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.

11,982 results found
Article

Alberta stroke program early CT score (ASPECTS)

The Alberta stroke programme early CT score (ASPECTS) 1 is a 10-point quantitative topographic CT scan score used in patients with middle cerebral artery stroke. It has also been adapted for the posterior circulation (see below).  Scoring system Segmental assessment of the MCA vascular territo...
Article

Albert Salomon

Albert Salomon (1883-1976), a German surgeon, was the first physician to study x-rays of breast tissue. Early life to be completed Development of mammography Salomon worked at the Royal Surgical University Clinic in Berlin and from about 1913 x-rayed 3000 breast specimens obtained from the ...
Article

Albert Soiland

Albert Soiland (1873-1946), was a key figure in the establishment of radiology as an independent medical specialty in the United States. He is most famously remembered for his crucial role in the founding of the American College of Radiology. He was also a pioneering radiotherapist. Early life ...
Article

Alexander disease

Alexander disease (AD), also known as fibrinoid leukodystrophy, is a rare fatal leukodystrophy, which usually becomes clinically evident in the infantile period, although neonatal, juvenile and even adult variants are recognised. As with many other diseases with variable age of presentation, the...
Article

Aliasing artifact (CT)

Aliasing artifact, otherwise known as undersampling, in CT refers to an error in the accuracy proponent of analogue to digital converter (ADC) during image digitisation.  Image digitisation has three distinct steps: scanning, sampling, and quantization.  When sampling, the brightness of each p...
Article

Aliasing in MRI

Aliasing in MRI, also known as wrap-around, is a frequently encountered MRI artifact that occurs when the field of view (FOV) is smaller than the body part being imaged. The part of the body that lies beyond the edge of the FOV is projected onto the other side of the image. This can be correcte...
Article

Alien limb syndrome

Alien limb syndrome is a rare neurological phenomenon in which a patient has the impression that their limb does not belong to them and is controlled by some external force 1.  It can occur in a number of neurodegenerative diseases, typically those with cortical involvement, including: cortico...
Article

All-access pass to online courses

All-access pass to online courses are available to institutions who can purchase access to all Radiopaedia.org online courses for a flat per-user fee. You can purchase all-access passes from your verified institution's page or directly from the all-access pass page. Find out more. 
Article

Allan Macleod Cormack

Allan M Cormack (1924-1998) was a South African physicist who was instrumental in the development of the CT scanner. Early life Allan Macleod Cormack graduated in physics from Cape Town University in 1944 and was subsequently a doctoral student at Cambridge University where he worked with Otto...
Article

Allantoic cyst

Allantoic cysts are a type of true cyst of the umbilical cord. Pathology The allantois forms from the part of the fetal yolk sac that eventually becomes the primitive hindgut (the cloaca). The cloaca divides into the hindgut posteriorly and the urogenital sinus anteriorly. The allantois remain...
Article

Allelic heterogeneity

Allelic heterogeneity is a genetics term referring to same gene mutations resulting in different phenotypes 1. An example of a condition demonstrating allelic heterogeneity is Joubert syndrome and related disorders. 
Article

Allen and Ferguson classification of subaxial cervical spine injuries

Allen and Ferguson classification is used for research purposes to classify subaxial spine injuries. It is based ofn the mechanism of injury and position of the neck during injury. This classification was proposed by Allen and Ferguson in 19823 and at the time of writing (July 2016) remains the ...
Article

Allergic bronchopulmonary aspergillosis

Allergic bronchopulmonary aspergillosis (ABPA) is at the mild end of the spectrum of disease caused by pulmonary aspergillosis and can be classified as an eosinophilic lung disease 2-4. Epidemiology This entity is most commonly encountered in patients with longstanding asthma, and only occasio...
Article

Allergic fungal sinusitis

Allergic fungal sinusitis is the most common form of fungal sinusitis and is common in warm and humid climates. On imaging, it usually presents as opacification and expansion of multiple paranasal sinuses, unilaterally or bilaterally, with content that is centrally hyperdense on CT. MRI shows T2...
Article

Allgrove syndrome

Allgrove syndrome (also known as triple A syndrome) is an autosomal recessive condition that consists of three main findings: achalasia alacrima ACTH insensitivity
Article

Allodynia

Allodynia refers to pain due to a stimulus which does not normally provoke pain. Temperature or physical stimuli can provoke allodynia, and it often occurs after injury to a site. Etymology The word allodynia is derived from the Greek words άλλος (állos) meaning "other" and οδύνη (odýni) meani...
Article

All-trans retinoic acid syndrome

All-trans retinoic acid (ATRA) syndrome (more recently known as differentiation syndrome (DS)8) is a condition that can occur with patients with acute promyelocytic leukaemia who are on therapeutic all-trans-retinoic acid (ATRA). All-trans-retinoic acid (ATRA) is a normal constituent of plasma....
Article

Alobar holoprosencephaly

Alobar holoprosencephaly is a subtype of holoprosencephaly (HPE), and is the most severe of the classical three subtypes, with both semilobar and lobar holoprosencephaly having less severe clinical manifestations. For a general discussion of epidemiology, clinical presentation, and pathology, p...
Article

Alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin (A1AT) deficiency is a hereditary metabolic disorder and is the most common genetic cause of emphysema and metabolic liver disease in children. It results in the unopposed action of neutrophil elastase and subsequent severe basal pan lobular emphysema and respiratory symptoms...
Article

Alpha angle

Alpha angle can refer to two different musculoskeletal measurements: alpha angle (developmental dysplasia of the hip) alpha angle (femoroacetabular impingement)
Article

Alpha angle (developmental dysplasia of the hip)

The alpha angle is a measurement used in the ultrasonographic assessment of developmental dysplasia of the hip (DDH). The angle is formed by the acetabular roof to the vertical cortex of the ilium and thus reflects the depth of the bony acetabular roof. This is a similar measurement to the acet...
Article

Alpha decay

All nuclei with the atomic number Z>82, are considered unstable. These are considered “neutron-rich” and undergo the decay process by emitting a particle containing two neutrons and two protons. Alpha decay is the process in which an alpha particle (containing two neutrons and two protons) is e...
Article

Alpha thalassemia/mental retardation syndrome X-linked (ATRX)

Alpha-thalassemia/mental retardation syndrome X-linked (ATRX) is an important genomic marker of gliomas. Loss/mutation of ATRX is almost never seen in patients with 1p/19q co-deletion (i.e. they are essentially mutually exclusive). Oligodendrogliomas will, therefore, have intact ATRX and 1p19q c...
Article

Alport syndrome

Alport syndrome is an X-linked dominant disease characterised by progressive sensorineural hearing loss, renal disease and, at times, ocular lesions. Clinical presentation haematuria sensorineural hearing loss: typically high frequency 2 ocular abnormalities  anterior lenticonus: most commo...
Article

Altered breast density between two mammograms

Mammographic screening detects early breast cancers and thereby reduces potential mortality. However, its sensitivity is inversely related to breast density 1.  Altered density between two mammograms can arise in a number of situations: Affecting both breasts: interval commencement/cessation ...
Article

Alternating radiolucent and radiodense metaphyseal lines

Alternating radiolucent and radiodense metaphyseal lines can be seen with a number of conditions and the differential diagnosis is wide: growth arrest lines bisphosphonate therapy rickets: especially those on prolonged treatment, e.g. vitamin D dependent rickets osteopetrosis chemotherapy ...
Article

Alternatives (multiple choice questions)

Alternatives are part of multiple choice questions, comprising the options from which an examinee must choose the correct answer.  Each multiple choice question should have, ideally, 5 alternatives, one of which is the correct answer (the "key"). In some instances, 5 options are not appropriate...
Article

Alvarado score

The Alvarado score is a clinical decision rule and predictor of the likelihood of acute appendicitis: right lower quadrant tenderness (+2) elevated temperature (37.3°C or 99.1°F) (+1) rebound tenderness (+1) migration of pain to the right lower quadrant (+1) anorexia (+1) nausea or vomitin...
Article

Alveolar rhabdomyosarcoma

Alveolar rhabdomyosarcomas are a type of rhabdomyosarcoma and account for 20-40% of all rhabdomyosarcomas 1-2. Epidemiology Unlike embryonal rhabdomyosarcomas, which are more common, these tumours occur in slightly older individuals, typically 10-25 years of age 1.  Pathology Location Altho...
Article

Alveolar sarcoidosis

Alveolar sarcoidosis is an atypical pulmonary manifestation of sarcoidosis.  Epidemiology This appearance may be apparent in approximately 4% of those with pulmonary sarcoidosis on plain film 1 and up to 15% on CT 2. Pathology This appearance is thought to result from the aggregation of a va...
Article

Alveolar soft part sarcoma

Alveolar soft part sarcomas are rare, highly vascular, deep soft tissue malignancy that is classically seen in the lower extremities of young adults. They account for <1% of all soft tissue sarcomas. Epidemiology There is a slight female predilection in patients less than 30 years old 1. Path...
Article

Alveoli

The alveoli are tiny hollow air sacs that comprise the basic unit of respiration. Gross Anatomy Alveoli are found within the lung parenchyma and are found at the terminal ends of the respiratory tree, clustered around alveolar sacs and alveolar ducts.  Each alveolus is approximately 0.2 mm in ...
Article

Alzheimer disease

Alzheimer disease (AD) is a common neurodegenerative disease, responsible for 60-80% of all dementias, and imposing a significant burden on developed nations. It is the result of accumulation and deposition of cerebral amyloid-β (Aβ) and is the most common cerebral amyloid deposition disease.  ...
Article

Alzheimer type I glia

Alzheimer type I glia are a type of glial cell. They are large multinucleated astrocytes encountered in glial tumours and progressive multifocal leukoencephalopathy (PML) 1. 
Article

Alzheimer type II glia

Alzheimer type II glia are a type of glial cell. They are a pathological reactive astrocyte seen in the brain, unrelated to Alzheimer disease. They are seen most frequently in Wilson disease, but also in other systemic metabolic disorders, particularly those with elevated ammonia levels, typical...
Article

Amastia

Amastia is a rare congenital condition characterised by the absence of breast tissue, nipple and areola. This may occur unilaterally or bilaterally. Pathology During embryological development, breasts first appear as ectoderm ridges during the 6th week of gestation. This ridge grows thicker an...
Article

Amaurosis fugax

Amaurosis fugax is the transient monocular loss of vision, normally lasting a few seconds to a few minutes, secondary to vascular ischaemia or insufficiency.  Epidemiology It has an incidence of 50,000 per year in the United States.  Clinical presentation Patients present with transient mono...
Article

Amazia

Amazia is a rare congenital condition defined by the absence of glandular parenchyma in either one or both of the breasts and a normal nipple and areola complex.  Epidemiology This is a very rare entity and the true prevalence is not known. Although there are strict definition criteria, the di...
Article

Ambient cistern

The ambient cistern is part of the subarachnoid cisterns, filled with CSF. Gross anatomy The ambient cistern is a thin, sheet-like extension of the quadrigeminal cistern that extends laterally surrounding around the midbrain and posterior to the thalami. It acts as the connection between the q...
Article

Amelia

Amelia refers to a skeletal dysplasia characterised by the complete absence of upper or lower extremity or all four limbs. It may be associated with other congenital anomalies, i.e. omphalocoele and diaphragmatic hernias 3. Epidemiology Amelia is a very rare congenital anomalies with incidence...
Article

Ameloblastic fibroma

Ameloblastic fibromas appear as unilocular lucent mandibular lesions, most frequently in the posterior mandible, and are usually associated with impacted teeth, centred on the unerupted crown. They, therefore, appear very similar to unilocular ameloblastomas. They are composed of enamel and embr...
Article

Ameloblastic fibro-odontoma

Ameloblastic fibro-odontoma (AFO) is a rare benign mixed odontogenic tumour that usually arises in the maxilla and mandible. According to the 2005 WHO classification of odontogenic tumours, it is defined as a benign tumour that resembles ameloblastic fibroma but contains enamel and dentin. Epid...
Article

Ameloblastoma

Ameloblastomas are locally aggressive benign tumours that arise from the mandible, or, less commonly, from the maxilla. Usually present as a slowly but continuously growing hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life, which can be severely disfiguring if...
Article

American Academy of Orthopedic Surgeons classification of periprosthetic hip fractures

The American Academy of Orthopedic Surgeons classification of periprosthetic hip fractures divides the femur into three separate regions: level I: proximal femur distally to the lower extent of the lesser trochanter  level II: 10 cm of femur distal to level I  level III: femur distal to level...
Article

American Board of Radiology

The American Board of Radiology (ABR) is a national certifying board for radiologists in the United States of America. It is a member of the American Board of Specialities. The ABR currently requires three sets of examination for certification: core exam certifying exam maintenance of certif...
Article

American College of Radiology

The American College of Radiology (ACR) was founded in 1923 by Albert Soiland, an American radiologist 2. Its contemporary core purpose, according to its website, is "To serve patients and society by empowering members to advance the practice, science and professions of radiological care" 1. Hi...
Article

American College of Radiology published guidelines

The American College of Radiology (ACR) publishes and updates imaging guidelines, sometimes in collaboration with other bodies, on a range of imaging pathologies and reporting issues: breast lesions: BI-RADS liver lesions: LI-RADS prostate lesions: PI-RADS thyroid nodules: TI-RADS adrenal i...
Article

American Journal of Roentgenology

The American Journal of Roentgenology, also known as AJR, is a peer-reviewed monthly journal published by the American Roentgen Ray Society (ARRS). Its current editor in chief is Dr Thomas H Berquist. Its global circulation is close to 25,000 paying subscribers 16.  Journal title Like many of ...
Article

American Roentgen Ray Society

The American Roentgen Ray Society (ARRS) is the first and oldest learned society for radiologists in the United States, it was founded in 1900. Its current President is Bernard F King, Jr. ARRS publishes the peer-reviewed journal American Journal of Roentgenology (AJR). Its current editor i...
Article

Amiodarone hepatotoxicity

Amiodarone hepatotoxicity is one of the complications that can occur with amiodarone therapy.  Clinical presentation In the majority of patients, it is discovered incidentally during routine testing of liver biochemistry and rarely do the hepatic effects develop into symptomatic liver injury o...
Article

Amiodarone lung

Amiodarone lung is an interstitial lung disease seen in patients being administered amiodarone and can manifest in a number of histopathologic patterns. Epidemiology The reported prevalence of pulmonary toxicity in patients receiving amiodarone is ~10% (range 2-18%) 8. Patients are usually el...
Article

Amniocentesis

Amniocentesis, also known as amniotic fluid testing or AFT, is a diagnostic or therapeutic medical procedure primarily used in prenatal diagnosis of chromosomal abnormalities and fetal infections. A small amount of amniotic fluid (15-20 ml), which contains fetal tissue, is extracted from the am...
Article

Amnion

Amnion refers to a membranous structure which covers and protects the embryo. It forms inside the chorion. The amnion usually fuses with the outer chorion by around 14 weeks of gestation. Radiographic features Ultrasound The amnion can be visualised in most pregnancies before the 12th week of...
Article

Amnioreduction

An amnioreduction is a procedure where an amniocentesis is performed for intentional reduction of amniotic fluid volume. This is sometimes performed in the context of extreme polyhydramnios (particularly in the recipient twin in twin to twin transfusion syndrome).
Article

Amniotic bands

Amniotic bands refer to free floating blind ending amnion with an intact chorionic membrane. In certain situations, they lead to the amniotic band syndrome. They should not be confused with amniotic shelves which refer to the presence of amnion folding around pre-existing uterine adhesions. Some...
Article

Amniotic band syndrome

Amniotic band syndrome (ABS) comprises of a wide spectrum of abnormalities, all of which result from entrapment of various fetal body parts in a disrupted amnion. Due to the randomness of entrapment, each affected individual has the potential to form a unique deficit. Epidemiology The phenomen...
Article

Amniotic fluid discordance

An amniotic fluid discordance is usually defined as a difference in amniotic fluid volumes in a twin pregnancy. It is a predictor of poor fetal outcome in twin pregnancy related complications. Pathology Causes of amniotic fluid discordance include : twin-twin transfusion syndrome placental i...
Article

Amniotic fluid embolism to lung

Amniotic fluid embolism is a special type of pulmonary embolism where the embolus is comprised of amniotic fluid. It can be a highly fatal complication of pregnancy, with an 80% maternal mortality rate.  Epidemiology It is thought to complicate 1/8000-80,000 pregnancies. Clinical presentation...
Article

Amniotic fluid index

The amniotic fluid index (AFI) is an estimate of the amniotic fluid volume in a fetus. It is part of the fetal biophysical profile.  Technique uterus is divided into four imaginary quadrants with linea nigra and umbilicus acting as the vertical and the horizontal axis respectively the deepest...
Article

Amniotic fluid in the first trimester

Amniotic fluid in the first trimester has been estimated from weeks 7-12. Although the amniotic fluid index (AFI) is calculated in the second trimester, one can get an idea of whether the amount of amniotic fluid is too much or too little at an earlier time point. The amniotic fluid volume is r...
Article

Amniotic fluid volume

Amniotic fluid volume (AFV) is a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion. Physiology Change in volume through gestation The AFV undergoes characteristic changes with gestation. It progressively ri...
Article

Amniotic shelf

Amniotic shelf (also known as an amniotic sheet 4) refers to a sheet like projection that can result from uterine synechiae that has been encompassed by the expanding chorion and amnion. In contrast to amniotic bands, they are not thought to be associated with any fetal deformity.  Epidemiology...
Article

Amoebic colitis

Amoebic colitis is a type of infectious colitis, more common in tropical and subtropical areas. The causative agent is the trophozoite form of the protozoan Entamoeba histolytica. In most cases of transmission, the cyst form lives in the colon as commensal and remains asymptomatic. Clinical pre...
Article

Amoebic hepatic abscess

Amoebic hepatic abscesses are a form of hepatic abscess resulting from Entamoeba histolytica infection. Clinical presentation Patients may experience general malaise or present with frank sepsis and right upper quadrant pain. Although the causative pathogen is found worldwide, it is endemic to...
Article

Amorphous calcification within breast

Amorphous or indistinct calcifications are a morphological descriptive term for breast calcification and are defined as having small, hazy, faint calcifications with no clearly defined shape or form.  Radiographic features 80-200 micrometer in diameter small, hazy calcification often magnifi...
Article

Amphiarthroses

Amphiarthroses are a functional class of joint that permit a small amount of movement under normal conditions. Examples symphyses (secondary cartilaginous joints) symphysis pubis intervertebral discs sternomanubrial joint  See also  synarthroses diarthroses
Article

Ampulla of Vater

The ampulla of Vater is a conical structure at the confluence of the common bile duct (CBD) and the main pancreatic duct that protrudes at the major duodenal papilla into the medial aspect of the descending duodenum. The entire structure is encased by smooth muscle fibers that compose the sphinc...
Article

Ampullary adenocarcinoma

Ampullary adenocarcinomas are rare biliary tumours arising from the distal biliary epithelium at the ampulla of Vater.  Although classically presenting on imaging with the double duct sign, the tumour itself may be occult or of limited characterisation imaging.  Epidemiology These are rare tu...
Article

Ampullary ectopic pregnancy

Ampullary ectopic pregnancy is the commonest type of tubal ectopic pregnancy and accounts for ~70% of such cases.  According to one study the disruption of the tubal wall was less than as in isthmic ectopic pregnancy 2.
Article

Ampullary tumour

The term ampullary tumour generally refers to either benign or malignant neoplasms that arise from the glandular epithelium of the ampulla of Vater, including 1: ampullary adenoma (adenoma of ampulla of Vater) ampullary carcinoma (carcinoma of ampulla of Vater) According to some authors, ampu...
Article

Amputation

The term amputation refers to the disconnection of all or part of a limb from the body. Specifically amputation is defined as removal of the structure through a bone. This is in contrast to disarticulation, which is removal of the structure through a joint. When due to trauma, traumatic amputat...
Article

Amsterdam criteria for HNPCC

The Amsterdam criteria are used in the diagnosis hereditary non polyposis colorectal cancer (HNPCC). Amsterdam Criteria I Initial description in 1991: > or equal to 3 relatives with colorectal cancer (CRC) > or equal to 1 case in a first degree relative > or equal to 2 successive generation...
Article

Amsterdam wrist rules

The Amsterdam wrist rules are validated clinical decision rules for determining which patients require radiographic imaging (wrist radiography) for acute wrist pain following trauma. The initial study evaluated 882 patients and were published in 2015 1. The decision rules assessed different clin...
Article

Amyand hernia

Amyand hernia is a rare form of an inguinal hernia in which the vermiform appendix is located within the hernial sac. It is seen in less than 1% of inguinal hernia. It should not be confused with an appendix-containing femoral hernia, known as De Garengeot hernia. Clinical presentation Clinic...
Article

Amygdala

The amygdala is a very well studied part of the limbic system and forms part of the mesial temporal lobe.  Gross anatomy The amygdala is a complex structure, located dorsomedially in the temporal lobe, forming the ventral superior, and medial walls of the inferior horn of the lateral ventricle...
Article

Amyloid arthropathy

Amyloid arthropathy is the extracellular deposition of the fibrous protein amyloid within the skeletal system. It is a skeletal manifestation of amyloidosis and may involve either the axial skeleton (especially the cervical spine) or the appendicular skeleton. Clinical presentation Shoulder pa...
Article

Amyloidosis

Amyloidosis is a heterogeneous disease, or even considered a constellation of diseases, resulting in the deposition of relatively similar proteins. It has many causes and can affect essentially any organ system. Epidemiology  There may be male predilection. Typically affects middle-aged indivi...
Article

Amyoplasia congenita

Amyoplasia congenita is a syndrome characterized by multiple specific congenital joint contractures, associated with substitution of muscular tissue by fibrosis and adipose tissue. Epidemiology The estimated incidence is at  1: 10000 live births. There may be a higher prevalence with twin preg...
Article

Amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig disease or Charcot disease, is the most common form of motor neurone disease 1,4 resulting in progressive weakness and eventual death due to respiratory insufficiency. Epidemiology ALS typically is diagnosed in middle age. There is ...
Article

Anal atresia

Anal atresia, or imperforate anus, refers to a spectrum of anorectal abnormalities ranging from a membranous separation to complete absence of the anus. Epidemiology The estimated incidence is 1 in 5000 live births. Pathology Clinically there is no anal opening. Subtypes can be classified in...
Article

Anal canal

The anal canal is the terminal part of the gastrointestinal tract. Anatomically, the anal canal is referred to as the terminal alimentary tract between the dentate line and anal verge. However, histologically it extends more proximally and includes the columns of Morgagni and anal sinuses. Surgi...
Article

Anal canal cancer protocol (MRI)

Anal canal cancer is relativity rare, however, there are several protocols that exist for assessment of various pelvic pathology. One method adopted for optimum assessment for anal cancer is (Auckland-New Zealand) Overview: whole pelvis T1 +/- T2FS Fine 3 mm slices through region of concern (...
Article

Anal canal fistula assessment (MRI)

MR of the pelvis can demonstrate hidden areas of pelvic infection and secondary extensions which are important to detect prior to the sugary to minimize high rate of recurrence post intervention. Also pelvic MRI assists to delineate the anatomic relationships of the fistula to sphincters which c...
Article

Anal cancer

Anal cancer is a relatively uncommon, accounting for less than 2% of large bowel malignancies, and most of the cases are made of squamous cell carcinoma.  Epidemiology It accounts for less than 2% of large bowel malignancies and 1-6% of anorectal tumours (~1.5% of all gastrointestinal tract ma...
Article

Anal cancer (staging)

The most recent version of TNM staging of anal cancer is as follows: Primary tumour (T) TX: primary tumour cannot be assessed T0: no evidence of primary tumour Tis: carcinoma in situ (Bowen disease, high-grade squamous intraepithelial lesion [HSIL], anal intraepithelial neoplasia II-III (AIN...
Article

Anal margin

Anal margin or perianal skin is arbitrarily defined as a skin tissue with a radius of 5 cm from the anal verge, consisting of keratinizing squamous epithelial tissue containing hair follicles. See also anal margin neoplasms
Article

Anal sphincter

The anal sphincter is divided into an internal and external anal sphincter. It surrounds the anal canal.  Gross anatomy Internal anal sphincter continuation of inner rectal muscle thickened, circular muscle fibres, up to 5 mm thick composed of visceral muscle External anal sphincter Compo...
Article

Anal triangle

The anal triangle forms the posterior half of the diamond-shaped perineum. The triangle's three corners are defined by the tip of the coccyx posteriorly and both ischial tuberosities anterolaterally. The anterior border is the transverse perineal muscles and the posterolateral borders are the sa...
Article

Anal verge

The anal verge is part of the anal region and consists of a band of squamous epithelial tissue which lacks hair follicles and extends from the inter-sphincteric groove to the perianal skin. 
Article

Anaplastic astrocytoma

Anaplastic astrocytomas are WHO grade III lesions, with imaging appearances and prognosis between those of diffuse low-grade astrocytomas (WHO grade II) and glioblastomas (WHO IV), and similarly, they are classified on the basis of IDH mutation as IDH-mutant, IDH-wild-type and NOS (when IDH stat...
Article

Anaplastic ependymoma

Anaplastic ependymomas (WHO grade III ependymomas), in comparison to lower grade ependymomas, are characterised by a higher proliferative rate and a greater tendency to infiltrate surrounding brain or disseminate into cerebrospinal fluid causing drop metastases 1. The relevance of grading ependy...
Article

Anaplastic ganglioglioma

Anaplastic gangliogliomas are uncommon aggressive variants of the far more common low-grade ganglioglioma (WHO grade I). The aggressive component is the glial (usually astrocytic) component, which demonstrates nuclear pleomorphism, increased mitotic rate and increased cellularity, as well as mic...
Article

Anaplastic meningioma

Anaplastic meningiomas (also known as malignant meningiomas) are uncommon, accounting for only ~1% of all meningiomas 1. Along with rhabdoid meningioma and papillary meningioma are considered WHO grade III tumours and demonstrate aggressive local growth and high recurrence rate.  It should be n...

Updating… Please wait.
Loadinganimation

Alert accept

Error Unable to process the form. Check for errors and try again.

Alert accept Thank you for updating your details.