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.

14,959 results found
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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...
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Allantois

Allantois refers to one of the fetal membranes that contributes to umbilical cord formation. It takes part in waste material collection and gas exchange. During embryonic development, the allantois transforms into urachus, which in turn becomes the median umbilical ligament. Related pathology ...
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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. 
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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 ...
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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...
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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...
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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
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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...
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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 leukemia who are on therapeutic all-trans-retinoic acid (ATRA). All-trans-retinoic acid (ATRA) is a normal constituent of plasma ...
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Alobar holoprosencephaly

Alobar holoprosencephaly is a subtype of holoprosencephaly 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, please r...
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Alpers syndrome

Alpers syndrome, also known as Alpers-Huttenlocher syndrome or progressive cerebral poliodystrophy, is a rare childhood neurodegenerative POLG-related disorder. Along with Leigh syndrome, it is one of the commonest childhood mitochondrial disorders 1.  Epidemiology Alpers syndrome is incredibl...
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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 panlobular emphysema and respiratory symptoms....
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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...
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Alpha angle (disambiguation)

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

The alpha angle is a radiological measurement proposed for the diagnosis and evaluation of surgical treatment in cam-type femoroacetabular impingement (FAI). When initially described in 2002, Notzli et al. suggested that the pathological value was >50°.  According to one study, a value measure...
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Alphabet inspired signs

There are many alphabet-inspired signs in radiology: C sign (MSK) delta sign delta sign (brain) empty delta sign (brain) double delta sign (MSK) D sign (cardiac) E sign H-shaped vertebrae H sign J-shaped sella J sign (shoulder) L sign (brain) M sign (brain) lambda sign lambda sign...
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Alpha decay

Alpha decay is the process in which an alpha particle (containing two neutrons and two protons) is ejected from the nucleus. An alpha particle is identical to the nucleus of a helium atom. All nuclei with the atomic number (Z) greater than 82, are considered unstable. These are considered “neutr...
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Alpha-fetoprotein

Alpha-fetoprotein (AFP) is an important plasma protein synthesized by the yolk sac and fetal liver. In adults, its main utility is as a tumor marker, primarily for hepatocellular carcinoma or teratoma. Functionally it is the fetal homologue of albumin i.e. it acts as a major carrier protein in t...
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Alphanumeric system of dental notation

The alphanumeric system of dental notation is a modification of Palmer notation for numbering and naming teeth made for electronic transcription. Its use is primarily in the United Kingdom 1,3,4. Permanent teeth First, the jaws are divided into four quadrants 1-5. Each quadrant is denoted by t...
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Alpha thalassemia/intellectual disability syndrome X-linked (ATRX) gene (tumor marker)

Alpha-thalassemia/intellectual disability syndrome X-linked (ATRX) gene is an important genomic marker of gliomas and is either intact (ATRX wild-type) or mutated (ATRX-mutant) and is correlated with other important genomic markers including IDH, 1p19q codeletion and p53 expression 1,2.  ATRX a...
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Alport syndrome

Alport syndrome is an X-linked dominant disease characterized by progressive sensorineural hearing loss, renal disease and, at times, ocular lesions. Clinical presentation hematuria sensorineural hearing loss: typically high frequency 2 ocular abnormalities anterior lenticonus: most common ...
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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 ...
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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 ...
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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...
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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...
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Alveolar echinococcosis

Alveolar echinococcosis, also referred as hepatic alveolar echinococcosis or E. alveolaris, is a more aggressive and invasive form of hepatic hydatid disease caused by Echinococcus multilocularis. It mimics a slow-growing tumor, as in contrast to E. granulosus it does not form a well defined enc...
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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 tumors occur in slightly older individuals, typically 10-25 years of age 1.  Pathology Location Althou...
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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...
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Alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare, highly vascular, deep soft tissue mesenchymal 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...
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Alveoli

The alveoli (singular: alveolus) 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 app...
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Alzheimer disease

Alzheimer disease 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.  Epide...
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Alzheimer type I glia

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

Amastia is a rare congenital condition characterized 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...
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Amaurosis fugax

Amaurosis fugax is the transient monocular loss of vision, normally lasting a few seconds to a few minutes, secondary to vascular ischemia or insufficiency.  Epidemiology It has an incidence of 50,000 per year in the United States.  Clinical presentation Patients present with transient monoc...
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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...
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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 around the midbrain and posterior to the thalami. It acts as the connection between the quadrigeminal...
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Amelia

Amelia refers to a skeletal dysplasia characterized by the complete agenesis of an upper or lower extremity or all four limbs. It may be associated with other congenital anomalies, i.e. omphalocele and diaphragmatic hernias 3. Epidemiology Amelia is a very rare congenital anomaly with an incid...
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Ameloblastic fibroma

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

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

Ameloblastomas are locally aggressive benign tumors 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 ...
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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...
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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 Specialties. It is headquartered in Tucson, Arizona. Vincent P Mathews is its current President. The American Board of Radiology current...
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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...
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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: adrenal incidentalomas: white paper breast lesions: BI-RADS head and neck cancer: NI-RADS liver lesions: LI-...
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American Dental Association Universal Numbering System

The American Dental Association Universal Numbering System is a tooth notation system primarily used in the United States. Teeth are numbered from the viewpoint of the dental practitioner looking into the open mouth, clockwise starting from the distalmost right maxillary teeth. Permanent teeth...
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American Journal of Neuroradiology (AJNR)

American Journal of Neuroradiology (AJNR) is the premier publication of the American Society of Neuroradiology and was first published in 1980. Its founding editor was Juan M Taveras (1919-2002), the pioneering American neuroradiologist, who was a co-founder of the American Society of Neuroradio...
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American Journal of Roentgenology

The American Journal of Roentgenology, also known as AJR, or informally, the Yellow Journal, is a peer-reviewed monthly journal published by the American Roentgen Ray Society (ARRS). Its current editor in chief is Andrew Rosenkrantz. Its global circulation is close to 25,000 paying subscribers 1...
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American Roentgen Ray Society

The American Roentgen Ray Society (ARRS), founded in 1900, is the oldest learned society for radiologists in the United States. It publishes the monthly American Journal of Roentgenology (AJR).Its current President is Ruth C Carlos. Journals American Journal of Roentgenology (AJR) current edi...
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American Society of Neuroradiology

American Society of Neuroradiology (ASNR) was established in 1962 to ensure that neuroradiologists in the United States could freely exchange ideas and act with a common voice. It publishes the American Journal of Neuroradiology (AJNR). History At the VIth Symposium Neuroradiologicum held in R...
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American X-Ray Journal

The American X-Ray Journal was the first radiology journal in the United States. Its first issue was published in May 1897, its founder and first editor was an American physician Heber Robarts (1852-1922), who took an early keen interest in the new Roentgen rays. Robarts was also a co-founder of...
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Amino acids

Amino acids are the monomeric building blocks of proteins. Amino acids concatenate into chains, which are arbitrarily divided into peptides, polypeptides, or proteins according to chain length. Generally, chains of 10 or fewer amino acids are deemed to be peptides, chain length from 10-100 are p...
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Amiodarone deposition in the liver

Amiodarone deposition in the liver is one of the complications that can occur with amiodarone therapy.  Terminology Increased density in the liver in patients treated with amiodarone is often described in the literature as amiodarone hepatotoxicity. However, it is often an incidental finding w...
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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...
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Ammonia (N-13)

13NH3 is a PET tracer used for studies of myocardial perfusion imaging. It is produced in a cyclotron by proton irradiation of the enriched water of the oxygen-16. Ammonia (N-13) is administered intravenously, at a dose of 10-20 mCi (370-740 Mbq) in adults; its physical half-life is 10 minutes. ...
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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...
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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 visualized in most pregnancies before the 12th week of...
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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).
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Amniotic bands

Amniotic bands refer to free-floating blind-ending amnion with an intact chorionic membrane. In certain situations, they lead to 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 adv...
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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...
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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...
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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 1/8,000-80,000 pregnancies. Clinical presentatio...
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Amniotic fluid index

The amniotic fluid index (AFI) is an estimate of the amniotic fluid volume in a pregnant uterus. It is part of the fetal biophysical profile.  Technique the uterus is divided into four imaginary quadrants with the linea nigra and a mediolateral line running through the umbilicus acting as the ...
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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...
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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...
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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...
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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 a commensal and patients remain asymptomatic. Cl...
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Amoebic hepatic abscess

Amoebic hepatic abscesses are a form of hepatic abscess resulting from Entamoeba histolytica infection. Epidemiology Hepatic abscess is the most common extraintestinal form of E. histolytica infection 6. Although the causative pathogen is found worldwide, it is endemic to the Middle East and ...
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Amorphous calcifications (breast)

Amorphous calcifications, previously known as indistinct calcifications, are a morphological descriptor for breast calcifications that are small and/or hazy such that no clearly defined shape/form can be ascribed.  Pathology Many benign and malignant conditions may be seen in association with ...
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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
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Ampulla (disambiguation)

Ampulla (plural: ampullae) is an anatomical term used for tubular structures with a short segmental bulbous dilatation: ampulla (fallopian tube) ampulla (lacrimal system) ampulla (esophagus) ampulla (rectum) ampulla (semicircular ducts) ampulla (spleen) ampulla of Vater ampulla (vas defe...
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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...
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Ampullary adenocarcinoma

Ampullary adenocarcinomas are rare biliary tumors arising from the distal biliary epithelium at the ampulla of Vater.  Although classically presenting on imaging with the double duct sign, the tumor itself may be occult or of limited characterization imaging.  Epidemiology These are rare tumo...
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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.
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Ampullary tumor

The term ampullary tumor 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, ampul...
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Amputation (generic)

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

Amyand hernias (alternative plural: herniae) are a rare form of inguinal hernia in which the vermiform appendix is located within the hernial sac. They are seen in less than 1% of inguinal hernias.  It should not be confused with an appendix-containing femoral hernia, known as a De Garengeot he...
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Amygdala

The amygdala (plural: amygdalae) 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 grey matter structure located anterior and superior to the temporal horn of the lateral ventricle and head of the hippocampus. ...
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Amylase

Amylase is widely employed as a marker of acute pancreatitis and a significant elevation is diagnostic. Physiology α-amylase is a digestive enzyme that is predominantly secreted by the acinar cells of the exocrine pancreas. It is also secreted by the salivary glands. Pancreatic amylase is enco...
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Amyloid arthropathy

Amyloid arthropathy results from the extracellular deposition of the fibrous protein amyloid within the skeletal system and is a skeletal manifestation of amyloidosis particularly in patients on long term haemodialysis. It may involve either the axial skeleton (especially the cervical spine) or ...
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Amyloidosis

Amyloidosis (plural: amyloidoses) 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 any organ system. Epidemiology  The disease may have a male predilection. It typically aff...
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Amyopathic dermatomyositis

Amyopathic dermatomyositis (ADM) is recognized as a distinct subtype of dermatomyositis where there is a typical skin rash of classic dermatomyosiytis but without muscle involvement. Sub types This form may be further divided into  anti-melanoma differentiation-associated gene 5 (MDA5) antibo...
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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...
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Amyotrophic lateral sclerosis

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

Anemia is the presence of reduced hemoglobin in the blood. Formally, the World Health Organization (WHO) defines anemia by the hemoglobin concentration in the blood according to age and sex 1: adult men: <130 g/L adult women: <120 g/L Values for pregnant women and children are different. Pat...
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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...
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Anal canal

The anal canal is the terminal part of the gastrointestinal tract, whilst the anus (plural: anuses or ani) specifically refers to the opening separating the anal canal from the outside, at the distal most aspect of the anal verge. Anatomically, the anal canal is referred to as the terminal alime...
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Anal canal cancer protocol (MRI)

MRI protocol for anal canal cancer is a group of MRI sequences put together to asses extension and stage anal canal tumors. Note: This article is intended to outline some general principles of protocol design. The specifics will vary depending on MRI hardware and software, radiologist's and ref...
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Anal cancer

Anal cancer is relatively uncommon, accounting for less than 2% of large bowel malignancies. Most cases are squamous cell carcinoma on histology. Epidemiology It accounts for less than 2% of large bowel malignancies and 1-6% of anorectal tumors (~1.5% of all gastrointestinal tract malignancies...
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Anal cancer (staging)

The most recent version of TNM staging of anal cancer is as follows: Primary tumor (T) TX: primary tumor cannot be assessed T0: no evidence of primary tumor Tis: carcinoma in situ (Bowen disease, high-grade squamous intraepithelial lesion [HSIL], anal intraepithelial neoplasia II-III (AIN II...
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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. A radius of 5 cm approximately equates to a circle of area of 78.5 cm2 centered on the anal verge. See...

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