Shorted fetal femur is a morphological descriptor and is usually defined when the femoral length falls below the 5th centile for gestational age (some define it when it is under the 2.5th centile 5) or less than 0.91 predicted by the bi-parietal diameter. It can occur in isolated or in associati...
Shortened fetal humerus is a morphological description and is usually defined when the humeral length falls below the 5th percentile or less than 0.9 as predicted by the biparietal diameter (BPD). It can occur in isolation or in association with a number of other anomalies.
The humeral length i...
Shortening of the fourth/fifth metacarpals and less commonly metatarsals is seen in a variety of apparently disparate conditions.
Common causes 2:
post-infective (e.g. osteomyelitis, yaws, tuberculosis dactylitis)
Short limb skeletal dysplasias are skeletal dysplasias which are characterised by limb shortening
Rhizomelic (proximal limb shortening)
particularly type II
Short stem hip arthroplasties are a special type of hip joint replacement where as the name states the stem is shorter than usual. It is known by various trade names including the NANOS system. In selected patients it is thought to result in fewer complication rates 1.
Short umbilical cord has been variably defined. Considering the mean length of the umbilical cord is 50-70 cm 1-2, a short cord in absolute terms is usually taken as one that is under 35-40 cm in length at term 1-2.
Recognised associations include
Shoulder instability is tendency of the glenohumeral joint to sublax or dislocate due to loss of it's normal functional or anatomical stabilizers:
static or anatomical:
glenohumeral joint capsule
negative adhesive force...
Silicone injection into various parts of the body has been used in many countries to achieve what are perceived to be cosmetic improvements. Most common sites for such injections are the breasts, face, and buttocks, although anywhere can be targeted.
This article is a general discussion of the...
Simultanagnosia is the inability of one to perceive more than one object at a time. It is a characteristic symptom of Balint syndrome and can also be seen with posterior cortical atrophy (PCA).
Sincipital encephalocoeles are congenital herniations of cerebral parenchyma through a cranial defect. There are three main types 1,2:
frontonasal encephalocoele (~50%): more common in Asia and Latin America 4
naso-ethmoidal encephalocoele (30%): more common in North America 4
Single layer periosteal reaction is a uniformly dense, single thin layer of new bone about 1-2 mm from the cortical surface. Passive hyperaemia causes increased osteoblastic activity and production of new bone. It is seen in:
premature infants for up to 6 months
early fracture healing
The differential for a single pleural mass is essentially the same as that for multiple pleural masses with the addition of a few entities.
solitary fibrous tumour of the pleura (pleural fibroma)
localised mediastinal malignant mesothelioma
The nasal passage and paranasal sinuses (collectively sinonasal) plays host to a number of diseases and conditions, which can be collectively termed sinonasal disease. One way of classifying separate entities is as follows:
inflammatory and infective conditions
A Sister Mary Joseph nodule is a metastatic lesion involving the umbilicus. The most common primary source is an intra-abdominal adenocarcinoma.
Umbilical metastases are uncommon, reportedly present in 1-3% of all intra-abdominal and/or pelvic malignancy 7.
Skeletal “don’t touch” lesions (also called leave me alone lesions) are so radiographically characteristic lesions that an additional diagnostic tests such as a biopsy are unnecessary and can be frankly misleading and lead to additional unnecessary surgery. Thus a radiologic diagnosis should be ...
Skeletal dysplasia (also known as osteochondrodysplasia) refers to any abnormality in bone formation. There is a very wide clinicopathological spectrum and any part of the skeleton can be affected.
The overall prevalence is estimated at ~2 per 10,000 live births 3.
There are a number of skeletal lesions with giant cells on histology, which may occasionally lead to mischaracterization of the lesion.
Below is a list of lesions with giant cells as an important histological feature, to aid in differential diagnosis if the histological diagnosis of a lesion do...
Skeletal metastases are common and result in significant morbidity in patients with metastatic disease. Although the diagnosis is often straightforward, especially as in many cases there is a well-documented history of metastatic malignancy, sometimes they may mimic benign disease or other prima...
The presence of intramuscular oedema (increased high T2/STIR signal) on MRI carries an extremely broad differential. They include:
effects of direct injury or tear
denervation injury: denervation changes in muscles
early myositis ossificans
The presence of skin thickening on mammography is variably defined, usually being more than 2mm 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.
Angle formed by:
line joining the nasion with the centre of the pituitary fossa
line joining the anteri...
Skull tumours can be (as with tumours anywhere else) both primary and secondary, and benign or malignant.
giant cell tumour (GCT)
aneurysmal bone cyst (ABC)
epidermoid and dermoid cysts
Regular, smooth generalised 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 ischaemia 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 aetiologies (each discussed...
A small for dates fetus can result from a number of factors
structural anomalies (syndromes)
fetal Warfarin syndrome
hydantoin embryopathy (Dilantin TM)
The following differentials can be considered when small lung volumes are seen:
prior surgery, e.g. lobectomy, lung volume reduction surgery
skeletal deformities, e.g. kyphosis, scoliosis
systemic lupus erythematosus (SLE)
neuromuscular disorders, e.g. p...
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 is related to smoking. Smoking affects the lungs in numerous ways, and can be classified under the following headings:
smoking related interstitial lung diseases (SR-ILD)
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 tumours 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 paediatric population are listed below.
The WHO 2002 classification of soft tissue tumours is as follows:
This, however, has been revised under the 2013 WHO tissue tumour classification system 4.
lipomatosis of nerve 8850/0
Solid lesions with enhancement is 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 wit...
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 tumour
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 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 centre 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 gynaecological 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 th...
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 fibres 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 fibres). 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 cord transection, as the name implies, refers to a tear within the spinal cord as a result of a significant traumatic injury. It is an important radiological finding that can influence the decision on potential surgery in the setting of spinal trauma.
Spinal dysraphism is a broad term given to a group of anomalies where there are malformations in the dorsum of the embryo. Neural tube defects come under this group as well.
There is often abnormal fusion of the midline embryonic neural tube leading to abnormal development of the ve...
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 haematomas 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 haematoma is important for treatment, as is distinguishing it, to the extent possible, from other ent...
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%)
intramedually metastases (1%)
Each of these are discussed separately. Below ...
Synovial cysts of the spine are cystic formations connected to the facet joint and containing synovial fluid lined by a cuboid or pseudostratified columnar epithelium. They may be result in lumbar radiculopathy in a significant number of cases.
They may be asymptomatic an...
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 localised 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).
Symptoms include abdominal mass and ...
Splenic calcifications can occur is various shapes and forms and can occur from a myriad of aetiological 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 haemangiomas 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 haemangioma: commonest benign sp...
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 is a term which refers to enlargement of the spleen. The normal adult splenic length upper limit is usually around 12-15 cm. It can also be helpful to know how to calculate splenic index, volume and mass by CT and MR techniques. Massive splenomegaly is a term used when the spleen we...
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 ...
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 / coeliac disease
In each, the radiologic features are not sensitive enough to confi...
Stapes prosthesis are used in the stapedectomy surgery procedure which aims to improve conductive hearing loss due to oval window closure secondary to otosclerosis or post inflammatory conditions. The procedure is also performed to correct congenital abnormalities or discontinuity or fracture re...
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 ischaemia/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
acromioclavicular degenerative disease
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 necrotising 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...
Substernal goitre is a goitre (enlarged thyroid gland) with intrathoracic extension.
It remains unclear which goitres are to be termed substernal, but a recently proposed definition is a goitre that requires mediastinal exploration and dissection for complete removal or an intrathoracic compone...
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 haemosiderin along the leptomeninges, with eventual neurological dysfunction.
On imaging, it is classically characterised on MRI as a rim of low signal coating the surface of the brain or spinal cord, particularly no...
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 term...
Supernumerary ribs occur most commonly as a cervical rib or arising from the lumbar vertebra. In extremely rare situations, there can be sacral, coccygeal, intrathoracic, or aberrant lumbar ribs 3.
trisomy 8 syndrome
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 aetiological factors:
diffuse metastatic disease
transitional cell carcinoma (...
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 helps, especially when under the pressure of the exam situation. Differentials from the sections of the sieve can be considered in turn, helping to extend the list in a structured way. They include:
Suspicious breast calcifications are calcifications within the breast that are not benign. These calcification need further work up and biopsy. These can be divided as
suspicious calcification of intermediate concern
suspicious calcification raising high probability of malignancy
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 periosteal reaction of the newborn (Caffey disease), most common cause before 6 months old
juvenile idiopathic arthritis
Synchronous primary lung carcinoma (SPLC) is a term given to the occurrence of two or more primary lung carcinomas within different portions of the lung in the same time period.
They are thought to the carry the same pathophysiological mechanism as metachronous lung carcinoma (i.e. two or more ...
Syndactyly 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 live births 6,8. T...
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:
Appearance on plain radiographs comprises v...
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...