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.

721 results found
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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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Transverse view of abdomen

A transverse abdominal view is one of the standard views on fetal echocardiography and is very useful for assessing situs abnormalities. In case of situs solitus (normal situs), the stomach is on the left and liver on the right. The descending aorta lies anterior and to the left of the spine whi...
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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 abruptio placenta scale

The traumatic abruptio 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 homogeneo...
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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 fetus. It measures: alpha-fetoprotein Beta hCG unconjugated oestriol Interpretation An abnormal test result doesn't indic...
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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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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...
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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 Risk factors a long umbilical cord polyhydramnios small fetus excessive fetal movements Radiograph...
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T sign (obstetrics)

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

Turner syndrome, also known as 45XO or 45X, is the most common of the 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...
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Twin anaemia polycythaemia sequence

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 twin-to-twin transfusion syndrome cases 2. ...
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Twin embolisation syndrome

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 ischaemic st...
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Twin growth discordance

Twin growth discordance is a term used in obstetric imaging to describe 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 10t...
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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...
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Twin-peak sign (twin pregnancy)

The twin peak sign (also known as the lambda (λ) sign) is a triangular appearance of the chorion insinuating between the layers of the intertwin 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 tw...
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...
Article

Two diameter pocket method

The two diameter pocket (TDP) method is an alternative method of assessing amniotic fluid volumes on ultrasound. However, it is not thought to be a good predictor of adverse neonatal outcome 2. Sonographic assessment According to this method 1,2: TDP <15 cm2: indicative of oligohydramnios TD...
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Umbilical arterial aneurysm

An umbilical arterial aneurysm (UAA) is an extremely rare but potentially lethal vascular anomaly which is usually detected in utero.  Pathology Location It tends to favour the placental end of the umbilical artery in the cord. Associations Concurrently associated anomalies are thought to b...
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Umbilical arterial Doppler assessment

Umbilical arterial (UA) Doppler assessment is used in surveillance of fetal well-being in the third trimester of pregnancy. Abnormal umbilical artery Doppler is a marker of uteroplacental insufficiency and consequent intrauterine growth restriction (IUGR) or suspected pre-eclampsia.  Umbilical ...
Article

Umbilical cord

The umbilical cord is a fetal organ that connects the placenta to the developing fetus and is a vital passage for nutrients, oxygen and waste products to and from the fetus.  The umbilical cord inserts into the centre of the placental bulk and into the fetus at the umbilicus. Variations in inse...
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Umbilical cord coiling index

Umbilical cord coiling index is defined as a number of coils per one centimetre of length of the cord. The normal index is one coil for a length of five centimetres. If the number of coils is more per centimetre it is called as a hypercoiled and less than it is called as a hypocoiled umbilical c...
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Umbilical cord cyst

Umbilical cord cysts can refer to any cystic lesion associated with the umbilical cord. They can be single (commoner) or multiple. Epidemiology They may be seen in ~3% of pregnancies in the first trimester 8. Pathology Umbilical cord cysts can represent either true or false cysts: true cyst...
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Umbilical cord entanglement

Umbilical cord entanglement is a feature which can mean either one or more loops of the cord being encircled around any part of the fetal body 3 or two umbilical cords getting entangled with each other. In the latter situation, it is a classical feature of a monochorionic-monoamniotic twin pregn...
Article

Umbilical cord haematoma

Umbilical cord haematoma describes the formation of a haematoma secondary to bleeding from the umbilical cord. Pathology The haematomas can be either spontaneous or iatrogenic. Spontaneous bleeding is very rare and documented to be around 0.02% of pregnancies. Majority of the cases are iatroge...
Article

Umbilical cord knot

Umbilical cord knot is a term given to denote either true umbilical cord knot: often the term "umbilical cord knot" is used to describe this entity 1 or false umbilical cord knot: usually of no clinical significance See also umbilical cord entanglement
Article

Umbilical cord prolapse

Umbilical cord prolapse is a situation where the umbilical cord protrudes into the cervical canal. Epidemiology The estimated incidence is at  ~ 0.2-0.5% of all pregnancies 4,5.  Pathology Associations Recognised associations include multifetal pregnancy: twin gestation non cephalic/abnor...
Article

Umbilical cord pseudocyst

Umbilical cord pseudocysts are a type of cystic lesion occurring in relation to the umbilical cord. Epidemiology Although the true incidence not accurately known, they are comparatively much more common than true umbilical cord cysts. Pathology The pseudocyst basically comprises of mucoid de...
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Umbilical cord thrombosis

Umbilical cord thrombosis is a potentially fatal complication and can mean either a thrombosis of the umbilical vein or either or both the umbilical arteries. Umbilical vein thrombosis occurs more frequently than thrombosis of one or both umbilical arteries (umbilical arterial thrombosis) Epide...
Article

Umbilical vein

The umbilical vein is the conduit for blood returning from the placenta to the fetus until it involutes soon after birth. The umbilical vein arises from multiple tributaries within the placenta and enters the umbilical cord, along with the (usually) paired umbilical arteries. Once it enters the...
Article

Umbilical vein varix

Umbilical vein varix (UVV) refers to a focal dilatation of the umbilical vein. Epidemiology Associations UVVs were initially thought to have a high association with other anomalies which include: chromosomal anomalies: 5-12% with FIUVV 2,3 Down syndrome   underlying congenital cardiovascul...
Article

Umbilical venous dilatation

Umbilical venous dilatation is a rare entity and often tends to occur as an isolated finding 4. Dilatation of the umbilical vein can arise from a number of pathologies: umbilical venous varix (UVV): particularly if focal fetal hydrops: a focal dilatation due to an umbilical venous varix with...
Article

Umbilical venous flow assessment

Umbilical venous flow in the physiological situation comprises of a monophasic non-pulsatile flow pattern in the umbilical vein with a mean velocity of 10-15 cm/s. The presence of pulsatility implies a pathological state unless in the following situations: early in pregnancy: up to ~13 weeks ge...
Article

Urethral agenesis

Urethral agenesis (or urethral atresia) refers to a situation where there is a congenital absence of the urethra.  It can be a cause of fetal obstructive uropathy. Pathology Associations prune belly syndrome 5 bladder agenesis 2 Radiographic features Antenatal ultrasound May show a dilate...
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Uterine artery

The uterine artery is seen bilaterally and is a branch of the anterior division of the internal iliac artery. Gross anatomy Course It runs medially in the pelvis, within the base of the broad ligament, to the outer surface of the uterus. From lateral to medial it has a descending, transverse ...
Article

Uterine artery embolisation

Uterine artery embolisation (UAE) is an interventional radiological technique to occlude the arterial supply to the uterus and is performed for various reasons. History Uterine artery embolisation has been practised for more than 20 years for controlling haemorrhage following delivery / aborti...
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Uterine artery embolisation: MRI assessment

Uterine artery embolisation (UAE) is used as an alternative to hysterectomy in selected patients and MRI assessment is key in allowing not only pre-procedure assessment but also assessing post-procedural outcome.   For a general discussion of the underlying condition refer to the article on ute...
Article

Uterine artery flow notching

Uterine artery flow notching refers to a phenomenon observed in uterine arterial Doppler ultrasound assessment. Pathology Associations The presence of notching after 22 weeks is associated with several other conditions including adverse pregnancy outcomes. These include pregnancy induced hyp...
Article

Uterine artery pseudoaneurysm

Uterine artery pseudoaneurysm (UAP) is a rare cause of secondary postpartum haemorrhage.  Clinical presentation UAP usually presents as delayed (secondary) postpartum haemorrhage, that is per vaginal bleeding which occurs more than 24 hours and up to 6 weeks postpartum. However, some reported ...
Article

Uterine dehiscence

Uterine dehiscence is, usually, used to refer to the process of gradual myometrial rupture without a rupture of membranes. However, the term is used synonymously with uterine rupture by some authors. It is often described in the context of C-section scar where it is also termed an incisional deh...
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Uterine duplication anomalies

Uterine duplication anomalies are a group of Müllerian duct anomalies where fusion of the Müllerian duct associated structures fail to some degree: uterus didelphys: class III bicornuate uterus: class IV (second commonest duplication anomaly) septate uterus: class V (commonest duplication ano...
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Uterine enlargement (differential)

Uterine enlargement can occur in a number of situations from both diffuse and focal processes. These include:  gestation related events normal intrauterine pregnancy molar pregnancy - gestational trophoblastic disease  postpartum uterus - still larger than usual hormonal causes exogenous h...
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Uterine perforation

Uterine perforation represents a serious complication that can occur as a result of any type of intrauterine procedure or implantation. Some authors use the term uterine rupture synonymously with the term uterine perforation. Pathology Causes IUCD insertion: IUCD related uterine perforation ...
Article

Uterine rupture

Uterine rupture is a rare but nevertheless potentially catastrophic complication that can occur in pregnancy.  Epidemiology The incidence rate in pregnancy is at 0.05% 6.   Clinical presentation Uterine rupture is usually an acute presentation with haemodynamic instability and abdominal disc...
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Uterine tube

The uterine tube, also known as the Fallopian tube or less commonly the oviduct, is a paired hollow tube that bridges between each ovary and the uterus and functions to convey the mature ovum from the former to the latter. If conception occurs, it normally does so within the tube. It can be affe...
Article

Uteroplacental blood flow assessment

Uteroplacental blood flow assessment is an important part of fetal well-being assessment and evaluates Doppler flow in the uterine arteries and rarely the ovarian arteries. Pathology In a non-gravid state and at the very start of pregnancy the flow in the uterine artery is of high pulsatility ...
Article

Uterus

The uterus is a hollow, thick-walled, muscular organ of the female reproductive tract that lies in the lesser pelvis.   Gross anatomy The uterus has an inverted pear shape. In the adult, it measures about 7.5 cm in length, 5 cm wide at its upper part, and nearly 2.5 cm in thickness. It weighs ...
Article

VACTERL association

VACTERL is an acronym that describes a non-random constellation of congenital anomalies. It is not a true syndrome as such and is equivalent to the VATER anomaly. Epidemiology The estimated incidence is 1 in 10,000-40,000 births 3. Pathology The acronym VACTERL derives from: V: vertebral an...
Article

VACTERL-H association

The VACTERL-H association is a rare non-random association which bears the features of the standard VACTERL association with added fetal hydrocephalus. Unlike the standard VACTERL association which is sporadic, the VACTERL-H is hereditary with both X-linked 3 and autosomal recessive 2 inheritan...
Article

Vagina

The vagina is a midline fibromuscular tubular organ positioned in the female perineum extending superiorly from the vulva, to the cervix and uterus in the pelvis.  Gross anatomy The vagina is 8-10 cm in length, extending posterosuperior from the vestibule through the urogenital diaphragm to th...
Article

Variation in cord insertion

There can be several variations with cord insertion into the placenta: central insertion (~90%): normal situation eccentric cord insertion: lateral insertion of the umbilical cord >2 cm from the placental margin term sometimes used synonymously with marginal cord insertion marginal cord inse...
Article

Variation in fetal presentation

There can be many variations in the fetal presentation which is determined by which part of the fetus is projecting towards the internal cervical os. This includes: cephalic presentation: fetal head presenting towards the internal cervical os, considered normal and occurs in the vast majority o...
Article

Variation in placental morphology

There can be several variations in placental morphology. These include: single lobed discoid placenta (single disc): most common scenario bilobed placenta: two near equal size lobes succenturiate lobe(s): one of more smaller accessory lobes circumvallate placenta: rolled placental edges with...
Article

Vasa praevia

Vasa praevia refers to a situation where there are aberrant fetal vessels crossing over or in close proximity to the internal cervical os, ahead of the fetal presenting part. These vessels are within the amniotic membranes, without the support of the placenta. Vasa praevia is a rare but potentia...
Article

Vein of Galen aneurysmal malformation

Vein of Galen aneurysmal malformations (VGAMs), probably better termed as median prosencephalic arteriovenous fistulas, are uncommon intracranial anomalies that tend to present dramatically during early childhood with features of a left-to-right shunt and high-output cardiac failure. Epidemiolo...
Article

Velamentous cord insertion

Velamentous cord insertion is one of the types of abnormal umbilical cord insertion into the placenta. Epidemiology The estimated incidence is ~1% in singleton and 9-15% in twin pregnancies, respectively 11. It is also more common in placenta previa than in normally located placentas. The prev...
Article

Ventricular septal defect

Ventricular septal defects (VSD) represent defects in the interventricular septum that allow a haemodynamic communication between the right and left ventricles. It typically results in a left-to-right shunt. Epidemiology They represent one of the most common congenital cardiac anomalies and ma...
Article

Vermian lobulation

Evaluation of vermian lobulation is essential in assessment of the vermian maturity. MRI is a useful tool in assessment of the fetal posterior fossa. Normal Vermian lobulation by weeks 1: By 21 weeks - Prepyramidal fissure can be seen between the tuber and pyramis. 21 to 22 weeks - Preculmina...
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Vermian maturity assessment (approach)

Radiological evaluation of the posterior fossa is an essential part of the routine fetal assessment, including vermian maturity assessment. Radiographic features Ultrasonography is a readily available diagnostic tool in the assessment of the fetal posterior fossa but is sometimes limited due t...
Article

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 drug cl...
Article

Walker-Warburg syndrome

Walker-Warburg syndrome (WWS), sometimes known as HARDE syndrome, is an extremely rare lethal form of congenital muscular dystrophy. It is primarily characterised by: fetal hydrocephalus: almost always present neuronal migrational anomalies: agyria (cobblestone lissencephaly / lissencephaly ty...
Article

Wharton jelly

Wharton jelly refers to the gelatinous substance within the umbilical cord. Gross anatomy Wharton jelly is derived from extra-embryonic mesoderm and is largely made up of mucopolysaccharides (hyaluronic acid and chondroitin sulphate) while containing smaller amounts of fibroblasts and macropha...
Article

Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) is an extremely rare chromosomal anomaly characterised by partial deletion of the p arm of chromosome 4 (4p16.3). Clinicopathological spectrum CNS agenesis of the corpus callosum hypertelorism coloboma craniofacial calvarial asymmetry cleft lip + / - palate...
Article

Yolk sac

Yolk sac is the first anatomical structure identified within the gestational sac. It plays a critical role in embryonal development by providing nutrients, serving as the site of initial haematopoiesis, providing endocrine, metabolic and immunological functions and contributing to the developmen...

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