
The Luftsichel sign is seen in some cases of left upper lobe collapse and refers to the frontal chest radiographic appearance due to hyperinflation of the superior segment of the left lower lobe interposing itself between the mediastinum and the collapsed left upper lobe.
Lumbar (or 13th) ribs are a rare anatomical variant and represent transitional vertebrae at the thoracolumbar junction with a prevalence of ~1% 1. It presents as an additional rib coming off T13 or L1 (depending on numbering classification) and may be unilateral or bilateral. Lumbar ribs are mos...
The lungs are the functional units of respiration and are key to survival. They contain 1500 miles of airways, 300-500 million alveoli and have a combined surface area of 70 square meters (half a tennis court). Each lung weighs approximately 1.1 Kg. They are affected by a wide range of patholog...
Lung abscess is a circumscribed collection of pus within the lung, and potentially life threatening. They are often complicated to manage and difficult to treat.
As a result of the widespread availability of antibiotics, the incidence of lung abscesses has dramatically reduced. Si...
Lung architectural distortion in thoracic radiology refers to a descriptive term give when the normal pulmonary bronchial, vascular, fissural or septal anatomy is disrupted and manifested as loss of smooth course of the fissures, crowding of dilated bronchioles or vessels with angulated course 1...
Lung atelectasis refers to collapse or incomplete expansion of pulmonary parenchyma. Note that the term "atelectasis" is typically used when there is partial collapse, whereas the term "collapsed lung" is typically reserved for when the entire lung is totally collapsed.
Lung cancer, or frequently, if somewhat incorrectly, known as bronchogenic carcinoma, is the most common cause of cancer in men, and the 6th most frequent cancer in women worldwide. It is the leading cause of cancer mortality worldwide in both men and women and accounts for approximately 20% of ...
The International Association for the Study of Lung cancer (IASLC) 7th edition for lung cancer staging is as follows. This has now been updated and superseded by the 8th edition in 2016.
T staging descriptor
The parameters assessed on the T stage include size, endobronchial location, local inv...
This is a basic article for medical students and non-radiologists
Lung cancer is the most common cancer worldwide and refers to malignancy originating in the airways or pulmonary parenchyma.
Patients may be asymptomatic until locally advanced or metastatic disease. The m...
Lung cancer screening with low-dose CT (LDCT) is an imaging strategy that is beginning to be adopted for high-risk patients in some health systems. Lung cancer is the most common cause of cancer death worldwide, and there is accumulating higher level evidence that a mortality benefit exists with...
Lung carcinomas of the salivary gland type are also known as salivary gland–type tumours of the lung (SGTTLs) or bronchial gland neoplasms.
The usual consignation to the group of non-small cell lung cancer (NSCLC) may be unfortunate because the clinical behavior of SGTTLs can be quite differen...
A commonly used mnemonic for recalling the features of consolidation is:
A: acinar rosettes
A: air bronchogram/alveologram
B: bat-wing distribution
C: coalescent/confluent ill-defined "fluffy" appearnce
C: consolidation: diffuse, perihilar/bibasilar, lobar/segmental,...
A lung decortication is a cardiothoracic surgical procedure usually performed for situations such as a chronic thoracic empyema or a chronic haemothorax where a diseased, often chronically infected, pleura is debrided from the adjacent lung and removed. It is also sometimes performed of selected...
Lung entrapment is a term given to non expandable lung due to active pleural inflammation, malignancy, or haemothorax.
The term is similar but not entirely synonymous with trapped lung, which is due to pleural inflammation from remote disease resulting in fibrous thickening of the pleura.
Lung fissures are a double-fold of visceral pleura that either completely or incompletely invaginates lung parenchyma to form the lung lobes.
Each lung has an oblique fissure separating the upper lobes from the lower lobes and the right lung has a horizontal fissure that separates the right up...
Lung hyperinflation is a common feature of patients with chronic obstructive pulmonary disease (COPD). It is also linked to ageing and other chronic diseases that cause airflow obstruction.
The airflow limitation during expiration is produced by two factors:
destruction of the lung ...
Lung parenchyma is the portion of the lung involved in gas transfer - the alveoli, alveolar ducts and respiratory bronchioles. However, some authors include other structures and tissues within the definition.
parenchymal lung disease
Lung torsion is a very rare situation typically described as an adverse event after a pneumonectomy. In extremely rare situations it can also occur after less invasive procedures such as video-assisted thoracic surgery (VATS) 11 or even spontaneously in the native lung.
It has a ...
Lung transplant complications can occur at variable time intervals following transplantation. It is important for radiologists to be aware of specific complications as chest imaging is routinely used in post transplant assessment.
When reporting a postoperative radiograph or CT, it is importan...
Lung volume reduction surgery (LVRS) is an emerging promising palliative treatment option for select patients with severe, debilitating pulmonary emphysema. It usually involves bilateral wedge resection of 20-30% of the most diseased lung through a median sternotomy. It has been proposed that L...
Lung-RADSTM (or lung imaging reporting and data system) is a classification proposed to aid with findings in low dose CT screening exams for lung cancer. The goal of the classification system is to standardize follow-up and management decisions. The system is similar to the Fleischner criteria b...
Lymphangioleiomyomatosis (LAM) is a rare multi-system disorder that can occur either sporadically or in association with the tuberous sclerosis complex (TSC) and is often considered a forme fruste of TSC.
It almost exclusively affects women of child-bearing age 7. The estimated in...
Lymphangitic carcinomatosis, or lymphangitis carcinomatosa, is the term given to tumour spread through the lymphatics of the lung and is most commonly seen secondary to adenocarcinoma.
The demographics will reflect that of the underlying malignancy (see below).
A mnemonic for the causes of lymphangitic carcinomatosis is:
Certain Cancers Spread By Plugging The Lymphatics
L: larynx and lung
Lymphocele of the thoracic duct (thoracic duct cyst) is usually asymptomatic or less commonly may present as left supraclavicular fossa mass 1.
The clinical significance of a thoracic duct cyst lies in its misidentification as a pathological lesion at radiological assessment, whi...
Lymphocytic interstitial pneumonitis (LIP) is a benign lymphoproliferative disorder characterised by lymphocyte predominant infiltration of the lungs. It is classified as a subtype of interstitial lung disease. It also falls under the umbrella of non-lymphomatous pulmonary lymphoid disorders.
Lymphomatoid granulomatosis (LG), also known as angiocentric lymphoma or angiocentric immunoproliferative lesion, is a rare type of non-Hodgkin's lymphoma.
There is a recognised association with antecedent infection with the Epstein Barr virus (EBV).
It can affect a variety of org...
Pulmonary manifestations of lymphomatoid granulomatosis are important since the lung is one of the most frequent sites of involvement in lymphomatoid granulomatosis. It forms under the group of pulmonary angiitis and granulomatosis.
Some consider the condition to be midway between ov...
Macrocystic honeycombing refers to a morphological sub type of honeycombing. Many publications consider the individual lung cysts to be greater than 4mm to be classified into this category. This form is considered to be more associated with UIP 3.
Major aortopulmonary collateral arteries (MAPCAs) are persistent tortuous fetal arteries that arise from the descending aorta and supply blood to pulmonary arteries in the lungs usually at the posterior aspect of hilum.
Embryologically, the intersegmental arteries regress with the no...
Malignant pleural disease usually heralds a poor prognosis, whether it represents a primary pleural malignancy or metastatic involvement.
Clinical presentation is variable. Patients may be asymptomatic or have pleuritic pain. If associated with a sizeable pleural effusio...
A number of staging systems have been described for staging of malignant pleural mesothelioma. Below is the International Mesothelioma Interest Group TNM staging system.
T - Tumour
Tx: primary tumour cannot be assessed
T0: no evidence of primary tumour
Marijuana (cannabis or bong) lung refers to the presence of large apical bullae in patients who regularly smoke marijuana. A definite causative link between smoking marijuana and bullous lung disease has not been established, and the association may just be coincidental.
The Masaoka staging system is commonly adopted for thymomas 1-3, and is the most important determinant of survival following surgical resection 4:
stage I: intact thymic capsule
stage II: capsular invasion into adjacent mediastinal fat or pleura
stage III: macroscopic invasion into adjacent o...
Maximum Intensity Projection (MIP) consists of projecting the voxel with the highest attenuation value on every view throughout the volume onto a 2D image 1.
Such an algorithm is rather simple: for each XY coordinate, only the pixel with the highest Hounsfield number along the Z-axis is represe...
Mean pulmonary arterial pressure (MPAP) can be estimated by echocardiogram ultrasound study. It is calculated by the formula:
(PASystolic pressure +2 PADiastolic pressure) / 3
Normal MPAP is less than 20 mmHg and considered elevated when it exceeds 25 mmHg at rest or 30 mmHg with exertion.
Meconium aspiration occurs secondary to intrapartum or intrauterine aspiration of meconium, usually in the setting of fetal distress, and usually in term or post-term infants.
Aspirated meconium can cause small airways obstruction and a chemical pneumonitis.
Medial pneumothorax refers to the abnormal collection of air on medial aspect of the pleural cavity. This occurs when the quantity of air is small.
Chest radiograph (supine)
Seen as a linear lucent area along the medial aspect of lung at the interface of the pleural surf...
Medial stripe sign refers to an area of increased lucency at the interface of the medial lung and the mediastinum in case of medial pneumothorax. A small volume of pneumothorax generally accumulates anteriorly or medially which can be difficult to detect hence this sign holds a certain significa...
Mediastinal haemangioma is a location specific subtype of a haemangioma.
There incidence account for less than 0.5% among all mediastinal masses 1.
Up to half of patients may be asymptomatic 1. Others may present with non-specific symptoms, such as cough, c...
Mediastinal lipomatosis refers to a condition where there is a deposition of a large amount of mature adipose tissue in the mediastinum. It is a relatively common benign cause of mediastinal widening.
It is the result of increased deposition of normal unencapsulated fat 1.
Mediastinal lymph node enlargement can occur from a wide range of pathologies. It may occur on its own in association with other lung pathology.
The spectrum of conditions than can result in mediastinal lymphadenopathy is exhaustive and includes:
sarcoidosis (see: pulmonary manifest...
Mediastinal lymphadenopathy associated with interstitial lung disease can be a frequent feature although its presence has limited value in the differential diagnosis. In certain forms of interstitial lung disease, the extent of lymph node enlargement may correlate to disease activity or progress...
Mediastinal lymphoma is common, either as part of disseminated disease or less commonly as the site of primary involvement.
Lymphomas are responsible for approximately 15% of all primary mediastinal masses, and 45% of anterior mediastinal masses in children 1. Only 10% of lymphoma...
Mediastinal mass may be caused by a wide variety of neoplastic and non-neoplastic pathology. It is helpful to clarify the location of the mass since this significantly reduces the breadth of the differential diagnosis.
Broadly speaking, there are four parts to the mediastinum which are largely...
Mediastinal paragangliomas are rare tumours derived from chromaffin cells (neuroectodermal cells) associated with sympathetic ganglion of the autonomic nervous system. They can arise from two major cluster of sympathetic ganglion cells: paraaortic (aorticopulmonary) and paravetebral (aorticosymp...
Mediastinal pseudocyst is the extension of pancreatic pseudocyst into the the posterior mediastinum through oesophageal or aortic hiatus or rarely through foramen of Morgagni. It is a rare complication of acute or chronic pancreatitis.
It can present with symptoms due to ...
Mediastinal teratomas are germ cell tumours located in the anterior mediastinum.
Mediastinal teratomas are the most common extra-gonadal germ cell tumours. They account for approximately 15% of anterior mediastinal masses in adults and approximately 25% of anterior mediastinal mas...
The differential diagnoses for mediastinal widening include:
traumatic aortic injury
aberrant right subclavian artery
azygous continuation of the IVC
pulmonary masses abutting the mediastinum
The mediastinum is a space in the thorax that contains a group of non-delineated organs and their surrounding connective tissue. It lies in the midline of the chest between the pleura of each lung and extends from the sternum to the vertebral column.
The mediastinum contains all...
The International Thymic Malignancy Interest Group (ITMIG) classification of mediastinal compartments was developed to reflect the division of the mediastinum based on cross-sectional imaging.
The ITMIG classification divides the mediastinum into three compartments: prevascular...
Medical devices in the thorax are regularly observed by radiologists when reviewing radiographs and CTs.
tubing, clamps, syringes lying on or under the patient
rubber sheets, foam mattresses, clothing, hair braids, nipple piercings etc may also be visible
These devices ...
Mega oesophagus or diffuse oesophageal dilatation can be caused by a variety of conditions.
Some of the more common causes are given below 1-3:
malignant stricture, e.g. oesophageal canc...
Melioidosis is an infectious disease caused by Burkholderia pseudomallei (previously known as Pseudomonas pseudomallei) and is a multisystem disorder which may affect the lungs, brain, visceral organs or musculoskeletal system.
Melioidosis is a disease of the monsoon season in the...
The melting ice cube sign describes the resolution of pulmonary haemorrhage following pulmonary embolism (PE).
When there is pulmonary haemorrhage without infarction following PE, the typical wedge-shaped, pleural-based opacification (Hampton's hump) resolves within a week while preserving its...
Mendelson syndrome or peptic pneumonia refers to acute chemical pneumonitis caused by the aspiration of stomach contents in patients under general anesthesia.
The etiologic agents is believed to be aspiration of acidic stomach contents, other compounds, e.g. bile, may also play a rol...
A mesenchymal hamartoma of the chest wall is a very rare benign chest wall tumour. It is sometimes classified as a non-neoplastic developmental anomaly rather than a tumour.
They typically present in neonates or infants 1-3.
Many present with a chest wall m...
Mesothelioma, in general, is an aggressive malignant tumour of the mesothelium. The overwhelming majority arise from the pleura, pleural mesothelioma, which this article will focus on.
Given the presence of the mesothelium in different parts of the body, mesothelioma can arise in various locati...
Metastases to the thymus are rare, although they are probably under reported due to lack of symptoms.
Varied primary tumours have been reported to metastasise to the thymus 1,2:
Metastatic axillary lymphadenopathy of unknown primary can be a very chellanging situation.
Usual potential sites include:
occult breast cancer: the incidence of an axillary lymph node manifestation from an occult primary breast cancer is low, ranging from 0.3-0.8% of all patients ...
Metastatic pulmonary calcification (MPC) is a form of pulmonary calcification where there is calcium deposition in normal lung pulmonary parenchyma.
It can occur in a variety of benign and malignant disorders such as:
chronic renal failure: considered commonest cause 5
Methotrexate lung disease is specific aetiological type of drug induced lung disease. It can occur due to administration of methorexate which is an antimetabolite, which is given for various reasons but commonly to treat rheumatoid arthritis. It is also given alone or in combination with other c...
In medical imaging literature, a Mickey Mouse appearance has been given to imaging features that depict that of Mickey Mouse when viewed from the front. It has been described in the following:
progressive supranuclear palsy 1
synonymously with a finger in glove sign
the flared ...
Microcystic honeycombing is an imaging descriptor on thoracic HRCT/CT which is typically given to denote extremely small cysts typically occurring in a sub pleural location on a background of interstitial lung disease. It is typically described in association with non specific interstitial pneu...
Microlithiasis merely means very small stones and may refer to:
The mid (or middle) zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends between the superior and inferior aspects of the hilum
Middle East Respiratory Syndrome coronavirus (MERS-CoV) infection is an uncommon viral infection (<1000 cases) with the first case reported in Saudi Arabia in 2012. It most commonly causes pneumonia and acute renal failure with a mortality rate of ~40%. MERS-CoV raises concern because of its sim...
Distribution of bronchiectasis can help in narrowing the differential diagnosis.
Middle lobe bronchiectasis is typically seen in:
non tuberculous mycobacterial infections
middle lobe syndrome in children
upper lobe bronchiectasis
The differential diagnosis for a middle mediastinal mass includes 1-3:
aneurysm, e.g. aortic, pulmonary artery, bronchial artery
foregut duplications cyst (e.g. oesophageal, bronchial)
primary/secondary cardiac tumour
The middle mediastinum is an artificial space of the mediastinum divided from the remainder of the extra-pleural intrathoracic cavity by arbitrary lines. It forms the largest component of the inferior mediastinum.
superiorly: superior mediastinum, divided by the thora...
Migrating pericardial cysts or wandering pericardial cysts are an unusual form of pericardial cysts. They are usually pedunculated and change in position on serial imaging but have all other imaging characteristics supportive of a pericardial or pleuro-pericardial cyst.
Getting a film with miliary nodules in the exam is one of the many exam set-pieces that can be prepared for.
The film goes up and after a couple of seconds pause, you need to start talking:
There are multiple tiny soft-tissue density nodules present throughout both lungs with...
The term miliary opacities refers to innumerable, small 1-4 mm pulmonary nodules scattered throughout the lungs. It is useful to divide these patients into those who are febrile and those who are not.
Additionally, some miliary opacities are very dense, narrowing the differential - see multiple...
Miliary sarcoidosis is a rare thoracic manifesation of sarcoidosis where there a numerous miliary like nodule scattered throughout the lungs. It is thought to represent less than1% of cases.
From the limited case reports available, there is some suggestion that this form may occu...
Miliary tuberculosis is an uncommon pulmonary manifestation of tuberculosis. It represents haematogeneous dissemination of uncontrolled tuberculous infection and carries a relatively poor prognosis.
It is seen both in primary and post-primary tuberculosis and may be associated with tuberculous ...
Minimal aortic injuries are traumatic aortic lesions that usually involve the intima and are recognised more frequently due to the use of high-resolution imaging.
Minimal aortic injuries account for 10-28% of all blunt traumatic aortic injuries 1,6,7. The proportion of this type o...
Minimally invasive adenocarcinoma of the lung is a relatively new category in the classification for adenocarcinoma of the lung. Lesions that fall into this category refer to small solitary adenocarcinomas < 3 cm with either pure lepidic growth or predominant lepidic growth with ≤ 5 mm of stroma...
Minimum intensity projection (MinIP) is a data visualization method that enables detection of low-density structures in a given volume. The algorithm uses all the data in a volume of interest to generate a single bidimensional image, in other words, its consists of projecting the voxel with the ...
A misplaced or malpositioned endotracheal tube a relatively common complication that is detected on post intubation radiographs.
if the ETT is too high it can rub against the vocal cords and cause cord trauma
if the ETT is too low it can selectively intubate the right or left ma...
Mitral annular calcification (MAC) refers to deposition of calcium (along with lipid) in the annular fibrosa of the mitral valve.
Annular calcification is seen in up to 35% of elderly patients. It is common in females over 65 years, in those with myxtomatous degeneration of the mi...