Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

11,225 results found
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Artificial rupture of membranes

An artificial rupture of membranes (AROM) is a procedure that can be used for the induction of labour. Procedure  A sterile, plastic, thin hook is brushed against the membranes just inside the cervix (termed a membrane sweep) This causes the fetal head to move down against the cervix, usually ...
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Artificial urethral sphincters

Artificial urethral sphincters, also known as inflatable artificial sphincters and urinary control systems, are devices used for the treatment of urinary stress incontinence (e.g. due to pelvic floor dysfunction in female or prostate surgery in male) and are sometimes used in combination with a ...
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Aryepiglottic folds

The aryepiglottic folds are two ligamentomuscular structures within the supraglottic larynx that function to protect the airway when swallowing. Gross Anatomy Each aryepiglottic fold is comprised of the superior ligamentous edge of the quadrangular membrane and covering mucous membrane1, the e...
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Arytenoid cartilage

The arytenoid cartilages are paired hyaline cartilages that articulate with the sloping upper border of the lamina of the cricoid cartilage by the cricoarytenoid joint. This joint allows movement of the arytenoid cartilages, which is vital in approximating, tensing and relaxing the vocal folds. ...
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Asbestos

Asbestos is a set of six naturally occurring silicate minerals from mixture of calcium magnesium, iron, and sodium exploited commercially for their desirable physical properties, particularly their resistance to heat and burning. They all form thin elongated fibrous crystals, and can be manufact...
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Asbestos body

An asbestos body is a histological finding in interstitial lung disease that is suggestive of significant occupational asbestos exposure. They are usually identified following a parenchymal lung biopsy 3. Macrophage ingestion of the asbestos fibres triggers a fibrogenic response via the release...
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Asbestosis

Asbestosis refers to later development of diffuse interstitial fibrosis secondary to asbestos fibre inhalation and should not be confused with other asbestos related diseases. Epidemiology Asbestosis typically occurs 10-15 years following the commencement of exposure to asbestos and is dose re...
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Asbestos related benign pleural disease

Asbestos related benign pleural disease forms a large part of asbestos related lung changes. The spectrum comprises of: pleural effusions: benign-asbestos induced pleural effusions can be associated with functional impairment usually occur within 10 years of exposure but can also develop muc...
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Asbestos related diseases

Asbestos related disease, in particular affecting the lung, comprise of a broad spectrum of entities related to the inhalational exposure to asbestos fibres. They can be divided into benign and malignant changes 1-3. Benign pleural and parenchymal lung disease asbestos related benign pleural d...
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Ascariasis

Ascariasis is due to infection with the Ascaris lumbricoides adult worm, and typically presents with gastrointestinal or pulmonary symptoms, depending on the stage of development.   Epidemiology Ascaris lumbricoides is widely distributed in tropical and subtropical regions and in other humid a...
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Ascending aorta

The ascending aorta is the first part of the aorta, and begins at the aortic valve, located obliquely just to the left of the midline at the level of the the third intercostal space. It terminates as it exits the fibrous pericardium where it becomes the aortic arch, in the plane of Ludwig, a hor...
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Ascending aorta dilatation

Dilatation of the ascending aorta is a common finding in the elderly but unusual in younger patients. Pathology 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...
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Ascending aortic aneurysm

Ascending aortic aneurysms are the most common subtype of thoracic aortic aneurysms and may be true or false injuries.  Epidemiology Ascending aortic aneurysms represent 60% of thoracic aortic aneurysms.  Clinical presentation Typically ascending aortic aneurysms are an incidental finding an...
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Ascending cervical artery

The ascending cervical artery is 1 of the 4 branches of the thyrocervical trunk (off the first part of the subclavian artery). It is a small artery that ascends medial to the phrenic nerve on the prevertebral fascia. It contributes many small spinal branches into the intervertebral foramina of ...
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Ascending colon

The ascending colon is the second part of the large bowel. Gross anatomy The ascending colon is the continuation of the caecum superior to the ileocaecal valve. It is secondarily retroperitoneal, although it has its own mesentery in approximately 25% of patients and is 15 cm in length 1,2. Th...
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Ascending lumbar communicant vein

The ascending lumbar communicant vein is a communication between the left ascending lumbar vein and the left renal vein. Because of its retroperitoneal location, when dilated, it may be mistaken for a lymph node on non-contrast studies with thick collimation. The image shows the left renal vein...
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Ascending lumbar vein

The ascending lumbar vein is a paired structure which forms a part of the venous drainage of the lumbar vertebral column. Summary location: near midline on the side of the vertebral column in the lumbar region origin and termination: continuation of the lateral sacral veins; joins the subcost...
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Ascending pharyngeal artery

The ascending pharyngeal artery, the smallest branch of the external carotid artery, is a long, slender vessel, deeply seated in the neck, beneath the other branches of the external carotid and under the stylopharyngeus. Summary origin: a branch of the external carotid artery course: vertical...
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Ascending ramus of the lateral sulcus

Ascending ramus of the lateral sulcus, is located at the anterior end of the lateral sulcus (sylvian fissure), just posterior to the anterior ramus, and passes superiorly into the inferior frontal gyrus separating the pars triangularis from the pars opercularis of the frontal operculum.  Termin...
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Ascending transtentorial herniation

Ascending transtentorial herniation is a situation where space-occupying lesions in the posterior cranial fossa cause superior displacement of superior parts of the cerebellum through the tentorial notch.  Clinical presentation nausea and/or vomiting  rapid progression toward a decreased leve...
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Ascites

Ascites is defined as an abnormal amount of intraperitoneal fluid. Clinical presentation Patients with a large volume of ascites can present with abdominal distension (which may be painful), nausea, vomiting, dyspnoea and peripheral oedema 7, 9. Pathology Ascitic fluid is traditionally chara...
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Aseptic loosening of hip joint replacements

Aseptic loosening is considered relatively common complication of hip joint replacements. It is usually considered a long-term complication and is often considered as the most common complication 3. Pathology Aseptic loosening can occur as a result of inadequate initial fixation, mechanical lo...
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Asherman syndrome

Asherman syndrome, also known as uterine synechiae, is a condition characterised by the formation of intrauterine adhesions, which are usually sequela from injury to the endometrium, and is often associated with infertility. Epidemiology There is a tendency for the condition to develop soon af...
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ASIA impairment scale for spinal injury

The American Spinal Injury Association (ASIA) was developed by the American Spinal Injury Association in 2006, and at the time of writing (July 2016), remains the most widely used scale. This scale is part of the ASIA spinal cord injury classification. It divides spinal cord injuries into 5 cat...
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Askin tumour

The original description of the Askin tumour (by Askin and Rosai in 1979 1), and many studies following it have led to a great deal of confusion. Until recently it has been considered a separate entity or as a type of peripheral primitive neuroectodermal tumour, usually of the chest wall. Recen...
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As low as reasonably achievable (ALARA)

As low as reasonably achievable (ALARA) is a principle of radioprotection stating that whenever ionizing radiation has to be applied to humans, animals or materials exposure should be as low as reasonably achievable. It is fundamental to the principles of radiation protection.
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Aspergilloma

Aspergillomas are mass-like fungus balls that are typically composed of Aspergillus fumigatus, and are a non-invasive form of pulmonary aspergillosis. It usually falls under the subgroup chronic pulmonary aspergillosis. Terminology Although the term mycetoma is frequently used to describe thes...
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Aspergillus

Aspergillus is a fungal genus consisting of approximately 180 species.  It is a ubiquitous fungus found frequently in urban areas especially in decomposing organic matter or water damaged walls and ceilings. Only a few Aspergillus species are associated with human disease.  Aspergillus species ...
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Aspergillus clavatus

Aspergillus clavatus is one of the species of Aspergillus that can cause pathology in humans. It is allergenic and causes a hypersensitivity pneumonitis called malt-workers lung. See also Aspergillus Aspergillus fumigatus Aspergillus flavus Aspergillus clavatus
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Aspergillus flavus

Aspergillus flavus is a fungus and one of the species of Aspergillus that is common in the environment and responsible for pathology in humans. It is the second most common cause of pulmonary aspergillosis (after Aspergillus fumigatus) and can additionally cause corneal, otomycotic, and nasoorb...
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Aspergillus fumigatus

Aspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in immuno-compromised individuals. A. fumigatus is a saprotroph (an organism that gets its energy from non-living organic matter) that is widespread in nature, typicall...
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Asphyxiating thoracic dysplasia

Asphyxiating thoracic dysplasia, also known as Jeune syndrome, is a type of rare short limb skeletal dysplasia, which is primarily characterised by a constricted long narrow thoracic cavity, cystic renal dysplasia and characteristic skeletal features. It is also sometimes classified as one of th...
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Aspiration bronchiolitis

Aspiration bronchiolitis, or diffuse aspiration bronchiolitis, is a condition characterised by a chronic inflammation of bronchioles caused by recurrent aspiration of foreign particles. Clinical presentation The onset of aspiration bronchiolitis can be more insidious than aspiration pneumonia,...
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Aspiration pneumonia

Aspiration pneumonia is caused by a direct chemical insult due to the entry of a foreign substance, solid or liquid, into the respiratory tract. Clinical presentation Aspiration may be clinically silent, or it may present with dyspnoea, cough, or fever. The clinical and radiographic features d...
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Asplenia

Asplenia refers to absence of the spleen thereby leading to deficient splenic function. Epidemiology Seen in 3% of neonates with structural heart disease and in 30% of patients who die from cardiac malposition. The male-to-female ratio is 2:1. Pathology Asplenia can be classified into two  t...
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Asplenia syndrome

Asplenia syndrome (also known as right isomerism or Ivemark syndrome) is a type of heterotaxy syndrome. Epidemiology There is an increased male predilection. Asplenia syndrome is usually diagnosed in neonates.4 Clinical manifestation In contrast to polysplenia syndrome, most patients die bef...
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Assessment of thyroid lesions (general)

Assessment of thyroid lesions is commonly encountered in radiological practice. Thyroid mass hyperplastic / colloid nodule / nodular hyperplasia: 85% adenoma follicular: 5% others: rare carcinoma papillary: 60-80% of carcinomas follicular: 10-20% medullary: 5% anaplastic: 1-2% thyroi...
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Assessment of thyroid lesions (ultrasound)

Ultrasound along with nuclear medicine, is an important modality for assessment of thyroid lesions, and it is also frequently used to guide biopsy. Diagnostic criteria for thyroid nodules continue to evolve with improving ultrasound technology. Radiographic features Ultrasound Calcification ...
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Asterion

The asterion is the junction on the side of the posteroinferior calvarium where three sutures meet: parietomastoid suture occipitomastoid suture lambdoid suture It is located at the posterior end of the parietotemporal suture, whereas the pterion is located at the anterior end. It is one of...
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Asteroid hyalosis

Asteroid hyalosis is a degenerative condition of the eye where there is an accumulation of calcium soaps in the vitreous chamber. Epidemiology The prevalence increases with age from 0.2% in 43-54-year-olds to 2.9% in 75-86-year-olds. The overall prevalence is 1.2%. It is more commonly unilater...
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Asthma

Asthma is a relatively common condition that is characterised by at least partially reversible inflammation of the airways and reversible airway obstruction due to airway hyperreactivity. It can be acute, subacute or chronic. Epidemiology Asthma is one of the most common chronic diseases in th...
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Asthma (summary)

Asthma is a heterogeneous disease, usually characterised by chronic airway inflammation and airway hyperreactivity. It is defined by two main features 1: a history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that vary over time and in intensity, AND v...
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Asthmatic pulmonary eosinophilia

Asthmatic pulmonary eosinophilia is a form of pulmonary eosinophilia which is commonly attributed to Aspergillus fumigatus. Although many cases have not shown any allergen. Radiographic features Plain radiograph - patterns normal hyperinflation (in acute attacks or chronic severe asthma) fe...
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Astroblastoma

Astroblastomas are rare glial tumours usually found in the cerebral hemispheres of young adults and children.  Epidemiology They occur at all ages range from early childhood to 6th decade but are most commonly seen in children, adolescents, and young adults with a mean age between 10-30 years ...
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Astrocytes

Astrocytes are cells of the central nervous system which act as both physical and physiological support for the neurones that are embedded between them. They are particularly abundant in the grey matter, where they are the most abundant glial cells 1. They are highly branched and contribute to ...
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Astrocytic tumours

Astrocytic tumours are primary central nervous system tumours that either arises from astrocytes or appear similar to astrocytes on histology having arisen from precursor cells. They are the most common tumours arising from glial cells. They can be divided into those that are diffuse in growth ...
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Asymmetrical density in mammography

Asymmetrical mammographic density is a mammographic morphological descriptor. It is given when there is increased density in one of the breasts, on either one or both standard mammographic views but without evidence of a discrete mass. An asymmetrical density can be further characterised as: ma...
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Asymmetrical intrauterine growth restriction

Asymmetrical intrauterine growth restriction is a type of intrauterine growth restriction (IUGR) where some fetal biometric parameters are disproportionately lower than others, as well as falling under the 10th percentile. The parameter classically affected is the abdominal circumference (AC). ...
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Asymmetrically large jugular bulb

Asymmetrically large jugular bulbs are entirely normal and asymptomatic; its only significance is to distinguish it from pathology. The size of the jugular bulbs is variable, with the right side being significantly larger than the left in two-thirds of people. A normal but large bulb will have...
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Asymmetric fatty bone marrow of the petrous apex

Asymmetric pneumatisation of petrous apex results in asymmetric fatty bone marrow within the petrous apex. It is a common incidental finding on brain and skull base MRI. Clinical presentation Asymptomatic. Pathology Asymmetric pneumatisation of the petrous apex results in the presence of bon...
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Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID)

Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID) is a triad of congenital cerebral anomalies. Radiographic features markedly asymmetric enlargement of the lateral ventricles may be the initial finding on routine fetal morphology ultrasound. inter...
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Asymmetry in breast size

Asymmetry in breast size can arise from a number of factors. Pathology Breasts are rarely absolutely the same size or volume. Normal variation is common. Most females have slight discrepancies in breast size. Asymmetric progressive breast enlargement is unusual but known. The role of the breas...
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ATA guidelines for assessment of thyroid nodules

The American Thyroid Association (ATA) guidelines for assessment of thyroid nodules are meant to improve inter- and intra-reader consistency during assessment of thyroid nodules on ultrasound, and to facilitate communication with referring endocrinologists. The 2015 guidelines stress the import...
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Ataxia telangiectasia

Ataxia telangiectasia is a rare multisystem disorder which carries an autosomal recessive inheritance, sometimes classified as a phakomatosis. It is characterised by multiple telangiectasias, cerebellar ataxia, pulmonary infections and immunodeficiency.  On brain imaging, it usually demonstrate...
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Atelectasis (summary)

Atelectasis describes loss of lung volume secondary to collapse. It has many causes, the root of which is bronchial obstruction with absorption of distal gas. Atelectasis may be subsegmental, segmental, lobar, or involve the entire lung.  Reference article This is a summary article; read more ...
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Atelencephaly

Atelencephaly (also termed atelencephalic microcephaly) is a rare and extreme disorder with only a handful of published cases. In this anomaly, the derivatives of the telencephalon are absent or dysplastic, while more caudal structures are normal or mildly deformed. It falls under the aprosencep...
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Atelosteogenesis

Atelosteogenesis (AO) refers to a group of lethal skeletal dysplasias. Pathology Sub types atelosteogenesis type I atelosteogenesis type II atelosteogenesis type III 4
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Athletic pubalgia

Athletic pubalgia refers to pain around the pubic symphysis and can have different causes, including what has become known as sports hernia or sportman's hernia and osteitis pubis. Athletic pubalgia is a clinical syndrome of chronic lower pelvic and groin pain, usually encountered in athletes. ...
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Atlanto-axial articulation

The atlanto-axial articulation is a complex of three synovial joints, which join the atlas (C1) to the axis (C2). Gross anatomy Articulations paired lateral atlanto-axial joints: classified as planar-type joint between the lateral masses of C1 and C2, though somewhat more complex in shape wit...
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Atlanto-axial subluxation

Atlanto-axial subluxation is a disorder of C1-C2 causing impairment in rotation of the neck. The anterior facet of C1 is fixed on the facet of C2. It may be associated with dislocation of the lateral mass of C1 on C2. Pathology Aetiology congenital os odontoideum Down syndrome (20%) Morqui...
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Atlantodental interval

The atlantodental interval (ADI), as the name suggests, is the horizontal distance between the anterior arch of the atlas and the dens of the axis, used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis. It is the distance (in mm) between the posteri...
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Atlanto-occipital articulation

The atlanto-occipital articulation is comprised of a pair of condyloid synovial joints that connect the occiput (C0) to the first cervical vertebra (atlas/C1). Gross anatomy Articulations Each joint is comprised of two concave articular surfaces on the superior aspect of the lateral mass of a...
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Atlanto-occipital assimilation

Atlanto-occipital assimilation is the fusion of the atlas (C1) to the occiput and is one of the transitional vertebrae.  Epidemiology Atlanto-occipital assimilation occurs in approximately 0.5% (range 0.25-1%) of the population 2-4.  Clinical presentation Atlanto-occipital is typically asymp...
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Atlanto-occipital dissociation injuries

Atlanto-occipital dissociation (AOD) injuries are severe and include both atlanto-occipital dislocations and atlanto-occipital subluxations. Pathology The tectorial membrane and alar ligaments provide most of the stability to the atlanto-occipital joint, and injury to these ligaments results i...
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Atlas (C1)

The atlas is the first cervical vertebra, commonly called C1. It is an atypical cervical vertebra with unique features. It articulates with the dens of the axis and the occiput, respectively allowing rotation of the head, and flexion, extension and lateral flexion of the head.  Unlike the rest o...
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Atoll sign

The atoll sign in radiology can refer to: reverse halo sign (atoll in thoracic CT) atoll sign in liver MRI: suggestive of an inflammatory hepatic adenoma
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Atoll sign (liver MRI)

The atoll sign in hepatic imaging has been described when a liver lesion shows a peripheral rim of high T2 signal intensity with the centre of the lesion appearing isointense to the background of non-cirrhotic liver on T2WI mimicking an atoll. It is considered a characteristic sign of an inflamm...
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Atresia

Atresia refers to a situation where there is underdevelopment of a structure with very rudimentary remnant tissues. This contrasts with an agenesis meaning there is no development of the structure as all. The term atresia is often used with hollow structures such as a bronchus or intestine.  Fo...
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Atretic parietal cephalocele

Atretic parietal cephaloceles (APC), also known as atretic cephaloceles, are small subscalp lesions that consist of dura, fibrous tissue, and dysplastic brain tissue. Epidemiology Common presentation in infants and young children.  Clinical presentation Palpable midline parietal soft tissue ...
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Atrial escape

Atrial escape refers to a chest x-ray sign of massive left atrial enlargement and is an exaggerated version of the double density sign.   Normally, the right border of the left atrium is not visible. As it enlarges it forms a distinct border projecting through the right heart shadow, medial to ...
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Atrial-oesophageal fistula

Atrio-oesophageal fistulas are rare pathological connections between the left atrium and the oesophagus.  Clinical presentation The presentation is non-specific. Patients may complain of fever, malaise, and/or dysphagia, or present with neurological symptoms 3.  Pathology The chief cause of ...
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Atrial septal defect

Atrial septal defects (ASDs) are the second most common congenital heart defect after ventricular septal defects and the most common to become symptomatic in adulthood. They are characterised by an abnormal opening in the atrial septum allowing communication between the right and left atria. Du...
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Atrioventricular septal defect

Atrioventricular septal defects (AVSDs), also known as atrioventricular canal defects or endocardial cushion defects, comprise of a relatively wide range of defects involving the atrial septum, ventricular septum and one or both of the tricuspid or mitral valve. They can represent 2-7% of congen...
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Atrophic gastritis

Atrophic gastritis is a chronic condition of autoimmune and non-autoimmune aetiology.  Pathology Two types of atrophic gastritis have been described 1-3: type A: autoimmune gastric body and fundus atrophy secondary to antiparietal cell antibodies decreased secretion of acid and intrinsic fa...
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Attenuation

Attenuation is the reduction in power and intensity of sound waves as they travel through tissue.
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Attenuation coefficient

The attenuation coefficient is quantified as the measure of how easily a material can be penetrated by an x-ray beam. It quantifies how much the beam is "attenuated" (i.e. weakened) by the material it is passing through.
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Atypical adenomatous hyperplasia of the lung

Atypical adenomatous hyperplasia (AAH) of the lung is a putative precursor lesion of adenocarcinoma of the lung. This entity replaces part of a spectrum of the previous bronchoalveolar carcinoma. It is defined as a peripheral focal proliferation of atypical cuboidal or columnar epithelial cells ...
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Atypical callosal dysgenesis

Atypical callosal dysgenesis is a term used to denote an unusual pattern of dysgenesis of the corpus callosum. The development of the corpus callosum occurs between the 12th and 16-20th weeks of gestation 2-3. It begins with the genu and then continues posteriorly along the body to the splenium...
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Atypical cervical vertebrae

Of the cervical vertebrae, the atlas (C1), axis (C2) and vertebra prominens (C7) are considered atypical cervical vertebrae. The atlas (C1) lacks a body or spinous process. It has an anterior and posterior arches with lateral masses. Its superior articular surfaces articulate with the occiput a...
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Atypical choroid plexus papilloma

Atypical choroid plexus papillomas are WHO grade II tumours derived from choroid plexus epithelium with intermediate clinical and pathological features between the much more common, and more indolent, WHO grade I choroid plexus papilloma and the more aggressive WHO III choroid plexus carcinoma. ...
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Atypical ductal hyperplasia

Atypical ductal hyperplasia (ADH) is a histologically borderline lesion that has some, but not all the features of ductal carcinoma in situ (DCIS). Sometimes the distinction between ADH and DCIS is simply on the basis of the number of ducts involved.  Pathology Atypical ductal hyperplasia is a...
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Atypical ectopic pregnancy

Atypical ectopic pregnancy generally refers to an ectopic pregnancy which occurs outside the fallopian tube. Locations include: interstitial ectopic: 3% (often also termed cornual ectopic), also essentially a type of tubal ectopic cornual ectopic (<1%) ovarian ectopic: 0.5-1% (ovarian pregna...
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Atypical lobular hyperplasia

Atypical lobular hyperplasia (ALH) is a pre-malignant lesion of the breast which falls at the milder end of the spectrum of lobular neoplasia. It is therefore considered a part of borderline breast disease.  Clinical presentation It is usually asymptomatic and mammographically occult and is in...
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Atypical lumbar vertebrae

Of the five lumbar vertebrae, L5 is considered atypical due to its shape. The remaining lumbar vertebrae are largely typical. For a basic anatomic description of the structure a generic vertebra, see vertebrae.
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Atypical meningioma

Atypical meningioma refers to a more aggressive form of meningioma and denotes a WHO grade II tumour (along with two histological variants, clear cell meningioma and chordoid meningioma). Atypical meningiomas account for 20-30% of all meningiomas 1,3.  It should be noted that epidemiology, clin...
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Atypical pneumonia

Atypical pneumonia refers to the radiological pattern associated with patchy inflammatory changes, often confined to the pulmonary interstitium, most commonly associated with atypical bacterial aetiologies such as Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophilia. Viral...
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Atypical ribs

Owing to their features, the first, eleventh and twelfth ribs are considered atypical ribs. Of all ribs, the first is the strongest, broadest and most curved. Ribs eleven and twelve are unique, among other reasons, by not being attached to the sternum.
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Atypical small acinar proliferation

Atypical small acinar proliferations (ASAP) are premalignant lesions of the prostate, which can be found in as many as 5% of prostate biopsies. They are suspicious glands without adequate histologic atypia to establish a definitive diagnosis of prostate cancer. Some studies showed that there is ...
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Atypical teratoid/rhabdoid tumour

Atypical teratoid/rhabdoid tumours (AT/RTs) are an uncommon WHO Grade IV tumour, which in the vast majority of cases occurs in young children less than two years of age. It most frequently presents as a posterior fossa mass.  AT/RTs were until relatively recently classed as medulloblastomas, al...
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Atypical thoracic vertebrae

T1 and T9 to T12 are considered atypical vertebrae. T1 bears some resemblance to low cervical vertebrae. T9 has no inferior demifacet. T10 often, but not always, shares features with T11 and T12.  For a basic anatomic description of the structure a generic vertebra, see vertebrae.
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Aubergine sign (penis)

The aubergine sign (also known as egg-plant sign or deformity) is a clinical sign of a fractured penis. Haemorrhage beyond the tunica albuginea produces swelling and bruising of the penis simulating the appearance of an aubergine.  
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Auditory brainstem response tracing (mnemonic)

This mnemonic helps when remembering the ascending order of structures that corresponds to each waveform in an auditory brainstem response (ABR) tracing: E COLI Mnemonic E: eighth nerve action potential (wave I) C: cochlear nucleus (wave II) O: olivary complex (superior) (wave III) L: late...
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Aunt Minnie

The term Aunt Minnie is radiological shorthand for a lesion/finding which has characteristic appearances and cannot, within reason, be anything but one thing. History and etymology The term was coined by Ed Neuhauser, Chief of Radiology at Boston Children’s Hospital, and popularised by Ben Fel...

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