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.
The Currarino triad (not to be confused with Currarino-Silverman syndrome, the eponymous name for pectus carinatum type 2 deformity) or ASP triad, is characterised by:
anorectal malformation or congenital anorectal stenosis
sacrococcygeal osseous defect
e.g anterior sacral men...
Cloverleaf skull, also known as kleeblattschädel, refers to a type of severe craniosynostosis which gives the skull a cloverleaf shape. It is very rare, with less than 130 case reports globally. It typically results from intrauterine premature closure of the sagittal, coronal and lambdoid suture...
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.
The butterfly sign refers to the normal appearance of the choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1.
In the CNS, the term should not be confused with a butterfly glioma, which is a glioblastom...
Bunch of grapes sign refers to the ultrasound appearance of multiple cystic spaces or lesions and it has been described in a number of settings:
within the uterus as a result of hydropic swelling of trophoblastic villi within a hydatidiform mole
in bronchiectasis, where on a chest radiograph, ...
The uterine tube, also known as the fallopian tube, is a paired structure 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 affected by a wide range of patholo...
Hemimegalencephaly is a rare congenital disorder of cortical formation with hamartomatous overgrowth all or a part of a cerebral hemisphere. This results from either increased proliferation or decreased apoptosis (or both) of developing neurons 2.
Hemimegalencephaly is a cryptogen...
The banana sign is one of the many notable fruit inspired signs.
It is seen on axial imaging through the posterior fossa of the fetus and is associated with the Chiari II malformation. It describes the way the cerebellum is wrapped tightly around the brain stem as a result of spinal cord tether...
In fetal sonographic assessment, an absent nasal bone is a feature which can sometimes be used as an adjunctive marker for fetal aneuploidy.
It is assessed on a midline sagittal view. In this section the nasal bone is often seen as a bright echogen...
An eccentrically-located gestational sac towards the fundus of the uterus is the normal sonographic appearance; however an abnormally eccentric gestational sac on ultrasound may be apparent due to a number of causes
interstitial ectopic pregnancy 1
normally implanted pregnancy in...
Pregnancy of uncertain viability (PUV) is a term given to an intrauterine pregnancy in a situation where there are not enough criteria (usually on ultrasound grounds) to confidently categorise an intrauterine pregnancy as either viable or a failed pregnancy.
Fetal bowel dilatation can occur from many causes, which include:
intestinal atresias: mainly distal
apple-peel intestinal atresia
megacystis microcolon hyperperistalsis syndrome 4
congenital chloride d...
Interstitial ectopic pregnancy (also known as an intramural) is an important type of ectopic pregnancy with higher risks of rupture and haemorrhage compared to usual tubal ectopic pregnancies.
The term interstitial pregnancy is sometimes interchangeably used with cornual pregnancy...
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...
In utero bowel perforation results in a chemical peritonitis (meconium peritonitis) from peritoneal leakage of sterile meconium.
It can result from many causes which include:
in utero intestinal ischaemia
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.
IUCD insertion: IUCD related uterine perforation
Holoprosencephaly (HPE) is a rare congenital brain malformation resulting from incomplete separation of the two hemispheres.
Classically three subtypes have been recognised, however additional entities are now included in the spectrum of the disease. The three main subtypes, in order of decreas...
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.
Please refer on the general article of holopros...
Twin pregnancies are the most common multifetal pregnancies.
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.
Fetal ductus venosus flow assessment can be sonographically assessed in a number of situations in fetal ultrasound:
first-trimester screening for aneuploidic anomalies
second-trimester scanning when there are concerns regarding
intrauterine growth restriction (IUGR)
fetal cardiac compromise
The corpus luteum is a temporary endocrine structure involved in ovulation and early pregnancy.
During ovulation, the primary follicle forms the secondary follicle and subsequently the mature vesicular follicle.
At ovulation the follicle ruptures expelling the ovum into the fallopian tube. The...
Trauma is a leading cause of mortality in pregnancy. Pregnancy increases the incidence and severity of abdominal trauma in females.
Trauma affects up to 7% of pregnancies, and the incidence of pregnancy in level 1 trauma patients is estimated to be ~2% 1.
Ectopic pregnancy refers to the implantation of a fertilised ovum outside of the uterine cavity.
The overall incidence has increased over the last few decades and is currently thought to affect 1-2% of pregnancies. The risk is as high as 18% for first trimester pregnancies with bl...
A pseudogestational sac or pseudosac is the concept that a small amount of intrauterine fluid in the setting of a positive pregnancy test and abdominal pain could be erroneously interpreted as a true gestational sac in ectopic pregnancy.
The sign was originally reported before the use of endova...
Velamentous cord insertion is one of the types of abnormal umbilical cord insertion into the placenta.
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...
Ovarian hyperstimulation syndrome (OHSS) is a complication of ovarian stimulation treatment (ovarian induction therapy) for in vitro fertilisation. Rarely, it may also occur as a spontaneous event in pregnancy (see spontaneous ovarian hyperstimulation later in the article).
The clinical syndrom...
Asymmetric ventriculomegaly, interhemispheric cyst and dysgenesis of the corpus callosum (AVID) is a triad of congenital cerebral anomalies.
markedly asymmetric enlargement of the lateral ventricles may be the initial finding on routine fetal morphology ultrasound.
Absent end-diastolic flow (AEDF) in an umbilical artery Doppler assessment is a useful feature which indicates underlying fetal vascular stress if detected in mid or late pregnancy. It is often classified as Class II in severity in abnormal umbilical arterial Dopplers 9.
Placental insufficiency is a term given to a situation where the placenta cannot bring enough oxygen and nutrients to the growing fetus.
Fetuses may present with intra-uterine growth restriction (IUGR) (especially asymmetrical IUGR).
It can be primarily caused...
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...
Ovarian vein thrombosis (actually most often a thrombophlebitis) occurs most commonly in postpartum patients and can result in pulmonary emboli. A presentation is usually with acute pelvic pain in the postpartum period, then termed puerperal ovarian vein thrombosis or postpartum ovarian vein th...
Intrauterine growth restriction (IUGR) is commonly defined as an estimated fetal weight (EFW) at one point in time during pregnancy being at or below the 10th percentile for gestational age 2.
Some authors define the term IUGR when fetal biometric parameters fall under the 5th percentile or fal...
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...
Umbilical cord cysts can refer to any cystic lesion associated with the umbilical cord. They can be single (commoner) or multiple.
They may be seen in ~3% of pregnancies in the first trimester 8.
Umbilical cord cysts can represent either true or false cysts:
A persistent right umbilical vein (PRUV) is an uncommon vascular anomaly which is often detected in utero.
The estimated prevalence is at ~2 per 1000 births 1-2.
In the normal situation, the right umbilical vein begins to obliterate in the ~4th week of gestation and di...
A fetal goitre is an enlargement of the thyroid gland in utero. It can occur with either hyper or hypothyroidism (and in isolated cases of euthyroidism 8).
The mechanism is different depending on whether the underlying cause is hyper or hypothyroidism.
Noonan syndrome (NS) is a genetically and phenotypically heterogenous non aneuploidic congenital RASopathy. Affected individuals can bear some clinical features similar to that of Turner syndrome.
The estimated incidence is at ~1 in 1000-2500 11. As individuals have normal number...
Pre-placental abruption or haemorrhage can be subamniotic or subchorionic in location.
most often painless
Symptoms may be similar to placental abruption in other locations; however, it may not have as poor a prognosis as other placental abruption.
Noonan syndrome with multiple lentigines, previously known as LEOPARD syndrome (LS), is a rare autosomal dominant RASopathy that has many similarities to Noonan syndrome.
Despite a change in formal name, the 'LEOPARD' acronym is still useful to summarise the clinical feat...
Lithopaedions, also referred as stone babies, are a rare phenomenon which occurs most commonly when a fetus dies during an ectopic pregnancy.
The estimated incidence is at ~ 1.5 to 1.8% of abdominal ectopic pregnancies 4.
If the dead fetus is too large to be re-absorbe...
Encephalocoele, also known as meningoencephalocele, is a form of neural tube defect and a type of cephalocoele where brain tissue and overlying meninges herniate out through a defect in the cranium.
It should be distinguished from cranial meningocele in which the lesion contains o...
The group of the most common congenital infections are referred to by the mnemonic TORCH or STORCH. They usually cause mild maternal morbidity, but are related to serious fetal consequences 4.
O: other (e.g. syphilis, varicella-zoster, parvovirus B19)
Sequential morphological ultrasound changes of the endocervical canal with cervical incompetence can be remembered using the mnemonic:
Trust Your Vaginal Ultrasound
T-shaped (normal internal cervical os)
A helpful mnemonic for remembering some causes and complications of oligohydramnios is:
R: renal abnormalities (decreased urine output)
P: premature rupture of membranes
C: chromosomal anomalies
Ruptured corpus luteal cysts are one of the commonest causes of spontaneous haemoperitoneum in a woman of reproductive age.
Presentation is variable, ranging from completely asymptomatic to severe abdominal pain due to peritoneal irritation.
The corpus luteum ...
Fetal choledochal cysts are choledochal cysts diagnosed in utero.
The estimated incidence rate of choledochal cysts is ~1 in 2 million live births 2. There is a recognsed female predilection and a greater occurrence in Asian populations.
Haemorrhagic corpus luteal cysts result from bleeding into corpus luteal cysts.
Commonly described findings include
complex adnexal mass
adnexal thick walled cystic lesion with lace like strands
adnexal thick walled cystic lesion with low-level echoes withi...
11-13 week antenatal scan is considered a routine investigation advised for the fetal well being as well as for early screening in pregnancy (see antenatal screening).
It includes multiple components and is highly dependant on the operator. Traditionally three factors are used to calculate the ...
Endometrial thickness is a commonly measured parameter on routine gynaecological ultrasound and MR imaging. The appearance, as well as the thickness of the endometrium, will depend on whether the patient is of reproductive age or post-menopausal and, if of reproductive age, at what point in the ...
Antenatal screening and diagnosis are currently available for a few selected genetic conditions, including trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome) and neural tube defects.
For an overview of the conditions and their manifestations, please refer to t...
Placental trophotropism refers to a phenomenon where there is dynamic migration of the placenta at its insertion through gestation. The placenta tends to grow in areas of good blood supply and nutrition and atrophies in areas with poor blood supply and poor nutrition. It may play a role in the d...
Haematometrocolpos refers to a blood-filled distended uterus and vagina usually due to an anatomical mechanical obstruction precluding the evacuation of the menstrual blood.
The estimated incidence in teenagers is at ~1 in 1000-2000 5.
imperforate hymen: in ~2...
Nuchal translucency is a finding during a specific period in the late first trimester and early second trimester (11.3-13.6 weeks) and should not be confused with the nuchal thickness, which is measured in the second trimester.
Increased nuchal translucency is thought to be related t...
Hydatidiform moles are one of the most common but benign forms of gestational trophoblastic disease.
It is a common complication of gestation, estimated to occur in one of every 1,000-2,000 pregnancies 3. These moles can occur in a pregnant woman of any age, but the rate of occur...
Partial hydatidiform mole (PHD) is a sub type of a hydatidiform mole which in turn falls under the spectrum of gestational trophoblastic disease.
Clinical signs and symptoms such as abdominal pain, cramps of the lower abdomen and vaginal bleeding during pregnancy are non...
Complete hydatidiform mole (CHM) is a type of molar pregnancy and falls at the benign end of the spectrum of gestational trophoblastic disease.
CHM is the commonest type of gestational trophoblastic disease.
Complete moles are characterised by the absence of a fetus o...
Coexistent molar pregnancy refers to an extremely rare situation where there is a molar pregnancy occurring simultaneously with normal intra-uterine pregnancy.
The estimated incidence is at ~1:10,000-100,000 gestations (for a complete hydatidiform mole and a normal pregnancy) 2.
Exencephaly is a lethal congenital fetal brain developmental anomaly (neural tube defect) considered to be a precursor to anencephaly in the acrania-exencephaly-anencephaly sequence.
It is characterised by calvarial absence and loss of fetal brain tissue to variable degrees and is co...
Acrania is a rare lethal congenital anomaly characterised by an absence of the calvaria.
The estimated incidence is at ~1:1000 pregnancies 4.
The condition is thought to result from abnormal migration of mesenchymal tissue, which normally covers the cerebral hemisphe...
Megalencephaly (MEG) is a disorder characterised by an abnormally large brain. It is primarily a proliferative disorder of embryonic origin. It may involve all or part of the cerebral hemispheres and can be bilateral or unilateral. It is often associated with polymicrogyria or agyria.
HELLP syndrome is a pregnancy-related condition and is an abbreviation for:
elevated liver enzymes and
It is considered a severe and life threatening form of pre-eclampsia although it can occur without co-existing pre-eclampsia.
The estimated inciden...
Fetal circulation differs from the adult circulation due to the presence of certain vessels and shunts.
These shunts will close after birth, and most of these fetal vessels will be seen as remnants in the adult circulation. The function of these shunts is to direct oxygen-rich venous blood to ...
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...
Agenesis of the ductus venosus (ADV) is a rare fetal vascular anomaly.
According to the data obtained from the screening tests performed at 11-14 weeks of pregnancy, its incidence is reported to be 1/2500 12.
In a large case series, Acherman et al. 13 defined five drai...
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%).
Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumours.
Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situations:
Down syndrome: around 80...
Post-axial polydactyly refers to polydactyly where the additional digit is on the ulnar margin of the hand, or lateral to the 5th toe.
Post-axial polydactyly is more common than pre-axial polydactyly, with an estimated incidence of 1 in 3000.
MURCS association refers to the combination of:
MU: Müllerian duct aplasia
R: renal aplasia /renal agenesis
CS: cervicothoracic somite dysplasia
Omphalocoeles, or exomphalos, are congenital midline abdominal wall defects at the base of the umbilical cord insertion with herniation of gut (or occasionally other content) out of the fetal abdomen.
The estimated occurrence can be up to 1:4000 of live births 3.
Umbilical cord pseudocysts are a type of cystic lesion occurring in relation to the umbilical cord.
Although the true incidence not accurately known, they are comparatively much more common than true umbilical cord cysts.
The pseudocyst basically comprises of mucoid de...
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...
Wharton jelly refers to the gelatinous substance within the umbilical cord.
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...
Pseudo-omphalocoele is the spurious sonographic appearance giving an impression of an anterior abdominal wall defect.
Pseudo-omphalocoele may be seen in:
scanning errors where there is a deformation of the fetal abdomen by transducer pressure and th...
The Jarcho-Levin syndrome (JLS) or spondylothoracic dysostosis is a rare autosomal recessive heterogeneous disorder which can occur to variable severity. Previously the condition spondylocostal dysostosis was also considered as part of the JLS spectrum but is now considered a distinct pathologic...
Cystic hygroma, also known as cystic or nuchal lymphangioma, refers to the cystic variety of congenital lymphangioma which, most commonly, occur in the cervicofacial regions, particularly at the posterior cervical triangle.
They usually occur in the fetal/infantile and paediatri...
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.
Intramembranous ossification describes the process of ossification from mesenchymal cells (stem cells) without a cartilaginous template and is involved in the healing process of fractures. The stages of intramembranous ossification osteogenesis are as follows:
mesenchymal cells differentiate in...
Cleft lip +/- cleft palate is one of the commonest of neonatal facial anomalies. In ~80% of cases the two features tend to occur together 6.
It is estimated to occur with an incidence of ~1 in 700 to 1000 live births 1. This can increase to 4% for a sibling of a previously affecte...
A nuchal cord (NC) is a term given to situation where there are one or more loops of umbilical cord wrapped around the fetal neck for ≥360°.
The prevalence is dependent on the extent of coiling and range from ~25% for a single loop to 2.5% for a double loop to ~0.5% for more than ...
Antenatal choroid plexus cysts are benign and are often transient typically resulting in utero from an infolding of the neuroepithelium.
They should not be confused with adult choroid plexus cysts (which are very commonly found at autopsy and likely degenerative), large intraventricular simpl...
Fetal megacystis refers to the presence of an unusually large bladder in a fetus.
The estimated incidence of antenatal imaging is at ~1:1500 pregnancies.
It can result from a number of causes but the main underlying mechanism is either a distal stenosis or reflux.
An oesophageal atresia refers to an absence in contiguity of the oesophagus due to an inappropriate division of the primitive foregut into the trachea and oesophagus. This is the most common congenital anomaly of the oesophagus.
It is thought to occur in ~1:3000-4500 live births ...
IUCD related uterine perforations are one of the causes of uterine perforation. It is rare, but a serious complication of an IUCD insertion, and is often clinically silent.
The incidence rate is reported at ~2 in 1000 2.
Perforation at the time of insertio...
The anatomy curriculum is one of our curriculum articles and aims to be a collection of articles that represent the core anatomy knowledge for radiologists and imaging specialists.
Head and neck anatomy
Abdominal and pelvic anatomy
Lowe syndrome (also known as the the oculocerebrorenal syndrome of Lowe) is a multi-system disorder characterised by anomalies primarily affecting the eyes, nervous system, and kidneys.
It is an extremely rare, pan-ethnic, x-linked disease, with estimated prevalence in the general po...
The lemon sign, noted on antenatal imaging, is one of the many notable fruit inspired signs. It is a feature when there appears to be an indentation of the frontal bone (depicting that of a lemon). It is classically seen as a sign of a Chiari II malformation and also seen in the majority (90-98%...
Fetal pyelectasis refers to a prominence of the renal pelvis in utero that is a relatively common finding, which in the majority of cases resolves spontaneously.
Please refer to the article on fetal hydronephrosis for a continued discussion on this matter.
Although there is an ...
Fetal hydronephrosis represents the abnormal dilatation of the fetal renal collecting system, with pelvi-ureteric junction obstruction the most commonly encountered cause.
Please, refer to the article on fetal pyelectasis for a dedicated discussion on this relatively common and usually benign ...
Cerebroplacental ratio (CPR) is an obstetric ultrasound tool used as a predictor of adverse pregnancy outcome in both small for gestational age (SGA) and appropriate for gestational age (AGA) fetuses. An abnormal CPR reflects redistribution of cardiac output to the cerebral circulation, and has ...
Nuchal fold thickness is a parameter that is measured in a second-trimester scan (at ~18-22 weeks) and should not be confused with nuchal translucency (which is measured in the first trimester).
The proposed aetiology of increased nuchal thickness is the result of congenital heart di...
Fetal tachycardia is an abnormal increase in the fetal heart rate. It is variably defined as a heart rate above 160-180 beats per minute (bpm) and typically ranges between 170-220 bpm (higher rates can occur with tachyarrhythmias).
The estimated prevalence is ~0.4-1% of pregnancie...
Aase-Smith syndrome (or Aase syndrome) is an extremely rare congenital disorder.
congenital hypoplastic anaemia - fetal anaemia
cleft lip, cleft palate
hydrocephalus (due to Dandy-Walker anomaly)