The presence of skin thickening on mammography is variably defined, usually being more than 2 mm in thickness. It can result from a number of both benign and malignant causes. They include:
inflammatory breast cancer: one of the most concerning causes of skin thickening: this usually...
The skull base angle allows the diagnosis of platybasia and basilar kyphosis. There are several different techniques that may be used on sagittal images from MRI or CT.
Traditionally, basal angle measurements were based on plain skull images. With the advent and generalization of MR imaging it ...
Skull tumors can be (as with tumors anywhere else) both primary and secondary, and benign or malignant.
giant cell tumor (GCT)
aneurysmal bone cyst (ABC)
epidermoid and dermoid cysts
Regular, smooth generalized thickening
congestive cardiac failure (CCF)
anticoagulation or bleeding diathesis
IgA vasculitis (Henoch-Schonlein purpura)
Small bowel imaging aims at assessment of the disorders of small intestine.
barium follow through
Small bowel or mesenteric ischemia may be a life-threatening condition, arising from any one of numerous causes of disturbance of the normal blood flow through the small bowel wall.
It can be divided into acute and chronic forms, with the main underlying etiologies (each discussed s...
A small for dates fetus can result from a number of factors
structural anomalies (syndromes)
fetal Warfarin syndrome
hydantoin embryopathy (Dilantin TM)
The following differential diagnoses can be considered when small lung volumes are seen:
prior surgery, e.g. lobectomy, lung volume reduction surgery
pleural disease, e.g. pleural thickening
skeletal deformities, e.g. kyphosis, scoliosis
systemic lupus erythematosus (SLE)...
A small placenta if observed on antenatal ultrasound can arise from a number of situations. They include:
variation in placental morphology: where only part of the placenta is seen
bilobed placenta: with only one lobe seen
succenturiate lobe: with either main lobe or succenturiate lobe not se...
Smoking related lung diseases are the respiratory manifestations of disease that are related to the smoking of tobacco. Smoking affects the lungs in numerous ways, and can be classified under the following headings:
smoking related-interstitial lung diseases (SR-ILD)
respiratory bronchiolitis ...
Snake eyes, also known as snail eyes, is a term used to refer to the appearance of the facial nerve on coronal CT within its canal in the petrous temporal bone as the tympanic segment doubles back next to the labyrinthine segment. Anteriorly, these two segments converge at the geniculate ganglio...
Soft tissue calcification is commonly seen and caused by a wide range of pathology.
There is a wide range of causes of soft tissue calcification 1:
dystrophic soft tissue calcification (most common), e.g. chronic venous insufficiency 2
vascular, e.g. arterial calcifica...
Soft tissue lesions with predominately low T1 and T2 signal have a reasonably long differential, including:
densely calcified/ossified lesions
Soft-tissue sarcomas are a heterogeneous group of malignant tumors of mesenchymal origin (sarcoma) that originate from the soft tissues rather than bone. They are classified on the basis of tissue seen on histology. The commoner sarcomas in the adult and pediatric population are listed below.
Solid lesions with enhancement are by far the most commonly encountered appearance of pituitary region masses.
by far the most common entity
typically enhances less vividly than other entities
elevates the dura of the diaphragma sella (as the origin is wi...
Solid periosteal pattern is thought to evolve from single layer and multilayered periosteal reactions, forming a solid layer of new bone adjacent to the cortex.
It can be seen in:
Solitary filling defect with a ureter, as seen on conventional IVU or CT IVU has some differentials, including:
within the lumen
within the wall
transitional cell carcinoma (TCC)
When multiple fi...
Ill-defined solitary osteolytic lesions can be caused by following entities 1:
giant cell tumor
fibrosarcoma of bone
malignant fibrous histiocytoma
Solitary lucent lesion of the skull is a relatively frequent finding. The differential is heavily influenced by the patient's age.
renal cell cancer
epidermoid and dermoid
Solitary pulmonary nodule (SPN) is defined as a relatively well defined round or oval pulmonary parenchymal lesion equal to or smaller than 30 mm in diameter. It is surrounded by pulmonary parenchyma and/or visceral pleura and is not associated with lymphadenopathy, atelectasis, or pneumonia 9.
The differential diagnosis of a solitary sclerotic bone lesion is heavily influenced by the age of the patient, and includes:
solitary either because no others are present or no others have been imaged
enostosis (bone island)
Solitary sclerotic bone lesion with a lucent center have a number of differentials:
Well defined solitary osteolytic lesions can be seen with following conditions 1-2:
subchondral geodes or cysts
unicameral bone cyst
aneurysmal bone cyst
epidermoid inclusion cyst
Obstetric and gynecological ultrasound is rampant with numerous cut off values. Some of these get revised over the years. The following list is a useful aid to refer to and revise.
rate of increase of a mean sac diameter per day in early pregnancy
generally accepted value for a thi...
The speckled appearance of the anterior horn of lateral meniscus is a feature that can be seen as a normal variant on MRI scans. It is usually seen near its central attachment site. It is often explained by fibers of the anterior cruciate ligament and the covering synovium inserting into the men...
Spiculated periosteal reaction represents spicules of new bone forming along vascular channels and the fibrous bands that anchor tendons to bone (Sharpey fibers). A spiculated periosteal reaction signifies a rapid underlying process that prevents formation of new bone under the raised periosteum...
Spinal cord compression is a surgical emergency, usually requiring prompt surgical decompression to prevent permanent neurological impairment.
There are numerous causes of cord compression. These can be divided according to the location of the compressing mass:
Spinal dysraphisms refer to a broad group of malformations affecting the spine and/or surrounding structures in the dorsum of the embryo. They are a form of neural tube defect.
The neural tube is formed by the lengthwise closure of the neural plate, in the dorsum of the embryo.
The differential diagnosis for a spinal epidural mass includes:
herniated nucleus pulposus
epidural arteriovenous malformation
Spinal fractures are usually the result of significant trauma to a normally formed skeleton, or the result of trauma to a weakened spinal column. Examples include:
Jefferson fracture: ring fracture of C1
hangman fracture: bilateral pedicle or pars fracture of C2
Spinal hematomas are a rare clinical entity and are often idiopathic. Prompt diagnosis and treatment are crucial, lest they cause permanent neurological damage.
Identifying the location of the hematoma is important for treatment, as is distinguishing it, to the extent possible, from other entit...
Spinal metastases is a vague term which can be variably taken to refer to metastatic disease to any of the following:
vertebral metastases (94%)
may have epidural extension
intradural extramedullary metastases (5%)
intramedullary metastases (1%)
Each of these are discussed separately. Below...
Spinal vascular malformations (SVM) are rare but knowledge of them is important as if undiagnosed and untreated they can lead to serious complications.
There are two main types of SVMs 1,2:
spinal arteriovenous fistula (AVF): 70% of SVMs
pial: small, large, or giant
dural AVF (DA...
Splenic abscesses, like abscesses elsewhere, are localized collections of necrotic inflammatory tissue caused by bacterial, parasitic or fungal agents. They uncommonly affect the spleen due to its efficient reticuloendothelial system phagocytic activity and, consequently, are more likely seen in...
Splenic amyloidosis is rare as an isolated entity. Most often it is associated with either systemic amyloidosis or hepatic amyloidosis.
In general, splenic involvement in amyloidosis is rather frequent (5-10% of cases 6,7).
Symptoms include abdominal mass a...
Splenic calcifications can occur is various shapes and forms and can occur from a myriad of etiological factors.
The usual calcification observed in radiographs are the multiple, miliary form presenting numerous small rounded densities averaging from three to five millimeters in diameter where ...
Splenic epithelial cysts, also referred as splenic epidermoid cysts or primary splenic cysts, are unilocular fluid lesions with thin and smooth walls and no enhancement. They represent ~20% of cysts found in the spleen, and are usually an innocuous incidental imaging finding.
Note that most (~8...
Splenic haemangiomatosis involves multiple, diffuse splenic hemangiomas replacing its entire parenchyma. It is a very rare entity.
It can occur as a manifestation of systemic angiomatosis or, less commonly, confined to the spleen (diffuse isolated splenic haemangiomatosis). There is ...
There are a number of splenic lesions and anomalies:
Benign mass lesions
splenic cyst (mnemonic)
splenic hemangioma: commonest benign spl...
Splenic pseudocysts, also referred as secondary splenic cysts, are acquired cystic lesions not delineated by a true epithelial wall. They represent the majority of the splenic cystic lesions, corresponding to approximately 80% of them (c.f. splenic epithelial cysts). The main causes are:
Splenomegaly refers to enlargement of the spleen. The upper limit of normal adult splenic length is traditionally cited at 12 cm, but lengths upwards of 14 cm can be seen in normal, taller males 7.
Massive splenomegaly is variably defined, including when the spleen is 5 standard deviations abov...
Spontaneous nipple discharge in a non lactating breast can result from many causes which include:
papillary lesions of breast: present in ~35-50% of cases with spontaneous nipple discharge
ductal carcinoma in situ: 5-21%
Spontaneous splenic rupture (SSR) (or atraumatic splenic rupture) is rare, especially when compared to traumatic splenic rupture.
The pathogenesis of atraumatic splenic rupture is not well understood. Splenomegaly is present in almost all patients (~95%), although rupture of normal ...
Cricket is a popular game in Commonwealth countries. Sports injuries in this game can be associated with three positional aspects of the game: bowling, batting or fielding. Radiologists should know the different kind of injuries related to this game for a better clinical association. Injuries ca...
Overhead elbow sports injuries are a group of pathologies seen in sports activities with overhead throwing or strokes, e.g. tennis, volleyball, baseball, javelin throwing. There has been a tremendous increase in the number of participants in these sports activities worldwide.
Snowsport injuries cover a broad range of activities from alpine or Nordic skiing, snowboarding, and recreational play (e.g. tobogganing, tubing).
Snowsports are popular with over 70 million people globally participating each year 1. While the injury rate varies depending on loca...
Sprue is the collective term for the malabsorptive gastrointestinal enteropathies although it may be used to refer directly to tropical sprue. It is composed of two entities:
non-tropical sprue / celiac disease
In each, the radiologic features are not sensitive enough to confir...
Storage disorders comprise a bewildering collection of inherited metabolic conditions which share the accumulation of a metabolite within various cells in the body due to dysfunction of specific enzymes or transport proteins. Accumulation of metabolites eventually results in cellular and/or orga...
Brain ischemia/infarction in children and young adults can result from several causes.
cyanotic heart disease
mitral valve prolapse
Subacromial impingement is by far the most common form of shoulder impingement and occurs secondary to attrition between the coracoacromial arch and the supraspinatus tendon or subacromial bursa.
type III acromion
low lying acromion
There are a wide range of causes for subarachnoid FLAIR hyperintensity, both pathological and artifactual.
FLAIR vascular hyperintensities in acute stroke 1,4,8
A subcutaneous abscess is a manifestation of a spectrum of soft tissue skin infection which includes cellulitis and necrotizing fasciitis. It is a form of abscess which lies within the dermis and subdermal cutaneous layers. Along with dental abscesses, subcutaneous abscesses are the most common ...
Subcutaneous calcification can be associated with a number of disorders. The list includes:
basal cell nevus syndrome
as a manifestation of systemic lupus erythematosus
Subdiaphragmatic free gas is one of the ways of detecting presence of free intraperitoneal gas (i.e. pneumoperitoneum). It is the presence of free, extraluminal gas in the anterior subhepatic space.
Subdiaphragmatic free gas is well appreciated as the g...
Subluxed facet joint is the mildest form of facet dislocation in which the ligamentous injury leads to partial uncovering of facet joint (c.f. complete uncovering in perched facet). This results in mild anterior displacement of one vertebral body on another (anterolisthesis).
Subperiosteal bone resorption is the most consistent and specific finding of hyperparathyroidism and is virtually pathognomonic of the condition.
While the terminal tufts of the phalanges are the most commonly involved bones, many others are involved:
tufts of the distal...
Subpulmonic effusions are a pleural effusion that can be seen only on an erect projection. Rather than layering laterally and blunting the costophrenic angle, the pleural fluid lies almost exclusively between the lung base and the diaphragm.
The fluid ca...
Subsegmental atelectasis is a descriptive term for a minor peripheral form of lung atelectasis.
Some authors also term it discoid atelectasis or plate-like atelectasis due to its appearance.
It is usually due to a lack of adequate inspiration, and not due to any underly...
Sunburst appearance is a type of periosteal reaction giving the appearance of a sunburst secondary to an aggressive periostitis. It should not be confused with the sunburst sign of meningioma vascularity.
The sunburst appearance occurs when the lesion grows too fast and the periosteum does not...
Superficial siderosis is a rare condition which results from the deposition of hemosiderin along the leptomeninges, with eventual neurological dysfunction.
On imaging, it is classically characterized on MRI as a rim of low signal coating the surface of the brain or spinal cord, particularly not...
Superficial thrombophlebitis, also called superficial venous thrombosis (SVT), is a pathological condition characterized by the presence of a thrombus in the lumen of a superficial vein, accompanied by inflammatory reaction of adjacent tissues.
Some authors, however, reserve the te...
Supernumerary ribs occur most commonly as a cervical rib arising from C7 or a lumbar rib arising from L1. In extremely rare situations, there can be sacral, coccygeal, intrathoracic, or aberrant lumbar ribs 3. Rarely supernumerary ribs (cervical and lumbar ribs aside) have been found as 'normal'...
Superscan is intense symmetric activity in the bones with diminished renal and soft tissue activity on a Tc99m diphosphonate bone scan.
This appearance can result from a range of etiological factors:
diffuse metastatic disease
transitional cell c...
The differential for suprasellar cystic lesions is large and predominantly includes developmental and neoplastic conditions.
Rathke's cleft cyst
enlarged perivascular spaces...
A surgical sieve is an approach to differential diagnosis that prompts the user to consider various types of pathologies systematically. Various versions of this mnemonic exist:
NAIVE MD DICTionary
Where "3-Scotland" rel...
Suspected physical abuse (previously termed non-accidental injury, NAI) in infants and young children represent both ethical and legal challenges to treating physicians.
Radiologists may be the first clinical staff to suspect non-accidental injuries when confronted with a particular injury patt...
Suspicious breast calcifications are calcifications within the breast that have a morphology and/or distribution on mammography indicating a significant probability of malignancy. These merit further workup and biopsy 1.
Some calcifications may be more conspicu...
Swan neck deformity is a deformity of the digits that consists of:
hyperextension of the proximal interphalangeal (PIP) joints
compensatory flexion of the distal interphalangeal (DIP) joints
Swan neck deformity is seen in 3,4:
rheumatoid arthritis (classical association)
There are a large number of causes for a symmetrical periosteal reaction 1,2:
chronic venous insufficiency
physiologic periostitis, most common cause before 6 months old
juvenile idiopathic arthritis
Syndactyly (plural: syndactylies) refers to a congenital fusion of two or more digits. It may be confined to soft tissue (soft tissue syndactyly/simple syndactyly) or may involve bone (bony syndactyly/complex syndactyly).
The overall estimated incidence is at ~1 per 2,500 to 5,000...
Syndesmophytes are calcifications or heterotopic ossifications inside a spinal ligament or of the annulus fibrosus. They are seen in only a limited number of conditions including:
They can be classified as...
Syringobulbia is a rare entity and refers to a syrinx that extends into the medulla oblongata 1.
Some authors use syringobulbia to refer to a syrinx present in any portion of the brainstem rather than specifically involving the medulla oblongata, and therefore encompassing syringop...
Syrinx is the collective name given to hydromyelia, syringomyelia, syringobulbia, syringopontia, syringomesencephaly, and syringocephalus.
The use of the general term 'syrinx' has grown out of the difficulty in distinguishing between hydromyelia and syringomyelia using current imag...
Thoracic manifestations of systemic lupus erythematosus can be variable.
For a general discussion, and for links to other system specific manifestations, please refer to the article on systemic lupus erythematosus.
pleuritis: considered one of the c...
There are many types of talar dislocation given its multiple articulations:
total talar dislocation
Talar fractures are an uncommon injury, accounting for <5% of all foot fractures. Recognition of the unique talar anatomy is important for correct diagnosis.
talar head fractures
talar neck fractures
talar body fractures
talar dome osteochondral fracture
Tauopathies are a heterogeneous group of neurodegenerative diseases characterized by abnormal metabolism of misfolded τ (tau) proteins leading to intracellular accumulation and formation of neurofibrillary tangles (NFT). These neurofibrillary tangles are deposited in the cytosol of neurons and g...
Telecanthus (rare plural: telecanthi) represents an increased intercanthal distance. It is often used interchangeably with hypertelorism, referring to increased distance between the eyes.
Causes and associations
trauma: naso-orbito-ethmoidal (NOE) fractures
Destructive lesions of the temporal bone (petrous pyramid, middle ear and antrum) have a relatively broad differential including 1:
lesions affecting petrous pyramid
vestibular schwannoma (acoustic neuroma)
neuroma of trigeminal and facial nerve
glomus jugulare ...
Temporomandibular joint (TMJ) effusions are unusual in asymptomatic patients, and thus should trigger a careful search for underlying pathology. It usually precedes osteoarthritis of the TMJ. Effusions are seen in:
rheumatoid arthritis (RA)
Tension pneumothoraces occur when intrapleural air accumulates progressively in such a way as to exert positive pressure on mediastinal and intrathoracic structures. It is a life-threatening occurrence requiring both rapid recognition and prompt treatment to avoid a cardiorespiratory arrest.
The differential diagnosis for a terminal ileitis is quite extensive, and includes:
inflammatory bowel disease
Crohn disease (most common)
backwash ileitis due to ulcerative colitis
There is only a short list of terminal tuft masses, which can arise from the adjacent soft tissues and erode the terminal tuft as well as arising from the terminal tuft itself:
epidermal inclusion cyst: history of penetrating trauma
tenosynovial giant cell tumor: occur laterally
The terminal zones of myelination are located at the posterior aspect of the lateral ventricles (the peritrigonal regions) and are the only part of the cerebral white matter that may exhibit high T2 signal in a normal brain at 2 years of age, when myelination of cerebral white matter normally be...
Testicular cancers are the most common neoplasm in men between the ages of 20 and 34 years.
Testicular cancer is uncommon, accounting for less than 1% of all internal organ malignancies 2.
The demographics of affected individuals depends on the age of the histology of the tumor. ...
Testicular microlithiasis is a relatively common condition that represents the deposition of multiple tiny calcifications throughout both testes.
The most common criterion for diagnosis is that of five microcalcifications in one testicle, although definitions have varied in the past. In the ma...
Testicular trauma is the third most-common cause of acute scrotal pain and may result in various degree of damage to the testes.
Testicular rupture and testicular ischemia/infarct are two severe complications which need to be ruled out. Other injuries that can occur include 1:
The four "Ds" of radiology reporting are the basic sequential tasks that a radiologist performs when reporting/reading a case, whether it be in training, the exam environment or in day-to-day clinical practice.
The 4 "Ds"
Diagnosis or differential diagnoses
Third inflow refers to anatomical variants leading to an additional venous inflow to the liver apart from the usual dual blood supply (portal vein and hepatic artery). They tend to be associated with parenchymal pseudolesions (focal hyperenhancement on post-contrast imaging, focal fat infiltrati...
There are a number of causes and mimics of thoracic aortic dilatation.
post-stenotic dilatation, e.g. bicuspid aortic valve
thoracic aortic aneurysm
atherosclerosis (usually descending thoracic aorta)
The differential for thoracic aortic stenosis includes:
aortitis (especially Takayasu arteritis)
Williams syndrome: supravalvular aortic stenosis
congenital rubella syndrome: supravalvular aortic stenosis
Thoracoliths are rare, calcified pleural-based nodules that are almost always incidental findings. They are usually considered mobile, and more common on the left.
The exact etiology is unknown and theories include 1,2:
calcified fibrin body
degenerated pleural lipoma
Threatened miscarriage (or threatened abortion) is mainly a clinical term, used when a pregnant woman in first 20 weeks of gestation presents with spotting, mild abdominal pain and contractions, with a closed cervical os.
It occurs in 20-25% of pregnancies and is associated with ...