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.

828 results found
Article

Thymic sail sign

The thymic sail sign represents a triangular-shaped inferior margin of the normal thymus seen on a neonatal frontal chest radiograph. It is more commonly seen on the right side, but can also be bilateral. It is seen in 3-15% of all cases. This sign should not be confused with the spinnaker sail ...
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Thyroid inferno

Thyroid inferno refers to the color Doppler appearance of the thyroid gland in active Graves disease (inclusive of variants such as Marine Lenhart syndrome), and consists of multiple small areas of color flow seen diffusely throughout the gland representing increased vascularity and arteriovenou...
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Tiger stripe appearance

The tiger stripe appearance refers to the characteristic alternating hypo and hyperintense bands on MRI in Lhermitte-Duclos disease. This rare cerebellar tumor appears like the coat of a tiger. See also tigroid pattern - in brain
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Tip of the iceberg sign (ovarian dermoid cyst)

Tip of the iceberg sign refers to one of the characteristic appearances of an ovarian dermoid cyst. If there are echogenic cyst contents of sebum and hair, they cause marked posterior acoustic attenuation so that only the superficial part of the cyst is seen. Just like an iceberg, you may only b...
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Tombstone iliac wings

Tombstone iliac wings, also referred to as Mickey Mouse ears pelvis 1, are an imaging descriptor for the iliac wings of individuals with achondroplasia. These are seen to be small and squared and have been likened to the appearance of tombstones or the ears of Mickey Mouse.
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Toothpaste sign

The toothpaste sign in spinal imaging represents an extrusion of an intervertebral disk into the epidural space. It is called after the shape of extruded material relatively to the parent disk in a sagittal plane.
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Track sign (femur)

The track sign is the presence of two sclerotic lines, running parallel to the long axis of the bone, on a frontal radiograph of the femur. It represents visualization of the linea aspera-pilaster complex, an anatomic variant 1. The linea aspera is the roughened vertical ridge of bone which run...
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Tramp-stamp edema

Tramp-stamp edema is a colloquial term used by some radiologists to denote posterior lumbar subcutaneous edema. The term is used to describe edema in the distribution seen with lower back tattoos, usually in young women, which are known pejoratively as tramp-stamps.  This edema is thought to be...
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Tram-track sign (bone)

The tram-track sign is sometimes seen on delayed bone scan images. They can appear as symmetric linear increase in tracer accumulation along diaphyseal and metaphyseal surfaces of long bones. Corresponding to similar periosteal reaction seen on radiographs. Bone scan findings precede radiographi...
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Tram-track sign (brain)

Tram-track sign in the brain refers to the parallel calcification of the cortex in patients with Sturge-Weber syndrome 1.  It should not be confused with other tram-track signs elsewhere in the body. 
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Tram-track sign (chest)

Tram-track sign may be used in chest radiography or CT to denote the thickened non-tapering (parallel) walls of cylindrical bronchiectasis. It should not be confused with other tram-track signs elsewhere in the body. 
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Tram-track sign (disambiguation)

Tram-track sign may refer to a variety of appearances characterized by near-parallel lines in a number of contexts and regions including: tram-track sign (brain): cortical calcification in Sturge-Weber syndrome tram-track sign (orbit): e.g. optic nerve meningioma tram-track sign (chest): thic...
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Tram-track sign (orbit)

Tram-track sign refers to the parallel thickening and enhancement around the optic nerve, and is most frequently seen in the setting of optic nerve meningioma. It may however also be seen in 1: orbital pseudotumour perioptic neuritis orbital sarcoidosis oribtal leukemia orbital lymphoma or...
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Transient ischemic dilatation

Transient ischemic dilatation (TID) is a paradoxical phenomenon seen in myocardial perfusion SPECT imaging.   With severe balanced coronary artery disease, myocardial ischemia may result in apparent enlargement of the left ventricular cavity during stress. The cause of this is not entirely clea...
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Transmantle sign (brain)

The transmantle sign is an MRI feature of focal cortical dysplasia (FCD), almost exclusively seen in type II focal cortical dysplasia (Taylor dysplasia - also known as transmantle cortical dysplasia for this reason). However, it is not always present, seen in ~45% (range 21-72%) of patients with...
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Tree-in-bud sign (lung)

Tree-in-bud sign or pattern describes the CT appearance of multiple areas of centrilobular nodules with a linear branching pattern. Although initially described in patients with endobronchial tuberculosis, it is now recognised in a large number of conditions. Pathology Pathogenesis The tree-i...
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Trethowan sign

The Trethowan sign is used to diagnose slipped capital femoral epiphysis (also called slipped upper femoral epiphysis). In this sign, the line of Klein passes above the femoral head. It is best done on both AP and true lateralcit projections. On the AP view of a normal hip, the Klein line inter...
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Triangular cord sign (biliary atresia)

The triangular cord sign is a triangular or tubular echogenic cord of fibrous tissue seen in the porta hepatis at ultrasonography and is relatively specific for the diagnosis of biliary atresia 1,2. This sign is useful in the evaluation of infants with cholestatic jaundice, helping in the diffe...
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Trident acetabulum

Trident acetabulum is an appearance which can be seen in several skeletal dysplasias 1. It is characterized by small bony spurs at the medial and lateral acetabular margins with a more subtle central spur, resembling a trident, the three-pronged spear of classical Greece 1. The trident is most ...
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Trident hand

A trident hand is a description where the hands are short with stubby fingers, with a separation between the middle and ring fingers.  The appearance mimics a trident, the three-pronged spear of classical Greece. The trident is most commonly associated with the sea god Poseidon in Greek mytholo...
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Trident sign (osmotic demyelination)

The trident sign describes the typical appearances of the pons in osmotic demyelination syndrome, whereby the symmetrical high T2/FLAIR signal abnormality centrally in the pons is shaped like a trident, the three-pronged spear of classical Greece 1. The predominant involvement of the transverse ...
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Trident sign (persistent trigeminal artery)

The trident sign of a persistent primitive trigeminal artery refers to the appearance of the intracranial circulation on lateral projection. The internal carotid artery, the abnormal vessel and superior portion of the basilar artery resemble the Greek letter tau (thus tau sign). This configurati...
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Triple bubble sign

The triple bubble sign is the classic radiographic appearance observed in jejunal atresia 1,2. The appearance is due to a proximal obstruction caused by the atretric jejunum. It is equivalent to the double bubble sign, but a third bubble is seen because of proximal jejunal distention.
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Troisier sign

Troisier sign is the clinical finding of a hard and enlarged left supraclavicular node (Virchow node), and is considered a sign of metastatic abdominal malignancy. Terminology It is sometimes referred to as the Virchow node, which is the name given by Rudolf Virchow (1821-1902) 6, a German pat...
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Trough line sign

The trough line sign is a sign of posterior shoulder dislocation on AP films.  In a posterior dislocation, the anterior aspect of the humeral head becomes impacted against the posterior glenoid rim. With sufficient force, this causes a compression fracture on the anterior aspect of the humeral ...
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Trousseau sign

Trousseau sign of latent tetany (not to be confused with Trousseau syndrome) is highly specific for hypocalcemia 1. It may be elicited by placing a blood pressure cuff over the upper arm and inflating to above systolic pressure for 2-3 minutes. This reduces arterial supply to the forearm. The is...
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Trumpeted internal acoustic meatus sign

A trumpeted internal acoustic meatus (IAM) is an indirect sign of an acoustic schwannoma and is useful in helping to differentiate between one and other cerebellopontine angle entities, especially from a meningioma which typically does not extend into the meatus and is more often associated with...
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T sign (obstetrics)

The "T sign" is really the absence of a twin-peak sign (or lambda (λ) sign) and is used in ultrasound assessment of a multifetal pregnancy. It refers to the lack of chorion extending between the layers of the intertwin membrane, denoting a monochorionic pregnancy. The intertwin membrane comes t...
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Tubal ring sign

Tubal ring sign, also referred to as bagel sign or blob sign, one of the ultrasound signs of a tubal ectopic. It comprises of an echogenic ring which surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy. Differential diagnosis...
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Tuberculous dactylitis

Tuberculous dactylitis, also known as spina ventosa, is a rare skeletal manifestation of tuberculosis where the short tubular bones (i.e. phalanges, metacarpals, metatarsals) are affected. Epidemiology Tuberculous osteitis is one of the commonest bacterial osteitides. Typically the dactylitis ...
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Tuberculous spondylitis versus pyogenic spondylitis

Tuberculous spondylitis and pyogenic spondylitis are both common causes of spinal infection. Imaging findings of these 2 diseases can be challenging to distinguish, yet crucial because the treatments for these infections are particularly different 2. Radiographic features Useful distinguishing...
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Tulip bulb sign

Tulip bulb sign refers to the characteristic appearance of annuloaortic ectasia as seen on CT angiography. There is symmetric dilatation of the three sinuses of Valsalva, with extension into the ascending aorta and effacement of the sinotubular junction.  It is seen especially in Marfan syndro...
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Tullio phenomenon

The Tullio phenomenon describes the precipitation of vertigo and nystagmus by a loud noise. Pathology Etiology The tympanic membrane and ossicular chain must be intact with a mobile footplate. It may be seen in several situations: Ménière disease superior semicircular canal dehiscence syndr...
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Turtle back sign

Turtle back sign, also referred as tortoise shell appearance, represents a very characteristic pattern of the schistosomiasis cirrhotic liver in which calcified fibrotic septa are seen aligned perpendicular to the liver capsule resembling the turtle's carapace. It is considered pathognomonic for...
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Twin-peak sign (twin pregnancy)

The twin peak sign (also known as the lambda (λ) sign) is a triangular appearance of the chorion insinuating between the layers of the intertwin membrane and strongly suggests a dichorionic twin pregnancy. It is best seen in the first trimester (between 10-14 weeks) 5. While the presence of a tw...
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Two-slice-touch rule (knee MRI)

The two-slice-touch rule is a sign on MRI of the knee used to increase the sensitivity of diagnosing meniscal tears. This rule states a meniscal tear is present if abnormal findings are present on two or more images - these do not have to be contiguous, e.g. can occur on sagittal and coronal sl...
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Unfolded aorta

The term unfolded aorta refers to the widened and 'opened up' appearance of the aortic arch on a frontal chest radiograph. It is one of the more common causes for apparent mediastinal widening and is seen with increasing age. It occurs due to the discrepancy in the growth of the ascending aorta...
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Upper lobe pulmonary venous diversion

Upper lobe pulmonary venous diversion (cephalisation) reflects elevation of left atrial pressure and can occur with pulmonary edema. It produces stag-antler's sign on a frontal chest x-ray. The normal left atrial pressure is 5-10 mmHg. An elevation of left atrial pressure to 10-15 mmHg will res...
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Upper T sign

The upper T sign is one of the features useful in identifying the central sulcus of the cerebral cortex on cross-sectional imaging. It relies on identifying the superior frontal sulcus which intersects the precentral sulcus in a "T" junction, thus defining the precentral gyrus. The central sulc...
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Urachus sign

The urachus sign is a radiographic sign of pneumoperitoneum. It represents the outline of the median umbilical ligament with free abdominal gas in a supine patient, as seen on a plain abdominal radiograph.
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Ureteric jet

Ureteric jets (or ureteral jets) are the visualization of the normal physiological periodic efflux of urine from the distal end of each ureter into the bladder.  Physiology When the urine passing down the ureter reaches the vesicoureteric junction it is forced out into the bladder via a strong...
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U sign (central sulcus)

The U sign denotes the characteristic U-shaped appearance of the subcentral gyrus which surrounds the inferolateral end of the central sulcus and abuts the lateral (Sylvian) fissure. It has been found, at least in one study, to be the most reliable anatomical feature to identify the central sulc...
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Vacuum phenomenon in shoulder

Vacuum phenomenon in the shoulder refers to the presence of intra-articular gas in the shoulder joint. It is a very common occurrence, particularly in external rotation. This can cause circular or linear areas of low signal intensity on GRE MR images of the shoulder obtained with external rotati...
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Vegetable and plant inspired signs

There are many signs in radiology which are vegetable- and plant-inspired, they include: Unprocessed produce celery stalk anterior cruciate ligament: ACL mucoid degeneration celery stalk metaphysis: osteopathia striata and congenital rubella infection Christmas tree intestinal atresia cocon...
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Veiled right kidney sign

The veiled right kidney sign is a sonographic sign described in pneumoretroperitoneum, most commonly due to duodenal perforation. It refers to the appearance of the right kidney on transabdominal ultrasound 1-4. On ultrasound, there is difficulty in obtaining images of the right kidney due to i...
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Venetian blind artifact (uterus)

The Venetian blind artifact (shadows) is a sonographic finding that is typically associated with adenomyosis but can also occur in uterine fibroids. The Venetian-blind artifact associated with adenomyosis is typically "thin" whereas when associated with uterine fibroids, there are also edge shad...
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Venous distension sign

The venous distension sign is a finding that may be identified on sagittal imaging of the dural venous sinuses which is said to have a diagnostic sensitivity and specificity of 94% for intracranial hypotension. The sign is positive when there is a convex inferior margin of the midportion of the...
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Ventricular interdependence

Ventricular interdependence (or ventricular coupling) is a phenomenon whereby the function of one ventricle is altered by changes in the filling of the other ventricle. This leads to increase in volume of one ventricle associated with a decreased volume in the opposite ventricle 1. This conditi...
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Venus necklace

A Venus necklace is a term almost never used, but for the sake of completeness is included here. It is used by some authors 1 to describe a series of T2 hyperintense lesions on the inferior surface of the corpus callosum in the midline (callososeptal interface), most frequently seen in multiple ...
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Vertebral body squaring (differential)

Vertebral body squaring refers to the loss of normal concavity of the anterior border. It is seen in a variety of conditions including:  Differential diagnosis Ankylosing spondylitis Ankylosing spondylitis is the most common cause of vertebral body squaring. It usually involves multiple level...
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Vertebral scalloping

Vertebral scalloping is a concavity to the posterior (or less commonly anterior) aspect of the vertebral body when viewed in a lateral projection. A small amount of concavity is normal, as is concavity of the anterior vertebral body (see vertebral body squaring). Posterior scalloping Causes of...
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Vertebra plana

Vertebra plana (a.k.a. pancake / silver dollar / coin-on-edge vertebra) is the term given when a vertebral body has lost almost its entire height anteriorly and posteriorly, representing a very advanced compression fracture. Plural is vertebrae planae. It can occur in a variety of settings, incl...
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Viking helmet appearance

The viking helmet appearance refers to the lateral ventricles in coronal projection in patients with dysgenesis of the corpus callosum. The cingulate gyrus is everted into narrowed and elongated frontal horns.  An alternative name is moose head appearance. 
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Volcano sign (meningioma)

Volcano sign refers to the appearance of classical meningioma that resembels the appearance of volcano (viewed in cross-section MRI, parallel to dural attachment) in which there is triangular hyperostosis at the base of the meningioma (mountain) with the tumor being the cloud around it. The intr...
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Waldenström sign (hip)

Waldenström sign is the increased distance between the pelvic teardrop and the femoral head. It is a highly specific sign of a hip joint effusion. Radiographic features Plain radiograph >11 mm total distance or >2 mm difference compared to contralateral hip 1,2 measured between the lateral a...
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Walking man sign (chest x-ray)

The walking man sign is seen on a lateral chest radiograph and is a sign of left atrial enlargement. It results from posterior displacement of the left main bronchus such that it no longer overlaps the right bronchus. The left and right bronchus thus appear as an inverted 'V', mimicking the legs...
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Wall-echo-shadow sign (ultrasound)

The wall-echo-shadow sign (also known as WES sign) is an ultrasonographic finding within the gallbladder fossa referring to the appearance of a "wall-echo-shadow": a curvilinear hyperechogenic line representing the gallbladder wall a thin hypoechoic space representing a small amount of bile a...
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Wasp-waist sign (spine)

The wasp-waist sign is a radiographic appearance seen in patients with Klippel Feil syndrome. It results from fusion of the vertebral bodies such that the anteroposterior diameter at the level of the affected discovertebral joint is smaller than the diameter at the superior and inferior limits o...
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Water bottle sign (heart)

The water bottle sign or configuration refers to the shape of the cardiac silhouette on erect frontal chest x-rays in patients who have a very large pericardial effusion. Typically the effusion has accumulated over many weeks to months (e.g. in patients with malignancy) and the pericardium has g...
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Water-lily sign (hydatid cyst)

The water-lily sign is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily. It is classically described on plain radiographs (mainly chest X-ray) when the collapsed membran...
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Watermelon skin sign

The watermelon skin sign refers to diffuse, radiating, streaky areas of low signal intensity in prostate on T2WI in patients with prostatic tuberculosis 1.  
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Wave sign

The wave sign refers to the indentation of the normal thymus in young children by the ribs, resulting in a wavy border.
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Weapon and munition inspired signs

Weapon and munition inspired signs include the following with their corresponding pathologic conditions: bayonet deformity Turner syndrome chondrodysplasia bullet-shaped vertebra mucopolysaccharidosis achondroplasia cannonball metastases metastases from renal cell carcinoma dagger sign ...
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Westermark sign

Westermark sign is a sign of pulmonary embolus seen on chest radiographs. It is one of several described signs of pulmonary embolus on chest radiographs. Pathology The theory behind the sign is either obstruction of the pulmonary artery or distal vasoconstriction in hypoxic lung 3. In one stu...
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Wheel within a wheel sign (hepatic candidiasis)

The wheel within a wheel sign describes one of several possible ultrasound findings of hepatic candidiasis. The finding consists of a round lesion with three layers corresponding to the following histopathological changes 2: peripheral hypoechoic area (fibrosis) middle hyperechoic area (inflam...
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Whirlpool sign (mesentery)

The whirlpool sign of the mesentery, also known as the whirl sign, is seen when the bowel rotates around its mesentery leading to whirls of the mesenteric vessels.  Terminology The term whirlpool sign is used in other contexts: see whirlpool sign (disambiguation). Radiographic features It is...
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Whirlpool sign (ovarian torsion)

The whirlpool sign or whirl sign of ovarian torsion is characterized by the appearances of a twisted ovarian pedicle seen on US or even on CT.  Terminology The term whirlpool sign is used in other contexts: see whirlpool sign (disambiguation).
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White cerebellum sign

White cerebellum sign, also called reversal sign or dense cerebellum sign, is encountered when there is a diffuse decrease in density of the supratentorial brain parenchyma, with relatively increased attenuation of the thalami, brainstem and cerebellum. This sign indicates irreversible brain dam...
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White matter buckling sign

The white matter buckling sign is helpful in distinguishing an extra-axial intracranial mass from an intra-axial one and represents the white matter projecting into gyri being compressed and displaced by the mass, even in the presence of edema (which would usually expand gyri, if the mass were i...
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White pyramid sign (kidney)

The white pyramid sign refers to the CT appearance of the medullary pyramids of the kidney which can be seen normally on unenhanced CT scans as high-attenuation triangular structures.  Bilateral high-attenuation renal pyramids are an occasional incidental normal finding. Additionally, the unila...
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Widened intercondylar notch

A widened intercondylar notch on knee radiographs is a sign associated with: haemophilic arthropathy (most commonly bilateral) juvenile rheumatoid arthritis (most commonly bilateral) tuberculosis arthropathy (usually unilateral) 3
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Widow's peak hair anomaly

Widow's peak hair anomaly refers to a frontal hairline projection. Epidemiology Associations Aarskog syndrome Opitz syndrome Waardenburg syndrome frontonasal dysplasia craniofrontonasal dysplasia Clinical presentation Prominent V-shaped hairline projection. Ocular hypertelorism might be...
Article

Wimberger ring sign

Wimberger ring sign , often simply just called Wimberger ring, refers to a circular calcification surrounding the osteoporotic epiphyseal center of ossification in scurvy, which may result from bleeding. It must not be confused with Wimberger sign, pathognomonic for congenital syphilis. Histor...
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Wimberger sign

The Wimberger sign, also called Wimberger corner sign, refers to localised bilateral metaphyseal destruction of the medial proximal tibias. It is a pathognomonic sign for congenital syphilis. It must not be mixed up with Wimberger ring sign seen in scurvy, which is sometimes also confusingly re...
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Windsock sign (aortic dissection)

The windsock sign refers to appearances seen in type A thoracic aortic dissections on contrast CT. It results from intimo-intimal intussusception between the true and false dissected lumens of the thoracic aorta. The altering density of contrast between the dissection lumens which taper distally...
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Windsock sign (duodenal web)

The windsock sign is a typical appearance of a duodenal web (intraluminal duodenal diverticulum) on upper gastrointestinal contrast series which consists of an intraduodenal barium contrast-filled sac that is surrounded by a narrow lucent line (web or intraluminal mucosal diaphragm) which is wel...
Article

Winking owl sign (spine)

The (absent) pedicle sign, also called the winking owl sign, occurs on plain film when a pedicle is absent. The term, winking owl sign, where the missing pedicle corresponds to the closed eye, the contralateral pedicle to the other open eye, and the spinous process to the beak of the animal on ...
Article

X-marks-the-spot sign (large bowel volvulus)

The X-marks-the-spot is a sign of complete bowel volvulus and refers to the crossing loops of the bowel at the site of the transition. It has been reported to improve diagnostic confidence in detecting cecal and sigmoid volvulus. This is in contrast to the split-wall sign which indicates partial...
Article

Yin-yang sign (solitary fibrous tumor)

The yin-yang sign is a radiologic appearance described in solitary fibrous tumor of the dura on MR. On T2-weighted images, these tumors have two separate solid components, one that is hyperintense and one that is iso- to hypointense relative to brain parenchyma. Histologically, the former repre...
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Yin-yang sign (vascular)

The yin-yang sign, also known as the Pepsi sign, is a radiological sign described in both true and false aneurysms on various imaging modalities. Radiographic features Ultrasound On Doppler ultrasound, the yin-yang sign indicates bidirectional flow due to the swirling of blood within the true...
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Y sign (epidural lipomatosis)

The Y sign refers to a common appearance in lumbar epidural lipomatosis where excess fat in the extradural space compresses the dural sac into the shape of the letter "Y". 
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Zebra sign (cerebellum)

The zebra sign has been termed to describe the finding of layering of blood in amongst the folia of the cerebellum, particularly in the setting of remote cerebellar hemorrhage.1 This type of hemorrhage is characterized by a streaky pattern, like a zebra's stripes, due to blood spreading in the ...
Article

Zebra spleen

Zebra spleen, also referred to as psychedelic spleen or more correctly inhomogeneous splenic enhancement refers to the transient heterogeneous parenchymal enhancement of the spleen during the arterial or early portal venous phases of contrast enhancement in CT, MRI, or ultrasound imaging. It is...
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Zebra stripe sign (bones)

The zebra stripe sign occurs where children with osteogenesis imperfecta have been treated with cyclical bisphosphonate therapy, e.g. pamidronate. When the drug is delivered in cycles, dense bone is formed while treatment is being given. This results in dense stripes across the metaphyses of bon...

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