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.

51 results found
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Baastrup syndrome

Baastrup syndrome (also referred to as kissing spines) results from adjacent spinous processes in the lumbar spine rubbing against each other and resulting in hypertrophy and sclerosis with focal midline pain and tenderness relieved by flexion and aggravated by extension.  Epidemiology It tend...
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Backwash ileitis

Backwash ileitis is seen in patients with ulcerative colitis (UC), where the entire colon is involved. In such cases the terminal ileum is oedematous. Backwash ileitis extends contiguously backward from the caecum without skip regions. One source estimates it to occur in 6% of patients with UC,...
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Ballet sign

The ballet sign refers to the paralysis of voluntary movements of the eyeball with preservation of the automatic movements. Sometimes this sign is present with exophthalmic goitre and hysteria.
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Ball of wool sign (hydatid cyst)

The ball of wool sign, also referred to as the yarn sign or congealed water lily sign, is an ultrasound appearance, representing degeneration of hydatid cysts (WHO class CE 4). The inner side of the cyst detaches from the cyst wall and folds on itself, causing a change from anechoic (fluid) to a...
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Balloon on a string sign (ureter)

The balloon on a string sign refers to the appearance of the ureter on intravenous urography in ureteropelvic junction obstruction. It is seen due to the high and eccentric point of the exit of ureter from a dilated renal pelvis. 
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Bamboo spine

Bamboo spine is a radiographic feature seen in ankylosing spondylitis that occurs as a result of vertebral body fusion by marginal syndesmophytes. It is often accompanied by fusion of the posterior vertebral elements as well.  A bamboo spine typically involves the thoracolumbar and/or lumbosacr...
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Banana sign (cerebellum)

The banana sign is one of the many notable fruit inspired signs. It is seen on axial imaging through the posterior fossa of the fetus and is associated with the Chiari II malformation. It describes the way the cerebellum is wrapped tightly around the brain stem as a result of spinal cord tether...
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Bare orbit sign (sphenoid wing)

The bare orbit sign, is described as a characteristic appearance of the orbit, seen when the innominate line is absent. The innominate line is a projection of the greater wing of the sphenoid, and its absence or destruction is responsible for this appearance. It is the classical frontal radiogr...
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Battle sign (base of skull fracture)

Battle sign in an eponymous name given to mastoid ecchymosis (bruising of the scalp overlying the mastoid process) and is suggestive of a base of skull fracture, most commonly a petrous temporal bone fracture.  History and etymology Mr William Henry Battle (1855-1936) was an English surgeon, w...
Article

Bat wing 4th ventricle

Bat wing 4th ventricle sign refers to the morphology of the fourth ventricle in the Joubert anomaly and related syndromes. The absence of a vermis with apposed cerebellar hemispheres give the fourth ventricle an appearance reminiscent of a bat with its wings outstretched. It is best demonstrate...
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Bat wing opacities (lungs)

Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4. Differential diagnosis Bat's wing pulmonary opacities can be caused by: pulmonary oedem...
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Bayonet deformity

Bayonet deformity is a term used to describe the shape of the wrist in certain conditions: Madelung deformity hereditary multiple exostosis with pseudo-Madelung deformity retarded bone growth of the distal ulna with outward bowing of the radius with distal radioulnar joint subluxation Colles...
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Beak sign (arterial dissection)

The beak sign of arterial dissection represents a wedge of haematoma at the distal end of the false lumen. It is here that false lumen propagation is occurring. It manifests as an acute angle between the dissection flap and the outer wall. It may be filled with contrast-enhanced blood (high atte...
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Beak sign (pyloric stenosis)

Beak sign in pyloric stenosis is one of the fluoroscopic (barium meal) findings which is useful in the diagnosis of congenital hypertrophic pyloric stenosis.  Radiographic features Barium meal A beak-like tapering projection of barium is seen entering into the narrowed and compressed pyloric ...
Article

Bear paw sign (kidney)

The bear paw sign is seen in xanthogranulomatous pyelonephritis and refers to the cross-sectional appearance of the kidney which is said to resemble the paw of a bear. The renal pelvis is contracted whereas the calyces are dilated, mimicking the toe-pads of the paw.
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Beck triad

Beck triad is a collection of three clinical signs associated with pericardial tamponade which is due to an excessive accumulation of fluid within the pericardial sac. The three signs are: low blood pressure (weak pulse or narrow pulse pressure) muffled heart sounds  raised jugular venous pre...
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Big rib sign

The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.  It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.  This s...
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Bilateral adrenal gland hyperenhancement

Bilateral adrenal gland hyperenhancement or intense adrenal enhancement may be a feature of hypotension and forms part of the CT hypoperfusion complex. Adrenal gland hyperenhancement has been described in paediatric and small adult series or individual cases of haemorrhagic shock, pancreatitis,...
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Bird beak sign (disambiguation)

Bird beak sign is used in many contexts to denote a rapid tapering to a point, reminiscent of a bird's beak. Described bird beak signs include:  beak sign (arterial dissection) beak sign (pyloric stenosis) bird beak sign (oesophagus) bird beak sign (right colon) bird beak sign (sigmoid colo...
Article

Bird beak sign (oesophagus)

The bird's beak sign of the oesophagus is used to refer to the tapering of the inferior oesophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the rat-tail sign. The appearance, although classically occurring in primary achalasia, ca...
Article

Bird beak sign (right colon)

The bird beak sign of the right colon is tapering obstruction of the inferior part of right colon seen on contrast enema or CT scan with rectal contrast indicating caecal volvulus. This sign can help to differentiate caecal volvulus from caecal bascule, in particular on a contrast/barium enema ...
Article

Bird beak sign (sigmoid colon)

Bird's beak sign of the sigmoid is one of the signs of sigmoid volvulus. It represents gradual narrowing/tapering of sigmoid colon up to the level of obstruction during contrast/barium insertion to the rectum or on CT. When located in the sigmoid colon, it suggests the diagnosis of sigmoid volv...
Article

Black turbinate sign (nasal cavity)

The black turbinate sign refers to an area of non-enhancing mucosa on MRI in a patient with angioinvasive fungal sinus infection / rhinocerebral mucormycosis. Mucormycosis is caused by fungi that include Mucor, Rhizopus, and Absidia species.  It is seen in diabetic and immunocompromised patient...
Article

Blade of grass sign (Paget disease)

The blade of grass sign, also called the candle flame sign, refers to the lucent leading edge in a long bone seen during the lytic phase of Paget disease of bone.  The blade of grass sign is characteristic of Paget disease of bone. This is akin to osteoporosis circumscripta cranii seen in the s...
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Blend sign (brain)

The blend sign refers to a CT appearance of early intracranial haematoma growth. It is defined as blending of a hypoattenuating area and a hyperattenuating region with a well-defined margin.
Article

Bone within a bone appearance

Bone within a bone is a descriptive term applied to bones that appear to have another bone within them. There are numerous causes including: normal thoracic and lumbar vertebrae (neonates and infants) growth recovery lines (after infancy) cortical splitting and new periostitis sickle cell d...
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Boomerang sign (knee)

The boomerang sign is defined as a small displaced flap from a longitudinal horizontal type medial meniscal tear which is displaced inferiorly into the medial meniscotibial recess. The imaging diagnosis of this type of tear is crucial because it is normally hidden from the surgeon during routine...
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Boomerang sign (splenium)

The boomerang sign refers to a boomerang-shaped splenial lesion (splenium of corpus callosum) which is seen as a hyperintense lesion on T2-WI, FLAIR and DWI 1. This sign can be seen in: transient lesion of the splenium ischaemia posterior reversible encephalopathy syndrome (PRES) diffuse ax...
Article

Bouchard node

Bouchard nodes are a clinical sign relating to bony nodules of the the proximal interphalangeal joints, and are much less common than Heberden nodes. They generally (but not always) correspond to palpable osteophytes. Clinical presentation They are sometimes painful, and are typically associat...
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Bouquet of flowers appearance (medullary sponge kidney)

A bouquet of flowers appearance is a description given to the appearances of medullary sponge kidney on a traditional intravenous pyelogram (IVP) study. The ectatic distal collecting ducts contain the microcalcifications typical of the disease. This is also known as the bunch of grapes appearanc...
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Boutonniere deformity

Boutonniere deformity is one of the musculoskeletal manifestations of rheumatoid arthritis in the hand with: flexion contracture of the proximal interphalangeal (PIP) joints extension of the distal interphalangeal (DIP) joints  The defect appears in the tendon which splays open. The appearanc...
Article

Box-shaped heart

A box-shaped heart is a radiographic description given to the cardiac silhouette in some cases of Ebstein anomaly. The classic appearance of this finding is caused by the combination of the following features: huge right atrium that may fill the entire right hemithorax shelved appearance of th...
Article

Bracket sign (pars marginalis)

The bracket sign of the pars marginalis, also known as the pars bracket sign, refers to the appearances of the superior most extent of the pars marginalis of the cingulate sulcus on axial imaging. It forms two roughly symmetric brackets, open anteriorly. The next sulcus anteriorly is the central...
Article

Bracket sign (pericallosal lipoma)

The bracket sign refers to a radiographic appearance seen with the tubulonodular variety of pericallosal lipoma. It reflects calcification seen at the periphery of the midline lipoma. It is best seen on coronal imaging and historically was identified on frontal radiographs. It should not be con...
Article

Breast within a breast sign

The breast within a breast sign refers to the common mammographic appearance of breast hamartomas (fibroadenolipomas). Since these benign lesions are well-circumscribed and contain a mixture of fibrous, glandular and fatty tissue (just like normal breast), it is not surprising that they appear v...
Article

Bridging vessel sign

The bridging vessel sign refers to an appearance of vessels coursing from the uterus into an adjoining pelvic mass (a vascular bridge). This sign helps to differentiate a pedunculated subserosal uterine leiomyoma from other juxtauterine masses of ovarian, adnexal or bowel origin. Colour and pow...
Article

Bright dot sign (atypical liver haemangioma)

The bright dot sign refers to the presence of a bright dot within a lesion which remains hyperattenuating on arterial and portal venous phase CT, corresponding to early nodular enhancement seen on dynamic MRI of liver haemangioma.  This can be used as an indicator that the lesion in question is...
Article

Bright rim sign (anterior talofibular ligament injury)

The bright rim sign in anterior talofibular ligament injury refers to a sign seen on MRI. A cortical defect with a bright dot-like or curvilinear high-signal-intensity, usually at the fibular attachment site, is seen on MRI. It has been described as an indicator of ATFL injury 1. See also brig...
Article

Bright rim sign in dysembryoplastic neuroepithelial tumours

The bright rim sign has been described in dysembryoplastic neuroepithelial tumours (DNETs) and is seen, as the name so aptly describes, as a rim of high signal around the DNET on FLAIR sequences.
Article

Bronchial cut-off sign

The bronchial cut-off sign refers to the abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucus plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse. 
Article

Bronchorrhoea

Bronchorrhoea is the expectoration of copious amounts of mucus from the lungs. It has been defined as production of more than 100 mL of mucus in 24 hours, which is more than is usually seen in chronic lung disease (e.g. chronic bronchitis typically produces 25 mL/24 hrs) 2. It may be a feature o...
Article

Brudzinski sign (meningism)

Brudzinski sign occurs in meningitis (of any aetiology) where passive flexion of one leg causes flexion in the opposite leg. Passive flexion of the neck brings about flexion of the legs as well. Historical context First described by Jósef Brudziñski (1874-1917), paediatrician from Warsaw, Pola...
Article

Bubbly consolidation

Bubbly consolidation describes internal or central lucencies which represent normal aerated lung lobule within infarcted, consolidated, lung parenchyma. It is one of the highly specific imaging appearances of focal pulmonary haemorrhage or possibly pulmonary infarct secondary to pulmonary emboli...
Article

Bulging fissure sign

The bulging fissure sign refers to lobar consolidation where the affected portion of the lung is expanded. It is now rarely seen due to the widespread use of antibiotics. The most common infective causative agents are 1: Klebsiella pneumoniae: Klebsiella pneumonia Streptococcus pneumoniae: pn...
Article

Bullet and bodkin sign

Bullet and bodkin sign is the appearance of the ureter when there is an abrupt transition in the ureteral caliber. Bullet in the name is represented by the dilated proximal ureteric segment which appears to be perched on the constricted / non-dilated encased ureter which gives an appearance of a...
Article

Bullet-shaped vertebra

Bullet-shaped vertebra refers to the anterior beaking of the vertebral body. It is seen in the following conditions: mucopolysaccharidosis (Morquio disease, Hurler disease) achondroplasia congenital hypothyroidism  See also weapons and munitions inspired signs
Article

Bunch of grapes sign (disambiguation)

Bunch of grapes sign refers to the ultrasound appearance of multiple cystic spaces or lesions and it has been described in a number of settings: within the uterus as a result of hydropic swelling of trophoblastic villi within a hydatidiform mole in bronchiectasis, where on a chest radiograph, ...
Article

Butterfly glioma

Butterfly gliomas are a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing-like extensions across the midline.  Most freq...
Article

Butterfly sign (choroid plexus)

The butterfly sign refers to the normal appearance of the choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1. In the CNS, the term should not be confused with a butterfly glioma, which is a glioblastom...
Article

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...
Article

Button sequestrum

A button sequestrum is a small sequestrum of devascularised bone surrounded by lucency. Although classically described in osteomyelitis and eosinophilic granuloma it is also occasionally seen in fibrosarcoma and lymphoma. Differential diagnoses osteoid osteoma tuberculous osteitis radiatio...

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