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.

991 results found
Article

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 an echogenic ring that surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy. Differential diagnosis It ...
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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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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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Tulip sign

The tulip sign is a sonographic clue for in-utero diagnosis of severe hypospadias. The configuration of a tulip is given by the severe curvature of the penis in association with the penoscrotal transposition of a bifid scrotum.
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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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Tumor deposits

Tumor deposits (in the context of rectal cancer) are discrete nodules of tumor tissue within the mesorectum, often found along the path of draining vessels, and are distinct from lymph node metastases. They are found in >50% of MRI studies of patients with rectal cancer 1. Radiographic features...
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Turtleback sign

Turtleback sign, also known as tortoise shell appearance, represents a characteristic appearance of chronic hepatic schistosomiasis in which liver margins are irregular and nodular. Dystrophic calcifications within a polygonal network of fibrous septa are seen in the periphery, often perpendicul...
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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 decreased curvature of the aortic arch on a frontal chest radiograph giving an ‘opened up’ appearance. It is one of the more common causes for apparent mediastinal widening and is seen with increasing age, usually associated with aortic calcifica...
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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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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 (disambiguation): celery stalk sign anterior cruciate ligament celery stalk metaphysis Christmas tree intestinal atresia coconut left atrium coffee bean sign cotton w...
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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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Veil of obscuration sign (shoulder)

Veil of obscuration sign is a sign of posterior shoulder dislocation. It is generally seen on AP radiographs depicting a comminuted fracture of lesser tuberosity that projects over the glenohumeral joint giving rise to a "cloud-like" density or "veil of bone" density, which hides a posterior sho...
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Venetian blind appearance (uterus)

The Venetian blind (a.k.a. rain shower 2) appearance is a sonographic finding that is typically associated with adenomyosis but can also occur in uterine fibroids. The Venetian blind appearance associated with adenomyosis is typically "thin" whereas when associated with uterine fibroids, there a...
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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 has been 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 mul...
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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 (plural: vertebrae planae), also known as the pancake, silver dollar or 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. Pathology It can occur in a var...
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Viking helmet appearance

The Viking helmet appearance refers to the morphology of the lateral ventricles in the coronal plane 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. Other names include st...
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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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Waist sign hydrosalpinx

The waist sign arises from the folding of a distended tube upon itself producing indentations on diametrically opposite sides. The waist sign is specific for hydrosalpinx and virtually pathognomonic when seen in association with a tubular-shaped cystic mass. See also cogwheel sign beads on a ...
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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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Walnut kernel microbleed pattern

The walnut kernel microbleed pattern along with the starfield pattern and corpus callosum diffusion restriction appears to be the most important imaging markers of cerebral fat embolism 1-3. In this pattern, there is a diffuse presence of round microbleeds (punctate focal hypointensities) of mo...
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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, also known as the camalote 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...
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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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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 ...
Article

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). Radiographic features It appears as twisting of ...
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Whirlpool sign (testicular torsion)

The whirlpool sign of the spermatic cord is a direct sign of testicular torsion, both complete and incomplete (i.e. <360°). It is considered to be the most specific and sensitive sign for testicular torsion. Terminology The term whirlpool sign is used in other contexts: see whirlpool sign (dis...
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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, also known as dense renal medulla sign (DRM) or hyperdense renal pyramids 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. Etiology incidental normal fi...
Article

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) tuberculous arthropathy (usually unilateral) 3
Article

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. History...
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Wimberger sign

The Wimberger sign, also called Wimberger corner sign, refers to localized 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 intimointimal intussusception between the true and false dissected lumens of the thoracic aorta. The altering density of contrast between the dissection lumens which taper distally ...
Article

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...
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Windswept knees

Windswept knees refer to the appearance of a bilateral knee deformity where one knee is in valgus and the other is in varus. The name describes the position of the knees if the wind blew across the legs of a patient, causing the contralaterally opposing deformity. Etiology Most causes produce ...
Article

Winking owl sign (spine)

The (absent) pedicle sign, also called the winking owl sign, occurs on plain radiograph of the spine when a pedicle is absent 5. The term, winking owl sign, where the missing pedicle corresponds to the closed eye, the contralateral pedicle to the other round open eye, and the spinous process to...
Article

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

The X-marks-the-spot sign of large bowel volvulus 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 obstruction...
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...
Article

Yo-yo on a string sign (Stener lesion)

The yo-yo on a string sign denotes the characteristic appearance of the torn, proximally retracted and superficially displaced ulnar collateral ligament (UCL) due to a Stener lesion. Mechanism The sign occurs as a consequence of the tear of the ulnar collateral ligament of the thumb (gamekeepe...
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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". NB: Y sign also refers to the appearance of incudomalleolar disarticulation on CT, more commonly known to radiologists as t...
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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 supratentorial surgeries (temporal lobe resection), neuro-vascular neck surgeries, lumbar spinal surgeries possibly secondary to dural tear and inter...
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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 i...
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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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