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.

710 results found
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Squamous dysplasia of lung

Squamous dysplasia (SD) of lung is a type of preinvasive lung lesion and is considered a precursor to bronchogenic squamous cell carcinoma. It is sometimes considered a low end of the spectrum of carcinoma in situ (CIS) of lung 2.
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Stafne cyst

Stafne cysts, also known as a static bone cavity of the mandible or lingual salivary gland inclusion defect, are cortical defects near the angle of the mandible below the mandibular canal. Strictly speaking, it is not a cyst since it does not contain any fluid. It is usually an incidental findin...
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Status epilepticus

Status epilepticus (SE) is an acute and prolonged seizure that persists for a sufficient length of time or is repeated frequently enough that recovery between attacks does not occur. It is a clinical emergency associated with a high morbidity and mortality. Epidemiology The estimated incidence...
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Stenogyria

Stenogyria refers to a pathological condition in which shallow sulci separate multiple "narrow gyri" 1. It is often reported in association with Chiari type II malformation. It differs from polymicrogyria because the cortex is histologically normal organized. Moreover in stenogyria the general s...
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Streak ovaries

Streak ovaries are a form of ovarian dysgenesis and are associated with Turner syndrome. Occasionally they may be functional and secondary sexual characteristics may develop.  Pathology Streak ovaries are seen when there is abnormality or absence of the X chromosome.  Associations Turner syn...
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Stress shielding of the proximal femur

Stress shielding of the proximal femur refers to bone loss of the non-weighting femur after hip arthroplasty. It can complicate them with cortical thinning and bone loss leading to prosthesis failure.
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Struma ovarii tumour

Struma ovarii tumour is a subtype of an ovarian teratoma and is composed entirely or predominantly of thyroid tissue and containing variable-sized follicles with colloid material. Epidemiology It accounts for 0.3-1% of all ovarian tumours and ~3% of all mature cystic teratomas 1. Clinical pre...
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Stump appendicitis

Stump appendicitis refers to inflammation of the residual appendiceal tissue post appendectomy. Partial removal of appendix with a residual stump, allows for a chance of recurrent appendicitis. Chances of a partial removal is found to be higher in cases where there is a wrong identification of ...
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Stunned myocardium

Stunned myocardium refers to a situation in which an acute transient myocardial ischemic event results in a prolonged wall motion abnormality which eventually resolves. The term is usually distinguished from "hibernating" myocardium, in which a chronic ischaemic process leads to chronic left ve...
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Subacute hypersensitivity pneumonitis

Subacute hypersensitivity pneumonitis develops when hypersensitivity pneumonitis continues beyond the acute phase (i.e. continues for weeks to months). While some publications suggest the disease to needs to prevail for between 1-4 months to fall into this category 6, it is important to realise ...
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Subareolar abscess

Subareolar breast abscess are relatively uncommon and tend to occur mostly in young women.  Clinical features Mastalgia, signs of inflammation, lump formation in the subareolar region and nipple discharge. In chronic cases fistula formation and nipple deformity may be seen. Pathology Locatio...
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Subcapsular perirenal haematoma

A subcapsular perirenal haematoma is a form of perirenal haematoma where blood accumulates beneath the renal capsular margin. Pathology It can arise from a number of causes trauma, important in assessing renal trauma grading post procedural, e.g. extracorporeal shock-wave lithotripsy (ESWL) ...
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Subchorionic haemorrhage

Subchorionic haemorrhage (SCH) occurs when there is perigestational haemorrhage and blood collects between the uterine wall and the chorionic membrane in pregnancy. It is a frequent cause of first and second trimester bleeding. Epidemiology It typically occurs within the first 20 weeks of gest...
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Subconjunctival fat prolapse

Subconjunctival fat prolapse is an acquired herniation of intraconal fat due to the weakening of the Tenon capsule by normal aging, surgery, or trauma. It presents clinically with a fat-containing epibulbar mass in the lateral canthal area. Epidemiology  Subconjunctival fat prolapse occurs mai...
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Subcortical arteriosclerotic encephalopathy

Subcortical arteriosclerotic encephalopathy (SAE), also known as Binswanger disease or small vessel dementia, refers to slowly progressive exclusively white-matter multi-infarct dementia.  A genetically transmitted form of the disease is known as familial arteriopathic leukoencephalopathy or CA...
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Subcortical leukomalacia

Subcortical leukomalacia corresponds to a continuous disease spectrum of periventricular leukomalacia (PVL) as the vascular border zones shift towards the periphery as the brain further matures. For this reason white matter lesions move from the periventricular to the subcortical zone. Please r...
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Subcutaneous emphysema

Subcutaneous or surgical emphysema, strictly speaking, refers to air in the subcutaneous tissues. But the term is generally used to describe any soft tissue emphysema of the body wall or limbs since the air often dissects into the deeper soft tissues and musculature along fascial planes. Clinic...
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Subdural hygroma

Subdural hygromas refer to a cerebrospinal fluid (CSF) accumulation in the subdural space. In many cases it is considered an epiphenomenon of head injury when it is called a traumatic subdural hygroma.  Clinical presentation The vast majority of patients are asymptomatic, however some symptoms...
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Subependymal giant cell astrocytoma

Subependymal giant cell astrocytomas (SGCAs or alternatively SEGAs) are benign tumours (WHO grade I), seen almost exclusively in young patients with tuberous sclerosis. They can be either asymptomatic or symptomatic due obstructive hydrocephalus, surgery treatment is often curative.  On imaging...
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Subgaleal haematoma

Subgaleal haematoma describes scalp bleeding in the potential space between the periosteum and the galea aponeurosis. It most commonly occurs after vacuum assisted delivery, but may also be seen following head trauma. In patients with intracranial haemorrhage or skull fractures, the incidence o...
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Subspine impingement of the hip

Subspine impingement of the hip is a type of extra-articular hip impingement, also known as anterior inferior iliac spine impingement. This condition occurs when a low-lying or enlarged anterior inferior iliac spine contacts the femoral neck with hip flexion. Presenting symptoms of this conditio...
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Subtalar dislocation

Subtalar dislocations is the simultaneous dislocation of the talonavicular and talocalcaneal joints, without tibiotalar or talar neck fractures 1, and comprises 1-2% of all dislocations, Pathology Mechanism Subtalar dislocations are often associated with high energy trauma, usually, motor veh...
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Subungual exostosis

Subungual exostoses are benign osteocartilaginous tumours that occur beneath the nail bed.  Epidemiology These lesions are most commonly found in children and young adolescents 1-2.  Clinical presentation Although they can be found beneath any nail, they most commonly affect the big (first) ...
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Succenturiate lobe

A succenturiate lobe is a variation in placental morphology and refers to a smaller accessory placental lobe that is separate to the main disc of the placenta. There can be more than one succenturiate lobe. Epidemiology The estimated incidence is ~2 per 1000 pregnancies. Radiographic features...
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Superior cerebellar artery infarct

Superior cerebellar artery infarcts affect the superior cerebellar hemispheres, cerebellar vermis and parts of the midbrain. The superior cerebellar artery is the most constantly identified vessel arising from the basilar artery with its origin just below the posterior cerebral artery in the dis...
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Superior labral anterior posterior tear

Superior labral anterior posterior (SLAP) tears are injuries of the glenoid labrum, and can often be confused with a sublabral sulcus on MRI.  Pathology SLAP tears involve the superior glenoid labrum, where the long head of biceps tendon inserts. Unlike Bankart lesions and ALPSA lesions, they ...
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Superior vena cava obstruction

Superior vena cava (SVC) obstruction can occur from extrinsic compression, intrinsic stenosis or thrombosis. Malignancies are the main cause and are considered an oncologic emergency. Superior vena cava syndrome (SVCS) refers to the clinical syndrome with symptoms that results from this obstruct...
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Suprascapular neuropathy

Suprascapular neuropathy or suprascapular nerve entrapment occurs if the suprascapular nerve is compressed as it passes through the suprascapular notch or spinoglenoid notch. Clinical presentation Non-specific posterior shoulder pain and weakness.  Pathology Aetiology masses (e.g. ganglion ...
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Suprasellar cistern lipoma

Suprasellar cistern lipomas are uncommon, usually incidental findings, with characteristic imaging features and a very limited differential diagnosis.  For a general discussion of intracranial lipomas please refer to the general article: intracranial lipoma.  Epidemiology Suprasellar cistern ...
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Supratentorial ependymoma

Supratentorial ependymomas are a type of location-specific ependymoma. They account for 30% of ependymomas, and in most instances are within or abutting the ventricles (third and fourth ventricles). In approximately 40% of cases they are remote from the ventricular surface, located within the pa...
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Sutural diastasis

Sutural diastasis is an abnormal widening of the skull sutures. It may be physiological in a neonate during a growth spurt.  Pathology In non-traumatic scenarios accelerated growth of the sutural connective tissue without concurrent ossification is the underlying pathology.  Aetiology trauma...
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Suture calcification in breast

Suture calcification in breast can be seen after a lumpectomy and/or radiation therapy. It is theorized that tissue damage from radiation therapy delays the resorption of the suture. The residual suture material is thought to act as a nidus for calcification. Radiographic features Mammography ...
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Symmetrical intrauterine growth restriction

Symmetrical intrauterine growth restriction is a type of intrauterine growth restriction (IUGR) where all fetal biometric parameters tend to be less than expected (below the 10th percentile) for the given gestational age. Both length and weight parameters are reduced. Please, refer to the artic...
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Synaptophysin

Synaptophysin is a membrane glycoprotein found in presynaptic vesicles and is commonly used as an immunohistochemical marker for cells of neuronal (e.g. gangliogliomas) and neuroendocrine lineage (e.g. pheochromocytomas and paragangliomas) 1,2.  In the brain, it has been suggested that perisoma...
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Synchronous breast cancer

Synchronous breast cancers are two breast cancers that occur in either breast at the same time.  Epidemiology Up to 10% of all breast cancers may be synchronous (particularly found with the use of breast MRI). The occurrence of bilaterality is greatest with invasive lobular carcinoma. Radiogr...
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Syndrome of inappropriate antidiuretic hormone secretion

Syndrome of inappropriate antidiuretic hormone secretion (SIADH or SIAD) was described in patients with lung cancer who developed hyponatraemia associated with continued urinary sodium loss. The result is often dilutional hyponatremia in which the sodium remains normal but total body fluid incre...
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Synovial chondromatosis

Synovial chondromatosis (or Reichel syndrome) is a disorder characterised by loose cartilaginous bodies which may, or may not be calcified or ossified. It is classified under two main types: Primary synovial chondromatosis: predominantly mono-articular disorder of unknown aetiology. Secondary...
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Synovial sarcoma

Synovial sarcomas are relatively common intermediate-to-high grade malignant soft tissue tumours, often with an initial indolent course, affecting young patients, and most commonly involving the soft tissue surrounding the knees. Epidemiology Synovial sarcomas typically present in adolescents ...
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Tanycytes

Tanycytes are one of the three types of ependymal cells, themselves a type of glial cell. They are found lining the floor of the third ventricle and the median eminence of the hypothalamus 1.   It is believed that these specialised cells are involved in the feedback mechanisms on the anterior p...
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Tissue tropism

Tissue tropism is a phenomenon by which certain host tissues preferentially support the growth and proliferation of pathogens. This concept is central to the radiological evaluation of infectious disease.  Pathology As infections that display tissue tropism will thrive in certain tissue locati...
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Triploidy

Triploidy is a rare lethal chromosomal (aneupliodic) abnormality caused by the presence of an entire extra chromosomal set.  Epidemiology It is considered the 3rd commonest fatal chromosomal anomaly 7. While it is thought to affect as much as 1-2% of conceptions, the vast majority are thought ...
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Tuberculoma

Tuberculomas or tuberculous granulomas are well defined focal masses that result from Mycobacterium tuberculosis infection and are one of the more severe morphological forms of tuberculosis. Tuberculomas most commonly occur in the brain (see: CNS tuberculosis) and the lung (see: pulmonary tuberc...
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Tumour markers

Tumour markers are a group of molecules in serum that are elevated in various malignancies and are often used to monitor treatment response as well as alert for potential progressive disease when in remission. Commonly used markers include: AFP beta-hCG CA 19-9 CA-125 CEA chromogranin A P...
Article

Verocay bodies

Verocay bodies are a histological feature of schwannomas and represent a particular growth pattern of Antoni type A pattern in which tumour cells form alternating parallel rows of nuclear palisades separated by regions of acellularity 1. 
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Vimentin

Vimentin is a fairly widespread cytoskeletal component encoding for intermediate filaments. It can be used as a target for immunohistochemistry to help characterise numerous tissues and tumours. 
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Vitamin A

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 photo-isomerisation within the rods and cones. Related pathology Patho...
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Vitamin B1

Vitamin B1 (thiamine) is a water soluble vitamin that is an important coenzyme for two reactions in the citric acid cycle (Kreb’s cycle). It therefore is vital for cellular ATP production, particularly in the central nervous system. Related pathology Pathological manifestations only occur with...
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Vitamin B12

Vitamin B12 (cobalamin) 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 atom fatty acids. Related patholog...
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Vitamin B2

Vitamin B2 (riboflavin) is a water soluble vitamin that is an important component of the cofactors FAD and FMN. The flavoproteins contribute to many cellular reactions, including the metabolism of several other vitamins.  Deficiency is not reported but may be present with deficiencies of other ...
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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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