An angiosarcoma of the spleen is a rare malignant splenic neoplasm. The term is usually given to describe a primary angiosarcoma of the spleen although angiosarcoma elsewhere can also rarely metastasise to the spleen. Despite its absolute rarity, a splenic angiosarcoma is considered the most co...
The angle of the longitudinal arch is one of the angles drawn on the weightbearing lateral foot radiograph. The angle is formed between the calcaneal inclination axis and a line drawn along the inferior edge of the 5th metatarsal.
The normal angle is 150-170°.
In pes cavus, as the height of th...
The angular gyrus is a portion of the parietal lobe of the brain. It is one of the two parts of the inferior parietal lobule, the other part being the supramarginal gyrus. It plays a part in language and number processing, memory and reasoning 1.
It lies as a horseshoe...
The angular interface sign is used to characterise an exophytic renal mass, in which the exophytic renal mass has an angular interface with the renal parenchyma. In other words, the exophytic lesion has a tapered pyramidal contour or definite apex within the renal parenchyma.
Due to its high se...
The angular vein drains the anterior region of the scalp 1. It is formed by the union of the supratrochlear and supraorbital veins and becomes the facial vein 1,2,3.
The angular vein is formed at the medial canthus as the supratrochlear vein and supraorbital vein unite 1,2. The a...
Anhydramnios is a term where there is a complete or near-complete lack of amniotic fluid (sometimes referred to as "liquor volume").
Anhydramnios can result in a number of situations:
fetal renal tract anomalies
Potter syndrome (bilateral renal agenesis): most common
Animal and animal produce inspired signs may sound a little silly, but the radiology literature is replete with such signs, some more fanciful than others.
Fish and seafood
fish vertebra (also known as codfish vertebra): biconcave vertebrae as seen in osteoporosis
fishtail deformity of the el...
Anisotropy is an artefact encountered in ultrasound, notably in muscles and tendons during a musculoskeletal ultrasound. In musculoskeletal applications, the artefact may prompt an incorrect diagnosis of tendinosis or tendon tear.
When the ultrasound beam is incident on a fibrillar structure as...
Ankle AP view is part of a three view series of the distal tibia, distal fibula, proximal talus and proximal metatarsals.
the patient may be supine or sitting upright with their leg straighten on the table
the foot is in dorsiflexion
the toes will be pointing directly toward...
The ankle horizontal beam lateral view is a modified lateral view part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus.
The horizontal beam lateral is a highly adaptable projectio...
Ankle lateral view is part of a three view ankle series; this projection is used to assess the distal tibia and fibula, talus, navicular, cuboid, the base of the 5th metatarsal and calcaneus.
patient is in a lateral recumbent position on the table
the lateral aspect of the kn...
Ankle AP mortise view is part of a three view series of the distal tibia, distal fibula, talus and proximal metatarsals. It is the most pertinent projection for assessing the articulation of the tibial plafond and two malleoli with the talar dome, otherwise known as the mortise joint of the ankl...
Ankle and foot radiography is the plain radiographic investigation of the distal tibia and fibula, the tarsal bones and metatarsals. Radiographic examination of the foot and ankle are often requested together, however, there is a plethora of literature to aid in the correct request of x-ray exam...
Ankle brachial index (ABI) is a means of detecting and quantifying peripheral arterial disease. It can be performed in conjuction with ultrasound for better results.
Many patients with peripheral arterial disease may be asymptomatic (~20-50%), but they may also present with
Ankle fractures account for ~10% of fractures encountered in trauma, preceded only in incidence by proximal femoral fractures in the lower limb. They have a bimodal presentation, involving young males and older females. Ankle injuries play a major part in post multitrauma functional impairment t...
The ankle joint forms the articulation between the foot and the leg. It is a primary hinge synovial joint lined with hyaline cartilage.
The ankle joint is comprised of the tibia, fibula, talus, and calcaneus as well as the supporting ligaments, muscles and neurovascular bundles. ...
Ankle radiographs are frequently performed in emergency departments, usually, after trauma, the radiographic series is comprised of three views: an anteroposterior, mortise, and a lateral. They may be performed to assess degenerative or inflammatory arthritis as well as to look for the sequela o...
The ankle radiograph checklist is just one of the many pathology checklists that can be used when reporting to ensure that you always actively exclude pathology that is commonly missed; this is particularly helpful in the examination setting, e.g. the FRCR 2B rapid-reporting.
The ankle series is comprised of an anteroposterior (AP), mortise and lateral radiograph. The series is often used in emergency departments to evaluate the distal tibia, distal fibula, and the talus; forming the ankle joint.
See approach to an ankle series.
Ankle radiographs are p...
Ankle teardrop sign is one of the radiological signs of an ankle joint effusion. It represents the presence of fluid in the inferior part of the anterior compartment of ankle.
An ankle x-ray, also known as ankle series or ankle radiograph, is a set of two x-rays of the ankle joint. It is performed to look for evidence of injury (or pathology) affecting the ankle, often after trauma.
This is a summary article. For more information, you can read a mo...
Ankylosing spondylitis (less commonly known as Bechterew disease and Marie Strümpell disease) is a seronegative spondyloarthropathy, which, as the name suggests, results in fusion (ankylosis) of the spine and sacroiliac (SI) joints, although involvement is also seen in large and small joints.
Thoracic manifestations of ankylosing spondylitis can be varied. For a general discussion of the condition refer to the parent article on ankylosing spondylitis.
It can affect the tracheobronchial tree and the lung parenchyma, and the disease spectrum includes:
upper lobe fibrocystic changes
Annular fissures are a degenerative deficiency of one or more layers that make up the annulus fibrosus of the intervertebral disc.
Many authors prefer the term annular fissure over annular tear, as the latter seems to imply acute injury 1,2. In the setting of severe trauma with di...
Annular pancreas is a morphological anomaly which can cause duodenal obstruction. This condition is important to recognise, as radiologists are frequently the first to make the diagnosis.
The incidence is probably 1 in 250, however incidence is not accurately reported 1. It is as ...
Annulo-aortic ectasia refers to a proximal dilatation of the aortic root at the level of the aortic annulus, it is also the same level as the sinus of Valsalva.
Annulo-aortic ectasia occurs with connective tissue diseases such as Marfan disease and Ehlers-Danlos syndrome. It is a cys...
The annulus fibrosus surrounds the nucleus polposus and together they form the intervertebral disc.
The annulus comprises 15 to 20 collagenous (type I) laminae which run obliquely from the edge of one vertebra down to the edge of the vertebra below. The direction of the fibres al...
The anode represents the component of the x-ray tube where x-rays is produced. It is a piece of metal, shaped in the form of a bevelled disk with the diameter between 55 and 100mm, 7mm thick, connected to the positive side of the electrical circuit. The anode converts the energy of the electrons...
Anode heel effect refers to the intensity of the x-ray beam, produced from the X-ray tube, which is not uniform in all portions of the beam.
In general, the beam consists of a central ray and a diverging beam. The rays towards the cathode end of the tube have more intensity. This...
Anomalous course of a coronary artery is a type of congenital coronary artery anomaly. It may represent a benign and incidental finding, but can also be a malignant course predisposing patients to life-threatening myocardial ischaemia or arrhythmias, depending on where the artery runs.
Anomalous left coronary artery from the pulmonary artery (ALCAPA), also known as Bland-White-Garland syndrome (BWG), is a rare congenital coronary artery anomaly and is considered one of the most severe of such anomalies.
There are two forms, based on onset of disease, each of which has differe...
An anomalous pancreaticobiliary junction describes the abnormal junction of the pancreatic duct and common bile duct that occurs outside the duodenal wall to form a long common channel (> 15 mm).
The anomalous junction is often associated with a choledochal cyst or a biliary tract carcinoma and...
Anophthalmia refers to a complete absence of ocular development. It is often considered to represent the most severe form of microphthalmia.
It can occur in 3 different situations:
primary anophthalmia: complete absence of eye tissue due to a failure of the part of the brain that fo...
Anorectal disease is a group of conditions that affect the anus and rectum. The most common conditions in this group include haemorrhoids, anal fissures, anorectal abscess and anal fistula.
This is a summary article; we do not have a more in-depth reference article.
ANOVA (ANalysis Of VAriance) is a statistical technique commonly seen in radiology research.
ANOVA analyses are conceptually similar to the student t-test, but involve comparison of multiple groups at once. The alternative to an ANOVA would be multiple head-to-head t-tests, but this would likel...
Anoxic brain injury, also known as global hypoxic-ischaemic injury, is seen in all age groups (from antenatal to the elderly) as a result of numerous aetiologies. The pattern of injury depends on a number of factors including:
age of the patient (brain maturity)
neonatal hypoxic-ischaemic ence...
The ansa cervicalis is a component of the cervical plexus which gives muscular branches to the geniohyoid muscle of the suprahyoid group and all 4 of the infrahyoid muscles.
superior root: derived from the anterior primary rami of C1
inferior root: derived from the anter...
The ansa pancreatica is a rare type of anatomical variation of the pancreatic duct. It is a communication between the main pancreatic duct (of Wirsung) and the accessory pancreatic duct (of Santorini). Recently, the ansa pancreatica has been considered as a predisposing factor in patients with i...
The anteater nose sign refers to an anterior tubular elongation of the superior calcaneus which approaches or overlaps the navicular on a lateral radiograph of the foot. This fancifully resembles the nose of an anteater and is indicative of calcaneonavicular coalition 1,2.
History and etymolog...
Antegrade ureteric stents are performed under fluoroscopic guidance, typically by an interventional radiologist or urologist. It is performed via percutaneous access from the kidney. It is usually performed using the access from a prior percutaneous nephrostomy, a so-called 2-step procedure, alt...
Antenatal screening of Down syndrome (and other less common aneuploidies) should be available as a routine component of antenatal care. It allows families to either adjust to the idea of having a child with the condition or to consider termination of pregnancy.
For a general description of Down...
Antenatal screening and diagnosis are currently available for a few selected genetic conditions, including trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome) and neural tube defects.
For an overview of the conditions and their manifestations, please refer to t...
Antenatal soft ultrasound markers are fetal sonographic findings that are generally not abnormalities as such but are indicative of an increased age adjusted risk of an underlying fetal aneuploidic or some non chromosomal abnormalities.
Most of the described features do not constitute a structu...
An antepartum haemorrhage (APH) usually refers to PV bleeding during the second half of pregnancy (after 20 weeks gestation).
It can arise from many causes which include:
differential diagnosis fo...
The anterior abdominal wall forms the anterior limit of the abdominal viscera and is defined superiorly by the xiphoid process of the sternum and costal cartilages and inferiorly by the iliac crest and pubic bones of the pelvis.
The anterior abdominal wall has seven layers (from ...
Anterior angulation of the coccyx may be a normal variant but poses a diagnostic challenge for those considering coccygeal trauma.
Four types of coccyx have been described:
type I: the coccyx is curved slightly forward, with its apex pointing caudally (~70%)
type II: the coccy...
Anterior ankle impingement (AAI) syndrome is the result of chronic repetitive trauma with impingement of the anterior tibia against the talus.
Clinical features of anterior ankle impingement syndrome include painful and limited dorsiflexion and anterior joint line swellin...
A mnemonic that refers to the order of the ankle tendons that pass under the flexor retinaculum of the ankle running from medial to lateral is:
Tom Hates Dick
T: tibialis anterior
H: extensor hallucis longus
D: extensor digitorum longus
History and etymology
The phrase Tom, Dick...
The anterior atlanto-occipital membrane is a thin membrane that joins the upper border of the anterior arch of the atlas (C1) to the anterior inferior surface of the foramen magnum. It is a continuation of the anterior longitudinal ligament above the C1 level. It is immediately posterior to the ...
The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph.
The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly th...
The anterior cardiac veins are a group of parallel coronary veins that course over the anterior surface of the right ventricle, draining it and entering directly into the right atrium. They may occasionally drain into the small cardiac vein.
The anterior cardinal veins are paired transient embryologic venous vessels which deliver venous return to the heart starting at about 4 weeks of gestation 1.
The anterior cardinal veins begin their embryological development as symmetric venous channels draining blood from the cr...
The anterior cerebral artery along with the middle cerebral artery forms at the termination of the internal carotid artery. It is the smaller of the two, and arches anteromedially to pass anterior to the genu of the corpus callosum, dividing as it does so into its two major branches; pericallosa...
Anterior cerebral artery (ACA) territory infarcts are much less common than either middle or posterior cerebral artery territory infarcts.
ACA territory infarcts are rare, comprising ~2% of ischaemic strokes 1,2.
ACA stroke syndrome presents as 1,2,3:
The anterior cervical space is a small infrahyoid compartment of the head and neck. It is a fat containing space and is not enclosed by fascia 1.
posterior: carotid space
medial: visceral space
superior: submandibular space
The anterior choroidal artery (AChA) supplies several crucial anatomical structures of the brain important for vision and motor control. Identification of AChA is important because of its strategic and extensive area of supply as well as large variations in the territorial distribution.
Anterior choroidal artery syndrome is a rare entity characterised by the triad of hemiplegia, hemianaesthesia and contralateral hemianopia as a result of cerebral infarction in the anterior choroidal artery territory.
The syndrome may also be associated with neuropsychological disorders, includ...
The anterior commissure (AC) is a transversely oriented commissural white matter tract that connects the two cerebral hemispheres along the midline. It is a very important anatomical landmark that connects different parts of the limbic system on both sides and plays a role in the interhemispheri...
The anterior communicating artery (ACOM) arises from the anterior cerebral artery and acts as an anastomosis between the left and right anterior cerebral circulation. Approximately 4 mm in length, it demarcates the junction between the A1 and A2 segments of the anterior cerebral artery.
The anterior compartment of the arm is one of the two compartments of the arm.
A sheath of deep fascia surrounds the arm, the brachial fascia. Two intermuscular septa (medial and lateral) extend from it to attach to the humerus at the medial condylar ridge and lateral supracondylar ridge, respe...
The forearm is divided into the anterior compartment and the posterior compartment by the deep fascia, lateral intermuscular septum and the interosseous membrane between the ulna and radius.
The eight muscles located in the anterior compartment of the forearm can be divided into three...
The anterior compartment of the leg is one of the four compartments in the leg between the knee and foot. Muscles within this compartment primarily produce ankle dorsiflexion and toe extension.
The leg is separated into anterior, lateral, superficial posterior and deep posterior compartments by...
The anterior compartment of the thigh is one of the three compartments in the thigh. Muscles within this compartment primarily produce hip flexion and knee extension.
The thigh is separated into anterior, posterior and medial (adductor) compartments by intermuscular septa and surrounded by the ...
Anterior cord syndrome (also known as Beck's syndrome or anterior spinal artery syndrome) is a clinical subset of spinal cord injury syndromes, due to ischaemia/infarction of the anterior two-thirds of the spinal cord, typically sparing the posterior third.
The anterior corticospinal tract is formed at the level of the of the medullary pyramids, where the majority (90%) of descending corticospinal tract fibres decussate to form the lateral corticospinal tract. The majority of the remaining non-decussating 10% of fibres form the much smaller anterio...
The anterior cranial fossa constitutes the floor of cranial vault which houses the frontal lobes of the brain.
Structures present in the midline of anterior cranial fossa from anterior to posterior are:
groove for superior sagittal sinus
groove for anterior meningeal vessels
Anterior cruciate ligament (ACL) is one of the two cruciate ligaments that stabilise the knee joint.
The ACL arises from the anteromedial aspect of the intercondylar area on the tibial plateau and passes upwards and backwards to attach to the posteromedial aspect of the lateral ...
Anterior cruciate ligament (ACL) avulsion fractures or tibial eminence avulsion fractures are a type of avulsion fracture of the knee. This typically involves separation of the tibial attachment of the ACL to variable degrees. Separation at the femoral attachment is rare 5.
It is ...
Anterior cruciate ligament (ACL) ganglion cysts, commonly referred to simply as ACL cysts, along with ganglion cysts arising from the alar folds that cover the infrapatellar fat pad, make up the vast majority of intra-articular ganglion cysts of the knee.
Anterior cruciate ligamen...
Anterior cruciate ligament (ACL) mucoid degeneration, along with tears and anterior cruciate ligament ganglion cysts, is a relatively common cause of increased signal within the anterior cruciate ligament (ACL).
The appearance can mimic acute or chronic interstitial partial tears of the ACL. Ho...
Anterior cruciate ligament (ACL) tears are the most common knee ligament injury encountered in radiology practice.
The ACL is the most commonly disrupted ligament of the knee, especially in athletes who participate in sports that involve rapid starting, stopping, and pivoting (e.g. s...
Anterior hip dislocation is much less common than a posterior hip dislocation. It constitutes for only 5-18% of all hip dislocations.
While the posterior dislocation is often associated with fractures, the anterior dislocation is mostly an isolated injury 1.
It can be clas...
The anterior division of the mandibular division of the trigeminal nerve has four branches, which are all motor branches except one. The four branches are:
deep temporal nerves
lateral pterygoid nerves
The anterior ethmoidal artery is a branch of the ophthalmic artery. It supplies the anterior and middle ethmoidal sinuses, frontal sinus, the lateral nasal wall and the nasal septum (see nasal cavity).
It traverses the anterior ethmoidal foramen with the anterior ethmoidal nerve (which ...
The anterior ethmoid foramen is a small opening in the ethmoid bone. It is the anatomical border of anterior and posterior ethmoid air cells. It transmits the anterior ethmoidal artery, vein and nerve.
The anterior ethmoid foramen is situated 25 mm away from the lacrimal crest, 12 mm anterior t...
The anterior ethmoidal nerve is an extraconal branch of the nasociliary nerve, a branch of ophthalmic division of the trigeminal nerve. Some authors describe it as either the terminal branch or a direct continuation of the nasociliary nerve. It branches off distal to the infratrochlear nerve an...
Anterior glenolabral injuries are common in the setting of anterior shoulder dislocation and comprise a number of closely related entities.
bony Bankart lesion
anterior labroligamentous periosteal sleeve avulsion (ALPSA)
glenolabral articular disruption (GLAD)
Causes of anterior hip pain include:
pigmented villonodular synovitis (PVNS)
inflammatory arthropathy (e.g. rheumatoid arthritis)
Anterior horn syndrome is a fairly generic term used to refer to flaccid paralysis and areflexia due to involvement of the anterior grey matter horns of the spinal cord. Sensation is typically preserved.
Causes of anterior horn syndrome include:
anterior spinal artery ischaemia
The anterior humeral circumflex artery is a vessel arising from the axillary artery at the proximal part of the arm. It is smaller in size relative to the posterior humeral circumflex artery.
origin: branch of the axillary artery at the proximal part of the arm
location: proximal arm...
The anterior humeral line is key to demonstrating normal elbow alignment and should be used whenever reading a paediatric elbow radiograph to exclude a subtle supracondylar fracture.
A line drawn down the anterior surface of the humerus should intersect the middle third of the capitel...
The anterior inferior cerebellar artery (AICA) is one of three vessels that provides arterial blood supply to the cerebellum. It has a variable origin, course and supply, with up to 40% of specimens not having an identifiable standard AICA. The amount of tissue supplied by the AICA is variable (...
Anterior inferior cerebellar artery (AICA) territory infarcts are much less common than posterior inferior cerebellar artery (PICA) infarcts.
AICA territory infarcts are rare, comprising ~1% of ischaemic cerebellar strokes 2.
AICA stroke syndrome presents ...
The anterior inferior iliac spine (AIIS) is bony prominence on the anterior border of the ilium forming the superior border of the acetabulum.
Attachments include the Iliacus, origin of straight head of the rectus femoris, and also the the proximal ileofemoral ligament (Y-ligament or ligament o...
Anterior inferior iliac spine (AIIS) avulsion injuries are one of the six main types of pelvic apophyseal avulsion fractures.
As with many pelvic avulsion injuries, they most often occur in adolescents (mostly between the ages 14-17). There is a slight male predilection and they ...
The intercostal spaces are supplied by pairs of posterior and anterior intercostal arteries.
The 1st to 6th anterior intercostal arteries arise directly from the lateral aspect of the internal thoracic artery. The 7th to 9th arise from the musculophrenic artery, a branch of the i...
The anterior interosseous artery is one of the two branches of the short common interosseous artery (from the ulnar artery). The artery courses deep in the anterior compartment of the forearm on the anterior surface of the interosseous membrane along with the anterior interosseous nerve (from th...
The anterior interosseous nerve also known as the volar interosseous nerve arises from the median nerve in the forearm, and supplies the flexor pollicis longus, pronator quadratus and the lateral portion of flexor digitorum profundus.
The anterior interosseous nerve conti...
Anterior interosseous nerve syndrome (AINS), also known as Kiloh-Nevin syndrome, is one of three common median nerve entrapment syndromes; the other two being pronator teres syndrome and the far more common carpal tunnel syndrome.
AINS is a rare entrapment syndrome, with comparati...
The anterior jugular vein is a paired tributary of the external jugular vein.
It arises beneath the chin in the region of the hyoid bone or suprahyoid neck.
Origin and course
The anterior jugular vein has its origin as the confluence of several small superficial subma...
The anterior junction (junctional) line is a feature of frontal chest x-rays and chest CTs. It is a result of the parietal and visceral pleura meeting anteromedially. It normally contains a small amount of fat but can form a stripe of variable thickness if there is a lot of fat present or by the...
There are three anterior knee fat pads 1:
infrapatellar fat pad (of Hoffa)
fills the space between the patella ligament and the anterior intercondylar area of the tibia 2
posterior suprapatellar (prefemoral or supratrochlear) fat pad
anterior suprapatellar (quadriceps) fat pad
fills the spa...
Anterior knee pain is common with a variety of causes including:
inflammatory and depositional arthritis
bursitis around the knee
excessive lateral pressure syndrome (ELPS)
patellar cartilage defect