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.

13,606 results found
Article

Aging blood on MRI (mnemonic)

Aging blood on MRI is dependent on the varying MRI signal characteristics of hemorrhagic collections with time and can be very useful in correlating the imaging findings with the clinical picture. However, as it can be complicated to recall the MRI features of aging blood through the five stages...
Article

Agenesis (general)

The biological/medical term agenesis (plural: ageneses) refers to failure of an organ to grow or develop during the embryological period. Examples include: appendiceal agenesis cerebellar agenesis corpus callosum agenesis dental agenesis diaphragmatic agenesis dorsal pancreatic agenesis ...
Article

Agenesis of the appendix

Agenesis of the appendix is extremely rare, with an incidence at surgery of approximately 1 in 100,000 laparotomies 1. It is most commonly due to a sporadic etiology. However in the rare genetic condition, familial apple peel jejunal atresia, absence of the appendix is a recognized feature. Also...
Article

Agenesis of the diaphragm

Agenesis of the diaphragm is a congenital diaphragmatic developmental anomaly where all or part of diaphragm fails to form. It can sometimes be thought of as an extreme form congenital diaphragmatic herniation 1. Pathology The agenesis can either be unilateral or bilateral. Herniation of abdom...
Article

Agenesis of the left hepatic lobe

Agenesis of the left hepatic lobe is a rare variation in liver anatomy. It is clinically asymptomatic and discovered during imaging or surgery. Radiographic features absence of the left hepatic lobe (left of the falciform ligament, Couinaud segments II and III) absence of left hepatic artery,...
Article

Agenesis of the right hepatic lobe

Agenesis of the right hepatic lobe is a rare variation in liver anatomy. Radiographic features absence of the right hepatic lobe absence of right hepatic artery, right portal vein, and right hepatic biliary system compensatory hypertrophy of the left hepatic lobe and caudate lobe possible r...
Article

Agger nasi cells

Agger nasi air cells are the most anterior ethmoidal air cells lying anterolateral and inferior to the frontal recess and anterior and above the attachment of the middle turbinate. They are located within the lacrimal bone and therefore have as lateral relations the orbit, the lacrimal sac and t...
Article

Aggressive angiomyxoma

Aggressive angiomyxomas are rare tumors that arise in the pelvis and typically cross the levator ani muscles. Despite its name, it is essentially a benign tumor and the term "aggressive" is given due to a predilection for local recurrence. Only rarely does it metastasize. Epidemiology It is se...
Article

Aggressive fibromatosis

Aggressive fibromatosis is a type of musculoskeletal fibromatosis. While it is a non-metastasizing fibrous lesion, it is thought to be a true neoplasm that arises from the fascial and musculoaponeurotic coverings, sometimes at the site of a traumatic or post-surgical scar. Terminology The term...
Article

Aggressive granulomatosis post hip replacement

Aggressive granulomatosis post hip replacement is a potential complication of a hip joint replacement. Some authors use the same term for particle disease - if you are an expert on this we would love your help. Pathology Aggressive granulomas consist of well organized connective tissue contain...
Article

Aggressive vertebral hemangioma

Aggressive vertebral hemangiomata are a rare form of vertebral hemangiomata where significant vertebral expansion, extra-osseous component with epidural extension, disturbance of blood flow, and occasionally compression fractures can be present causing spinal cord and/or nerve root compression 1...
Article

Agnosia

Agnosia is a neurological disorder characterized by an inability to identify an object despite both having knowledge of that object and functional sensory input. For example, a patient with posterior cortical atrophy who characteristically have visual agnosia, will be unable to identify a hammer...
Article

Agraphia

Agraphia represents acquired impairments of writing ability secondary to damage or dysfunction of the central nervous system. Impairments caused solely by motor dysfunction (e.g. hand paresis or tremor) are not considered to be forms of agraphia 1. Clinical presentation Agraphia is rarely an i...
Article

Ahlbäck classification of osteoarthritis of the knee joint

This classification was proposed by Ahlback et al. in 1968. According to Ahlbäck system, knee joint osteoarthritis is classified as: grade 1: joint space narrowing (less than 3 mm) grade 2: joint space obliteration grade 3: minor bone attrition (0-5 mm) grade 4: moderate bone attrition (5-1...
Article

AICA-PICA dominance

AICA-PICA dominance refers to the principle that the cerebellar vascular territory supplied by the anterior inferior cerebellar artery and posterior inferior cerebellar artery have a reciprocal arrangement. That is the size of the AICA and the subsequent territory it supplies is inversely propor...
Article

Aicardi-Goutières syndrome

Aicardi-Goutières syndrome is a rare hereditary neurodegenerative disease which usually presents in early infancy with systemic and central nervous system inflammatory syndrome characterized by hepatosplenomegaly, vasculopathy and encephalopathy. Many of the features are similar to congenital TO...
Article

Aicardi syndrome

Aicardi syndrome is a rare severe developmental disorder. It results from an X-linked genetic defect that is fatal in males and therefore only manifests in females (except for rare 47, XXY cases). Note: Aicardi syndrome is distinct from Aicardi-Goutieres syndrome although both are named after J...
Article

AIDS cholangiopathy

AIDS cholangiopathy refers to an acalculous, secondary opportunistic cholangitis that occurs in AIDS patients as a result of immunosuppression.  Pathology Characterized by multiple irregular strictures essentially indistinguishable from primary sclerosing cholangitis (PSC). There are four path...
Article

AIDS-defining illness

AIDS-defining illnesses are conditions that in the setting of a HIV infection confirm the diagnosis of AIDS, and do not commonly occur in immunocompetent individuals 2. According to the CDC surveillance case definition 1, they are: Infectious bacterial infections: multiple or recurrent candid...
Article

AIDS embryopathy

Acquired immunodeficiency syndrome (AIDS) embryopathy is characterized by a group of dysmorphic features, which manifests either before or after birth in offsprings of women who are infected by HIV virus. The diagnosis, however, is in disfavour according to some authors 2. Pathology Transplace...
Article

AIDS-related diffuse large B-cell lymphoma

AIDS-related diffuse large B-cell lymphomas are one of the immunodeficiency-associated CNS lymphomas, and in western countries represented a dramatic increase in primary CNS lymphoma during the HIV/AIDS epidemic of the 1980s, although the incidence is likely lower in patients treated with HAART ...
Article

AIDS-related pulmonary lymphoma

AIDS-related pulmonary lymphoma (ARPL) is classified as a distinct form of pulmonary lymphoma. Pulmonary involvement is a common extranodal site in AIDS-related NHL. Pathology ARPL is typically a high-grade B-cell non-Hodgkin's lymphoma and the majority of patients have advanced HIV infection,...
Article

Ainhum

Ainhum, also known as dactylolysis spontanea, is a rare cutaneous condition in which a hyperkeratotic band partially or totally encircles a digit. The constriction thins the underlying bone, which is then prone to fracture. Some cases result in autoamputation. Epidemiology Some have suggested ...
Article

Air bronchogram

Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
Article

Air-bronchogram (summary)

This is a basic article for medical students and other non-radiologists Air-bronchograms are gas-filled bronchi surrounded by alveoli filled with fluid, pus or other material 1. It is a very useful sign because it is highly sensitive and specific for the presence of lung consolidation rather th...
Article

Air bubble artifact

The air bubble artifact on CT is due to the presence of abnormal gas in the oil coolant which surrounds the x-ray tube. The artifact manifests as subtle low density, which has only been described on brain scans. Cause The x-ray tube in a CT scanner is prevented from overheating by a heat excha...
Article

Air bubble sign (pulmonary hydatid)

The air bubble sign is seen in CT of complicated (ruptured or infected) pulmonary hydatid cyst and refers to small bubbles of gas within the periphery of pulmonary mass and is helpful, particularly in endemic areas, in suggesting the diagnosis over other masses (e.g. metastases or primary lung t...
Article

Air bubble sign (tension pneumocephalus)

The air bubble sign is seen on CT of the brain and represents multiple small foci of air within the subarachnoid space, especially the Sylvian fissure.1 Although described as a sign of tension pneumocephalus it is also seen in pneumocephalus without elevated pressures.2 It should not be confus...
Article

Air crescent sign (lung)

An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity. Terminology It should not be confused wi...
Article

Air gap technique

The air gap technique is a radiographic technique that improves image contrast resolution through reducing the amount of scattered radiation that reaches the image detector. In select situations, this technique can be used instead of an antiscatter grid as the primary scatter reduction method in...
Article

Air gap technique (general radiography)

The utilization of the air gap technique in general radiography is limited due to the need for equipment facilitation to create the air gap when it is not inherent in the standard technique. Horizontal-beam lateral hip There are many different methods of performing the horizontal beam lateral ...
Article

Air gap technique (mammography)

The air gap technique is utilized for the magnification mammography view. Magnification mammography is a high dose imaging technique which is generally utilized as a follow-up to a standard mammogram image series when a focal area needs to be more clearly examined 1. The air gap technique is ut...
Article

Air space disease

Air space disease, or alveolar lung disease, is a process in which there is a filling of the lung's alveoli / acini. Radiographic features lobar or segmental distribution poorly marginated airspace nodules tendency to coalesce air bronchograms bat's wing (butterfly) distribution...
Article

Air space nodule

An air space nodule is a small (few millimeters to 1 cm), ill-defined, nodular opacity that is often centrilobular in location and is non-specific, seen in many conditions. Commonly it represents a focal area of consolidation or peribronchiolar inflammation, and can indicate endobronchial spread...
Article

Airspace nodules

Airspace nodules are irregularly marginated nodular opacities with air bronchograms that tend to measure 8 mm in diameter. They are quite separate from pulmonary nodules that range in size, are homogeneous and well-defined (being surrounded by normal lung).
Article

Air space opacification

Air space opacification is a descriptive term that refers to filling of the pulmonary tree with material that attenuates x-rays more than the surrounding lung parenchyma. It is one of the many patterns of lung opacification and is equivalent to the pathological diagnosis of pulmonary consolidati...
Article

Air-space opacification (summary)

This is a basic article for medical students and other non-radiologists Air-space opacification is a descriptive term that refers to filling of the lung parenchyma with material that attenuates x-rays more than the unaffected surrounding lung tissue. It is the radiological correlate of the path...
Article

Air space opacities

The differential for air space opacities is extensive, and needs to be interpreted in context of chronicity (previous imaging) and clinical context. It is therefore useful to divide airspace opacities as follows: acute airspace opacities with lymph node enlargement acute airspace opacities: un...
Article

Air trapping

Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
Article

Airway centered interstitial fibrosis

Airway centered interstitial fibrosis is a rare subtype of pulmonary fibrosis with variable outcomes. Pathology It is characterized by fibrosis of the respiratory bronchioles and the peribronchiolar interstitium. It may be triggered by exogenous agents or endogenous autoimmune conditions such ...
Article

Airway foreign bodies in children

Airway foreign bodies in children are potentially fatal, which is why immediate recognition is important. Unfortunately, delayed diagnosis is common. Epidemiology Children under the age of four years are at increased risk of foreign body (FB) aspiration, with a slight male predominance 1.  Cl...
Article

Airway invasive aspergillosis

Airway invasive aspergillosis refers to a form of invasive aspergillosis that affects the airways as the major or only feature. Epidemiology It usually occurs in immunocompromised neutropenic patients, particularly AIDS patients. Aspergillosis affecting the airways as the major or only feature...
Article

Airway pressure release ventilation

Airway pressure release ventilation (APRV) is an alternative mode for mechanical ventilation. It can be adopted as a method of alternative method for difficult-to-oxygenate patients with acute lung injury / acute respiratory distress syndrome (ALI/ARDS). Its is usually not recommended in patien...
Article

Alagille syndrome

Alagille syndrome (AGS) is a congenital genetic multi-system disorder. Clinical presentation Infants typically present with symptoms relating to the liver where it is one of the most common causes of hereditary cholestasis. Genetics Alagille syndrome is inherited in an autosomal fashion with...
Article

Alanine peak

Alanine is one of the compounds examined in MR spectroscopy. It resonates at 1.48 ppm chemical shift. It is elevated in meningiomas.
Article

Alar fascia

The alar fascia is a thin fibroareolar membrane separating the (anterior) true retropharyngeal space from the (posterior) danger space. It is the ventral component of the deep layer of the deep cervical fascia. Notably, in the well patient, the alar fascia is not usually visible on cross-sectio...
Article

Alar ligament

The alar ligaments join the lateral margins of the sloping upper posterior margin of the dens of C2 to the lateral margins of the foramen magnum (adjacent to the occipital condyles) and lie on either side of the apical ligament. They may be oblique or vertical and are thickest at the occipital a...
Article

Alar ligament calcification

Alar ligament calcification​ is rare. The alar ligaments arise bilaterally from the upper portion of the odontoid process and run obliquely cephalad and laterally to insert on the medial surface of the occipital condyles. They stabilize the head during rotatory movements.  Epidemiology Focal c...
Article

Alar thoracic artery

The alar thoracic artery is a rare variant arterial glandular branch of the axillary artery (usually the second part) that supplies the axillary fat, lymph nodes and skin of the axilla.
Article

Alban Köhler

Alban Köhler (1874-1947) was a German radiologist best known for both his work in describing avascular necrosis of the navicular (now known as Köhler disease) and the publication of ‘Roentgenology - The Borderlands of the Normal and Early Pathological in the Skiagram’ a textbook exploring anatom...
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 (MCA) stroke. It has also been adapted for the posterior circulation (see below).  Scoring system Segmental assessment of the middle cerebra...
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, 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 recognized. As with many other diseases with variable age of presentation, the earl...
Article

Alexia

Alexia (or acquired dyslexia) is a neurological term refers to an acquired impairment of reading resulting from damage of critical brain areas. Clinical presentation Alexia can manifest itself as an impairment of oral reading and reading comprehension alike and can occur in combination with va...
Article

Aliasing artifact (CT)

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

Aliasing phenomenon (ultrasound)

Aliasing is a phenomenon inherent to Doppler modalities which utilize intermittent sampling in which an insufficient sampling rate results in an inability to record direction and velocity accurately.  Physics Unlike continuous wave Doppler, pulsed wave and color flow Doppler modalities alterna...
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

A-line (ultrasound)

An a-line is an ultrasonographic artifact appreciated during insonation of an aerated lung. 1 The term may be applied to the horizontal, echogenic long path reverberation artifacts that occur beneath the pleural line at multiples of the distance between the ultrasound probe and the visceral-par...
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-American physicist who was instrumental in the development of CT 1,3. Early life Allan Macleod Cormack was born on 23 February 1924 in Johannesburg, South Africa to a teacher, Amelia MacLeod and, an engineer, George Cormack, who had both emigrate...
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 leukemia 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 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...
Article

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...
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 panlobular emphysema and respiratory symptoms....
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 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)
Article

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...
Article

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...
Article

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 th...
Article

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...
Article

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...
Article

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 ...
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 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...
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 tumors occur in slightly older individuals, typically 10-25 years of age 1.  Pathology Location Althou...
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 (ASPS) 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...
Article

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...
Article

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...
Article

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. 
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...

Updating… Please wait.

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

 Thank you for updating your details.