Viral meningitides correspond to a relatively common and self-limited type of CNS infection clinically diagnosed based on the cerebrospinal fluid analysis and proportionally more frequent in young children than adults. Enteroviruses represent nowadays the most common cause of viral meningitis fo...
Viral respiratory tract infection is a broad term given to pulmonary infection from various viral agents.
They can be caused by any of a large number of viral agents, including but not limited to:
H1N1 pneumonia (swine influenza)
Virchow triad refers to the factors which can promote thrombosis, and are useful when thinking about the possible causes in a particular situation. They are:
factor V Laden deficiency
protein S deficiency
protein C deficiency
antithrombin III def...
Virgin abdomen is used to describe the abdomen of a patient who has never had any surgical procedure on their abdomen. It is usually used in the context of someone presenting with an acute small bowel obstruction and whether adhesions might be the underlying etiology. The conventional wisdom bei...
Visceral artery aneurysms are abnormal focal dilatations of arteries supplying abdominal organs. Visceral artery aneurysms include both true aneurysms and pseudoaneurysms.
Owing to different clinical manifestations and a unique, specific, pathology, renal artery aneurysms are discussed separate...
Visceral pleural invasion is a feature that can be seen in lung cancers. It is defined as tumor extension beyond the elastic layer of the visceral pleura. It is considered an aggressive sign and one of the most important adverse prognostic factors in non-small cell lung cancers 1.
The visceral space is one of the infrahyoid deep spaces of the head and neck.
The visceral space extends from the hyoid bone to the superior mediastinum (level of aortic arch / T4), and is surrounded by the middle layers of the deep cervical fascia.
The visibility of cases and playlists can be controlled by contributing author.
Public cases and public playlists are visible to all visitors to Radiopaedia.org and are indexed by search engines. Public cases are also returned as search results within Radiopaedia.org.
Unlisted cases and unlis...
Visual agnosia is a special type of agnosia where patients are unable to recognize objects despite having knowledge about them and being able to visually perceive them.
It typically occurs when there is damage to the ventral occipito-temporal pathway, such as in posterior cerebral atrophy (Bens...
Visual hallucinations are relatively uncommon, and can be due to a variety of 'organic' brain diseases, affecting a variety of regions of the brain. The use of the term organic here is by convention, and should not be taken to imply absence of brain dysfunction in psychiatric illness
Visual pathway deficits are determined by the location of the lesion or pathology. Understanding of the visual system is paramount and provided the globe is normal, the field defects can be defined from anterior to posterior as:
unilateral central scotoma
The visual system transmits visual information from the retina within the eyes to the primary visual cortex of the occipital lobe as well as the pretectal nuclei and superior colliculi of the midbrain.
Below the visual pathway is described from distal to proximal in a single hemi...
Vital capacity (commonly termed VC) is a spirometric parameter giving maximum amount of air that can be expelled from the lungs after a maximum inhalation. It is equal to the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume.
Vital capacity increases with
Vitamin A (the retinoids) are a group of fat-soluble vitamins required for many physiological functions, mainly vision, reproduction and epithelial maintenance. In the retina, a specific retinoid, 11-cis-retinal, is formed by photoisomerisation within the rods and cones.
Vitamin B1 (thiamine) is a water-soluble vitamin that is an important coenzyme for two reactions in the citric acid cycle (Kreb cycle). It therefore is vital for cellular ATP production, particularly in the central nervous system.
Thiamine is the preferred official spelling, howeve...
Vitamin B12 (hydroxocobalamin, hydroxycobalamin or B12a) is a water-soluble vitamin synthesised by intestinal flora that forms a cobalt-based coenzyme that is required for two vital cellular reactions, namely the production of methionine (an amino acid) and the metabolism of odd-number carbon at...
Vitamin B12 deficiency, also known as hypovitaminosis B12 or hypocobalaminaemia, is not uncommon, with potentially serious sequelae if not adequately treated.
Vitamin B12 deficiency presents with a wide spectrum of dysfunction, from no symptoms at all (i.e. subclinical di...
Vitamin B2 (riboflavin) is a water-soluble vitamin that is an important component of the cofactors flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN). The flavoproteins contribute to many cellular reactions, including the metabolism of several other vitamins.
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.
pellagra is the clinical syndrome of niacin deficiency, and may affe...
Vitamin B5 (pantothenic acid) is a water-soluble vitamin that is required to synthesise coenzyme A, a very important coenzyme in many cellular metabolic reactions.Vitamin B5 deficiency (hypovitaminosis B5) is extremely rare.
Vitamin B6 is a group of water-soluble vitamins that are derivatives of pyridine, namely pyridoxine, pyridoxal and pyridoxamine. All three form part of the coenzyme pyridoxal 5'-phosphate (PLP) which is involved in many cellular reactions including the synthesis of several amino acids and the me...
Vitamin B6 excess (hypervitaminosis B6) is caused by excessive consumption of supplemental pyridoxine, which is used as a therapeutic agent for several conditions.
This hypervitaminosis is almost exclusively seen in those taking pyridoxine as prescription medication, it remains i...
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, biotinidase deficiency and, possibly, increased b...
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 drug cl...
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 fibers which greatly increases its tensile strength. It also acts as an antioxidant.
Vitamin D (calciferol) is used to describe a group of five fat-soluble secosteroid vitamins required for the homeostasis of serum calcium and phosphorus. Vitamin D exists in two main forms (vitamers) in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3).
Vitamin D3 acts by re...
Vitamin E (the tocopherols) are a group of fat-soluble vitamins that act as antioxidants.
hypovitaminosis E is rarely seen outside premature infants
hypervitaminosis E is extremely rare as the toxicity of vitamin E is low except in chronic (usually >1 year) high doses. The commonest sequela is...
Vitamin K is a family of fat-soluble vitamins essential for normal blood-clotting function and comprises two vitamers that are found naturally: phytomenadione (also known as phylloquinone or K1) and menaquinone (or K2).
Menadione is a synthetic molecule which is occasionally called vitamin K3 h...
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. Vitamer is the name given to the different forms of a ...
The vitreous body or vitreous humor is a transparent, avascular gel that occupies ~80% of the globe and helps to maintain the position of the retina and the shape of the globe.
Situated within the globe between the lens and the optic cup, its anterior surface is indented by the...
Vitreous hemorrhage refers to bleeding into the vitreous chamber.
Vitreous hemorrhage has an incidence of approximately 7 in 100000 1,2.
The most common clinical presentation is with sudden, painless visual loss to varying degrees of severity 2. Associate...
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...
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...
Vocal cord paralysis/paresis (VCP), also known as vocal fold paralysis/paresis, refers to the impaired mobility of the true vocal cord or fold due to neurologic dysfunction.
Unilateral vocal cord paralysis usually presents with dysphonia (hoarseness), characterized as a b...
Vogt-Koyanagi-Harada syndrome is a multisystem disorder characterized by granulomatous panuveitis with exudative retinal detachments that is often associated with neurologic and cutaneous manifestations.
Vogt-Koyanagi-Harada usually affected those of Asian, Middle Eastern, Asian I...
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...
Volar intercalated segmental instability (VISI) is a type of instability involving the wrist. It is less often encountered than dorsal intercalated segmental instability (DISI).
It presents in most cases with nonspecific wrist pain and a "clunking" on the ulnar deviation ...
Volar plate avulsion injuries are a type of avulsion injury. The volar plate of the proximal interphalangeal (PIP) joint is vulnerable to hyperextension injury, in the form of either a ligament tear or an intra-articular fracture.
The volar plate forms the floor of PIP joint sepa...
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...
A Volkmann ischemic contracture refers to a complex and variable flexion deformity involving distal lumbes (typically the wrist and fingers) resulting from fibrosis and contracture of flexor muscles.
The number of deformities can occur where in the upper extremity this in...
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 tumors. Autoimmune VGKC encephalitis ca...
Volume coils are the transmit and receive radiofrequency coils which are used to both transmit and receive the radiofrequency signal in MRI. Most MRI scanners have what is called a body coil – which is a volume coil built into the bore of the magnet which transmits the radiofrequency for most ex...
The vomer is one of the facial bones and forms the postero-inferior part of the bony nasal septum.
Occasionally the sphenoid sinus may pneumatise the vomer 2.
Von Hippel-Lindau (vHL) disease is characterized by the development of numerous benign and malignant tumors in different organs (at least 40 types 1) due to mutations in the VHL tumor suppressor gene on chromosome 3.
The disease is rare with an estimated prevalence of 1:35,000-50,...
Features of von Hippel-Lindau disease can be remembered by the mnemonic:
I: increased risk of renal cell cancer
P: pancreatic lesions (cyst, cystadenoma, cystadenocarcinoma)
E: eye dysfunction (retinal hemangioblastoma)
L: liver, r...
Von Willebrand disease (vWD) is the most common inherited bleeding diathesis (easy bleeding).
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.
Voxel is a portmanteau of contractions of the two 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 may b...
Voxel size is an important component of image quality. Voxel is the 3-D analog of a pixel. Voxel size is related to both the pixel size and slice thickness. Pixel size is dependent on both the field of view and the image matrix. The pixel size is equal to the field of view divided by the matrix...
V/Q (ventilation/perfusion) scan is a scintigraphic examination of the lung that evaluates pulmonary vasculature perfusion and segmental bronchoalveolar tree ventilation.
diagnosis of suspected pulmonary embolism (PE)
monitor pulmonary function following lung transplant
The vulva (or pudendum) is the collective term given to the female external genitalia.
The vulva consists of the:
vestibule of the vulva
Individual component st...
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: tumor <2cm (greatest dimension) and confined to vulva/perineum; corresponds to T1
stage Ia: stromal invasion by <1mm
Stage Ib: stromal invasion by >1m...
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.
Squamous neoplastic lesions
classic vulvar intraepithelial neopla...
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.
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...
The WAGR syndrome stands for:
Wilms tumors (greatly increased risk)
Occurs from a mutation related to chromosome 11p13 3 which is in close proximity to the WT1 gene.
A Wagstaffe-Le Forte fracture refers to an avulsion fracture of the medial aspect of the distal fibula due to avulsion of the anterior tibiofibular ligament attachment.
lower extremity fractures
Waldenström macroglobulinemia, previously also known as lymphoplasmacytic lymphoma, is a type of B-cell lymphoma.
Recent publications classify Waldenström macroglobulinemia as a lymphoplasmacytic lymphoma with any level of an IgM paraprotein 10. Therefore the two entities are not ...
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.
>11 mm total distance or >2 mm difference compared to contralateral hip 1,2
measured between the lateral a...
Waldeyer's ring is a ring of lymphoid tissue located in the nasopharynx and oropharynx at the entrance to the aerodigestive tract.
The structures composing this ring are:
palatine tonsils (also called the faucial tonsils)
adenoid tonsils (nasopharyngeal tonsils)
the lateral ba...
Walker-Warburg syndrome (WWS), sometimes known as HARDE syndrome, is an extremely rare lethal form of congenital muscular dystrophy. It is primarily characterized by:
fetal hydrocephalus: almost always present
neuronal migrational anomalies: agyria (cobblestone lissencephaly / lissencephaly ty...
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...
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
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...
Wallerian degeneration 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 hemorrhage.
The wall filter in ultrasound is a way of filtering out low or high frequency Doppler signals. In clinical ultrasound, it is usually used to filter out very low frequencies that may add noise to a spectral Doppler waveform.
A typical use is removing the low frequency reverberation of an arteria...
Wandering spleen is a rare condition in which the spleen migrates from its usual anatomical position, commonly to the lower abdomen or pelvis.
Wandering spleen is rare, with a reported incidence of <0.5%.
Diagnosis is most commonly made between ages 20 and 40 years and is more co...
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.
History and etymology
Named for F O Ward after his original description of the region in 1838.
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.
Patients present ...
Warthin tumors, also known as lymphomatous papillary cystadenomas, are benign, sharply demarcated tumors 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 neoplasti...
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...
Watchman device is a permanent left atrial appendage closure device, which is percutaneously implanted to prevent embolization 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...
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...
Waterhouse-Friderichsen syndrome (also known as purpura fulminans 9 or hemorrhagic adrenalitis 10) is characterized by adrenal insufficiency that results from atraumatic adrenal hemorrhage in consequence of septicaemia.
Waterhouse-Friderichsen syndrome is due to septicaemia and comm...
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...
The watermelon skin sign refers to diffuse, radiating, streaky areas of low signal intensity in prostate on T2WI in patients with prostatic tuberculosis 1.
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.
Watershed cerebral infarction account for 5-10% of ...
The water siphon test may be performed as part of a barium swallow to assess for gastro-esophageal reflux. 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 esophagus, and is more sens...
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, ...
The wave sign refers to the indentation of the normal thymus in young children by the ribs, resulting in a wavy border.
Weapon and munition inspired signs include the following with their corresponding pathologic conditions:
metastases from renal cell carcinoma
Weaver syndrome (WS) is a rare congenital disorder.
increased birth weight: fetal macrosomia
accelerated osseous maturation: increased bone age
typical facial features
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 etiology affecting subcutaneous adipose tissue inter alia 1.
However, the understanding of lobular pan...
The Weber ankle fracture classification (or Danis-Weber classification) 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.
below the level of...
The weber (symbol: Wb) is the SI derived unit of magnetic flux, and superseded the maxwell, the CGS unit for magnetic flux.
As per all other eponymous SI units when the unit is written out in full it is not capitalised, but when shortened to its symbol it is capitalised.
Weber syndrome is a midbrain stroke syndrome that involves the cerebral peduncle and the ipsilateral fascicles of the oculomotor nerve 1-3.
ipsilateral CN III palsy
contralateral hemiplegia or hemiparesis
It is usually caused by an ischemic stroke, typically ...
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...
The Weigert-Meyer law describes the relationship of the upper and lower renal moieties in duplicated collecting systems to their drainage inferiorly.
With duplex kidney and complete ureteral duplication, the upper renal and lower renal moiety is drained by separate ureters, e...
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.
A Weil osteotomy is a from of osteotomy performed in the foot. It is considered a common technique used in the treatment of lesser metatarsal deformities of the forefoot. It is designed to make a controlled shortening of the length of the metatarsal in the transverse plane.
The Weiss classification is one of the classification systems used for lateral humeral condyle fractures and is based on the degree of displacement measured on an internal oblique view of the elbow:
type 1: <2 mm displacement
type 2: 2-4 mm displacement
type 3: >4 mm displacement
The degree ...
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
Wellens syndrome (also referred to as LAD coronary T-wave syndrome) refers to a specific ECG abnormality in the precordial T-wave segment. It can be associated with a critical stenosis of the proximal left anterior descending artery.
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. D-dime...