The Mickey Mouse sign in obstetric ultrasound denotes the characteristic "floating appearance" of the fetal cerebral lobes due to the absence of the cranium due to anencephaly.
The sign is best seen in the coronal plane (in relation to the fetal head), where the cerebral...
The frog eye sign is seen when the orbital structures show a characteristic protrusion due to fetal anencephaly. The term is particularly used in point of care ultrasound (POCUS) 1.
On obstetric ultrasound the frog eye sign is best appreciated in the coronal plane (in re...
The quadruple screening test, also known as the quad screen, AFP Plus quad test or multiple marker screening test, is a maternal antenatal screening blood test that can be used in conjunction with other investigations e.g. ultrasound soft markers, to estimate the risk of aneuploidy 1.
This is ...
The crisscross sign is a fetal ultrasound sign that describes the normal relationship between the ventricular outflows tracts of the fetal heart. The left ventricular outflow tract (LVOT); represented by the take-off of the aorta (Ao) from the left ventricle, is perpendicular (90o) to the right ...
An adenomyomatous polyp of the endometrium is a rare form of endometrial polyp and comprises of a pedunculated lesion that contains smooth muscle in addition to the usual components of an endometrial polyp. On outer examination, they may be difficult to differentiate from ordinary endometrial po...
Precipitous labor, also known as precipitous birth, is labor that happens too quickly, and is formally defined as fetal expulsion three hours or less after the start of regular uterine contractions. Contradictory and somewhat limited data demonstrates a higher risk of pregnancy-related complicat...
A mnemonic to remember the criteria for forceps delivery is:
F: fetus alive
O: os dilated
R: ruptured membrane / rotation complete
C: cervix take-up
E: engagement of head
P: presentation suitable
S: sagittal suture in AP diameter of inlet
A mnemonic to remember the basic risk factors of postpartum hemorrhage is:
P: prolonged labor / polyhydramnios / previous C-section
R: recent Hx of bleeding
U: uterine fibrosis
The humeral length (HL) is sometimes measured as an additional fetal biometric parameter in a second-trimester ultrasound scan. Its measurement can often compliment the femoral length especially in situations where there are short limb syndromes. Short humeral length have been associated with co...
Fetal MRI allows for detailed imaging of the developing fetus in utero. Fast sequences are required due to fetal movement 1. Fetal MRI is most commonly utilized when ultrasound (USS) findings are equivocal. Fetal anatomy can be evaluated in detail including the brain, upper aerodigestive tract, ...
Retroplacental abruption is a type of placental abruption where placental tissue prematurely separates from the uterus and blood accumulates between the basal plate (maternal side of the placenta) and the myometrium 1. The result is a retroplacental hemorrhage.
The size of a retroplacental abru...
The modified Golan classification of ovarian hyperstimulation syndrome, employing clinical findings and imaging appearances, is used to categorize ovarian hyperstimulation syndrome (OHSS) into the following three categories of severity with five grades 1,2:
mild OHSS: characterized by bilateral...
The Bishop score is a criterion for successful induction of labor, vaginal delivery and includes the age of gestation, parity, presenting part of the fetus, previous history of childbirths and consent of the patient. This score decides whether a patient needs cervical ripening or not 1,4.
Cervical ripening is the softening of the cervix that needs to occur before induction of labor and delivery of the fetus. The use of appropriate interventions (e.g. isoprostol, nitric oxide, PGE2, Foley's balloon in case of low-risk females, acupuncture 1-5) can lead to satisfactory cervical rip...
Acute non-traumatic abdominal pain in pregnancy requires a considered imaging approach due to the increased risks of fetal demise associated with undiagnosed diseases such as perforated acute appendicitis. Ultrasound is the first-line modality due to its wide availability and ability to diagnose...
The abdominal pain in pregnancy MRI protocol encompasses a set of MRI sequences for assessment of causes of non-traumatic abdominal pain in pregnancy.
Note: This article aims to frame a general concept of an MRI protocol for the assessment of the abdomen in pregnancy. Protocol specifics will va...
The third trimester in a gestation is the final trimester in a human pregnancy which is usually taken as extending from 28 weeks and 0 days of gestation to term (~38-40 weeks).
History and etymology
Trimester was first seen in English in 1821, a direct borrowing from the French word trimestre,...
The T sign has been described in several different pathologies:
T sign (obstetrics)
upper T sign (brain)
lower T sign (brain)
The second trimester in a gestation is the middle trimester in a human pregnancy that is usually defined as lasting from 13 weeks and 0 days to 27 weeks and 6 days of gestation.
History and etymology
Trimester was first seen in English in 1821, a direct borrowing from the French word trimestr...
Myometritis describes inflammation of the myometrium. It can fall under the broader umbrella term of pelvic inflammatory disease and can often be associated with endometritis. It can arise in a variety of situations with puerperal situations being the most common. In some situations, puerperal i...
Cerebellar clefts are rare congenital abnormalities of the posterior fossa, where cerebellar grey matter extends from the surface into the parenchyma, in some cases even reaching the fourth ventricle.
Language and speech disorders, cognitive impairment, truncal ataxia, o...
Abnormalities of the umbilical cord can be classified into 1:
umbilical cord coiling
hypocoiled umbilical cord
hypercoiled umbilical cord
straight umbilical cord
umbilical cord length abnormalities
long umbilical cord
short umbilical cord
umbilical cord thickne...
The term venous lakes may refer to:
cutaneous venous lakes, often occurring on the lower lip 1
osseous venous lakes occurring in the skull 2
placental (venous) lakes 3
Uterine inversion is a rare condition in which the uterus is essentially turned inside out. There are two types: "puerperal" (within six weeks of childbirth) and "non-puerperal". The reason for uterine inversion is unclear. In the puerperal form, it is theorized that excessive traction on the um...
Luteomas of pregnancy are a rare non-neoplastic condition in which luteinized stroll cells in the ovary markedly increase in size. Luteomas are hormonally active, and produce testosterone resulting in maternal and potentially fetal hirsutism and virilization.
More common in both m...
A mnemonic to remember the causes of small placenta is:
It can be read as percutaneous coronary intervention i.e. PCI 2
C: chromosomal anomaly e.g. Down syndrome
I: intrauterine infection
I: intrauterine growth retardation
High-risk pregnancies are any that actually or potentially threaten either the health or life of the mother or her fetus during pregnancy, labor, or birth. From a radiological perspective, high-risk pregnancies may undergo further screening or have close follow-up with growth and well-being scan...
The anterior cervical angle is a novel ultrasound parameter that is being used as a predictor of spontaneous preterm birth.
The angle between the uterine wall and the cervical canal is measured during the first and the second trimester by a transvaginal ultrasound. It is measured u...
Extrachorial placenta is a rare type of placenta where the chorionic vascular plate is smaller than the villous tissue, which gets uncovered in the periphery.
Extrachorial placentation is seen as a thickening of the chorionic plate without blood vessels. An edemato...
Radiation effects on embryonic and fetal development are generally considered low risk compared to the normal risks of pregnancy. Most diagnostic x-ray and nuclear medicine examinations are <50 mSv and have not been demonstrated to produce any significant impact on fetal growth and development. ...
The right ventricular outflow tract (RVOT) refers to the region of blood outflow from the right ventricle between the supraventricular crest and the pulmonary valve. It is comprised of the conus arteriosus (infundibulum), ventricular septum and right ventricular free wall. It is commonly assesse...
Trisomy 8 mosaicism or Warkany syndrome is a less severe variant of trisomy 8 and individuals with a low proportion of affected cells may exhibit a comparatively mild range of physical abnormalities and developmental delay. They are more likely to survive into childhood and adulthood but can exh...
Trisomy 8 is a chromosomal anomaly where there are three copies of chromosome 8. Complete trisomy 8 causes severe effects on the developing fetus and can be a cause of miscarriage. However, trisomy 8 can occur as a mosaic form, Warkany syndrome, that can be compatible with life.
Cesarean section (also known as C-section, CS and C/S) is the most frequently done major abdominal surgery in females, performed to deliver a baby as an alternative to normal vaginal delivery 1.
Many forms of cesarean section have been described, but the most popular variat...
Congenital hallux valgus is a very rare finding wherein a fetus or newborn shows lateral deviation of the first toe(s). When found on prenatal imaging, bilateral congenital/foetal hallux valgus is highly suggestive of fibrodysplasia ossificans progressiva 1,2.
An early structural scan is a first trimester obstetric ultrasound performed around 12-16 weeks gestation. It can have some similarity to the 11-13 week antenatal ultrasound and assess limited fetal anatomy. However, a formal evaluation of nuchal translucency is not part of this ultrasound asses...
Maternal serum alpha fetoprotein (MSAFP) is a screening test that examines the level of alpha fetoprotein (AFP) in a pregnant woman. AFP is produced by both the yolk sac and foetal liver during pregnancy.
Ideally, all pregnant women should undergo the screening test between 15-20 w...
Turtle sign is a clinical sign of fetal shoulder dystocia in which the fetal head retracts 3. The head bobbing, emerging and then pulling back could be conceptualised as similar to a turtle pulling its head into and out of its shell. The sign does not necessarily signify true shoulder dystocia 2.
Tricuspid regurgitation (TR) (also known as tricuspid insufficiency) is a common finding in imaging of the fetus. Tricuspid regurgitation represents the abnormal backflow of blood into the right atrium during right ventricular contraction due to valvular leakage (i.e. it is a valvulopathy).
Umbilical arterial systolic/diastolic (S/D) ratio is a parameter used in obstetric imaging as part of umbilical arterial (UA) Doppler assessment. It is the ratio between the systolic velocity and the diastolic velocity.
Reference range varies through the stage of pregnancy. If...
Umbilical arterial pulsatility index (UA-PI) is a parameter used in umbilical arterial (UA) Doppler assessment. It is calculated by subtracting the end-diastolic velocity (EDV) from the peak systolic velocity (PSV) and then dividing by the time-averaged (mean) velocity (TAV):
PI = (PSV - EDV) ...
The portal sinus is an L-shaped venous confluence in the fetal circulation. It is located in the liver, between the left and right intrahepatic portal veins. The umbilical vein drains into the portal sinus at its medial aspect, near the left inferior intrahepatic portal vein 1,2. The ductus veno...
Zika virus infection is a zoonosis which is associated with congenital birth defects, with microcephaly the most widely known.
Zika was once isolated to Africa and Asia, however, it spread to the Americas in the last decade 1. There were thousands of cases confirmed in the America...
There are four sutures in the fetal skull vault of obstetric importance:
1. frontal suture: it lies between the two frontal bones
2. sagittal suture: it lies between the two parietal bones
3. coronal suture: it lies between the parietal and frontal bones
4. lambdoid suture: it lies between t...
A marginal placental previa (or grade 2 placenta previa) is a form of placenta previa where placental tissue reaches the margin of the internal cervical os, but does not cover it.
The urinary tract dilatation (UTD) classification system is a proposed unified classification of urinary tract dilatation for prenatal and postnatal care. This classification was formed with the collaborations from eight societies (American College of Radiology (ACR), American Institute of Ultra...
Redating a pregnancy may occur when there is a discrepancy between the estimated due date (EDD) calculated by the last menstrual period (LMP) and that by ultrasound. Care should be taken when redating a pregnancy, especially in the third trimester, as there may be other reasons for a fetus to be...
Acute abdominal pain is a common acute presentation in clinical practice. It encompasses a very broad range of possible etiologies and diagnoses, and imaging is routinely employed as the primary investigative tool in its modern management.
A subgroup of patients with acute abdomina...
Band like structures in the gestational sac is not an uncommon finding in the first trimester or second trimester ultrasound scans and can represent a number of varying conditions
Acardius acormus is a morphologic subtype of an acardiac twin in a twin reversed arterial perfusion (TRAP) sequence. This entity is the least common of the four subtypes, comprising of cephalic structures only. It is seen in approximately 5% of cases.
Acardius anceps is a morphologic subtype of the acardiac twin in a twin reversed arterial perfusion (TRAP) sequence. This entity is the most well differentiated of the four subtypes, with a partly formed head, thorax, and abdomen. It is seen in approximately 10% of cases.
Acardius anephus is a morphologic subtype of an acardiac twin in the twin reversed arterial perfusion (TRAP) sequence. In this entity, no cephalic or structures are present, but the lower limbs are preserved. This is the most common subtype, seen in 60-75% of cases1.
A dichorionic triamniotic (DCTA) triplet pregnancy is a type a multifetal pregnancy where two of the triplets are monochorionic. This type of pregnancy can carry a unique set of complications.
A mnemonic for causes of abdominal distension (6 Fs) is:
F: fulminant mass
The umbilicus is the fibrous remnant of the fetal attachment of the umbilical cord after birth.
All layers of the anterior abdominal wall fuse at the umbilical ring, a small round defect in the linea alba located just inferior to the midpoint between the xiphoid process of the st...
A rare entity, fetal ventricular tachycardia presents with a rapid ventricular rate exceeding, and occurring independently from, the atrial rate. The ventricular rate is typically over 180 beats per minute 1. Atrioventricular dissociation is characteristic; two separate pacemakers dictate the a...
The eponym Fallopian may refer to:
Fallopian canal (facial nerve canal)
Fallopian tube (uterine duct)
Fallopian ligament (inguinal ligament)
History and etymology
It is named after Gabriele Falloppio (also known by his Latin name Fallopius), Italian anatomist (1523-1562).
Pseudo-TORCH syndrome is a term used to denote cases that clinically resemble congenital infection (see congenital TORCH infections) but where no organisms or serological, microbiological or immunological evidence of infection can be identified 1. It is now believed that pseudo-TORCH syndrome is...
The spelling fetus is the preferred spelling in the medical world, regardless of location. It is used by virtually all biomedical journals. Therefore it is also the preferred spelling on Radiopaedia and we never use the spelling foetus. This latter spelling is still often used by lay-people in t...
A fetal omental cyst is a type of fetal enteric cyst.
The most common type of omental cyst is considered a lymphangioma 2.
May be seen in an intra-abdominal cyst without any associated color flow. Omental cysts tend to be typically found...
An aortic arch view is one of the additional views performed on fetal obstetric ultrasound - fetal echocardiography. It is an oblique sagittal view which is obtained similar to a left anterior oblique angiogram or the sagittal arch view obtained in CT arteriography. The isthmus, after the origin...
Fetal macrocephaly is a term given when the fetal head circumference lies above 2 standard deviations for the expected stage of gestation. While it can be associated with certain syndromic anomalies, in the absence of associated anomalies, it does not appear to be a significant risk factor for a...
Alpha-fetoprotein (AFP) is an important plasma protein synthesized by the yolk sac and fetal liver. In adults, its main utility is as a tumor marker, primarily for hepatocellular carcinoma or teratoma. Functionally it is the fetal homologue of albumin i.e. it acts as a major carrier protein in t...
Folate deficiency (hypovitaminosis B9) is the most common vitamin deficiency in the Western world. It is especially important in pregnant women and common amongst alcoholics.
Deficiency arises in two distinct populations:
increased demand (pregnancy and lactation)
The gestational age (GA) of an embryo/fetus is most accurately determined by measuring the crown rump length (CRL) in the first trimester. The later the pregnancy, the larger the standard deviation of the estimated gestational age and thus estimated date of delivery (EDD) is. Mean sac diameter (...
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...
The term Cesarean scar niche (defect) refers to the presence of a hypoechoic area within the myometrium in the isthmus (lower uterine segment) with discontinuation of myometrium at the site of previous Cesarean section scar. A niche has been described as the indentation of myometrium of around 1...
This article lists a series of labeled imaging anatomy cases by body region and modality.
CT head: non-contrast axial
CT head: non-contrast coronal
CT head: non-contrast sagittal
CT head: angiogram axial
CT head: angiogram coronal
CT head: angiogram sagittal
CT head: venogram axial...
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...
Congenital goiter is a rare cause of neck swelling in neonates and is demonstrated as diffuse/nodular thyroid gland enlargement.
It is a common endocrine disease in newborns and affects approximately 1:2000-4000 live births.
There may be a difficult vaginal...
Arhinia refers to congenital failure of the external nose, nasal cavity, and olfactory apparatus to develop. It is an extremely rare condition that can be detected on prenatal ultrasound or MRI.
Arhinia may occur in a syndromic setting (such as ethmocephaly), but it has been repor...
Eclampsia is a condition involving seizures and hypertension in pregnancy. It is thought to result from hypertensive encephalopathy 1.
MR imaging has shown that cytotoxic edema and posterior reversible encephalopathy syndrome are common in eclampsia. The severity of ...
Pre-eclampsia is a disorder of pregnancy involving new-onset hypertension (systolic BP ≥140 mmHg or diastolic BP ≥90 mmHg) and involvement of one or more other organ systems.
Pre-eclampsia affects up to 8% of pregnancies 1.
diabetes mellitus 2
chronic hypertension ...
Aorto-ventricular tunnel (AVT) is an extremely rare form of congenital heart disease, representing an anomalous extracardiac communication between the ascending aorta and the left or right ventricles.
In most cases the anomalous communication is between the aorta and the left ventr...
There are several described cockade signs in radiology:
cockade sign (aorto-left ventricular tunnel) 1
cockade sign (appendicitis) 2
cockade sign (GI tumors) 4
cockade sign (hypertrophic pyloric stenosis) 3
cockade sign (intraosseous lipoma)
History and etymology
It is named after a cocka...
Craniorachischisis, also known as craniorachischisis totalis, is a rare birth defect and the most severe of the neural tube defects. It refers to the presence of both anencephaly and spina bifida.
In one study the prevalence of craniorachischisis was 0.51 per 10,000 live births in...
This is a basic article for medical students and other non-radiologists
Obstetrics and Gynecology imaging for students curriculum represents a core set of common pathologies seen on the wards, in theater and in the emergency O&G patient.
Fundamental to most imaging of the O&G patient is an und...
Angular pregnancies are those in which implantation occurs eccentrically along the fundus of the endometrial cavity, along with the lateral upper angle or cornua of the uterus.
In contrast to interstitial tubal pregnancy, angular pregnancies have a more medial location and are considered an int...
A telephone receiver deformity is a characteristic bowing of the shaft of the long bones, usually the humeri or femora, seen in thanatophoric dysplasia.
Ian Donald (1910-1987) was a Scottish obstetrician who pioneered the diagnostic use of ultrasound in medicine.
Ian Donald was born in Lisgeard, Cornwall, United Kingdom on 27 December 1910 6. His father was a general practitioner. In 1925 his family moved to South Africa where he at...
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: the prepyramidal fissure can be seen between the tuber and pyramis
Radiological evaluation of the posterior fossa is an essential part of the routine fetal assessment, including vermian maturity assessment.
Ultrasonography is a readily available diagnostic tool in the assessment of the fetal posterior fossa but is sometimes limited due t...
11-13 week antenatal (nuchal translucency) 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 dependent on the operator. Traditionally three factors are ...
Spondylocostal dysostosis (SCDO) is a rare condition characterized 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...
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...
Circummarginate placenta is an uncommon variation in placental morphology. The chorionic membranes insert inward from the margin of placental edge, similar to circumvallate placenta, but unlike circumvallate placenta, the placental edge is not thickened and rolled up, and there is no central dep...
The basal plate is a synonym for the maternal side of the placenta. The fetal side of the placenta is termed the chorionic plate.
Some pathologies and processes are localized to the basal plate, and evaluation of the basal plate is a part of placental grading.
The chorionic plate is a synonym for the fetal side of the placenta. The maternal side of the placenta is termed the basal plate.
Some pathologies and processes are localized to the chorionic plate, and evaluation of the chorionic plate is a part of placental grading.
Increased fetal abdominal circumference is usually given when the abdominal circumference lies above the 90th percentile. During the second and especially the third trimester, an increased abdominal circumference usually contributes to a high estimated fetal weight (large for dates fetus), which...
The neurenteric canal or canal of Kovalevsky is the transient communication of the amnion through notochordal canal to the yolk sac during notochordal formation at day 16-17.
Abnormalities during this stage produce the neurenteric cyst spectrum.
Kinking of the brainstem is a rare finding in fetal or pediatric neuroimaging, invariably seen in association with other cerebral abnormalities. It generally heralds a poor neurological outcome.
A kinked brainstem may be seen on fetal MRI, commonly after referral from ult...
Amniotic fluid in the first trimester has been estimated from weeks 7-12. Although the amniotic fluid index (AFI) is calculated in the second trimester, one can get an idea of whether the amount of amniotic fluid is too much or too little at an earlier time point.
The amniotic fluid volume is r...
Vitamin B9 (folate or folic acid) is a water-soluble vitamin, part of the vitamin B complex, 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).