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.

71 results found
Article

C sign

The C sign is an important radiological sign which may be seen on a lateral radiograph of ankle in those with a  tarsal coalition (talocalcaneal coalition).  Radiographic appearance A continuous C-shaped arc is seen on a lateral ankle radiograph which is formed by the medial outline of the tal...
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Caecal bar sign

The caecal bar sign is a secondary sign in acute appendicitis. It refers to the appearance of inflammatory soft tissue at the base of the appendix, separating the appendix from the contrast-filled caecum. See also arrowhead sign
Article

Callosal angle

The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).  Method Ideally the angle should be measured on a cor...
Article

Calyceal crescent sign

The calyceal crescent sign (Dunbar's crescents) refers to the early IVP appearance of markedly dilated renal calyces. It is formed by early contrast opacification of the dilated collecting ducts and ducts of Bellini with the characteristic shape as a result of the associated enlarged calyces.  ...
Article

Cannonball metastases

Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance. Metastases with such an appear...
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Capp triad

The Capp triad refers to the constellation of clinical and imaging findings in patients with spontaneous retropharyngeal haematomas, and consists of: tracheal and oesophageal compression anterior displacement of the trachea subcutaneous bruising over the neck and anterior chest
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Caput medusae sign - developmental venous anomalies

The caput medusae sign, refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus. The sign is seen on both CT and ...
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Caput medusae sign - portal hypertension

The caput medusae sign is seen in patients with severe portal hypertension. It describes the appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen to join the systemic veins.  The appearance is reminiscent of Medusa, a gorgon of...
Article

Cardiac chamber enlargement

Cardiac chamber enlargement can be recognised by cardiac contour changes, new or different interfaces with adjacent lung, and/or displacement of adjacent mediastinal structures. These are discussed separately: right atrial enlargement right ventricular enlargement left atrial enlargement lef...
Article

Carman meniscus sign

The Carman meniscus sign describes the lenticular shape of barium in cases of large and flat gastric ulcers, in which the inner margin is convex toward the lumen. It usually indicates a malignant ulcerated neoplasm; in cases of benign gastric ulcers, the inner margin is usually concave toward th...
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Cartilage interface sign

Cartilage interface sign, also referred as "double cortex sign", refers to the sonographic presence of a thin markedly hyperechoic line at the interface between the normally hypoechoic hyaline articular cartilage of the humeral head and an abnormally hypoechoic supraspinatus tendon, du...
Article

Caton-Deschamps index

Caton-Deschamps index is a ratio that is used in everyday practice as well as in research to measure patellar height and allows the diagnosis of patella alta and patella baja. Radiographic features Caton-Deschamps index is the ratio between the distance between the lower pole of the patella an...
Article

Celery stalk metaphysis

Celery stalk metaphysis refers to a plain film appearance of the metaphyses in a number of conditions characterised by longitudinally aligned linear bands of sclerosis. They are seen in: congenital infections congenital rubella 
 congenital syphilis 
 congenital CMV 
 
 ost...
Article

Celery stalk sign (ACL)

The celery stalk sign is a term given to the appearance of the anterior cruciate ligament which has undergone mucoid degeneration and  has been likened to that of a celery stalk. Its low signal longitudinal fibers are separated from each other by higher signal mucinous material, best seen on T2 ...
Article

Centipede sign

The centipede sign is seen as engorged mesenteric vessels in case of acute sigmoid diverticulitis which gives an appearance similar to centipede 1.
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Cervicothoracic sign

The cervicothoracic sign, a variant of the silhouette sign, is believed to have been coined by Benjamin Felson. It helps to discern the anterior or posterior location of a mass in the superior mediastinum on frontal chest radiographs.  As the anterior mediastinum ends at the level of the clavic...
Article

Cervix sign of pyloric stenosis

The cervix sign of pyloric stenosis describes indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis. See also antral nipple sign target sign of pyloric stenosis shoulder sign of pyloric stenosis
Article

Champagne glass pelvis

The champagne glass pelvis is a helpful sign in achondroplasia which the iliac blades are flattened, giving rise to a pelvic inlet and resembles a champagne glass. The acetabular angles are increased, and the sacrosciatic notch is small.
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Chang sign

The Chang sign refers to the dilatation and abrupt change in calibre of the main pulmonary artery due to pulmonary embolism 1.  See also knuckle sign in pulmonary embolism
Article

Chasing the dragon - toxic leukoencephalopathy

"Chasing the dragon" is a sign seen in toxic leukoencephalopathy caused by inhalation of heroin fumes.  Clinical presentation Three stages are recognised: cerebellar signs and motor restlessness pyramidal and pseudobulbar signs spasms, hypotonic paresis, and ultimately death Only...
Article

Cheerio sign - pulmonary nodule

Cheerio sign in thoracic imaging relates to pulmonary nodules with a central lucent cavity as seen on CT. It is due to proliferation of (malignant or non-malignant) cells around an airway. They are so named because of their resemblance to the breakfast cereal, Cheerios 1-2.  The Cheerio sign pu...
Article

Cheerio sign - SLAP III

The Cheerio sign has been described as a sign seen in a type III superior labral anterior posterior tear (SLAP lesion) of the glenoid labrum. In the cheerio sign, a rounded core of soft tissue is surrounded by a rim of contrast material and air.  SLAP type III is the bucket handle tear of the s...
Article

Chorionic bump

A chorionic bump is a finding that can be uncommonly seen in a first trimester scan (0.7% of pregnancies 1). It may represent a small haematoma bulging into the gestational sac or an anembryonic (failed) second pregnancy that is being resorbed. It is also seen in some patients undergoing inferti...
Article

Cingulate sulcus sign

The cingulate sulcus sign as been proposed as being useful as an MRI feature of idiopathic normal pressure hydrocephalus (NPH). It denotes the posterior part of cingulate sulcus being narrower than the anterior part. The divider between the anterior and posterior parts of the sulcus being a line...
Article

Claw sign

The claw sign is useful in determining whether a mass arises from a solid structure or is located adjacent to it and distorts the outline.  It refers to the sharp angles on either side of the mass, which the surrounding normal parenchyma forms when the mass has arisen from the parenchyma. As su...
Article

Cloaca - osteomyelitis

A cloaca (pl. cloacae/cloacas) can be found in chronic osteomyelitis. The cloaca is an opening in a involucrum which allows drainage of purulent and necrotic material out of the dead bone. If the tract extends to the skin surface, the portion extending beyond the involucrum to the skin surface ...
Article

Cloverleaf skull

A cloverleaf skull (also known as kleeblattschädel) refers to type of severe craniosynostosis which gives the skull a cloverleaf shape. It typically results from intrauterine premature closure of sagittal, coronal and lambdoid sutures. Pathology Associations thanatophoric dysplasia: classical...
Article

Cobblestoning

Cobblestoning (having a cobblestone appearance) can occur in a number of hollow organs with mucosa, most commonly the bowel, in the setting of Crohn's disease.  Longitudinal and circumferential fissures and ulcers separate islands of mucosa, giving it an appearance reminiscent of cobblestones. ...
Article

Cobra head sign

The cobra head sign (or spring onion sign) refers to dilatation of the distal ureter, surrounded by a thin lucent line, which is seen in patients with an adult-type ureterocoele. The cobra head appearance indicates an uncomplicated ureterocele. The lucent "hood" of the cobra represent...
Article

Cobweb sign of arterial dissection

The cobweb sign is seen in cases of arterial dissection (usually aortic dissection) on CTA examinations and represents strands or ribbons of media crossing the false lumen, and appearing as thin filiform filling defects. Although it is a specific sign for the false lumen, it is infrequently see...
Article

Coca-Cola bottle sign

The coca-cola bottle sign refers to the appearance of the muscles of the orbit in thyroid eye disease.  The belly of the muscle enlarges with sparing of the tendinous insertion, giving the appearance of the traditional coca-cola bottle. The enlargement of the muscles follows the I'M SLOW format...
Article

Cockade sign

The cockade sign is a classic appearance of an intraosseous lipoma of the calcaneus which presents as a well-defined lytic lesion with a central calcification resembling a cockade.  It is named after a cockade, which is a badge, usually in the form of a rosette or knot, and generally worn on th...
Article

Codman triangle periosteal reaction

Codman triangle is a type of periosteal reaction seen with aggressive bone lesions. With aggressive lesions, the periosteum does not have time to ossify with shells of new bone (e.g. as seen in single layer and mulitlayered periosteal reaction), so only the edge of the raised periosteum will oss...
Article

Coffee-bean sign

The coffee-bean sign (also known as bent inner tube sign 4 ) is a sign on an abdominal plain film of a sigmoid volvulus although some authors have also used the term to refer to closed loop small bowel obstructions. This contrasts to a kidney bean sign which is seen with a caecal volvulus. This...
Article

Cogwheel sign in pelvic imaging

The Cogwheel sign in pelvic imaging refers to an imaging appearance of thickening loops of the Fallopian tube seen on cross section. There are infolding projections (sometimes look like nodules)  into the Fallopian tube lumen which is likened to that of a cogwheel. The sign is typically describe...
Article

Coin lesion

Coin lesion refers to a round or oval, well-circumscribed solitary pulmonary lesion. It is usually 1-5 cm in diameter and calcification may or may not be present 1,3. Typically but not always the patient is asymptomatic 1.  Differential diagnosis The differential diagnosis for such lesions is ...
Article

Colon cut-off sign

Colon cut-off sign describes gaseous distension seen in proximal colon associated with narrowing of the splenic flexure in cases of acute pancreatitis. Though originally described in abdominal radiographs, this sign has also been demonstrated in contrast enemas and computed tomography1. This ap...
Article

Comb sign

The comb sign refers to the hypervascular appearance of the mesentery in active Crohn disease.  Fibrofatty proliferation and perivascular inflammatory infiltration outline the distended intestinal arcades. This forms linear densities on the mesenteric side of the affected segments of small bowel...
Article

Comet tail sign - chest

The comet tail sign is a finding that can be seen on computed tomographic scans of the chest. It consists of a curvilinear opacity that extends from a subpleural "mass" toward the ipsilateral hilum. The comet tail sign is produced by the distortion of vessels and bronchi that lead to a...
Article

Comet tail sign: Urology

Comet-tail sign (in urological imaging) is helpful in distinguishing a ureteric calculus from a phlebolith and strongly favours the later.  The sign refers to a tail of soft tissue extending from a calcification, representing the collapsed/scarred/thrombosed parent vein. When well seen it is sa...
Article

Concentric ring sign

The concentric ring sign is a pathognomonic sign for a subacute haematoma on MRI. A subacute haematoma may show 3 characteristic layers of  signal intensity: a thin peripheral rim of low signal intensity on all pulse sequences corresponding to haemosiderin. an inner peripheral high-signal int...
Article

Cone-shaped caecum

A number of conditions can result in a cone-shaped caecum, with the apex pointing at the base of the appendix. Pathology Aetiology infectious blastomycosis amebiasis Yersinia enterocolitis tuberculosis typhoid fever cytomegalovirus (CMV) infection inflammatory inflammatory bowel disea...
Article

Continuous diaphragm sign

The continuous diaphragm sign is a chest radiograph sign of pneumomediastinum or pneumopericardium if lucency is above the diaphragm, or of pneumoperitoneum if lucency is below the diaphragm.  Normally the central portion of the diaphragm is not discretely visualised on chest radiographs as it ...
Article

Convoluted cerebriform pattern

A convoluted cerebriform pattern is a term used to denote the appearance of an sinonasal inverted papilloma on MRI. The appearance is seen on both T2 and post contrast T1 images and appears as alternating roughly parallel lines of high and low signal intensity. This sign has been reported as p...
Article

Cookie bite skeletal metastases

Cookie bite metastases are characterised by a small focal eccentric lytic external cortex destruction in long tubular bones. This type destruction is typically described for metastases from bronchogenic carcinoma, however they can also occur with other tumours.
Article

Copper beaten skull

Copper beaten skull, also known as beaten brass skull, refers to the prominence of convolutional markings (gyral impressions on the inner table of the skull) seen throughout the skull vault. Demographics and clinical presentation The appearance of copper beaten skull is associated with raised ...
Article

Cord sign

The cord sign refers to cordlike hyperattenuation within a dural venous sinus on non-contrast enhanced CT of the brain due to dural venous sinus thrombosis. The sign is most commonly seen in the transverse sinus because along the origin of the tentorium it runs approximately in the axial plane s...
Article

Corduroy sign

The corduroy sign refers to a vertically oriented, thickened trabeculations seen in intraosseous haemangiomas of the spine. It is caused by replacement of the normal cancellous bone by thickened vertical trabeculae surrounded by fat marrow or vascular lacunae in intraosseous haemangiomas 2. Se...
Article

Corkscrew sign

The corkscrew sign describes the spiral appearance of the distal duodenum and proximal jejunum seen in midgut volvulus. It has been identified as a diagnostic indicator of midgut volvulus1. In patients with malrotation and volvulus, the distal duodenum and proximal jejunum do not cross the midl...
Article

Cortical rim sign

The cortical rim sign is useful in distinguishing acute pyelonephritis from a segmental renal infarct and is seen on contrast enhanced CT or MRI. The wedges of reduced enhancement seen in the setting of acute pyelonephritis represent oedema and ischaemia which involves the whole wedge or renal ...
Article

Cottage loaf sign

The cottage loaf sign occurs as a result of a right-sided diaphragmatic rupture with partial herniation of the liver through the diaphragmatic defect. The herniated component is separated by a waist at the diaphragm from the larger intra-abdominal component. This shape is reminiscent of a cottag...
Article

Cotton wool appearance of bone

The cotton wool appearance is a plain film sign of Paget disease and results from thickened, disorganized trabeculae which lead to areas of sclerosis in a previously lucent area of bone, typically the skull. These sclerotic patches are poorly defined and fluffy. See also Other Paget disease re...
Article

Courvoisier sign

Courvoisier sign or Courvoisier-Terrier's sign states that in a patient with painless jaundice and an enlarged gallbladder (or right upper quadrant mass), the cause is unlikely to be gallstones and therefore presumes the cause to be an obstructing pancreatic or biliary neoplasm until proven othe...
Article

Coxa magna

Coxa magna is the asymmetrical, circumferential enlargement and deformation of the femoral head and neck. Definitions in the literature vary but enlargement with asymmetry >10% in size is a reasonable cut-off for diagnosis 1.  Pathology Aetiology Legg-Calve-Perthes disease transient synov...
Article

Coxa profunda

Coxa profunda refers to a deep acetabular socket. On pelvis x-rays it is seen as the acetabular fossa being medial to the ilioischial line. It should be differentiated from protrusio acetabuli, where the femoral head is seen additionally medial to the ilioischial line. Coxa profunda is much more...
Article

Coxa valga

Coxa valga describes a deformity of the hip where there is increased angle between the femoral neck and femoral shaft.  Pathology Coxa valga is often associated with shallow acetabular angles and femoral head subluxation.  Aetiology bilateral neuromuscular disorders, e.g. cerebral palsy of...
Article

Craniotabes

Craniotabes is defined as a softening of the skull bones that may be normally present in newborns.    
Article

Crazy paving

Crazy paving refers to the appearance of ground-glass opacity with superimposed interlobular septal thickening and intralobular reticular thickening, seen on chest HRCT. It is a nonspecific finding that can be seen in a number of conditions.  Pathology Aetiology Common causes: acute respirat...
Article

Crescent in a doughnut sign

The crescent in a doughnut sign refers to the transverse ultrasound appearance of intestinal intussusception, and is a variation of the target sign (which is also known as the doughnut sign) The doughnut is formed by concentric alternating echogenic and hypoechogenic bands. The echogenic
 b...
Article

Crescent sign of arterial dissection

The crescent sign refers to the high signal crescent seen in the wall of a vessel when dissected. This may be seen both on T1 or T2 sequences depending on the age of the blood (see ageing blood on MRI). It is classically referred to in internal carotid artery dissection. It should not be confus...
Article

Crescent sign of avascular necrosis

The crescent sign of avascular necrosis is seen on conventional radiographs, and refers to a linear area of subchondral lucency seen most frequently in the anterolateral aspect of the proximal femoral head (which is optimally depicted on the frog-leg radiographic view). It indicates imminent art...
Article

Crossing sign

The crossing sign is seen on true lateral plain radiographs of the knee when the line of the trochlear groove crosses the anterior border of one of the condyle trochlea. it is a predictor of trochlear dysplasia. Trochlear dysplasia has been linked to recurrent patellar dislocation1,2,4. The cros...
Article

Crow feet sign

Crow feet sign is a characteristic but uncommon feature seen in round atelectasis. On CT, this is seen as linear bands radiating from mass into adjacent lung tissue which resembles the feet of the crow. This sign should not be confused with fibrotic changes occurring in the lung.
Article

CSF cleft sign

The CSF cleft sign in neuroimaging can be used to distinguish an extra-axial lesion from an intra-axial lesion, and is typically used in the description of a meningioma. Classically, the cleft was regarded as representing a thin rim of CSF between tumour and brain parenchyma. However, it often ...
Article

CT angiogram sign

The CT angiogram sign refers to vessels appearing prominent during a contrast enhanced CT as they traverse an airless low attenuation portion of consolidated lung. Although initially thought to be specific for bronchoalveolar carcinoma, it has now been recognised as a generic appearance provided...
Article

CT angiographic spot sign

The CT angiographic (CTA) spot sign is defined as unifocal or multifocal contrast enhancement within an acute primary intracerebral haemorrhage (ICH) visible on CTA source images and discontinuous from adjacent normal or abnormal blood vessels 1. It should not be present on pre-contrast images. ...
Article

CT comma sign

The CT comma sign is a characteristic sign seen in head trauma. It is the presence of concurrent epidural and subdural haematomas, which gives the characteristic appearance of this sign as a "comma" shape.
Article

Cupola sign

The cupola sign is seen on a supine chest or abdominal radiograph in the presence of pneumoperitoneum. It refers to dependant air that rises within the abdominal cavity of the supine patient to accumulate underneath the central tendon of the diaphragm in the midline. The superior border is well...
Article

Curtain sign

The curtain sign (or draped curtain sign) in neuroimaging refers to the appearance of a vertebral body mass that extends to the anterior epidural space. The posterior longitudinal ligament is strongly attached to the posterior vertebral body cortex in the midline and is more loosely attached la...
Article

Cyclops lesion

The cyclops lesion, also known as localised anterior arthrofibrosis, is a painful anterior knee mass that arise as a complication of anterior cruciate ligament (ACL) reconstruction. Epidemiology Cyclops lesions occur with an estimated frequency of ~5% (range 1-9.8%) of patients following ACL r...
Article

Cyst with dot sign

The cyst with dot sign is seen in neurocysticercosis and represents the parasitic cyst with, usually eccentric, scolex. It can be seen on both MRI and CT at: the vesicular stage (CSF density / intensity cyst - denser / hyperintense scolex) and colloidal vesicular stage (enhancement of wall an...

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