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.

10,989 results found
Article

Vitamin B3

Vitamin B3 (niacin or nicotinic acid) is a water soluble vitamin that is an important part of the coenzyme nicotinamide adenine dinucleotide (NAD+) which is involved in many reactions of cellular metabolism. Related pathology Pathological manifestation occur in niacin deficiency known as pella...
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Vitamin B5

Vitamin B5 (panthothenic acid) is a water soluble vitamin that is required to synthesise coenzyme A, a very important coenzyme in many reactions of cellular metabolism. Deficiency is not well characterised.
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Vitamin B6

Vitamin B6 is a group water soluble vitamins that are deratives of pyridine, namely pyridoxine, pyridoxal and pyridoxamine. All three form part of the coenzyme pyridoxal 5'-phosphate (PLP) which is involved many cellular reaction including the synthesis of several amino acids and the metabolism ...
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Vitamin B7

Vitamin B7 (biotin) is a water soluble vitamin that is a coenzyme for many reactions, including gluconeogenesis and the synthesis of fatty acids and amino acids. Biotin deficiency is caused by dietary insufficiency, pharmacological interactions and, possibly, increased biotinolysis in smokers a...
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Vitamin B9

Vitamin B9 (folate or folic acid) is a water soluble vitamin that is vital for the synthesis of several amino acids, the purines adenosine and guanine and the pyrimidine thymine (three of the four nucleotide bases and hence critical for the synthesis of nucleic acids.) The antimicrobial group s...
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Vitamin C

Vitamin C (ascorbic acid) is a water soluble vitamin that is a coenzyme for the formation of the structure protein collagen, particularly creating cross-linking of collagen fibres which greatly increases its tensile strength. It also acts as an antioxidant. Related pathology Pathological manif...
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Vitamin D

Vitamin D is used to describe a group of five fat-soluble secosteroid vitamins required for the homeostasis of serum calcium and phosphorus. Vitamin D is a prohormone that exists in two forms in humans (D2 and D3). Cholecalciferol (D3) acts by regulating calcium and phosphorus intestinal absorp...
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Vitamin E

Vitamin E (the tocopherols) are a group of fat-soluble vitamins that act as an antioxidant. Hypovitaminosis E is rarely seen outside premature infants. Hypervitaminosis E is extremely rare as vitamin E is the least toxic of all the vitamins.
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Vitamin K

Vitamin K (phylloquinone (K1) and menaquinone (K2)) are a group of fat-soluble vitamins essential for normal blood-clotting function. Menaquinone is synthesised by normal flora in the intestine although the amount produced in vivo in the human gut is likely negligible. Vitamin K serves as a coen...
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Vitamins

Vitamins are a group of organic compounds used in biochemical pathways. Many are components of coenzymes in particular metabolic reactions. Vitamins are generally not synthesised by the human body and hence must be acquired through the diet. In radiology, there are some imaging manifestations o...
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Vitreous haemorrhage

Vitreous haemorrhage refers to bleeding into the vitreous chamber. Epidemiology Vitreous haemorrhage has an incidence of approximately 7 in 100000 1,2.   Clinical features The most common clinical presentation is with sudden, painless visual loss to varying degrees of severity 2. There may b...
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Viva preparation

Viva preparation is key to successful completion of professional exams.  It is really important to think about the types of cases that you will be shown in the viva and preparing aurally for them. So, rather than learning sitting with your books, get a set of films, or using the Radiopaedia.org...
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Viva technique

Viva technique is hugely important when sitting oral examinations. You must remember that the examiners may well have been examining for several days and for hours at a time. They will have shown their films many times and will know them backwards! Moreover, their films will be beloved, so do no...
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Vocal cord paralysis

Vocal cord paralysis/palsy (VCP) can cause laryngeal dysfunction ranging from slight hoarseness to life-threatening airway obstruction. Pathology Left vocal cord paralysis is twice as common than right vocal cord paralysis, and unilateral vocal cord paralysis much less common than bilateral vo...
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Vogt-Koyanagi-Harada syndrome

Vogt-Koyanagi-Harada syndrome is a multisystem disorder characterised by granulomatous panuveitis with exudative retinal detachments that is often associated with neurologic and cutaneous manifestations. Epidemiology Vogt-Koyanagi-Harada usually affected those of Asian, Middle Eastern, Asian I...
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Voiding cystourethrography

Voiding cystourethrography (VCUG), also known as a micturating cystourethrography (MCU),  is a fluoroscopic study of the lower urinary tract in which contrast is introduced into the bladder via a catheter. The purpose of the examination is to assess the bladder, urethra, postoperative anatomy an...
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Volar intercalated segmental instability

Volar intercalated segmental instability (VISI) is a type of instability involving the wrist. It is less often encountered than dorsal intercalated segmental instability (DISI). Clinical presentation It presents in most cases with nonspecific wrist pain and a "clunking" on the ulnar deviation ...
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Volar plate avulsion injury

Volar plate avulsion injuries are a type of avulsion injury. The volar plate of the proximal interphalangeal (PIP) joint is vulnerable hyperextension injury as either an ligamentous or intra-articular fracture. Gross anatomy The volar plate forms the floor of PIP joint separating the joint spa...
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Voltage gated potassium channel (VGKC) antibody encephalitis

Voltage gated potassium channel (VGKC) antibody encephalitis is an autoimmune encephalitis with antibodies against the voltage gated potassium channel. It is one of the most common forms of autoimmune limbic encephalitis in the absence of primary extra-CNS tumours. Autoimmune VGKC encephalitis c...
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Vomer

The vomer is one of the facial bones and forms the postero-inferior part of the bony nasal septum. Variant anatomy Occasionally the sphenoid sinus may pneumatise the vomer 2.
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Von Hippel-Lindau disease

Von Hippel-Lindau (vHL) disease is characterised by the development of numerous benign and malignant tumours in different organs (at least 40 types 1) due to mutations in the VHL tumour suppressor gene on chromosome 3. Epidemiology The disease is rare with an estimated prevalence of 1:35,000-5...
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Von Willebrand disease

Von Willebrand disease (vWD) is the most common inherited bleeding diathesis (easy bleeding). Clinical presentation Bruising and mucosal bleeding are typical presentations, but there is a spectrum of severity. The more residual vWF a patient has, the less severe the bleeding. Pathology There...
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Voxel

Voxel is a contraction of the words 'volume' and 'element' and was coined as a 3-D equivalent of a pixel. It is an individual point in space on a 3-dimensional, regular matrix. The location of each voxel is encoded by its relative relationship to other voxels. A tensor is a voxel that contains ...
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Vulval cancer (staging)

Staging of vulval cancer is the FIGO staging system and is as follows: stage 0: carcinoma in situ (pre-invasive); corresponds to Tis stage I: tumour <2cm (greatest dimension) and confined to vulva/perineum; corresponds to T1 stage Ia: stromal invasion by <1mm Stage Ib: stromal invasion by >1...
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Vulval neoplasms

Vulval neoplasms are rare and mostly seen in an elderly female patients. Squamous cell carcinoma is most common malignancy of the vulva which only 30% of them are associated with oncogenic HPV viruses. Pathology Squamous neoplastic lesions  Premalignant  classic vulvar intraepithelial neopla...
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Waardenburg syndrome

Waardenburg syndrome is a rare congenital pigmentary disorder secondary to an abnormal distribution of neural crest-derived melanocytes during embryogenesis resulting in patchy areas of depigmentation. It is considered in the investigation of congenital sensorineural deafness. Epidemiology Est...
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Wackenheims line

Wackenheims line (also known as the clivus canal line or basilar line) is formed by drawing a line along the clivus and extending it inferiorly to the upper cervical canal. Normally the tip of the dens is ventral and tangential to this line. In basilar invagination odontoid process transects th...
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WAGR syndrome

The WAGR syndrome stands for: Wilms tumours (greatly increased risk) aniridia genital anomalies mental retardation Pathology Occurs from a mutation related to chromosome 11p13 3 which is in close proximity to WT1 gene. 
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Wagstaffe-Le Forte fracture

A Wagstaffe-Le Forte fracture refers to an avulsion fracture of the medial aspect of the distal fibula due to avulsion of the anterior talofibular ligament attachment. See also lower extremity fractures
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Waldenström sign (hip)

Waldenström sign is the increased distance between the pelvic tear drop and the femoral head. It is a non-specific sign of hip joint effusion. Radiographic features Radiograph >11 mm total distance or >2 mm difference compared to contralateral hip 1, 2 measured between the lateral aspect of ...
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Waldenström's macroglobulinaemia

Waldenström's macroglobulinaemia (WM), (previously also known as lymphoplasmacytic lymphoma (LPL)), is a type of B-cell lymphoma. It is a rare condition, accounting for only 1% of all lymphoproliferative disorders.  Recent publications classify Waldenström's macroglobulinaemia as an lymphoplasm...
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Waldeyer's ring

Waldeyer's ring is a ring of lymphoid tissue located in the nasopharynx and oropharynx at the entrance to the aerodigestive tract. Gross anatomy The structures composing this ring are: palatine tonsils (also called the faucial tonsils) adenoid tonsils (nasopharyngeal tonsils) the lateral ba...
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Walker-Warburg syndrome

Walker-Warburg syndrome (WWS), sometimes known as HARDE syndrome, is an extremely rare lethal form of congenital muscular dystrophy. It is primarily characterised by: fetal hydrocephalus: almost always present neuronal migrational anomalies: agyria (cobblestone lissencephaly / lissencephaly ty...
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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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Walled-off pancreatic necrosis

Walled-off pancreatic necrosis (WOPN) is a late complication of acute pancreatitis, although it can occur in chronic pancreatitis or as a result of pancreatic trauma. Differentiation of WOPN from pancreatic pseudocyst is essential because management differs. WOPN may need aggressive treatment to...
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Wallerian degeneration

Wallerian degeneration (WaD) is the process of antegrade degeneration of the axons and their accompanying myelin sheaths following proximal axonal or neuronal cell body lesions. It may result following neuronal loss due to cerebral infarction, trauma, necrosis, focal demyelination or haemorrhage...
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Wandering spleen

Wandering spleen is a rare condition in which the spleen migrates from its usual anatomical position, commonly to the lower abdomen or pelvis. Epidemiology Wandering spleen is rare, with a reported incidence of <0.5%. Diagnosis is most commonly made between ages 20 and 40 and is more common i...
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Ward triangle

Ward triangle refers to a radiolucent area between principle compressive, secondary compressive and primary tensile trabeculae in the neck of femur. It should be differentiated from Babcock triangle.
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Wartenberg syndrome

Wartenberg syndrome also known as cheiralgia paresthetica is due to compression of superficial branch of the radial nerve in the distal forearm. It can be secondary to tight watch band or handcuffs, compression from distal radius fracture or idiopathic.  Clinical presentation Patients present ...
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Warthin tumour

Warthin tumours, also known as lymphomatous papillary cystadenomas, are benign, sharply demarcated tumours of the salivary gland. They are of lymphoid origin and most commonly arise from parotid gland tail. They may be bilateral or multifocal in up to 20% of cases and are the most common neoplas...
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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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Watchman device

Watchman device is a permanent left atrial appendage closure device, which is percutaneously implanted to prevent embolisation of thrombus from the appendage into the systemic circulation in cases atrial fibrillation. It is used when there is contraindication to anticoagulation or high risk of l...
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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 (liver)

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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Water-siphon test

The water siphon test may be performed as part of a barium swallow to assess for gastro-oesophageal reflux in a hiatal hernia. It is performed in the supine RPO position with the patient drinking water continuously. The test is said to be positive if there is visible barium reflux in the oesopha...
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Waterhouse-Friderichsen syndrome

Waterhouse-Friderichsen syndrome is characterised by adrenal insufficiency that results from atraumatic adrenal haemorrhage in consequence of septicaemia.  Pathology Waterhouse-Friderichsen syndrome is due to septicaemia and common infective agents include 5: meningococcus: traditionally desc...
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Watershed cerebral infarction

Watershed cerebral infarctions, also known as border zone infarcts, occur at the border between cerebral vascular territories where the tissue is furthest from arterial supply and thus most vulnerable to reductions in perfusion.  Epidemiology Watershed cerebral infarction account for 5-10% of ...
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Waterston shunt

A Waterston shunt is a form of palliative surgery performed in patients with tetralogy of Fallot prior to the ability to repair the defect. It consists of a shunt formed between the ascending aorta and the right pulmonary artery. This does not relieve the right ventricular outflow obstruction, ...
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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 sig...
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Weaver syndrome

Weaver syndrome (WS) is a rare congenital disorder. Clinical spectrum increased birth weight: fetal macrosomia early overgrowth macrocephaly accelerated osseous maturation: increased bone age typical facial features broad forehead hypertelorism long philtrum micrognathia large ears h...
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Weber classification of ankle fractures

The Weber ankle fracture classification (sometimes Danis-Weber) is a simple system for classification of lateral malleolar fractures, relating to the level of the fracture in relation to the ankle joint. It has a role in determining treatment.  Classification type A below the level of the tal...
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Weber syndrome

Weber syndrome is a midbrain stroke syndrome that involves the fascicles of the oculomotor nerve resulting in an ipsilateral CN III palsy and contralateral hemiplegia or hemiparesis 1-3. Using imaging alone, it is difficult to distinguish Weber from Benedikt syndrome, unless clear involvement o...
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Weber-Christian disease

Weber-Christian disease or Pfeifer-Weber-Christian disease or idiopathic relapsing febrile nodular non-suppurative panniculitis was initially defined as a rare inflammatory disorder of unknown aetiology affecting subcutaneous adipose tissue inter alia 1. However, the understanding of lobular pa...
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Wedge fracture

Wedge fractures are hyperflexion injuries to the vertebral body resulting from axial loading. Most commonly affecting the anterior aspect, wedge fractures are considered a single-column (i.e. stable) fracture.  Less commonly wedge fractures refer to a subtype of tibial plateau fractures. This a...
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Weigert-Meyer law

The Weigert-Meyer law describes the relationship of the upper and lower renal moieties in duplicated collecting systems to their drainage inferiorly. Weigert-Meyer law With duplex kidney and complete ureteral duplication, the upper renal and lower renal moiety have their own ureters with each ...
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Weightbearing foot series (an approach)

Reporting a weightbearing foot series can be a daunting process if you are inexperienced and often results in the films being left for somebody else to report. This article attempts to demystify the whole process by providing a structured approach to their reporting. Technique The weightbearin...
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Well-defined breast cancers (differential)

Certain well-defined breast cancers tend lack the characteristic spiculation and can give false reassurance of more benign entities on both ultrasound and mammography. These include: certain high grade invasive ductal carcinomas: not enough time for a desmoplastic reaction to form spiculation ...
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Wells criteria for deep venous thrombosis

Wells criteria for deep venous thrombosis is a risk stratification score and clinical decision rule to estimate the pretest probability for acute deep venous thrombosis (DVT). It is intended to be combined with noninvasive diagnostic tests (e.g. ultrasound or D-dimer) for suspected cases. Crite...
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Wells criteria for pulmonary embolism

The Wells criteria for pulmonary embolism is a risk stratification score and clinical decision rule to estimate the probability for acute pulmonary embolism (PE) in patients in which history and examination suggests acute PE is a diagnostic possibility. It provides a pre-test probability which, ...
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Werner syndrome

Werner syndrome is a progeroid rare autosomal recessive condition attributed to chromosome 8. It should not to be confused with similarly sounding Wermer syndrome. Pathology Werner syndrome is characterised by premature senescence cataracts short stature scleroderma-like skin changes such ...
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Wernicke-Korsakoff syndrome

Wernicke encephalopathy, also referred as Wernicke-Korsakoff syndrome, is due to thiamine (vitamin B1) deficiency, and is typically seen in alcoholics. On imaging, it is commonly seen on MRI as areas of symmetrical increased T2/FLAIR signal involving the mamillary bodies, dorsomedial thalami, t...
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Wernicke's area

Wernicke's area (Brodmann area 22) is an area of the posterior temporal lobe in the dominant hemisphere concerned with the receptive components of speech. Gross anatomy Wernicke's area is located in the superior temporal gyrus, posterior to the posterior commissure line. Relations It is boun...
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Westermark sign (lungs)

Westermark sign is a sign of pulmonary embolus (PE) seen on chest radiographs. Along with Fleishner sign and Hampton hump, it makes one of the three described signs of pulmonary embolus on chest radiographs. Pathology In one study (PIOPED) this sign was present on ~10% of chest x-rays of pati...
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WFNS grading system

The WFNS (World Federation of Neurosurgical Societies) grading system uses the Glasgow Coma Scale and presence of focal neurological deficits to grade the severity of subarachnoid haemorrhage. This grading system was proposed in 1988, and this is one of the accepted systems (although not conside...
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Wharton jelly

Wharton jelly refers to the gelatinous substance within the umbilical cord. Gross anatomy Wharton jelly is derived from extra-embryonic mesoderm and is largely made up of mucopolysaccharides (hyaluronic acid and chondroitin sulphate) while containing smaller amounts of fibroblasts and macropha...
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What constitutes a perfect case

So what should the perfect case look like? Over time the quality of contributions to Radiopaedia.org is ever growing and a consensus is emerging as to the make up of a perfect case. For a general set of instructions refer to our case publishing guidelines. Below are some points to consider when...
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What Radiopaedia.org IS

Radiopaedia.org is more than just a website. It is the front end of a community whose aim is to develop the best researched, most comprehensive and most accessible online radiology reference site... read more.  Radiopaedia.org IS an opportunity to contribute to a project which will hopefully be...
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What Radiopaedia.org is NOT

We are attempting to create the best radiology resource which is no small task and is going to take the combined efforts of many many people. These are a couple of thoughts about what Radiopaedia.org is NOT: Radiopaedia.org is NOT a place to cut and paste content from textbooks, articles or oth...
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Wheels within wheels sign

This sign is seen in USG of patient with the hepatic candidiasis and described as central hypoechoic area (necrosis containing fungi) surrounded by an echogenic zone (inflammatory cells). Differs from bull’s-eye sign for reverse echogeniticity, as it consists a central echogenic nidus surrounde...
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When to use bold

Making a decision about when to use bold in an article is important since we know that adding bold and italics to articles reduces its readability. There are very few examples of when to use bold in an article on Radiopaedia.org and as such, if you're unsure, it's probably worthwhile not using ...
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When to use italics

Making a decision about when to use italics in Radiopaedia.org articles is important because the addition of bold and italic words in prose actually reduces readability. In literature, italics can be used for a number of things, including titles of works and foreign words. However, in order to ...
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Whipple disease

Whipple disease is a rare infectious multisystem disorder caused by the actinobacteria Tropheryma whipplei. Epidemiology The incidence of Whipple disease is not truly known, one Swiss study estimated it at approximately 1 per 1.5 million per year 7. The peak age for presentation is in the fif...
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Whipple disease (gastrointestinal manifestations)

Gastrointestinal manifestations are a key component of Whipple disease.  The gastrointestinal manifestations of t. whipplei are also known as intestinal lipodystrophy. Pathology Extensive infiltration of lamina propria with large macrophages infected by intracellular Tropheryma whipplei causes...
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Whipple disease (neurological manifestations)

Neurological manifestations of Whipple disease are rare. Whipple's disease can also appear as a primary neurological disorder in rare cases. It is rarely incidentally found as a differential diagnosis in patients with a progressive neurological deficit. It has been suggested that neurological i...
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Whipple disease (thoracic manifestations)

Thoraco-pulmonary manifestations of Whipple disease are uncommon and may result in later course of disease. Epidemiology Lung involvement is seen in 35-60% of patients with gastrointestinal whipple disease. Males are affected eight times than of females. Pathology Grossly there are areas of ...
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Whipple procedure

The Whipple procedure (or partial pancreaticoduodenectomy) is considered the definitive surgical operation to resect carcinoma in the head of the pancreas, periampullary carcinoma, or duodenal carcinoma 1. In the procedure, the head of the pancreas and adjacent duodenum is resected. The gallbla...
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Whipple triad

Whipple triad is the clinical presentation of pancreatic insulinomas and consists of: fasting hypoglycemia (<50 mg/dl) symptoms of hypoglycemia immediate relief of symptoms after the administration of IV glucose History and etymology As a good piece of trivia, one would suspect that Whipple...
Article

Whirlpool sign

The whirlpool sign, also known as the whirl sign, is seen when a structure twists upon itself. It is most commonly described in the abdomen where bowel rotates around its mesentery, with mesenteric vessels creating the whirls. It can also be seen in ovarian torsion. Whirlpool sign: mesenteric ...
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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 coat effect

The white coat effect (WCE), not to be confused with white coat hypertension, is a measure of change that is commonly defined as the difference between in-clinic and out-of-clinic blood pressure readings 1,2.  Alternatively, the white coat effect can be defined as the increase in the arterial b...
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White coat hypertension

White coat hypertension (abbreviated alternatively as WCH or WCHT), not to be confused with the white coat effect (WCE), is commonly defined as typical in-clinic blood pressure (BP) measurements of 140/90 mm Hg or more in the presence of multiple daytime out-of-clinic home or ambulatory BP readi...
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White epidermoid

White epidermoids are a rare type of epidermoid cyst that do not follow the usual near-CSF density and signal intensity on CT and MR respectively. To make matters worse the literature uses the term inconsistently, although generally the 'white' refers to the T1 weighted imaging appearance.  Rad...
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White matter buckling sign

The white matter buckling sign is helpful in distinguishing an extra-axial 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 oedema (which would usually expand gyri, if the mass were intra-axial)...
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White matter changes in HIV

White matter changes in HIV have overlapping appearances and varied in aetiology. These can be divided into: primary effects of HIV opportunistic infection neoplasms vascular disease metabolic and nutritional disorders Primary effects of HIV HIV encephalitis Opportunistic infection cyto...
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White matter disorders

White matter diseases are a group of conditions that predominantly or significantly affect the white matter of the brain. They comprise a vast heterogeneous group and have a variety of appearances and presentations. They cause disease by altering the process of normal myelination.  Useful group...
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White matter tracts

White matter tracts, also known as white matter fibres, are classified into three categories: Projection tracts tracts connecting the cortex with other area in the CNS, e.g. deep nuclei, brainstem, cerebellum or spine may be efferent (motor) or afferent tracts (sensory) white matter tracts t...
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White matter tracts of the spinal cord

The spinal cord has numeorus white matter tracts that ascend and descend in the peripheral substance of the cord. They can be divided by their location and function: anterolateral columns anterior corticospinal tract medial longitudinal fasiculus spinothalamic tracts lateral spinothalamic t...
Article

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.  In contrast, unilatera...
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WHO classification of anal canal tumours

The World Health Organisation classifies anal canal neoplasms into intraepithelial neoplasms and invasive neoplasms which are further divided to epithelial and non-epithelial tumours and secondary lesions: Epithelial tumours squamous cell carcinoma of anal canal adenocarcinoma of anal canal ...
Article

WHO classification of anal margin tumours

The WHO classification of anal margin tumours or perianal skin tumours is: intraepithelial tumours Bowen disease (precursor of squamous cell carcinoma) Paget's disease (precursor of adenocarcinoma) invasive tumours squamous cell carcinoma adenocarcinoma basal cell carcinoma  verrucous ca...
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WHO classification of CNS tumours

The WHO classification of CNS tumours is the most widely accepted system for classifying CNS tumours and was based on the histological characteristics of the tumour. Although the most recent version of the 'blue book' is the 4th edition from 2007, an update has been released in 2016 3, which sho...

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