Isolated unilateral absence of the pulmonary artery (IUAPA) is the congenital absence of the left or right pulmonary artery. When found in combination with other congenital vascular abnormalities it is known as unilateral absence of the pulmonary artery (UAPA).
Isomerism is a term which in general means 'mirror-image'. It is used in the context of heterotaxy and is of two types:
Mirror image of the structures on the left side of the chest along the left-right axis of the body, i.e. patients with isomeri...
The juxtaphrenic peak sign, also known as diaphragmatic tenting or Kattan sign, refers to the peaked or tented appearance of a hemidiaphragm which can occur in the setting of lobar collapse. It is caused by retraction of the lower end of diaphragm at an inferior accessory fissure (most common 1)...
Kaposi sarcoma is a low-to-intermediate grade mesenchymal tumour that involves the lymphovascular system. The tumour can involve the pulmonary, gastrointestinal, cutaneous and musculoskeletal systems.
There are four recognised variants 1:
classic (chronic): multiple distal lower ext...
Kartagener syndrome is a subset of primary ciliary dyskinesia, an autosomal recessive condition characterised by an abnormal ciliary structure or function, leading to impaired mucociliary clearance.
The prevalence of primary ciliary dyskinesia is approximately 1 in 12,000-60,000 ...
Getting a film with Kerley lines 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 bilateral basal interstitial lines that extend to the pleural surface - these are septal (Ke...
The Kirklin sign refers to a deformity of the normal gastric bubble on an upright chest radiograph due to a mass lesion of the gastric cardia or fundus.
The differential for a Kirklin sign includes:
gastrointestinal stromal tumour (GIST...
Klebsiella pneumonia, also known as Friedländer pneumonia, refers to pneumonia resulting from an infection from the organism Klebsiella pneumoniae.
There tends to be a higher prevalence in older patients with alcoholism and debilitated hospitalised patients 3.
Knuckle sign refers to the abrupt tapering or cutoff of a pulmonary artery secondary to embolus. It is better visualised on CT pulmonary angiography scan than chest x-ray. This is an important ancillary finding in pulmonary embolism (PE), and often associated with the Fleischner sign of dilated ...
The Kveim Stilzbach skin test is a sensitive and specific test for sarcoidosis, requiring the intradermal injection of homogenized spleen or liver material from a patient with known sarcoidosis. In patients with sarcoidosis, a typical sarcoid granuloma will develop at the injection site within 4...
This article lists a series of labelled imaging anatomy cases by system and modality.
CT head: non-contrast axial
CT head: non-contrast coronal
CT head: non-contrast sagittal
CT head: angiogram axial
CT head: angiogram coronal
CT head: angiogram sagittal
MR head: T2 axial
Lady Windermere syndrome refers to a pattern of pulmonary Mycobacterium avium complex (MAC) infection seen typically in elderly white women who chronically suppress the normal cough reflex. A fastidious nature and a reticence to expectorate are believed to predispose such persons to infections w...
There are a number of lambda signs:
lambda sign of twin pregnancy
lambda sign of sarcoidosis
The lambda sign is seen on gallium-67 scans in the setting of thoracic sarcoidosis. Bilateral hilar and right paratracheal lymph nodes are typically involved which can resemble the Greek letter lambda (λ).
lambda sign of twin pregnancy
Lane-Hamilton syndrome (LHS) refers to the rare concurrent association of idiopathic pulmonary haemosiderosis and coeliac disease 1.
It is typically seen in children under the age of 15 but can occasionally be seen in adults.
History and etymology
It was originally described by ...
Langerhans cells are dendritic cells of monocyte-macrophage lineage, containing large granules called Birbeck granules. They are normally found in epithelial surfaces, lymph nodes and other organs, and can also be found elsewhere, particularly in association with Langerhans cell histiocytosis.
Langerhans cell histiocytosis (LCH) is a rare multi-system disease with a wide and heterogeneous clinical spectrum and variable extent of involvement.
Langerhans cell histiocytosis was previously known as histiocytosis X. The newer term is preferred as it's more descriptive of its...
Large-cell lung cancer is one of the histological types of non-small cell carcinomas of the lung.
It is thought to account for approximately 10% of bronchogenic carcinoma 1.
Patients present with dyspnea, chronic cough and haemoptysis.
Large cell neuroendocrine carcinoma (LCNEC) of the lung is classified as a subtype of large cell carcinoma of the lung. It is also classified as a pulmonary neuroendocrine tumour.
The incidence peaks around the sixth decade 6. There is an increased male predilection 7.
When a pleural effusion is large and unilateral, concern for an underlying abnormality should be raised. Causes include:
primary effusion lymphoma
Leadless cardiac pacemakers are a recently introduced type of cardiac conduction device. These pacemakers are self-contained right ventricular single-chamber pacemakers that are implanted percutaneously via a femoral approach 1-3. There are currently two leadless cardiac pacemakers on the market...
Leaky lung syndrome refers to a form of non-cardiogenic pulmonary oedema.
Pulmonary oedema due to increased capillary permeability.
Leaky lung syndrome is considered a mild form of a part of the spectrum of acute lung injury with ARDS at the other end of the...
Leflunomide induced acute interstitial pneumonia is a form of drug induced interstitial lung disease. The precipitation of radiological evidence of pulmonary infiltrates, clinical acute respiratory illness in the context of a good temporal relationship with commencement of the agent and no clear...
Left atrial appendage (LAA) closure devices are implantable cardiac devices which are placed in the left atrial appendage for stroke prevention in patients with atrial fibrillation who have contraindications to pharmacological anticoagulation. Depending on the device they may be inserted percuta...
Left atrial enlargement may result from many conditions, either congenital or acquired. It has some characteristic findings on a frontal chest radiograph. CT or MRI may also be used for diagnosis.
An enlarged left atrium can have many clinical implications, such as:
The left atrium is one of the four chambers of the heart. It receives oxygenated blood from the pulmonary circulation that is then delivered to the left ventricle and then into the systemic circulation.
The left atrium is grossly cuboidal, and like the right atrium has an appenda...
The left horizontal (or minor) fissure is an accessory fissure found in around 8% of individuals examined with CT 3. In a prospective study of 2,000 consecutive normal chest X-rays (AP and lateral), a definite left horizontal fissure was identified in 1.6% of the subjects 1.
The left lower lobe (LLL) is one of two lobes in the left lung. It is separated from the left upper lobe by the left oblique fissure and subdivided into four bronchopulmonary segments.
Location and structure
The LLL lies in the posterior and lower aspect of the left hemithorax a...
The left lower lobe anteromedial segment (or cardiac segment) is one of the bronchopulmonary segments of the left lower lobe. It is the most anteromedial of the segments within the base of the left upper lobe.
It is the equivalent segment merger of the anterior and medial segments of the right ...
The left main bronchus divides into the left lower lobe bronchus and the left upper lobe bronchus. It is one of the secondary lobar bronchi.
The left lower lobe bronchus is very short and divides immediately into the segmental bronchi. There are usually 10 individual segmental b...
Left lower lobe collapse has distinctive features, and can be readily identified on frontal chest radiographs, provided attention is paid to the normal cardiomediastinal contours. However, the shadow cast by the heart does make it more difficult to see than the right lower lobe collapse.
For a ...
The left lower lobe lateral or lateral basal segment is one of the four bronchopulmonary segments of the left lower lobe. It is the most inferolateral of the segments in the left lower lobe, below the superior segment.
The left lower lobe posterior or posterior basal segment is one of the four bronchopulmonary segments of the left lower lobe. It is the most inferoposterior of the segments in the left lower lobe, below the superior segment.
Due to its low and posterior position, pathology in...
The left lower lobe superior or apical segment is one of the four bronchopulmonary segments of the left lower lobe. It is the most apical of the segments in the left lower lobe, posterior to the upper aspect of the oblique fissure and apicoposterior segment of the left upper lobe.
The left lung is one of two lungs, located in the left hemithorax on the left of the heart and mediastinum.
There are a few differences between the two lungs:
The left lung is smaller in volume than the right lung, with a smaller transverse dimension (due to the heart on the left) but a large...
The trachea bifurcates into the right and left main bronchi at the level of the carina, supplying air to the right and left lungs respectively. Each main or primary bronchus enters the hilum of its lung and gives rise to secondary lobar bronchi, which further divide into tertiary segmental bronc...
When a central venous catheter that is supposed to project over the superior vena cava is abnormally located to the left of the mediastinum a limited differential of left paramediastinal catheter position should be considered 1:
located within a vein
left sided superior vena cava
The left paraspinal (also known as the paraspinous or paravertebral) line (or stripe) is a feature of frontal chest x-rays. It is formed by the interface between the left lung and the left posterior mediastinal soft tissues 1. It is more commonly seen than the right paraspinal line.
The left paratracheal stripe is formed by the interface of the medial pleural surface of the left upper lobe and left lateral border of the trachea and/or the fat adjacent 1 with air within each structure forming the outline. It may not be visible if the left upper lobe contacts the left subclav...
The left pulmonary artery (LPA) is one of the branches of the pulmonary trunk, branching at the level of the transthoracic plane of Ludwig. It is shorter than the right pulmonary artery and represents a direct posterior continuation of the pulmonary trunk. It arches posterosuperiorly over the su...
The left superior intercostal vein drains the left posterosuperior hemithorax and is considered to be part of the azygos venous system even though it does not directly drain into the azygos vein.
Origin and course
The left superior intercostal vein forms by the union of the 2nd...
The left upper lobe (LUL) is one of two lobes in the left lung. It is separated from the left lower lobe by the left oblique fissure and subdivided into four bronchopulmonary segments, two of which represent the lingula.
Location and structure
The left upper lobe lies in the upp...
The left upper lobe anterior segment is one of the four bronchopulmonary segments of the left upper lobe. It is the most anterior of the segments in the left upper lobe lying below and anterior to the apicoposterior segment and above the oblique fissure.
The left upper lobe apicoposterior segment is one of the bronchopulmonary segments of the left upper lobe. As its name suggests, it is the most apical and posterior of the segments within the left upper lobe and is supplied by the left apicoposterior segmental bronchus.
It is the equivalent seg...
The left main bronchus divides into the left upper lobe bronchus and the left lower lobe bronchus. It is one of the secondary lobar bronchi.
The left upper lobe bronchus is very short and divides immediately into the segmental bronchi. There are usually 10 individual segmental b...
Left upper lobe collapse has distinctive features but can be challenging to identify on chest radiographs by the uninitiated.
For a general discussion refer to the article on lobar collapse.
The left upper lobe collapses anteriorly becoming a thin sheet...
Getting a film with left upper lobe collapse in the exam is one of the many exam set-pieces that can be prepared for.
This frontal chest radiograph shows a hazy (or veil-like*) opacification of the left hemithorax that is associated with superior displacement left hilum and horizon...
The left upper lobe inferior lingular segment is one of the four bronchopulmonary segments of the left upper lobe. It lies below the superior lingular segment of the left upper lobe.
The left upper lobe superior lingular segment is one of the four bronchopulmonary segments of the left upper lobe. It lies below the apicoposterior and anterior segments of the left upper lobe.
The left ventricle is one of four heart chambers. It receives oxygenated blood from the left atrium and pumps it into the systemic circulation via the aorta.
The left ventricle is conical in shape with an anteroinferiorly projecting apex and is longer with thicker walls than the ...
Legionella pneumonia, also known as Legionnaires' disease, refers to pulmonary infection primarily with the organism Legionella pneumophila. It is sometimes classified as atypical pneumonia.
Legionella pneumonia tends to be more prevalent among immunocompromised patients. Legione...
Lepidic predominant adenocarcinoma (LPA) of the lung, formerly known as non-mucinous bronchoalveolar carcinoma, is a subtype of invasive adenocarcinoma of the lung characterised histologically when the lepidic component comprises the majority of the lesion.
In 2011, the Internation...
Leptospirosis results from infection of the zoonoses Leptospira sp. The condition can have multi-organ manifestations. Commonly affected organs include:
lung: pulmonary leptospirosis
liver: hepatic leptospirosis
central nervous system: CNS leptospirosis
skeletal muscle: muscular leptospirosi...
The lesser diaphragmatic apertures allow the passage of smaller structures from the thoracic cavity to abdominal cavity across the diaphragm. They are very much smaller than the other diaphragmatic apertures:
two in the right crus of the diaphragm: transmit greater and lesser right splanchnic n...
The ligamentum arteriosum (or arteriosus) is the small fibrous remnant of the fetal ductus arteriosum, located between and connecting the proximal left pulmonary artery and the undersurface of the junction of the aortic arch and descending aorta, at the aortic isthmus. The left recurrent larynge...
Light chain deposition disease (LCDD) is a rare disease.
It can affect multiple organ systems.
renal manifestations of light chain deposition disease - renal involvement is a constant feature, resulting in proteinuria with or without nephrotic syndrome and renal failure.
Pulmonary manifestations of light chain deposition disease are rare when considering the full disease spectrum of light chain deposition disease.
The light chains are secreted by a plasma clone and deposit in the alveolar walls, small airways, and vessels.
Lines and tubes are important components in chest radiographic evaluation.
Nasogastric (NG) tube
See: nasogastric tube positioning.
NG tube tip ≥10 cm distal to the gastro-oesophageal junction
i.e. below the left hemidiaphragm
insertion into trachea or bron...
Lingula (plural lingulae) can refer to a number of different anatomical structures:
lingula (sphenoid bone)
History and etymology
Lingula is the diminutive form of lingua, Latin for the tongue. Thus lingula is used for a small tongue-l...
The lingula is a combined term for the two lingular bronchopulmonary segments of the left upper lobe:
superior lingular segment
inferior lingular segment
The two lingular segments are the most anterior of the segments in the left upper lobe lying below the apicoposterior and anterior segments...
Lipoblastoma of the lung is a fat derived thoracic tumour.
They occur during infancy and early childhood. More than 90% of cases are diagnosed in children less than 3 years of age, with nearly 75% occurring before the age of 12 months
Lipoblastomas are rare soft-tissue...
Lipoid pneumonia can either result from aspiration of oily substances (exogenous lipoid pneumonia) or endogenous accumulation of lipid substances in the alveoli (endogenous lipoid pneumonia).
Most patients are asymptomatic and often discovered incidentally.
Lipomatosis is a condition where there is diffuse excessive fat deposition within the body. This can especially affect certain regions.
neck and upper region of trunk
lipomatous hypertrophy of the interatrial septum
lipomatous metaplasia of th...
Liquefactive necrosis is a form of necrosis where there is transformation of the tissue into a liquid viscous mass.
In liquefactive necrosis, the affected cell is completely digested by hydrolytic enzymes leading to a soft, circumscribed lesion which can consist of fluid with remains...
This is a basic article for medical students and other non-radiologists
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 negativ...
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, fibrinosuppurative 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.
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 that usually manifests with lymphadenopathy, fevers, erythema nodosum, and arthritis.
It is important to not confuse this syndrome with Löffler syndrome, as the names are quite similar but the condi...
Low attenuation lymphadenopathy suggests underlying necrosis and can be seen in:
metastatic carcinoma (or lymphoma)
infections (tuberculous or fungal)
inflammatory necrotic disorders (e.g. Kikuchi-Fujimoto disease)
low attenuation ly...
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 abscesses are circumscribed collections of pus within the lungs. They are often complicated to manage and difficult to treat and, in some cases, may be life-threatening.
As a result of the widespread availability of antibiotics, the incidence of lung abscesses has dramaticall...
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 a broad term referring to the main histological subtypes of primary lung malignancies that are mainly linked with inhaled carcinogens, with cigarette smoke being a key culprit.
This article will broadly discu...
Lung cancer associated with cystic airspaces, rather than a distinct disease, represents a spectrum of radiological patterns of tumour growth mainly characterised by lesions arising or abutting the walls of cystic airspaces. Attention to this pattern has been brought in the recent decades primar...
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...
The IASLC (International Association for the Study of Lung Cancer) 7th edition lung cancer staging system was proposed in 2010 and has now been updated and superseded by the 8th edition, published in 2016.
Small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) used to be staged di...
The IASLC (International Association for the Study of Lung Cancer) 8th edition lung cancer staging system was introduced in 2016 and supersedes the IASLC 7th edition.
Standard-of-care lung cancer staging ideally should be performed in a multidisciplinary meeting using the information provided ...
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 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" appearance
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 in 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.