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.

60 results found
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Aberrant left pulmonary artery

Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterized by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and esophagus to reach the left lung. It may lea...
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Accessory ossicles

Accessory ossicles are secondary ossification centers that remain 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 occ...
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Accessory sutures

The parietal and occipital bones in particular are common regions for accessory sutures because of their multiple ossification centers. It is important to know these anatomic variations, mainly on the head trauma image studies in children, where it could be difficult to differentiate non-depres...
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Anatomy curriculum

The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists. General anatomy Neuroanatomy Head and neck anatomy Thoracic anatomy Abdominal and pelvic anatomy Spinal anat...
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Anterior fontanelle

The anterior or frontal fontanelle (or fontanel) is the diamond-shaped soft membranous gap at the junction of the coronal and sagittal sutures. It persists until approximately 18-24 months after birth, after which it is known as the bregma. The fontanelle normally measures between 0.6-3.6 cm (me...
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Anterior humeral line

The anterior humeral line is key to demonstrating normal elbow alignment and should be used whenever reading a pediatric elbow radiograph to exclude a subtle supracondylar fracture. The rule A line drawn down the anterior surface of the humerus should intersect the middle third of the capitell...
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Apophysis of the proximal 5th metatarsal

The apophysis of the proximal 5th metatarsal lies laterally and is oriented longitudinally parallel to the shaft. Apophysis of the fifth metatarsal base appears on plain radiographs at age 12 for boys and 10 for girls. Fusion of the apophysis to the metatarsal base usually occurs within the fol...
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Asplenia

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

Block vertebra is a type of vertebral anomaly where there is a failure of separation of two or more adjacent vertebral bodies. It is an anatomic variant. Pathology In a block vertebra, there is partial or complete fusion of adjacent vertebral bodies. Associations hemivertebrae/absent vertebr...
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Butterfly vertebra

Butterfly vertebra is a type of vertebral anomaly that results from the failure of fusion of the lateral halves of the vertebral body because of persistent notochordal tissue between them. Pathology Associations an anterior spina bifida, with or without an anterior meningocele can be part of...
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Canal of Nuck

The canal of Nuck is an abnormal patent pouch of parietal peritoneum extending anteriorly from the round ligament of the uterus into the labia majora through the inguinal ring into the inguinal canal. Incomplete obliteration of this canal is known as a patent processus vaginalis and can result i...
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Caudothalamic groove

The caudothalamic groove is an important landmark when performing neonatal cranial ultrasound. Gross anatomy As the name suggests, it is located between the caudate nucleus and thalamus, and is a shallow groove projecting from the floor of the lateral ventricle. It is approximately at the leve...
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Cerebellar agenesis

Cerebellar agenesis is a rare congenital abnormality which can result from failure to develop normal cerebellar tissue or destruction of normally developed tissue. For a more general overview of cerebellar malformations, please refer to the article on classification systems for malformations of...
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Congenital portosystemic shunt

​Congenital portosystemic shunts are rare, extrahepatic or intrahepatic, anatomical abnormalities shunting blood from the portal venous system to the systemic venous system and, thus, avoiding passage through the hepatic acinus. Terminology The term “portosystemic shunt” can be used to refer t...
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Ductus arteriosus

The ductus arteriosum (or arteriosus) is the thick short conduit for blood to bypass the non-ventilated lungs in the fetus. It is located between and connects the proximal left pulmonary artery and the undersurface of the aortic arch distal to the origin of the last branch of the arch, at the ao...
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Ductus venosus

Ductus venosus (DV) is a narrow, trumpet-shaped vessel which is seen in the fetal liver connecting the umbilical vein directly to the caudal inferior vena cava. The vessel plays a critical role in the fetal circulation by shunting oxygenated and nutrient-rich umbilical venous blood from the plac...
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Elbow ossification

Elbow ossification occurs at the six elbow ossification centers in a reproducible order. Being familiar with the order of ossification of the elbow is important in not mistaking an epicodylar fracture for a normal ossification center.  Appearance Order The order of appearances of the elbow os...
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Endochondral ossification

Endochondral ossification describes the process of ossification from mesenchymal cells (stem cells) with a cartilaginous template and is involved in the healing process of fractures. Bone formation occurs at centers of ossification (or ossification centers) which are either primary or secondary...
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Fetal circulation

Fetal circulation differs from the adult circulation due to the presence of certain vessels and shunts.  These shunts will close after birth, and most of these fetal vessels will be seen as remnants in the adult circulation. The function of these shunts is to direct oxygen-rich venous blood to ...
Article

Foramen ovale (cardiac)

The foramen ovale (or ovalis) is the opening in the interatrial septum in the fetal heart that allows blood to bypass the right ventricle and non-ventilated lungs, shunted from the right atrium to the left atrium. Specifically it represents the opening between the upper and lower portions of the...
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Fossa ovale

The fossa ovale (or ovalis) is the small oval depression in the interatrial septum at the site of the closed foramen ovale, which closes once fetal circulation ceases in the first few minutes of postnatal life. It represents the overlapping primary and secondary septa of the interatrial septum. ...
Article

Heterotaxy syndrome

Heterotaxy syndrome or situs ambiguus (also commonly, but etymologically less correctly, spelled situs ambiguous) is a disturbance in the usual left and right distribution of the thoracic and abdominal organs which does not entirely correspond to the complete or partial mirror image. It occurs ...
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Incomplete hippocampal inversion

Incomplete hippocampal inversion describes the situation where the normal inversion of the hippocampus fails to happen during development. Terminology Incomplete hippocampal inversion is the most correct description of this finding. Hippocampal malrotation is a term used by some authors 1 alth...
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Interrupted aortic arch

Interrupted aortic arch (IAA) is an uncommon congenital cardiovascular anomaly where there is a separation between the ascending and descending aorta. It can either be complete or connected by a remnant fibrous band. An accompanying large ventricular septal defect (VSD) and/or patent ductus arte...
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Intramembranous ossification

Intramembranous ossification describes the process of ossification from mesenchymal cells (stem cells) without a cartilaginous template and is involved in the healing process of fractures. The stages of intramembranous ossification osteogenesis are as follows: mesenchymal cells differentiate in...
Article

Kump's bump

Kump's bump is a superior convexity of the growth plate located in the anteromedial quadrant of the distal tibia physis, which is the first site of physeal fusion. Closure usually occurs at about 12-13 years of age. The Kump's bump should not to be mistaken for a fracture or abnormal physeal fus...
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Labeled imaging anatomy cases

This article lists a series of labeled imaging anatomy cases by system and modality. Brain CT head: non-contrast axial CT head: non-contrast coronal CT head: non-contrast sagittal CT head: angiogram axial CT head: angiogram coronal CT head: angiogram sagittal CT head: venogram axial CT ...
Article

Ligamentum venosum

The ligamentum venosum is a fibrous remnant which travels superiorly from the porta hepatis of the liver to the inferior vena cava. It is often obliterated in adults.  In the fetus, it is patent and known as the ductus venosus which shunts blood returning from the placenta in the umbilical vein...
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Lordosis

Lordosis (plural: lordoses) is the term used to refer to the normal anterior curvature of the cervical and lumbar spines when viewed from the side (concavity at the posterior aspect of the spine (cf kyphosis). Lordosis cervicis and lordosis lumbalis are the respective Terminologia Anatomica term...
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Mastoid fontanelle

The mastoid or posterolateral fontanelles (or fontanels) are paired bilateral soft membranous gaps at the junction of the parietomastoid, occipitomastoid, and lambdoid sutures. Each mastoid fontanelle persists until the second year of life, after which it is known as the asterion. It can be used...
Article

Meckel diverticulum

Meckel diverticulum is a congenital intestinal diverticulum due to fibrous degeneration of the umbilical end of the omphalomesenteric (vitelline) duct that occurs around the distal ileum. It is considered the most common structural congenital anomaly of the gastrointestinal tract. Epidemiology ...
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Mendosal suture

The mendosal suture (also known as the accessory occipital suture) is a normal calvarial suture. Gross anatomy The suture extends through the occipital bone, lying superior to the occipitomastoid suture and inferomedial to the lambdoid suture. It closes in utero or in the first few days of lif...
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Multicentric ossification

Multicentric ossification refers to normal, or variant of normal, ossification at more than one site within a single epiphysis or apophysis. It is important to be aware of common sites where multicentric ossification may occur, to avoid confusion with fracture, apophysitis and other entities. t...
Article

Neurenteric canal of Kovalevsky

The neurenteric canal or canal of Kovalevsky is the transient communication of the amnion through notochordal canal to the yolk sac during notochordal formation at day 16-17. Abnormalities during this stage produce the neurenteric cyst spectrum.
Article

Omega epiglottis

The omega epiglottis is a variant configuration of the normal epiglottis in which the lateral folds are curled inwards. The configuration is not necessarily pathologic but has been associated with higher rates of laryngomalacia 3.  Differential diagnosis When seen on lateral neck radiograph, a...
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Omega sign (disambiguation)

The omega sign can refer to a number of different anatomical structures or signs: omega sign (epiglottitis) omega sign (hand bump on the precentral gyrus)
Article

Orthoroentgenogram

Orthoroentgenogram is a radiographic study used to evaluate anatomic leg length and calculate leg-length discrepancies. This study utilizes a long ruler placed on the film, and three radiographs including bilateral hips, knees and ankles. Similar studies used to evaluate true leg length include...
Article

Ossification centers of the elbow

There are six ossification centers of the elbow that appear and develop in a relatively reproducible fashion, and are key to assessment of the pediatric elbow radiograph. Timing of their appearance varies in the literature but an approximation is given below. A useful mnemonic to remember the or...
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Ossification centers of the foot

Primary ossification centers present at birth Visible on x-ray from birth: calcaneus: 6 months in utero talus: 7 months in utero cuboid: 9 months in utero metatarsals: 9 weeks in utero phalanges: 3-10 months (proximal to distal) Primary ossification centers developing after birth Become ...
Article

Pediatric kidney size

The pediatric kidneys follow a growth curve. The measurements below are of the longest maximal dimension. Measurements in parentheses are one standard deviation. 0 months 1:  female: 4.15 cm (0.35); male: 4.22 cm (0.32) 2 months: 5.28 cm (0.66) 6 months: 6.15 cm (0.67) 10 months: 6.23 cm (0....
Article

Patent urachus

A patent urachus is one of the spectrum of congenital urachal anomalies. It has occasionally been termed "urachal fistula". Clinical presentation A patent urachus is often diagnosed in neonates when urine is noted leaking from the umbilicus. The umbilicus may also have an abnormal appearance o...
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Persistent right umbilical vein

A persistent right umbilical vein (PRUV) is an uncommon vascular anomaly which is often detected in utero. Epidemiology The estimated prevalence is ~2 per 1000 births 1,2. Pathology In the normal situation, the right umbilical vein begins to obliterate in the ~4th week of gestation and disap...
Article

Posterior fontanelle

The posterior fontanelle or occipital fontanelle (or fontanel) is the triangular soft membranous gap at the junction of the lambdoid and sagittal sutures. It persists until approximately 3 months after birth, after which it is known as the lambda. It can be used as an additional sonographic wind...
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Pseudosinus tract

A pseudosinus tract is a normal fibrous cord extending from the coccyx to an overlying sacral dimple. These have no associated mass and contain no fluid (if CSF drainage is occurring via the sacral dimple, then a true dorsal dermal sinus should be considered). Diagnosis Ultrasound Hypoechoic ...
Article

Radiocapitellar line

The radiocapitellar line is one of the key lines used to assess alignment on the elbow radiograph. It is particularly useful in the pediatric setting. The rule A line drawn down the neck of the radius should intersect the capitellum. It is important to ensure that you draw the line down the ra...
Article

Renal agenesis

Renal agenesis refers to a congenital absence of one or both kidneys. If bilateral (traditionally known as the classic Potter syndrome) the condition is fatal, whereas if unilateral, patients can have a normal life expectancy.  Epidemiology Unilateral renal agenesis affects approximately 1 in ...
Article

Sexual differentiation

Sexual differentiation refers to the embryological development of male and female phenotypes. Unlike sexual genotype which is determined at the time of fertilisation, the male and female phenotypes do not begin to differentiate substantially until the seventh week of gestation.  Males  Y chrom...
Article

Single umbilical artery

Single umbilical artery (SUA) results when there is a congenital absence of either the right or left umbilical artery. In the usual situation, there are paired umbilical arteries. For unknown reasons, the absence of the left umbilical artery is much more common (~70%). Epidemiology The estimat...
Article

Situs classification

Situs classification can be a daunting topic, but it falls into three main groups : situs solitus: the normal configuration of thoracic and abdominal organs situs inversus: mirror image of normal situs ambiguus: an intermediate configuration with duplication (isomerism) Situs is best thought...
Article

Situs solitus

Situs solitus refers to the normal position of the thoracic and abdominal organs. Radiographic features Plain radiograph On plain radiograph, careful attention should be directed at the location of the aortic arch, gastric fundus, cardiac apex, pulmonary fissures and the branching pattern of ...
Article

Sphenoidal fontanelles

The sphenoidal or anterolateral fontanelles (or fontanels) are paired bilateral soft membranous gaps at the junction of the coronal, sphenofrontal, sphenoparietal, sphenosquamosal, and squamosal sutures. Each mastoid fontanelle persists until approximately six months after birth, after which it ...
Article

Spleen size (pediatric)

The spleen size varies with a child's age. The three numbers below represent the 10th percentile, median, and 90th percentile for the long axis of the spleen (cm) 0-3 months: (3.3, 4.5, 5.8 cm) 3-6 months: (4.9, 5.3, 6.4 cm) 6-12 months: (5.2, 6.2, 6.8 cm) 1-2 years: (5.4, 6.9, 7.5 cm) 2-4...
Article

Sprengel deformity

Sprengel deformity, or congenital elevation of the scapula, is a complex deformity of the shoulder and is the most common congenital shoulder abnormality. An initial diagnosis can often be made on radiography, but CT or MRI is often necessary to evaluate the details of the abnormality. Clinical...
Article

Transverse vaginal septum

Transverse vaginal (transvaginal) septum (TVS) is a type of rare congenital uterovaginal anomaly (class II under the Rock and Adam classification). Epidemiology It is rare with a frequency of 1 in 70,000 females. Clinical presentation In the case of a complete septum, patients commonly prese...
Article

Triradiate cartilage

The triradiate cartilage is the Y- shaped epiphyseal plate that occurs at the junction where the ischium, ilium and pubis meet in the skeletally immature skeleton.   The vertical component of the "Y" is the meeting of the ischium and pubic bone, the anterior arm is the junction of the ilium and...
Article

Umbilical vein

The umbilical vein is the conduit for blood returning from the placenta to the fetus until it involutes soon after birth. The umbilical vein arises from multiple tributaries within the placenta and enters the umbilical cord, along with the (usually) paired umbilical arteries. Once it enters the...
Article

Umbilicus

The umbilicus is the fibrous remnant of the foetal attachment of the umbilical cord after birth. All layers of the anterior abdominal wall fuse at the umbilical ring, a small round defect in the linea alba located just inferior to the midpoint between the xiphoid process of the sternum and the p...
Article

Ventriculus terminalis

The ventriculus terminalis or terminal ventricle of Krause, also known as the 5th ventricle, is an ependymal-lined fusiform dilatation of the terminal central canal of the spinal cord, positioned at the transition from the tip of the conus medullaris to the origin of the filum terminale. This di...
Article

Vesico-urachal diverticulum

Vesico-urachal diverticulum is one of the congenital urachal remnant abnormalities. Gross anatomy It is the proximal equivalent of a urachal umbilical sinus, representing a result of the failure of the urachus to close at the urinary bladder, forming an out-pouching of variable length from the...
Article

Wolffian duct

The Wolffian duct (also known as the mesonephric duct) is one of the paired embryogenic tubules that drain the primitive kidney (mesonephros) to the cloaca. It also gives off a lateral branch forming the ureteric bud. In both the male and the female the Wolffian duct develops into the trigone of...

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