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 continuously improved upon by countless contributing members. Our dedicated editors oversee each edit for accuracy and style. Find out more about articles.
786 results found
Article
11-13 week antenatal scan
11-13 week antenatal (nuchal translucency) scan is considered a routine investigation advised for 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 used...
Article
3D ultrasound
Three-dimensional (3D) ultrasound is a technique that converts standard 2D grayscale ultrasound images into a volumetric dataset. The 3D image can then be reviewed retrospectively. The technique was developed for problem-solving (particularly in obstetric/gynecologic exams) and to potentially re...
Article
Aarskog syndrome
Aarskog syndrome or Aarskog–Scott syndrome (also known as the facio-digito-genital syndrome) is a rare anomaly characterized by short stature in association with a variety of structural anomalies involving mainly the face, distal extremities, and external genitalia.
Epidemiology
Population pre...
Article
Aase-Smith syndrome
Aase-Smith syndrome (or Aase syndrome) is an extremely rare congenital disorder characterized by anemia and skeletal deformity.
Epidemiology
Aase-Smith syndrome has a prevalence of less than 1 per 1,000,000 persons. There have only been 20 reported cases.
Clinical presentation
congenital hyp...
Article
Abdominal distension (mnemonic)
A mnemonic for causes of abdominal distension (6 Fs) is:
F: fat
F: fluid
F: flatus
F: feces
F: fetus
F: fulminant mass
Article
Abdominal ectopic pregnancy
Abdominal ectopic pregnancies are an extremely rare type of ectopic pregnancy.
Epidemiology
They are thought to represent ~1% of all ectopic pregnancies 6 with an estimated incidence of 1:1000-10,000 births.
Pathology
It is often thought that they most frequently result from a tubal rupture ...
Article
Abdominal pain in pregnancy protocol (MRI)
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...
Article
Abdominoschisis
Abdominoschisis (plural: abdominoschises) refers to a split or defect in the abdominal wall. Some authors use the term synonymously with a gastroschisis. When the defect continues into the thoracic region it is termed a thoracoabdominoschisis. A large abdominoschisis is considered part of the li...
Article
Abnormal ductus venosus waveforms
Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumors. "A wave" reversal can be seen in 5% of euploid fetuses 9.
Pathology
Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situ...
Article
Abnormally eccentric gestational sac
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 a
bicornu...
Article
Abnormally low sac position
An abnormally low sac position can result from several possibilities which include
impending/ongoing miscarriage
cervical ectopic pregnancy
Cesarean scar ectopic pregnancy
fundal fibroid or other mass compressing the sac downward
Article
Abnormally thickened endometrium (differential)
Abnormally thickened endometrium on imaging may occur for a number of reasons which may be categorized based on whether or not they are related to pregnancy. Etiologies may also be classified based on whether the patient is premenopausal or postmenopausal.
Differential diagnosis
Pregnancy-rela...
Article
Absent ductus venosus
Agenesis of the ductus venosus (ADV) is a rare fetal vascular anomaly.
Epidemiology
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.
Pathology
In a large case series, Acherman et al. 13 defined five drai...
Article
Absent fetal stomach on ultrasound (differential)
Non-visualization of the fetal stomach on ultrasound can occur with various physiological as well as pathological processes. It becomes a significant sonographic observation >14 weeks of gestation (about the time the fetus begins to swallow).
Causes include:
physiological emptying: transient
...
Article
Absent nasal bone
In a fetal sonographic assessment, an absent nasal bone is a feature that can sometimes be used as a surrogate marker for fetal aneuploidy.
Radiographic assessment
Antenatal ultrasound
It is assessed on a midline sagittal view. In this section, the nasal bone is often seen as a bright echogen...
Article
Absent septum pellucidum
An absent septum pellucidum may rarely be an isolated finding, or more commonly be seen in association with a variety of conditions.
Epidemiology
The septum pellucidum is partly or entirely absent in 2 or 3 individuals per 100,000 in the general population.
Pathology
An absent septum pelluc...
Article
Absent umbilical arterial end-diastolic flow
Absent end-diastolic flow (AEDF) in an umbilical artery Doppler assessment is a useful feature that 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.
Epidemiology
Associatio...
Article
Absent yolk sac
Absence of the yolk sac in the presence of an embryo on a transvaginal ultrasound is considered abnormal, and in general is associated with subsequent embryonic death.
See also
yolk sac
Article
Acardiac twin
An acardiac twin, also known a recipient twin, refers to the haemodynamically disadvantaged twin of a twin-pair in the setting of twin reversed arterial perfusion (TRAP) sequence. The acardiac twin undergoes secondary atrophy and is non-viable.
Epidemiology
Acardiac twinning is thought to affe...
Article
Acardius acormus
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.
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