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.

847 results found
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Aarskog syndrome

Aarskog syndrome or Aarskog–Scott syndrome (also known as the facio-digito-genital syndrome) is a rare anomaly characterized by short stature in association with a variety of structural anomalies involving mainly the face, distal extremities, and external genitalia. Clinical presentation The m...
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Aase-Smith syndrome

Aase-Smith syndrome (or Aase syndrome) is an extremely rare congenital disorder. Clinical features congenital hypoplastic anaemia - fetal anaemia triphalangeal thumbs broad thumb abnormal clavicles cleft lip, cleft palate hypoplastic radii hydrocephalus (due to Dandy-Walker anomaly) joi...
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AAST injury scoring scales

The American Association for the Surgery of Trauma (AAST) injury scoring scales are the most widely accepted and used system of classifying and categorising traumatic injuries. Injury grade reflects severity, guides management, and aids in prognosis. At the time of writing (mid 2016), 32 differe...
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AAST kidney injury scale

The American Association for the Surgery of Trauma (AAST) renal injury scale 3-4 is the most widely used grading system for renal trauma at the time of writing (late 2016). Severity is assessed according to the depth of renal parenchymal damage and involvement of the urinary collecting system a...
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AAST liver injury scale

The 1994 revision of the AAST (American Association for the Surgery of Trauma) liver injury scale is the most widely used liver injury grading system at the time of writing (late 2016).  Classification grade I haematoma: subcapsular, <10% surface area laceration: capsular tear, <1 cm  parenc...
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AAST spleen injury scale

The 1994 revision of the American Association for the Surgery of Trauma (AAST) splenic injury scale is the most widely used grading system for splenic trauma at the time of writing (late 2016).  Classification grade I subcapsular haematoma <10% of surface area capsular laceration <1 cm depth...
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ABC/2

ABC/2 is a fast and simple method for estimating the volume of intracerebral haemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software. Intracerebral haemorrhage volume is an important predictor of morbidity and mortality (and thus tria...
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Abdomen (AP supine view)

AP supine radiograph can be performed as a standalone projection or as part of an acute abdominal series, depending on the clinical question posed, local protocol and the availability of other imaging modalities. Patient position the patient is supine, lying on their back, either on the X-ray ...
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Abdomen (dorsal decubitus view)

The dorsal decubitus view is a supplementary projection often replacing the lateral decubitus view in the context of an unstable patient who is unable to roll nor stand. Used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred...
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Abdomen (lateral decubitus view)

The lateral decubitus abdominal radiograph is used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred to, or other imaging modalities (e.g. CT) are not available. The most useful position for detecting free intraperitoneal ai...
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Abdomen (oblique view)

AP oblique supine radiograph is normally performed when localising foreign bodies or lines within the abdominal cavity. Additionally, the oblique abdominal series can be utilised in the assessment of the upper intestinal tract during barium studies. Patient position the patient is laying 30 de...
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Abdomen (PA erect view)

The PA erect abdominal radiograph is often obtained in conjunction with the AP supine abdominal view in the acute abdominal series of radiographs. When used together it is a valuable projection in assessing air fluid levels, and free air in the abdominal cavity. The erect abdominal radiograph h...
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Abdomen (PA prone view)

PA prone radiograph is rarely performed, often utilised when a patient is unable to lay supine. The projection is adequate for the examination of the abdominal cavities, however, not as practical for the renal structures due to magnification. Patient position the patient is prone, either on th...
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Abdominal adhesions

Abdominal adhesions are bands of scar tissue (fibrous or fibrous fatty), most often occurring as a complication of previous abdominal surgery. Pathology Adhesions often occur with multiple abdominal operations or previous postoperative intra-abdominal complications history of intra-abdominal i...
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Abdominal and pelvic anatomy

Abdominal and pelvic anatomy encompasses the anatomy of all structures of the abdominal and pelvic cavities.
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Abdominal aorta

The abdominal aorta is the main blood vessel in the abdominal cavity that transmits oxygenated blood from the thoracic cavity to the organs within the abdomen and to the lower limbs. Summary origin: continuation of descending thoracic aorta at T12  course: descends anterior and slightly to th...
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Abdominal aortic aneurysm

Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or >3 cm in maximum diameter. Epidemiology The prevalence of AAAs increases with age. Males are much more commonly affected than females, with a ratio of 4:1. The...
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Abdominal aortic aneurysm rupture

Abdominal aortic aneurysm (AAA) rupture is a feared complication of abdominal aortic aneurysm and is a surgical emergency. It is part of the acute aortic syndrome spectrum. Epidemiology Abdominal aortic aneurysms are common and affect ~7.5% of patients aged over 65 years 6. Clinical presentat...
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Abdominal aortic aneurysm (summary)

Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or >3 cm in maximum diameter. Reference article This is a summary article; read more in our article on abdominal aortic aneurysm. Summary epidemiology prevalen...
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Abdominal aortic injury

Abdominal aortic injuries are a very rare form of traumatic aortic injury and are much less common than thoracic aortic injury.  Epidemiology Aortic injury occurs in <1% of blunt trauma patients, with abdominal aortic injury representing only ~5% of all aortic injuries 1. Males are more freque...
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Abdominal cavity

The abdominal cavity is divided into two major compartments, the peritoneum and retroperitoneum, early in fetal development. The parietal peritoneum is reflected over the peritoneal organs to form a series of supporting peritoneal ligaments, mesenteries and omenta. The peritoneal reflections ca...
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Abdominal ectopic pregnancy

Abdominal ectopic pregnancies are an extremely rare type of ectopic pregnancy. Epidemiology They are thought to represent ~1% of all ectopic pregnancies 6 with an estimated incidence of 1:1000-10,000 births. Pathology It is often thought that they most frequently result from a tubal rupture ...
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Abdominal hernia

Abdominal hernias (herniae also used) may be congenital or acquired and come with varying eponyms. They are distinguished primarily based on location and content. 75-80% of all hernias are inguinal. Content of the hernia is variable, and may include: small bowel loops mobile colon segments (s...
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Abdominal (lateral view)

The lateral view abdominal radiograph is a useful problem-solving view that can complement frontal views of the abdomen, often utilised in the context of forging dies or to better visualise lines such as a shunt. It is different than the lateral decubitus view of the abdomen and looks more like ...
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Abdominal opacities

An opacity projecting over the abdomen has a broad differential. Possibilities to consider include: foreign bodies ingested, e.g. coins, batteries, bones, etc artifacts, e.g. object attached to the cloth of the patient like a safety pin or button iatrogenic, e.g. haemostatic clips, gastric b...
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Abdominal organ echogenicity (mnemonic)

This mnemonic helps to remember the relative echogenicity of abdominal organs on ultrasound: Darling Parents So Love Kids Mnemonic From most to least echogenic: D: diaphragm P: pancreas S: spleen L: liver K: kidneys (cortex)
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Abdominal paracentesis

Abdominal paracentesis, more commonly referred to as an ascitic tap, is a procedure that can be performed to collect peritoneal fluid for analysis or as a therapeutic intervention. Indications diagnostic: especially for newly diagnosed ascites determine aetiology of ascites assess for bacter...
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Abdominal radiograph (AP supine view neonatal)

AP supine radiograph for neonates is a mobile examination performed on the neonatal unit. It can be taken as a standalone projection or as part of a series including a left lateral decubitus x-ray in cases of suspected perforation.  Patient position the patient is supine, lying on their back i...
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Abdominal radiography

Abdominal radiography can be useful in many settings. Before the advent of computed tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology and often allowed indirect evaluation of other abdominal viscera. Indications Although abdominal radiography has lower...
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Abdominal radiology: conditions (curriculum)

Abdominal radiology conditions are a broad group of heterogeneous conditions that are split into: true pathology (e.g. colonic carcinoma) the underlying process (e.g. large bowel obstruction) It is important to have an overview of these conditions and understand what imaging is useful in thei...
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Abdominal radiology for students (curriculum)

Abdominal radiology curriculum for medical students is broadly split into content that refers to imaging (the test and findings) and conditions that are considered key for this stage of training. Some non-abdominal conditions are included in this portion of the curriculum, including breast dise...
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Abdominal radiology: imaging (curriculum)

Imaging in general surgery is vital to ensure timely and accurate diagnosis for patients.  You need to know the gamut of tests that are available when to use the correct test, some important findings that commonly occur and (for some investigations) how to approach looking at the images that ar...
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Abdominal radiology: interpretation (curriculum)

Abdominal radiology interpretation is a key component of how to make the most of diagnostic imaging. You need to know how to look at the commonly performed radiology tests and how to make common diagnoses.
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Abdominal radiology: key findings (curriculum)

Abdominal radiology key findings are a group of imaging findings that are really important in imaging of the abdomen. They point to disease processes and help to narrow the differential diagnosis. It is important to know these and recognise them on imaging.
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Abdominal radiology: presentations (curriculum)

Abdominal radiology presentations are a relatively distinct group of presentations that precipitate assessment medical and surgical teams.
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Abdominal radiology: tests and when to use them (curriculum)

Abdominal radiology tests and when to use them are a set of articles that help to outline the common tests that may be used in radiology and what they are useful for. Plain films (erect chest and supine abdomen), as well as ultrasound and CT abdomen, will be the bread and butter of the imaging ...
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Abdominal surface anatomy

The abdomen, when looking from in front, is divided into nine regions by imaginary planes (two vertical and two horizontal) forming abdominal surface anatomy. The nine regions are of clinical importance when examining and describing pathologies related to the abdomen. The horizontal planes are o...
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Abdominal trauma

Abdominal trauma is usually divided into blunt and penetrating trauma. Findings of abdominal trauma haemoperitoneum splenic trauma: most common hepatic trauma renal trauma pancreatic trauma gastrointestinal tract (bowel) trauma: proximal jejunum is most commonly affected by blunt trauma,...
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Abdominal x-ray - an approach (summary)

Abdominal radiographs can be challenging examinations to look at. It is always best to approach radiographs in a systematic way. Bowel gas pattern Gas within the bowel forms a natural contrast with surrounding tissues since it has a very low density. Bowel can only be seen if it contains air/g...
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Abdominal x-ray (summary)

Abdominal radiographs can be a useful examination, but you need to think about the question you are asking before getting the test. Before the advent of computerised tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology (and often allowed indirect evaluation...
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Abdominoschisis

Abdominoschisis refers to a split or in the abdominal wall. Some authors use the term synonymously with a gastroschisis. When the defect continues into the thoracic region it is termed a thoraco-abdominoschisis. A large abdominoschisis is considered part of the limb body wall complex 2. See als...
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Abducens nerve

The abducens nerve is the sixth cranial nerve. It courses from its nucleus located in the dorsal pons to its innervation of the lateral rectus muscle and can be divided into four parts: nucleus and intraparenchymal portion cisternal portion cavernous sinus portion orbital portion Gross anat...
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Abductor digiti minimi (foot)

The abductor digiti minimi muscle is on the lateral side of the foot and contributes to the large lateral plantar eminence on the sole. Summary origin: lateral and medial processes of calcaneal tuberosity, and band of connective tissue connecting calcaneus with base of metatarsal V insertion:...
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Abductor digiti minimi (hand)

The abductor digiti minimi muscle overlies the opponens digiti minimi. Summary origin: pisiform, the pisohamate ligament, and tendon of flexor carpi ulnaris insertion: 5th proximal phalanx action: abducts 5th finger at metacarpophalangeal joint arterial supply: ulnar artery innervation: de...
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Abductor hallucis muscle

The abductor hallucis muscle forms the medial margin of the foot and contributes to a soft tissue bulge on the medial side of the sole. Summary origin: medial process of calcaneal tuberosity insertion: medial side of base of proximal phalanx of great toe action: abducts and flexes great toe ...
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Abductor pollicis brevis

The abductor pollicis brevis is a thin subcutaneous muscle located laterally in the thenar eminence of the hand. Summary origin: mainly from the flexor retinaculum few fibres originate from the tubercles of scaphoid and trapezium and tendon of abductor pollicis longus accessory slips may ori...
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Abductor pollicis longus

The abductor pollicis longus (APL) is a muscle found in the deep layer of the posterior compartment of the forearm. As it descends, it becomes superficial and passes under the extensor retinaculum and through the 1st extensor compartment of the wrist before attaching distally. Summary origin: ...
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Abernethy malformation

Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts and result from persistence of the embryonic vessels.  Epidemiology Type I malformations are thought to occur only in females, while type II have a male predomin...
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ABER position

The ABER position relates to MR arthrography of the shoulder joint and is a mnemonic for ABduction and External Rotation. In this position, labral tears are made conspicuous by tightening the inferior glenohumeral labroligamentous complex (which are also the most important glenohumeral ligament...
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Aberrant arachnoid granulations

Aberrant arachnoid granulations (AbAG) are arachnoid granulations that penetrated the dura but failed to migrate normally in the venous sinus. They are most often located in the greater wing of the sphenoid bone. Occasionally, they are seen in the posterior temporal bone wall. Clinical presenta...
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Aberrant internal carotid artery

Aberrant internal carotid artery is a variant of the internal carotid artery (ICA) and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the ICA 5. There is consequent enlargement of the usually small collaterals which course t...
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Aberrant left pulmonary artery

Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterised by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and oesophagus to reach the left lung. It may le...
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Aberrant right subclavian artery

Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are the commonest of the aortic arch anomalies 2.  Epidemiology The estimated incidence is 0.5-2%. Clinical presentation They are often asymptomatic, but around 10% of people may complain of tracheo-oesophageal symptom...
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Aberrations in the normal development and involution of the breast

Aberrations in the Normal Development and Involution of the breast (ANDI) is an all-encompassing term that is used to describe a wide spectrum of the benign breast diseases. As the name suggests, it is based on the theory that most of the encountered benign breast disorders are essentially minor...
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Abnormal bowel wall attenuation patterns

Abnormal bowel wall attenuation patterns on CT scan can be grouped under five categories: white enhancement gray enhancement water halo sign fat halo sign black attenuation The first three patterns are seen on contrast studies. White enhancement It is defined as uniform enhancement of th...
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Abnormal collection of barium anywhere (mnemonic)

A mnemonic used for abnormal collection of barium anywhere in the body : FEDUP Mnemonic F: fistula E: extravasation D: diverticulum U: ulcer P: perforation
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Abnormal ductus venosus waveforms

Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumours.  Pathology Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situations: aneuploidic anomalies Down syndrome: around 80...
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Abnormal intra-abdominal gas

Abnormal intra-abdominal gas is an important radiologic finding with many potential causes. It may be seen on a chest radiograph, abdominal radiograph, CT or MRI. pneumoperitoneum retropneumoperitoneum pseudopneumoperitoneum abnormally located bowel, e.g. Chilaiditi syndrome (bowel interpose...
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Abnormally eccentric gestational sac

An eccentrically-located gestational sac towards the fundus of the uterus is the normal sonographic appearance; however an abnormally eccentric gestational sac on ultrasound may be apparent due to a number of causes They include interstitial ectopic pregnancy 1 normally implanted pregnancy in...
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Abnormally low sac position

An abnormally low sac position can result from several possibilities which include impending / ongoing miscarriage cervical ectopic pregnancy fundal fibroid or other mass compressing the sac downward
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Abnormally thickened endometrium (differential)

Abnormally thickened endometrium on imaging may occur for a number of reasons which may be categorised based on whether or not they are related to pregnancy. Aetiologies may also be classified based on whether the patient is premenopausal or postmenopausal. Differential diagnosis Pregnancy-rel...
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Abnormal renal rotation

Abnormal renal rotation (renal malrotation) refers to an anatomical variation in the position of the kidneys, in particular to anomalous orientation of the renal hilum. It may occur unilaterally or bilaterally. It is almost always an asymptomatic incidental finding.  Epidemiology Malrotation i...
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Abnormal ultrasound findings in rheumatological diseases (definitions)

The OMERACT ultrasound group published a consensus in 2005 of widely accepted definitions of abnormal ultrasound findings in rheumatological diseases: erosion: an intra-articular discontinuity of the bone surface that is visible in two orthogonal planes joint effusion: abnormal hypoechoic or a...
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ABR certifying exam

The ABR certifying exam is the second of two exams necessary for certification in diagnostic and interventional radiology in the United States of America (the first is the core exam). It is taken 15 months after the end of the PGY 5 year (or three months after a one year PGY 6 fellowship). The ...
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ABR core exam

The ABR core exam is the first of two exams necessary for certification in diagnostic and interventional radiology in the United States of America. It is taken at the end of the PGY 4 year of radiology residency training. The exam is computer-based and occurs in two sessions (7.5 hours and 6 ho...
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Abscess

Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1: a central core consisting of necrotic inflammatory cells and local tissue peripheral halo of viable neutrophils surrounded by a 'capsule' with dilated blood vessel...
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Absent bow tie sign (knee)

The absent bow tie sign represents the loss of the normal appearance of the menisci on parasagittal MRI images, and is suggestive of meniscal injury. Normally the medial and lateral menisci appear as low signal bow-tie-shaped structures between the femoral condyles and tibial plateaux. As the n...
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Absent ductus venosus

Agenesis of the ductus venosus (ADV) is a rare fetal vascular anomaly. Epidemiology According to the data obtained from the screening tests performed at 11-14 weeks of pregnancy, its incidence is reported to be 1/2500 12. Pathology In a large case series, Acherman et al. 13 defined five drai...
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Absent fetal stomach on ultrasound (differential)

Non-visualisation of the fetal stomach on ultrasound can occur with various physiological as well as pathological processes. It becomes a significant sonographic observation >14 weeks of gestation (about the time the fetus begins to swallow). Causes include: physiological emptying: transient ...
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Absent infrarenal inferior vena cava

An absent infrarenal inferior vena cava (IVC) can be congenital due to the failure of development of the posterior cardinal and supracardinal veins, or acquired as result of intrauterine or perinatal inferior vena cava thrombosis. Epidemiology It is an extremely rare anomaly. Clinical present...
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Absent nasal bone

In fetal sonographic assessment, an absent nasal bone is a feature which can sometimes be used as an adjunctive marker for fetal aneuploidy. Radiographic assessment Antenatal ultrasound It is assessed on a midline sagittal view. In this section the nasal bone is often seen as a bright echogen...
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Absent patella

An absent patella is a rare finding and can be found with an equally rare set of associations: surgical removal of patella (patellectomy) nail patella syndrome 2 popliteal pterygium syndrome proximal focal femoral deficiency (PFFD) Meier-Gorlin syndrome 3
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Absent septum pellucidum

An absent septum pellucidum may rarely be an isolated finding, or more commonly be seen in association with a variety of conditions. Epidemiology The septum pellucidum is partly or entirely absent in 2 or 3 individuals per 100,000 in the general population.  Pathology An absent septum pelluc...
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Absent thumb

An absent thumb can have many associations. They include: Fanconi anaemia (pancytopenia-dysmelia syndrome) Franceschetti syndrome Holt-Oram syndrome phocomelia (e.g. thalidomide embryopathy) Poland syndrome (pectoral muscle aplasia and syndactyly) Rothmund-Thomson syndrome Seckel syndrome...
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Absent umbilical arterial end-diastolic flow

Absent end-diastolic flow (AEDF) in an umbilical artery Doppler assessment is a useful feature which indicates underlying fetal vascular stress if detected in mid or late pregnancy. It is often classified as Class II in severity in abnormal umbilical arterial Dopplers 9. Pathology The presence...
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Absent yolk sac

Absence of the yolk sac in the presence of an embryo on a transvaginal ultrasound is considered abnormal, and in general is associated with subsequent embryonic death. See also yolk sac
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Absorbed dose

Absorbed dose is a measure of the energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of medium, and so has the unit J/kg or gray (Gy) where 1Gy = 1Jkg-1. The absorbed dose is not a good indicator of the likely biological effect. 1 Gy of alpha r...
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Absorption (ultrasound)

In ultrasound, absorption is the reduction in intensity of the sound waves as it passes through tissue. Most of the energy lost is in the form of heat.
Article

Acaeruloplasminaemia

Acaeruloplasminaemia is an autosomal recessive type of neurodegeneration with brain iron accumulation and disorder of iron metabolism caused by a mutation in the caeruloplasmin (CP) gene resulting in production of dysfunctional caeruloplasmin. Epidemiology Acaeruloplasminaemia is a very rare d...
Article

Acardiac twin

Acardiac twins (or recipient twins) are haemodynamically disadvantaged non-viable twins that undergo secondary atrophy in association with a twin reversed arterial perfusion sequence. Epidemiology Acardiac twinning is thought to affect 1 in 100 monozygotic twin pregnancies and 1 in 35,000 preg...
Article

Accepted abbreviations

There are a number of accepted abbreviations that we use on Radiopaedia.org. We would like the site to be as standardised as possible and we have therefore chosen our accepted abbreviations and would ask that where possible these are used: a.k.a. not aka (short for "also known as") cf. not c.f...
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Accessory appendicular artery

The accessory appendicular artery (or artery of Seshachalam) is a branch of the posterior caecal artery, which in turn arises from the ileocolic artery, and runs in the mesoappendix. The exact prevalence of this accessory artery and its impact upon the risk of appendicitis varies among studies....
Article

Accessory breast tissue

Accessory breast tissue is a relatively common congenital condition in which abnormal accessory breast tissue is seen in addition to the presence of normal breast tissue. This normal variant can present as a mass anywhere along the course of the embryologic mammary streak (axilla to the inguinal...
Article

Accessory fissures of the lung

Accessory fissures of the lung usually occur at the borders of bronchopulmonary segments. They are common normal variants but are less commonly seen on imaging.  Some of the more common accessory fissure include 1: azygos fissure: most commonly seen accessory fissure inferior accessory fissur...
Article

Accessory gallbladder

Accessory gallbladders are a rare anatomical variant occurring in 0.03% of cases (approximately 1 in 3000 people). They can arise from either the left or right hepatic ducts or both. Accessory gallbladders arise from a bifid diverticulum of the hepatic duct in the 5th or 6th week of development ...
Article

Accessory hemiazygos vein

The accessory (or superior) hemiazygos vein forms part of the azygos system and along with the hemiazygos vein, it is partially analogous to the right-sided azygos vein. It drains the left superior hemithorax.  Gross anatomy Origin and course The accessory hemiazygos vein is formed by the con...
Article

Accessory left atrial appendage

An accessory left atrial appendage is a frequent fortuitous finding in cardiac imaging, encountered in ~10% of patients. They are more often seen as a small diverticular structure projecting from the right upper side of the left atrial wall. Differential diagnosis it must not be confused with ...
Article

Accessory meningeal artery

The accessory meningeal artery is a branch of the maxillary artery but can also branch from the middle meningeal artery. The artery passes upwards through the foramen ovale to supply the trigeminal ganglion and the dura mater of Meckel's cave and the middle cranial fossa. It also usually suppli...
Article

Accessory middle cerebral artery

The accessory middle cerebral artery is a variant of the middle cerebral artery (MCA) that arises from the anterior cerebral artery (ACA). It is different from a duplicated middle cerebral artery, in which the duplicated vessel originates also from the distal end of the internal carotid artery (...
Article

Accessory navicular syndrome

Accessory navicular syndrome occurs when a type II accessory navicular (or "os tibiale externum") becomes painful due to movement across the pseudojoint between the ossicle and the navicular bone. Radiographic features Ultrasound It can be inferred on musculoskeletal ultrasound if a patient's...
Article

Accessory occipital bone sutures

The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centres. The occipital bone has complex development, ossifying from six centres. The foramen magnum is surrounded by four ossification centres. On each side are the exo...
Article

Accessory ossicle of the anterior arch of the atlas

The accessory ossicle of the anterior arch of the atlas is a normal variant and is best appreciated on a lateral cervical/sagittal study. It is observed as a circular and corticated osseous density that articulates with the inferior aspect of the anterior arch of the atlas.  It is not associate...
Article

Accessory ossicles

Accessory ossicles are secondary ossification centres that are separate from the adjacent bone. They are usually round or ovoid in shape, occur in typical locations and have well defined smooth cortical margins on all sides. In most cases, they are congenital in origin, although they may occur ...

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