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Racing car sign (callosal dysgenesis)

The racing car sign refers to widely spaced lateral ventricles due to agenesis of the corpus callosum with intervening Probst bundles. Appearances on axial MRI or CT are reminiscent of a Formula One car seen from above, with the tyres represented by the widely-spaced frontal horns, and the dilat...

Pseudovein sign (bowel)

The pseudovein sign can occur with active gastrointestinal bleeding where contrast extravasation during angiography may have a curvilinear appearance as it pools in the gastric rugae or mucosal folds of bowel, mimicking the appearance of a vein. However, contrast in the “pseudovein” persists bey...

Pseudogestational sac

A pseudogestational sac, also known as a pseudosac or intra-cavitary fluid, is the concept that a small amount of intrauterine fluid in the setting of a positive pregnancy test and abdominal pain could be erroneously interpreted as a true gestational sac in ectopic pregnancy. The sign was origi...

Pleural mouse

A pleural mouse (plural: pleural mice), also known as a fibrin body is a 1-2 cm mobile rounded clump of fibrin left over after resolution of a pleural effusion 1.

Pine cone bladder

A pine cone bladder or Christmas tree bladder is a cystographic appearance in which the bladder is elongated and pointed with a thickened, trabeculated wall. It is typically seen in severe neurogenic bladder with increased sphincter tone (detrusor sphincter dyssynergia) due to suprasacral lesion...

Phrygian cap

Phrygian caps are the most common congenital anatomic variant of the gallbladder. It denotes folding of the fundus back upon the gallbladder body and is asymptomatic with no pathological significance. Radiographic findings A Phrygian cap may be identified on ultrasound, multiphase CT/MRI, or c...

Penumbra sign (bones)

The penumbra sign represents a rim of vascularized granulation tissue around a bone abscess cavity that has a higher T1 signal intensity than the cavity itself 1. It should not be confused with the ischemic penumbra of cerebral infarction. The penumbra is isointense to muscle on T1, enhances...

Peg-like tonsil (cerebellum)

Peg-like tonsils refer to the CT or MR appearances of pointed cerebellar tonsils on sagittal scans. The may help distinguish low-lying tonsils from cerebellar tonsillar ectopia due to a Chiari I malformation. The terminology of caudally displaced tonsils is discussed in the article on cerebell...

Pear-shaped bladder

Pear-shaped (or teardrop-shaped) bladder is one whose normal round or ovoid shape has been extrinsically compressed to resemble a pear. The pear may be inverted or upright, depending on how the excess pelvic tissue compresses the bladder. Pathology Etiology Causes of a pear-shaped bladder inc...

Papilledema

Papilledema refers to swelling of the optic disc related to increased intracranial pressure. Terminology Although papilledema literally means swelling of the optic disc (nerve head/papilla), it is distinguished in common ophthalmological parlance from optic disc edema 8-10. Papilledema refers ...

Open ring sign

The open ring sign is a relatively specific sign for demyelination, most commonly multiple sclerosis (MS), and is helpful in distinguishing between the causes of ring-enhancing lesions. Radiographic features The enhancing component is thought to represent advancing front of demyelination and ...

Nutmeg liver

A nutmeg liver appearance is due to a perfusion abnormality of the liver usually as result of hepatic venous congestion. When hepatic veins are congested, contrast is prevented from diffusing through the liver in a normal manner. This results in a mottled pattern of contrast enhancement in the a...

O'Donoghue unhappy triad

O'Donoghue unhappy triad or terrible triad often occurs in contact and non-contact sports, such as basketball, football, or rugby, when there is a lateral force applied to the knee while the foot is fixated on the ground. This produces an abduction-external rotation mechanism of injury ("pivot s...

Notch sign (disambiguation)

There are many so-called notch signs. They include: focal notch in the wall (or tail extending from) a 2nd branchial cleft cyst between the internal and external carotid arteries peripheral notches in the contour of a solitary pulmonary nodule (SPN) suggests malignancy thymic notch sign late...

Mosaic pattern of bone

The mosaic bone pattern, also referred to as the jigsaw pattern of bone, is seen in Paget disease, where thickened, disorganized trabeculae lead to areas of sclerosis interspersed with lucent and more normal bone. See also Other Paget disease-related signs: banana fracture blade of grass sig...

Monod sign (lungs)

The Monod sign simply describes gas that surrounds a mycetoma (most commonly an aspergilloma) in a pre-existing pulmonary cavity 1-3. It should not be confused with the air crescent sign which is seen in recovering angioinvasive aspergillosis 4. The air crescent sign heralds improvement in the ...

Mercedes-Benz sign (gallbladder)

In the gallbladder, the Mercedes-Benz sign describes a star-shaped pattern of gas-fissuring within gallstones initially described on an abdominal radiograph 2. Fissures, usually fluid-filled, are present in close to 50% of gallstones. Less than half of these fissured gallstones contain some amo...

Positive metacarpal sign

In the metacarpal sign, a line drawn along the heads of the 4th and 5th metacarpals will intersect the head of the 3rd metacarpal if shortening is present. The shortened 4th metacarpal is the key to the sign. The sign is positive in up to 9.6% of normal individuals 3. It is however seen in a va...

Linguine sign (breast)

Linguine sign, also known as the wavy line sign, is one of the imaging signs of intracapsular rupture of a breast implant 4. Pathology After implantation of a silicone or saline breast implant, a fibrous capsule (scar) forms around the implant shell. In an intracapsular rupture, the contents o...

Lemon sign

The lemon sign, noted on antenatal imaging, is one of the many notable fruit-inspired signs. It is a feature when there appears to be an indentation of the frontal bone (depicting that of a lemon). It is classically seen as a sign of a Chiari II malformation and also seen in the majority (90-98%...

Septal lines in lung

Septal lines, also known as Kerley lines, are seen when the interlobular septa in the pulmonary interstitium become prominent. This may be because of lymphatic engorgement or edema of the connective tissues of the interlobular septa. They usually occur when pulmonary capillary wedge pressure rea...

Kerr kink

The Kerr kink is a sign of renal tuberculosis. Scarring in the adjacent tissues due to chronic inflammation leads to a sharp kink at the pelviureteric junction (PUJ). History and etymology William "Bill" K Kerr, a Canadian urologist, described his eponymous sign in 1967 3.

Interstitial line sign

The interstitial line sign is an ultrasound finding in interstitial ectopic pregnancy. It is an echogenic line from the mass to the endometrial echo complex. Reportedly it has high sensitivity (80%) and specificity (98%).

Inanimate object inspired signs

Inanimate object inspired signs are numerous with many radiographic appearances likened to bottles, hooks, items of clothing, weapons etc. They are listed below in the 'related articles' section.

Honeycombing (lungs)

Honeycombing is a CT imaging descriptor referring to clustered cystic air spaces (between 3-10 mm in diameter, but occasionally as large as 2.5 cm) that are usually subpleural, peripheral and basal in distribution. They can be subdivided into: microcystic honeycombing macrocystic honeycombing ...

Hoffman-Rigler sign (heart)

The Hoffman-Rigler sign is a sign of left ventricular enlargement inferred from the distance between the inferior vena cava (IVC) and left ventricle (LV). Radiographic features On a lateral chest radiograph, if the distance between the left ventricular border and the posterior border of IVC e...

Hemithorax white-out (differential)

Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation: the position of the trachea. Is it central, pulled or pushed from the side of opacification? Is there pulmonary volume loss or vo...

Head cheese sign (lungs)

The head cheese sign (more recently termed the three-density pattern refers to a juxtaposition of regions with three (or sometimes more) different densities/regions of different attenuation within the lungs: ground-glass opacities (high attenuation) mosaic attenuation pattern (low attenuation)...

Sandwich sign (mesentery)

A sandwich sign, sometimes known as a hamburger sign, refers to a mesenteric nodal mass, either para-aortic or not, giving an appearance of a hamburger. Confluent lymphadenopathy on both sides of the mesenteric vessels gives rise to an appearance described as the sandwich sign 2. The sign is sp...

H-shaped vertebra

H-shaped vertebrae, also known as Lincoln log vertebrae, are a characteristic finding of sharply delimited central endplate depression, classically seen in approximately 10% of patients with sickle cell disease, and results from microvascular endplate infarction (Figure 1) 3. It may occasionall...

Griesinger sign (mastoid)

The Griesinger sign refers to edema of the postauricular soft tissues overlying the mastoid process as a result of thrombosis of the mastoid emissary vein. It is a complication of acute otomastoiditis and may be associated with dural sinus occlusive disease (DSOD). It is said to be a pathognomon...

Golden S-sign (lung lobe collapse)

The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden. Although typically seen with right upper lobe collapse, the S-sign can also be seen with the...

Garland triad

Garland triad, also known as the 1-2-3 sign or pawnbroker's sign, is a lymph node enlargement pattern on chest radiographs which has been described in sarcoidosis: right paratracheal nodes right hilar nodes left hilar nodes Hilar lymphadenopathy is symmetrical and usually massive...

String sign (bowel)

The gastrointestinal string sign (also known as the string sign of Kantor) refers to the string-like appearance of a contrast-filled bowel loop caused by its severe narrowing. Originally used to describe the reversible narrowing caused by spasms in Crohn disease, it is now used for any severe n...

Funnel trachea

Funnel trachea is a colloquialism for a congenital long-segment intrathoracic tracheal stenosis. The diameter of the trachea immediately below the cricoid is normal, and becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or completel...

Fruit-inspired signs

There are many fruit-inspired signs in radiology: apple core sign (disambiguation) apple core sign (colon) apple core sign (femur) apple-peel intestinal atresia banana and egg sign banana sign banana fracture berry aneurysm bowl of grapes sign bunch of grapes sign (disambiguation) bun...

Lipohemarthrosis

Lipohemarthrosis results from an intra-articular fracture with escape of fat and blood from the bone marrow into the joint, and is most frequently seen in the knee, associated with a tibial plateau fracture or distal femoral fracture; rarely a patellar fracture. They have also been described in ...

Fishhook ureters

Fishhook ureters, also known as J-shaped ureters or hockey stick ureters describe the appearance of the distal ureter in patients with significant benign prostatic hypertrophy. It has also been used to describe the appearance of a retrocaval ureter in type 1 or low loop variety. As the right ure...

Fat halo sign (inflammatory bowel disease)

The fat halo sign (in colonic imaging) refers to a feature seen on CT abdominal scans, and represents infiltration of the submucosa with fat, between the muscularis propria and the mucosa. It is characterized by an inner (mucosa) and outer (muscularis propria and serosa) ring of enhancing bowel ...

Eye of the tiger sign (globus pallidus)

The eye of the tiger sign refers to symmetric bilateral abnormal low signal on T2-weighted MRI (due to abnormal accumulation of iron) in the globus pallidus with central high signal (due to gliosis and spongiosis). The eye of the tiger sign is most classically associated with pantothenate kinas...

Erlenmeyer flask deformity

Erlenmeyer flask deformity (EFD), also known as metaphyseal flaring, refers to a radiographic appearance typically on a femoral radiograph demonstrating relatively reduced constriction of the diaphysis and flaring of the metaphysis as a result of undertubulation. The name refers to the resembl...

Eggshell calcification (lymph nodes)

Eggshell calcification refers to fine calcification seen at the periphery of a mass and usually relates to lamellar lymph node calcification. For similar appearance in the breast, see eggshell calcification (breast). Terminology In 1967 Jacobsen and Felson published criteria to help "avoid ove...

Echogenic fetal bowel

Echogenic fetal bowel is an observation in antenatal ultrasound imaging, in which fetal bowel appears to be brighter than it is supposed to be. It is a soft marker for trisomy 21 and has several other associations. When observed, it needs to be interpreted in the context of other associated abno...

Dural tail sign

The dural tail sign occurs as a result of thickening and enhancement of the dura and is most often seen adjacent to a meningioma. Initially, the sign was felt to be pathognomonic of meningiomas, however, it has become increasingly noted to be present in many other conditions, although without t...

Double line sign

The double line sign is a pathognomonic MRI finding seen at the periphery of a region of osteonecrosis or bone infarct, representing the border between the viable and non-viable bone 4. It is best seen on T2 and T2 FS sequences and consists of two serpentine lines: an inner bright line represent...

Double posterior cruciate ligament sign

The double posterior cruciate ligament (PCL) sign appears on sagittal MRI images of the knee when a bucket-handle meniscal tear (medial meniscus in 80% of cases) flips towards the center of the joint so that it comes to lie anteroinferior to the posterior cruciate ligament (PCL) mimicking a seco...

Double decidual sac sign

The double decidual sac sign (DDSS) is a useful feature on early pregnancy ultrasound to confirm an early intrauterine pregnancy (IUP) when the yolk sac or embryo is still not visualized. It consists of the decidua parietalis (lining the uterine cavity) and decidua capsularis (lining the gestati...

Dagger sign (spine)

The dagger sign is a radiographic feature seen in ankylosing spondylitis as a single central radiodense line on frontal radiographs related to ossification of the supraspinous and interspinous ligaments secondary to enthesitis 1. It is possible for the radiodense line to extend into the sacrum 2...

Dawson fingers

Dawson fingers are a radiographic feature of demyelination characterized by periventricular demyelinating plaques distributed along the axis of medullary veins, perpendicular to the body of the lateral ventricles and/or callosal junction. This is thought to reflect perivenular inflammation. They...

Cyclops lesion (knee)

The cyclops lesion, also known as localized anterior arthrofibrosis, is a painful anterior knee mass that arises as a complication of anterior cruciate ligament (ACL) reconstruction, although has rarely been reported in patients with ACL injuries that have not been reconstructed. Epidemiology ...

Crazy paving

Crazy paving refers to the appearance of ground-glass opacities with superimposed interlobular septal thickening and intralobular septal thickening, seen on chest HRCT or standard CT chest. It is a non-specific finding that can be seen in a number of conditions. Pathology Etiology Common cau...

Cotton wool appearance (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...

Corkscrew sign (midgut volvulus)

The corkscrew sign describes the spiral appearance of the distal duodenum and proximal jejunum seen in midgut volvulus 1. In patients with malrotation and volvulus, the distal duodenum and proximal jejunum do not cross the midline and instead pass in an inferior direction. These loops twist on ...

Coffee bean sign (sigmoid colon)

The coffee bean sign (also known as the kidney bean sign or bent inner tube sign) 4 is a radiological finding on an abdominal plain radiograph of a sigmoid volvulus although some authors have also used the term to refer to closed loop small bowel obstructions. Cecal volvulus may be confused wit...

Codman triangle periosteal reaction

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

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 a tumor and brain parenchyma. However, it often ...

Cervix sign (pyloric stenosis)

The cervix sign of pyloric stenosis describes the indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis on ultrasound examination. See also antral nipple sign (pyloric stenosis) target sign (pyloric stenosis)

Butterfly glioma

Butterfly gliomas are high-grade astrocytomas, IDH-mutant or glioblastomas, IDH-wildtype that cross 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. Butterfly ...

Bright rim sign (DNET)

The bright rim sign, also known as the hyperintense ring sign, has been described in dysembryoplastic neuroepithelial tumors (DNET). It is described as a well-defined rim of high signal around the DNET on FLAIR sequences. This T2/FLAIR hyperintense ring, whether complete or incomplete, is fairly...

Bat wing opacities (lungs)

Bat wing opacities, also known as butterfly opacities, refer to a pattern of bilateral perihilar lung shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3,4. Differential diagnosis Bat wing pulmonary opacities can be caused by: ...

Banana sign (cerebellum)

The banana sign is one of the many notable fruit inspired signs. This sign is seen on axial imaging through the posterior fossa of fetuses with associated conditions such as Chiari II malformation and/or spina bifida. In Chiari II malformation, the banana sign describes the way the cerebellum...

Bamboo spine (ankylosing spondylitis)

Bamboo spine is a pathognomonic 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...

Baastrup disease

Baastrup disease/syndrome (also referred to as kissing spines) is a cause of low back pain characterized by interspinous bursitis and other degenerative changes of the bones and soft tissues where adjacent spinous processes in the lumbar spine rub against each other. Epidemiology It tends to b...

Apple-peel intestinal atresia

Apple-peel intestinal atresia, also known as type IIIb or Christmas tree intestinal atresia, is a rare form of small bowel atresia in which the duodenum or proximal jejunum ends in a blind pouch and the distal small bowel wraps around its vascular supply in a spiral resembling an apple peel. Oft...

Antral nipple sign (pyloric stenosis)

The antral nipple sign refers to redundant pyloric mucosa protruding into the gastric antrum and is seen in hypertrophic pyloric stenosis on ultrasound examination. See also cervix sign (pyloric stenosis) target sign (pyloric stenosis)

Animal and animal produce inspired signs

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 marine life cluster of black pearls sign endosteal scalloping: medullary cavity masses, e.g. multiple myeloma fish vertebra (al...

String sign (artery)

The angiographic string sign, also known as the carotid string sign or slim sign, refers to the thin string of intravascular contrast material distal to a stenotic focus in the internal carotid artery (ICA). Pathology A thin stripe of flow is caused by decreased pressure and flow distal to th...

Spinnaker sign (mediastinum)

The spinnaker sign (also known as the angel wing sign) is a sign of pneumomediastinum seen on neonatal chest radiographs. It refers to the thymus being outlined by air with each lobe displaced laterally and appearing like spinnaker sails. This is distinct from the sail sign appearance of the nor...

Air crescent sign (lung)

An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis, or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity. Terminology It should not be confused w...

Air bronchogram

Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...

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