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.

695 results found
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Retroplacental complex

Retroplacental complex (RPC) is the region behind the placenta and is composed of decidua basalis and portions of myometrium including the maternal veins which drain the placenta. Radiographic features Ultrasound visualised post 20 weeks of gestation seen as an echo-poor, subplacental region...
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Retroplacental haemorrhage

Retroplacental haemorrhage (RPH) occurs when there is perigestational haemorrhage that is confined to the retroplacental space. Pathology This type of haemorrhage occurs behind the placenta. The haematoma therefore separates the placenta from the uterine wall. The source of bleeding is probabl...
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Reversal of umbilical arterial end diastolic flow

Reversal of umbilical artery end-diastolic flow (REDF) or velocity is often an ominous finding if detected after 16 weeks. It is classified as Class III in severity in abnormal umbilical arterial Dopplers 6. Epidemiology The estimated incidence is at ~0.5% of all pregnancies with a much higher...
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Rhizomelic dwarfism

Rhizomelic dwarfism is a type of dwarfism where the dominant feature is proximal (i.e. femoral, humeral) limb shortening. Pathology The following conditions fall under the heading of rhizomelic dwarfism 3 metatropic dysplasia achondrogenesis rhizomelic chondrodysplasia punctata achondropla...
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Rhombencephalon

The rhombencephalon, or hindbrain is a primary vesicle of the neural tube. Development During the fifth week of embryological development the rhombencephalon further subdivides into the secondary brain vesicles, the metencephalon and the myelencephalon 1.  The metencephalon goes on to form th...
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Right ventricular outflow tract view (fetal echocardiogram)

The right ventricular outflow tract (RVOT) view (or three vessel view/3VV) is one of the standard views in a fetal echocardiogram. It is a long axis view of the heart, highlighting the path from the right ventricle into the pulmonary trunk (right ventricular outflow tract). In this view, the r...
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Robert sign

Robert sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours. Related articles fetal death in utero
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Roberts syndrome

Roberts Syndrome (RBS) (also known as Roberts-SC phocomelia syndrome, pseudothalidomide syndrome, Appelt-Gerken-Lenz syndrome) is rare congenital malformation syndrome. It has an autosomal recessive inheritance. Clinical features general intrauterine growth restriction (IUGR) post-natal grow...
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Robinow syndrome

Robinow syndrome is a rare heterogenous genetic disorder with at least two distinct forms. Clinical spectrum The syndrome can affects several systems which include: mesomelic limb shortening: mesomelia hemivertebrae characteristic facies anomalies fetal facies hypertelorism 3 frontal bos...
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Rocker bottom foot

A rocker bottom foot (also known as a congenital vertical talus) is a congenital anomaly of the foot. It is characterised by a prominent calcaneus/heel and a convex rounded sole. Pathology It results from a dorsal and lateral dislocation of the talonavicular joint. Associations aneuploidic s...
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Rothmund-Thomson syndrome

Rothmund-Thomson syndrome (RTS) is an extremely rare autosomal recessive disorder with heterogeneous clinical features. Clinical features It is characterized by many features which include: poikiloderma: characteristic rash, typically develops in infancy sparse hair, eyelashes, and/or eyebro...
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Rubinstein-Taybi syndrome

Rubinstein-Taybi syndrome (RTS) is a very rare genetic multi-system disorder primarily characterised by mental retardation, broad and often angulated thumbs and halluces, and distinctive facial features. Epidemiology The estimated incidence is 1 in 100,000-125,000 live births 5. Clinical pres...
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Ruptured omphalocoele

Ruptured omphalocoele occurs when there is rupture of the outer membrane of an omphalocoele. When this happens the eviscerated fetal bowel looks free floating and distinction from gastroschisis becomes difficult. However the abdominal defect generally tends to be larger and may contain liver wit...
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Rupture of fetal membranes

A rupture of membranes (ROM) or amniorrhexis is a term used during pregnancy to describe a rupture of the amniotic sac. This can occur as part of normal birth (or "spontaneously")  if it occurs at full term at the onset of, or during, labor. It is also  colloquially known as "breaking water." S...
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Russell-Silver dwarfism

Russell-Silver dwarfism is a very rare syndrome characterised by: intrauterine growth restriction: tends to give an asymmetrical IUGR postnatal growth restriction relatively large calvarium: pseudohydrocephalus clinodactyly/clinobrachydactyly of the small finger a typical triangular type fa...
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Sacrococcygeal teratoma

Sacrococcygeal teratoma (SCT) refers to a teratoma arising in the sacrococcygeal region. The coccyx is almost always involved 6. Epidemiology It is the commonest congenital tumour in the fetus 11 and neonate 3. The incidence is estimated at ~1:35000-40000. There is recognised female predilecti...
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SADDAN syndrome

SADDAN syndrome is an acronym for (severe achondroplasia with developmental delay and acanthosis nigricans). It is an extremly rare condition and as the name stands comprises of skeletal brain and cutaneous anomalies. Pathology Genetics It (like achondroplasia) also results from a mutation i...
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Sakati-Nyhan syndrome

The Sakati-Nyhan syndrome, also known as Sakati-Nyhan-Tisdale syndrome or acrocephalosyndactly type III, is an extremely rare type of acrocephalopolysyndactyly. Its main features include: craniofacial defects congenital limb abnormalities congenital heart defects History and etymology It w...
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Sandal gap deformity

A sandal gap deformity is an imaging observation in antenatal ultrasound (typically second trimester) where there is an apparent increase in the interspace between the great toe of the foot from the rest of the toes (likened to the gap caused by a sandal).  While it can be a normal variant (esp...
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Scar endometriosis

Scar endometriosis is a term given to endometriosis occurring in a Caesarian section scar. It can be located at the skin, subcutaneous tissue, rectus muscle/sheath, intraperitoneally, or in the uterine myometrium (within uterine scar). Epidemiology The reported incidence of abdominal scar endo...
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Schizencephaly

Schizencephaly is a rare cortical malformation that manifests as a grey matter lined cleft extending from the ependyma to the pia mater. Terminology Some authors do not use the term schizencephaly, preferring to group these disorders under the blanket term of porencephaly. For the purpose of t...
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Seckel syndrome

Seckel syndrome is an autosomal recessive congenital dwarfing disorder. Epidemiology The estimated incidence is ~ 1:10,000. There is no recognised gender predilection. Clinical features It is clinically characterised by many features including intrauterine growth restriction (IUGR) postnat...
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Second trimester ultrasound scan

The second trimester scan is a routine ultrasound examination in many countries that is primarily used to assess fetal anatomy and detect the presence of any fetal anomalies.  The second trimester extends from 13 weeks and 0 days to 27 weeks and 6 days of gestation although the majority of thes...
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Semilobar holoprosencephaly

Semilobar holoprosencephaly is a subtype of holoprosencephaly (HPE) characterised by an incomplete forebrain division. It is intermediate in severity, being worse than lobar holoprosencephaly and better than alobar holoprosencephaly. Epidemiology Please refer on the general article of holopros...
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Shortened fetal femoral length

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 its under the 2.5th centile 5) or less than 0.91 predicted by the bi-pareital diameter. It can occur in isolated or in association...
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Shortened fetal humerus

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 predicted by the bipareital diameter (BPD). It can occur in isolation or in association with a number of other anomalies. The humeral length is n...
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Shortened fetal long bones

Shortened fetal long bones (SFLB) can involve either the upper limb and / or the lower limb. It is borad descriptive entity which can include short fetal femur short fetal humerus short fetal tibia - fibula short fetal radius - ulna Pathology Associations the presence of shorted fetal lon...
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Shortening of the cervical canal

Shortening of the uterine cervical canal as the name implies refers to an abnormal shortening of the uterine cervical length. It is considered a sign of cervical incompetence in pregnancy and can lead to premature delivery. Pathology Aetiology primary (i.e. congenital/idiopathic) secondary ...
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Short maxillary length

A short maxillary length can result from many congenital and acquired causes. If seen in an antenatal ultrasound scan, it is often considered to have a high association with trisomy 21 1.  Congenital conditions Many conditions that can cause midfacial hypoplasia will result in a short maxillar...
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Short rib polydactyly syndrome

Short rib polydactyly syndrome(s) (SRPS) comprise of a rare group of severe osteochondrodysplasias. There are four major recognised types present: type I: Saldino-Noonan type type II:: Majewski type type III: Verma-Naumoff type type IV: Beemer-Langer type There may also be other very rare t...
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SHORT syndrome

SHORT syndrome refers to an acronym which primarily comprises of the following features: S: short stature H: hyperextensibility of joints and/or inguinal hernia O: ocular depression R: Rieger anomaly T: teething delay In a addition to these there can be numerous associated minor features w...
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Short umbilical cord

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.  Pathology Associations Recognised associations include chromosomal anomalie...
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Simple hydropic degeneration of the placenta

Simple hydropic degeneration of the placenta is a form hydropic degeneration of the placenta that can occur in a first trimester pregnancy loss. In this situation the serum beta HCG will tends to be low and would show a decline. The overal sonographic appearance can vary dependant on the degree...
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Single umbilical artery

Single umbilical artery (SUA) results when there is a congenital absence of either the right or left umbilical artery. In the usual situation, there are paired umbilical arteries. For some unknown reason, the absence of the left umbilical artery is much more common (~70%). Epidemiology The est...
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Sirenomelia

Sirenomelia (also known as the mermaid syndrome) is a rare congenital malformation characterised by the fusion of lower limb structures. Epidemiology The estimated incidence is at ~1 in 60,000-70,000 of pregnancies 9. There may be greater male predilection (somewhat paradoxical given the usage...
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Skeletal dysplasia

Skeletal dysplasias (osteochondrodysplasias) refer to an abnormality in bone formation. There is a very wide clinicopathological spectrum and any part of the skeleton can be affected. Epidemiology The overall prevalence is estimated at ~2 per 10,000 live births 3. Pathology Types At least 3...
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Small for date fetus

A small for dates fetus can result from a number of factors Fetal factors aneuploidy trisomy triploidy skeletal dysplasis(s) structural anomalies (syndromes) Maternal factors Common hypertension medication(s): fetal Warfarin syndrome hydantoin embryopathy (Dilantin TM) cytotoxic dru...
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Small gestational sac

A small gestational sac in early first trimester is considered a poor prognostic factor. Some authors use the mean sac diameter to crown rump length difference of 5 mm or greater to be normal 1.   The smaller than expected sac diameter in pregnancies 36-42 days from the last menstrual period ha...
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Small placenta

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...
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Small yolk sac

A small yolk sac is considered a non-specific feature and, at the time of writing, there are not many publications about the clinical importance of small yolk sacs. According to some publications, a very small yolk sac may be a normal finding during early periods of normal embryologic developme...
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Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome (SLOS) also known as 7-dehydrocholesterol reductase deficiency is an inborn error of cholesterol synthesis.  Epidemiology The estimated incidence is at 1:20000-40000 live births. Prevalence may be greater in Nordic countries. Pathology The condition often results f...
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Snake under the skull sign

Snake under the skull sign is a vascular anomaly seen in holoprosencephaly. Pathology Due to the defect in the cleavage of the two hemispheres there is a fusion of the frontal lobes. This band of abnormal cortical tissue causes forward displacement of the anterior cerebral artery, so that it l...
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Snowstorm sign (complete hydatiform mole)

Snowstorm sign in obstetric imaging is classically seen in complete hydatiform mole. It is characterised by the presence of many hydropic villi which gives the ultrasonographic appearance of a central heterogeneous mass having a solid, hyperechoic area and interspersed with a multitude of cystic...
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Snowstorm sign (disambiguation)

Snowstorm sign may refer to: snowstorm sign: complete hydatiform mole (ultrasound) snowstorm sign: extracapsular breast implant rupture (ultrasound)
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Sonographic values in obstetrics and gynaecology

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. 1 mm rate of increase of a mean sac diameter per day in early pregnancy 2 mm generally accepted value for a th...
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Spalding sign (fetal demise)

The Spalding sign refers the overlapping of the fetal skull bones caused by collapse of the fetal brain.  It appears usually a week or more after fetal death in utero.  This finding was originally described on abdominal radiographs and is indicative of fetal demise.
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Spectrum of abnormal placental villous adherence

The spectrum of abnormal placental villous adherence describes the degree to which there is an invasion of chorionic villi into the myometrium because of a defect in the decidua basalis. Pathology Placental villous adherence is classified on the basis of depth of myometrial invasion: placenta...
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Spina bifida

Spina bifida is a type of neural tube defect/spinal dysraphism which can occur to varying degrees of severity. It is often considered the most common congenital CNS malformation. Epidemiology The estimated incidence is at 1:1000-2000 live births 2. Clinical presentation A constellation of fe...
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Spinal dysraphism

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.  Pathology There is often abnormal fusion of the midline embryonic neural, vertebral and mesenchymal structures.  Sub t...
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Spondylocostal dysostosis

Spondylocostal dysostosis (SCDO) is a rare condition characterised by short-trunk dwarfism secondary to developmental anomalies of the vertebrae and ribs. Previously the condition Jarcho-Levin syndrome (also known as spondylothoracic dysostosis) was grouped together with spondylocostal dysostosi...
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Spontaneous rupture of membranes

A spontaneous rupture of membranes (SROM) refers to a rupture of fetal membranes occuring on its own (c.f artificial rupture of membranes). When this occurs prior to ~ 37 weeks in gestation, it is then termed spontaneous premature rupture of membranes (SPROM) which it the usual cause of pre-term...
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Stenosis of the uterine cervix

Stenosis of the uterine cervix is the pathologic narrowing of the uterine cervix. The term cervical stenosis is clinically defined as cervical narrowing that prevents the insertion of a 2.5 mm wide dilator. Clinical presentation If the stenosis is severe enough it may result in proximal obstru...
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Stickler syndrome

Stickler syndrome refers to a group of disorders primarily affecting connective tissue. Pathology Several gene mutations have been idntified dependent on specific sub types which include: Stickler syndrome type I: COL2A1 Stickler syndrome type II: COL9A1 Stickler syndrome type III: COL11A1 ...
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Straight umbilical cord

Straight umbilical cord implies, as the name suggests, an umbilical cord with no coils. Epidemiology The reported incidence of a straight cord is about 3.7-5% of all pregnancies. Radiographic features Ultrasound the entire length of the umbilical cord shows no evidence of coiling Complicat...
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Strawberry skull

Strawberry skull refers to the shape of the head on an antenatal ultrasound. Epidemiology Associations In general, strawberry skull is considered one of the nonspecific 'soft markers' for abnormal fetal development. It is considered more closely associated with trisomy 18 (Edward syndrome). ...
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Subamniotic haemorrhage

Subamniotic haemorrhage is considered a type of perigestational haemorrhage. Pathology Subamniotic haematomas are classical placental pathological lesions resulting from the rupture of chorionic vessels (allantochorionic vessels) close to the cord insertion.  A subamniotic hemorrhage is conta...
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Subchorionic cyst

Subchorionic cyst is often considered a subtype of placental surface cyst (commonest type). They are often multiple and may be present in ~5-7% of term placentas 2. Occasionally they can compress chorionic or amniotic vessels leading to adverse fetal outcome. See also subchorionic haemorrhage
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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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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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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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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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Syndactyly

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). Epidemiology The overall estimated incidence is at ~1 per 2500 to 5000 live births 6,8. The...
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Syntelencephaly

Syntelencephaly, also known as middle interhemispheric variant (MIHV), is a mild subtype of holoprosencephaly that is characterized by an abnormal midline connection of the cerebral hemispheres between the posterior frontal and parietal regions.  Epidemiology Syntelencephaly is a congenital ma...
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TAR syndrome

TAR syndrome stands for thrombocytopaenia with absent radius and as the name implies is primarily characterised by the following two features: fetal thrombocytopaenia absent fetal radii (bilaterally) with the presence of both thumbs Epidemiology The condition is extremely rare with an estima...
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Terminal myelocystocele

Terminal myelocystoceles are an uncommon form of spinal dysraphism representing marked dilatation of the central canal of the spinal cord, herniating posteriorly through a dorsal spinal defect. The result is a skin-covered mass in the lower lumbar region, consisting of an ependyma-lined sac.  E...
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Thalidomide embryopathy

Thalidomide embryopathy refers to a syndrome resulting from in utero exposure to thalidomide, and is characterized by multiple fetal anomalies. Fetal exposure to thalidomide occurred primarily from 1957 to 1961, when it was used as a treatment for nausea in pregnant women.  Epidemiology  Expos...
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Theca lutein cyst

Theca lutein cysts (TLC), also known as hyperreactio luteinalis (HL), are a type of functional ovarian cysts. They are typically multiple and seen bilaterally. Pathology They are thought to originate due to excessive amounts of circulating gonadotrophins such as beta-hCG. Hyperplasia of the th...
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Thoracopagus conjoined twins

Thoracopagus conjoined twins are, as the name suggests, conjoined twins united at their thorax. Fusion is typically face-to-face, at the upper thorax to the umbilicus with a common sternum, diaphragm, and upper abdominal wall. Very often a common pericardial sac is present as well as a degree o...
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Threatened miscarriage

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.  Epidemiology It occurs in 20-25% of pregnancies and is associated with ...
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Three vessel and trachea view

The three vessel and trachea view (or 3VT view) is one of the fetal echocardiography views. In this view, aortic and ductal arches are combined into the DAo and appear as a V-shaped confluence. Both arches tend to be of similar size and are located towards the left of the trachea. The thymus is ...
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Tracheal atresia

Tracheal atresia (TA) is an extremely rare anomaly and refers to a congenital absence of the trachea. Epidemiology There may be a greater male predilection 5. Pathology Tracheal atresia falls under the spectrum of laryngeal-tracheo-bronchial atresia which in turn results either from an obstr...
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Transient abnormal myelopoiesis

Transient abnormal myelopoiesis (TAM) is a phenomenon that can happen in the fetuses or neonates with trisomy 21. The condition can mimic leukaemia. Epidemiology The estimated incidence is at ~10% of newborns with trisomy 21 3. Radiographic features Antenatal ultrasound In the context of kn...
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Transverse cerebellar diameter

In obstetric imaging, the fetal transverse cerebellar diameter (TCD) is often measured as an additional fetal biometric parameter. It is measured as the maximal diameter between the cerebellar hemispheres on an axial scan. The value of the transverse cerebellar diameter in mm's is considered rou...
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Trauma in pregnancy

Trauma is a leading cause of mortality in pregnancy. Pregnancy increases the incidence and severity of abdominal trauma in females.  Epidemiology Trauma affects up to 7% of pregnancies, and the incidence of pregnancy in level 1 trauma patients is estimated to be ~2% 1.  Pathology Aetiology ...
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Traumatic abruption placenta scale

The traumatic abruption placenta scale (TAPS) was devised to stratify placental injury findings on CT. Since placental abruption is a concern in a pregnant patient who has undergone traumatic injury, CT is occasionally the first imaging modality used to evaluate the placenta. 0: normal homogene...
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Trident hand

A trident hand is a description where the hands are short with stubby fingers, with a separation between the middle and ring fingers.  Associations It can be seen in various chondrodysplasias including achondroplasia.
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Triple screening

Triple screening refers to a screening blood test that is used to screen pregnant women for possible neural tube defects, Down syndrome and trisomy 18 in the developing baby. It measures: alpha-fetoprotein Beta hCG  unconjugated oestriol Interpretation An abnormal test result doesn't indica...
Article

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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Trisomies

Trisomies are chromosomal anomalies which usually occur due to non-disjunction. The vast majority of affected fetuses being spontaneously aborted, often very early during gestation. Only three are compatible with extra-uterine life (T13, T18, T21), and only one beyond early infancy (T21). In or...
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Trisomy 22

Trisomy 22 is an aneuploidic chromosomal anomaly which is usually fatal unless in mosaic forms. Pathology Variants Duplication of the short arm (p) and a small section of the long arm (q) of chromosome 22 can give result to the cat-eye syndrome - Schmidt-Fraccaro syndrome. Radiographic featu...
Article

True umbilical cord knot

True umbilical cord knots are a rare occurrence and as the name suggests represent a knot formation in the umbilical cord. Epidemiology They occur in less than 1% of pregnancies. Pathology Predisposing factors a long umbilical cord polyhydramnios small fetus excessive fetal movements. R...
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T sign (obstetrics)

The "T sign" is really the absence of a twin-peak sign (or lambda sign) and is used in ultrasound assessment of a mulifetal pregnancy. It refers to the lack of chorion extending between the layers of the intertwin membrane, denoting a monochorionic pregnancy. The intertwin membrane comes to an ...
Article

Tubal ectopic pregnancy

Tubal ectopic pregnancy (or adnexal ectopic pregnancy) is the most common location of an ectopic pregnancy. Epidemiology It is the most common type of ectopic by far, accounting for 93-97% of cases. Pathology Although the fallopian tube has many anatomical parts, for the purposes of ectopic ...
Article

Tubal ring sign

Tubal ring sign, also referred to as bagel sign or blob sign, one of the ultrasound signs of a tubal ectopic. It comprises of an echogenic ring which surrounds an unruptured ectopic pregnancy. It is said to have a 95% positive predictive value (PPV) for ectopic pregnancy. Differential diagnosis...
Article

Turner syndrome

Turner syndrome, also referred as 45X, is the most common of sex chromosome abnormalities in females.  Epidemiology The incidence is estimated at 1:2000-5000 of live births, although the in utero rate is much higher (1-2% of conceptions) due to a significant proportion of fetuses with 45X abor...
Article

Twin anaemia polycythaemia sequence

The twin anaemia polycythaemia sequence (TAPS) is considered a variant of the twin to twin transfusion syndrome (TTTS). Epidemiology TAPS may occur spontaneously in up to 5% of monochorionic twins and may also develop after incomplete laser treatment in TTTS cases 2. Pathology As with TTTS t...
Article

Twin embolisation syndrome

The twin embolisation syndrome (TES) is a rare complication of a monozygotic twin pregnancy following an in utero demise of the co-twin. Pathology It was traditionally thought to result from the passage of thromboplastic material into the circulation of the surviving twin which causes ischemic...
Article

Twin growth discordance

In obstetric imaging, twin growth discordance refers to a significant size or weight difference between the two fetuses of a twin pregnancy. To be classified as a growth discordance, some consider that the estimated fetal weight (EFW) of the smaller twin should fall under the 10th centile. Epid...
Article

Twin growth disparity

A twin growth disparity is a closely related term to twin growth discordance. In a twin growth disparity, there may be a significant size or weight difference between the two fetuses but estimated fetal weight of smaller twin does not fall below the 10th centile. ( In contrast to twin growth dis...
Article

Twin-peak sign (twin pregancy)

The twin peak sign (also known as the lambda (λ) sign) is a triangular appearance of the chorion insinuating between the layers of the inter twin membrane and strongly suggests a dichorionic twin pregnancy. It is best seen in the first trimester (between 10-14 weeks). 5 While the presence of a t...
Article

Twin pregnancy

Twin pregnancies are the most common multifetal pregnancies.  Epidemiology Multifetal pregnancies account for ~ 1% of all pregnancies, but are seen in much higher numbers in populations where in vitro fertilisation (IVF) is a common practice, most of which are twin pregnancies. Classification...
Article

Twin reversed arterial perfusion

Twin reversed arterial perfusion (TRAP) sequence is considered a severe variant of the twin to twin transfusion syndrome (TTTS). The hallmark of this condition which only happens in monochorionic pregnancies is the lack of placental perfusion of one of the twins (so called acardiac twin), with a...
Article

Twin-twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a potential complication that can occur in a monochorionic twin (either MCDA or MCMA) pregnancy.  Epidemiology This complication can occur in ~10% (range 15-25%) of monochorionic pregnancies giving an estimated prevalence of ~1:2000 of all pregnancie...

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