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.
16,888 results found
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
Abnormal renal rotation
Abnormal renal rotation, also known as renal malrotation, refers to an anatomical variation in the position of the kidneys, in particular to anomalous orientation of the renal hilum. It may occur unilaterally or bilaterally. It is almost always an asymptomatic incidental finding.
Epidemiology
...
Article
Abnormal testicular Doppler flow (differential)
Abnormal testicular Doppler flow (arterial, venous, or both) can be a differential challenge. Always remember that the patient's presenting history helps quite a bit in narrowing the differential.
Reduced flow
partial testicular torsion (<360 degrees)
venous outflow is obstructed first, resul...
Article
Abnormal ultrasound findings in rheumatological diseases (definitions)
The OMERACT ultrasound group published a consensus in 2005 of widely accepted definitions of abnormal ultrasound findings in rheumatological diseases:
erosion: an intra-articular discontinuity of the bone surface that is visible in two orthogonal planes 4
joint effusion: abnormal hypoechoic or...
Article
ABR certifying exam
The ABR certifying exam is the second of two exams necessary for certification in diagnostic and interventional radiology in the United States of America (the first is the core exam). It is taken 15 months after the end of the PGY 5 year (or three months after a one year PGY 6 fellowship).
The ...
Article
ABR core exam
The ABR core exam is set by the American Board of Radiology, and is the first of two exams necessary for certification in diagnostic and interventional radiology in the United States of America. It is taken at the end of PGY4 of radiology residency training.
The exam is computer-based and occur...
Article
Abrodil
Abrodil (marketed as Skiodan in the US) was a water-based iodinated contrast medium introduced for clinical use in 1930 3. It was developed by Bronner, Hecht and Schueller in Germany. Chemically, Abrodil is the sodium salt of monoiodomethanesulfonic acid.
It was initially employed for intraveno...
Article
Abscess
Abscesses are focal confined collections of suppurative inflammatory material and can be thought of as having three components 1:
a central core consisting of necrotic inflammatory cells and local tissue
peripheral halo of viable neutrophils
surrounded by a 'capsule' with dilated blood vessel...
Article
Abscopal effect
The abscopal effect is a term used in oncology which refers to a phenomenon in which a locoregional therapy for a tumor leads to systemic anti-tumor effects, such as shrinkage of distant (non-target) tumors.
While the precise mechanism(s) of action are not fully understood, there is a growing a...
Article
Absent azygos vein
An absent azygos vein is a very uncommon variant in which the azygos vein fails to develop. In cases of agenesis of the azygos vein, the hemiazygos and accessory hemiazygos veins play an important role in venous drainage, accounting for drainage of both the right and left intercostal veins 1-3.
...
Article
Absent bow tie sign (knee)
The absent bow tie sign represents the loss of the normal appearance of the menisci on parasagittal MRI images and is suggestive of meniscal injury.
Normally the medial and lateral menisci appear as low signal triangular structures linked by a thin body located between the femoral condyles and ...
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 infrarenal inferior vena cava
An absent infrarenal inferior vena cava can be congenital, due to the failure of development of the posterior cardinal and supracardinal veins, or acquired, as a result of intrauterine or perinatal inferior vena cava thrombosis.
Epidemiology
It is an extremely rare anomaly.
Clinical presentat...
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 patella
An absent patella is a rare finding and can be found with an equally rare set of associations:
surgical removal of patella (patellectomy)
nail patella syndrome 2
popliteal pterygium syndrome
proximal focal femoral deficiency (PFFD)
Meier-Gorlin syndrome 3
Article
Absent posterior limb sign
The absent posterior limb sign is one of the main MRI findings of prognostic significance in term neonates with suspected hypoxic-ischemic brain injury. An absent posterior limb sign is defined as loss of the normally distinct hyperintensity on T1-weighted images in the posterior part of the pos...
Article
Absent pulmonary valve syndrome
Absent pulmonary valve syndrome (APVS) also known as congenital absence of pulmonary valve or pulmonary valve agenesis is a rare cardiac outflow tract anomaly.
Pathology
It is characterized by a completely absent or rudimentary pulmonary valve. It can be associated with aneurysmal dilatation ...
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 thumb
An absent thumb can have many associations. They include:
Fanconi anemia (pancytopenia-dysmelia syndrome)
Franceschetti syndrome
Holt-Oram syndrome
phocomelia (e.g. thalidomide embryopathy)
Poland syndrome (pectoral muscle aplasia and syndactyly)
Rothmund-Thomson syndrome
Seckel syndrome ...
Unable to process the form. Check for errors and try again.