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 ...
≤11 ribs is associated with a number of congenital abnormalities and skeletal dysplasias, including:
Down syndrome (trisomy 21)
asphyxiating thoracic dysplasia (Jeune syndrome)
short rib polydactyly syndromes
chromosome 1q21.1 deletion...
The 1-2-3 rule is a simple aide-mémoire describing the nomenclature of any small simple anechoic structure in the ovary on ultrasound:
<1 cm = follicle
1-2 cm = dominant follicle
>3 cm = cyst
14-3-3 proteins are found in the cerebrospinal fluid (CSF) and are currently used to help identify patients with sporadic Creutzfeldt-Jakob disease (sCJD).
Seven distinct 14-3-3 proteins have been found in humans.
In diagnosing sCJD, the sensitivity of 14-3-3 protein is 92%, and its specifici...
Comparing 1.5 T vs 3.0 T (1.5 tesla vs 3.0 tesla) MRI systems identifies several differences; a 3 T system has
increased signal-to-noise ratio (SNR)
increased spatial resolution
increased temporal resolution
increased specific absorption rate (SAR)
increased acoustic noise
18q-deletion syndrome is a rare chromosomal anomaly where there is a deletion of part of the long arm of chromosome 18. Associated symptoms and findings vary widely, as do their severity. Characteristic clinical features include short stature, intellectual disability, hypotonia, facial, and dist...
1p19q codeletion stands for the combined loss of the short arm chromosome 1 (i.e. 1p) and the long arm of chromosome 19 (i.e. 19q) and is recognized as a genetic marker predictive of therapeutic response to both chemotherapy and combined chemoradiotherapy and overall longer survival in patients ...
1p36 deletion syndrome, or monosomy 1p36, is a chromosomal abnormality characterized most commonly by a deletion in the distal segment of the short arm of chromosome one 1.
The 1p36 deletion syndrome is present in approximately 1 in 5,000 live births. It is the most common termina...
The 2001 World Health Organization (WHO) classification of hepatic hydatid cysts is used to assess the stage of hepatic hydatid cysts on ultrasound and is useful in deciding the appropriate management depending on the stage of the cyst. This classification was proposed by the WHO in 2001 and, at...
The 2014 WHO classification is one of the classification systems for endometrial stromal tumors (EST).
Endometrial stromal tumors constitute <2% of all uterine tumors and <10% of uterine mesenchymal neoplasms 1.
Over the past four decades, EST classification has gone through various modificat...
20° oblique projection is a troubleshooting projection used in mammography, especially in young women and in follow-up patients.
The C-arm is turned approximately 20° for a superomedial-inferolateral oblique. With the patient's feet pointing towards the unit and her torso turned slig...
22q11.2 deletion syndrome, also known as the DiGeorge syndrome or velocardiofacial syndrome, is a syndrome where a small portion of the chromosome 22 is lost and results in a variable but a recognisable pattern of physical and behavioral features.
The estimated incidence is at ~ 1...
2-hydroxyglutarate is a metabolite that accumulates in the brains of patients with IDH-1 mutated (IDH-1 positive) brain tumors, particularly diffuse low-grade gliomas. Although not in widespread clinical use, it is likely that 2-hydroxyglutarate, which resonates at 2.25 ppm, will be able to be d...
The 3-6-9 rule is a simple aide-memoire describing the normal bowel caliber:
small bowel: <3 cm
large bowel: <6 cm
appendix: <6 mm
cecum: <9 cm
Above these dimensions, the bowel is generally considered dilated, and obstruction or an adynamic ileus should be considered.
3D conformal radiation therapy (3D-CRT) is a radiation therapy technique that involves CT planning where the volume to be treated is defined on a 3D data set. Therefore, organs at risk can also be delineated to shield these and reduce treatment side effects. Radiotherapy planning software is use...
3D fast spin-echo sequences are relatively recent MRI pulse sequences that are able to rapidly image relatively large volumes of tissue with high resolution whilst retaining many of the advantages of fast spin-echo sequences.
They are able to create the same weightings as traditional 2D sequen...
3D printing, a term often used synonymously with additive manufacturing, is a process of creating objects from three-dimensional digital information. In most cases, 3D printing is, in fact, additive manufacturing, a process in which objects are built by adding material layer by layer. This proce...
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...
4D syndrome is a term used to describe a manifestation of syndromic glucagonoma, a type of pancreatic endocrine tumor.
D: dermatitis 2
necrolytic migratory erythema - a widespread rash, tending to involve perioral and perigenital regions
oral rashes (angular stomatitis, cheilitis)
tend to re...
The 5-F rule refers to risk factors for the development of cholelithiasis in the event of upper abdominal pain:
fair: more prevalent in the Caucasian population 1
fat: BMI >30 kg/m2 and hyperlipidemia 3,4
fertile: one or more children
forty: age ≥40 years
cholelithiasis can occur in...
The 5 gauss line is the safety line drawn around the perimeter of the main magnet of the MRI scanner, specifying the distance at which the stray magnetic field is equivalent to 5 gauss (0.5 mT).
Five gauss and below are considered 'safe' levels of static magnetic field exposure for the general ...
The 5th metacarpal pit refers to the normal exaggeration of the pit-like depression in the head of fifth metacarpal.
It should not be mistaken for a boxer fracture (old or new) or an erosion.
The 5-tier ACR system was a previously used system for classification of radiologic breast findings, proposed by the American College of Radiology (ACR). It is no longer in widespread use, having been gradually superseded by the 6-tier BI-RADS classification system first published in 1992. Inter...
The 60/60 sign in echocardiography refers to the coexistence of a truncated right ventricular outflow tract acceleration time (AT <60 ms) with a pulmonary arterial systolic pressure (PASP) of less than 60 mmHg (but more than 30 mmHg). In the presence of right ventricular failure, it is consisten...
Aaron sign is a clinical sign that is defined as a feeling of distress and pain in the epigastric, umbilical and praecordial regions, on steady pressure over McBurney point, it is suggestive of chronic appendicitis.
History and etymology
Charles Dettie Aaron (1866–1951) was an American gastroe...
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.
Aase-Smith syndrome (or Aase syndrome) is an extremely rare congenital disorder characterized by anemia and skeletal deformity.
Aase-Smith syndrome has a prevalence of less than 1 per 1,000,000 persons. There have only been 20 reported cases.
The American Association for the Surgery of Trauma (AAST) injury scoring scales are the most widely accepted and used system of classifying and categorizing traumatic injuries. Injury grade reflects severity, guides management, and aids in prognosis. Currently (early 2019), 32 different injury s...
The American Association for the Surgery of Trauma (AAST) renal injury scale, most recently updated in 2018, is the most widely used grading system for renal trauma.
The 2018 update incorporates "vascular injury" (i.e. pseudoaneurysm, arteriovenous fistula) into the imaging criteria for viscera...
The AAST (American Association for the Surgery of Trauma) liver injury scale, most recently revised in 2018, is the most widely used liver injury grading system 3.
The 2018 update incorporates "vascular injury" (i.e. pseudoaneurysm, arteriovenous fistula) into the imaging criteria for visceral ...
The American Association for the Surgery of Trauma (AAST) splenic injury scale, most recently revised in 2018, is currently the most widely used grading system for splenic trauma.
The 2018 update incorporates "vascular injury" (i.e. pseudoaneurysm, arteriovenous fistula) into the imaging criter...
ABC/2, also confusingly written as 1/2ABC in some literature, is a fast and simple method for estimating the volume of intracerebral hemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software.
Intracerebral hemorrhage volume is an import...
The AP supine abdominal radiograph can be performed as a standalone projection or as part of an acute abdominal series, depending on the clinical question posed, local protocol and the availability of other imaging modalities.
This view is useful in assessing abdominal pathologies,...
The dorsal decubitus view is a supplementary projection often replacing the lateral decubitus view in the context of an unstable patient who is unable to roll nor stand. Used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred...
The kidneys, ureters, bladder (KUB) radiograph is optimized for assessment of the urogenital system, and should not be confused with the AP supine abdomen view. However, in cases where the patient may have both gastrointestinal and urogenital abnormalities, all pathologies will still be reported...
The lateral decubitus abdominal radiograph is used to identify free intraperitoneal gas (pneumoperitoneum). It can be performed when the patient is unable to be transferred to, or other imaging modalities (e.g. CT) are not available. The most useful position for detecting free intraperitoneal ai...
AP oblique supine radiograph is a projection often used in barium studies and foreign body localization.
This view is normally performed when localizing foreign bodies or lines within the abdominal cavity. Additionally, the oblique abdominal series can be utilized in the assessment...
The PA erect abdominal radiograph is often obtained in conjunction with the AP supine abdominal view in the acute abdominal series of radiographs.
The erect abdominal radiograph has virtually disappeared from clinical practice in the United Kingdom, with studies dating back to the 1980s affirmi...
The PA prone radiograph is rarely performed and is often utilized when a patient is unable to lay supine. The projection is adequate for the examination of the abdominal cavity, however, not as practical for the renal structures due to magnification.
This view is useful in visualiz...
The CT abdomen-pelvis protocol serves as an outline for an examination of the whole abdomen including the pelvis. It is one of the most common CT protocols for any clinical questions related to the abdomen and/or in routine and emergencies. It forms also an integral part of trauma and oncologic ...
The abdomen radiograph is a commonly requested examination in the pediatric patient. Children that present for abdominal x-rays are often very unwell, therefore specialized techniques and appropriate communication are essential for gaining the child's cooperation.
Abdominal adhesions are bands of scar tissue (ﬁbrous or ﬁbrofatty), most often occurring as a complication of previous abdominal surgery.
Adhesions often occur with
multiple abdominal operations or previous postoperative intra-abdominal complications
history of intra-abdominal inﬂa...
Abdominal and pelvic anatomy encompasses the anatomy of all structures of the abdominal and pelvic cavities.
This anatomy section promotes the use of the Terminologia Anatomica, the international standard of anatomical nomenclature.
The abdominal aorta (plural: aortas or aortae 4) is the main blood vessel in the abdominal cavity that transmits oxygenated blood from the thoracic cavity to the organs within the abdomen and to the lower limbs.
origin: continuation of descending thoracic aorta at T12
Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta measuring 50% greater than the proximal normal segment, or >3 cm in maximum diameter.
Abdominal aortic aneurysms represent the tenth most common cause of death in the Western world:
Abdominal aortic aneurysm (AAA) rupture is a feared complication of abdominal aortic aneurysm and is a surgical emergency. It is part of the acute aortic syndrome spectrum.
Abdominal aortic aneurysms are common and affect ~7.5% of patients aged over 65 years 6.
This is a basic article for medical students and other non-radiologists
Abdominal aortic aneurysms (AAA) are focal dilatations of the abdominal aorta that are 50% greater than the proximal normal segment or >3 cm in maximum diameter.
This is a summary article; read more in o...
Abdominal aortic injuries are a very rare form of traumatic aortic injury and are much less common than thoracic aortic injury.
Aortic injury occurs in <1% of blunt trauma patients, with abdominal aortic injury representing only ~5% of all aortic injuries 1. Males are more freque...
The abdominal cavity is divided into two major compartments, the peritoneum and retroperitoneum, early in fetal development.
The parietal peritoneum is reflected over the peritoneal organs to form a series of supporting peritoneal ligaments, mesenteries and omenta. The peritoneal reflections ca...
Abdominal compartment syndrome (ACS) is a disease defined by the presence of new end-organ dysfunction secondary to elevated intraabdominal pressure (IAP). Radiological diagnosis is difficult and usually suggested when a collection of imaging findings are present in the appropriate clinical sett...
A mnemonic for causes of abdominal distension (6 Fs) is:
F: fulminant mass
Abdominal ectopic pregnancies are an extremely rare type of ectopic pregnancy.
They are thought to represent ~1% of all ectopic pregnancies 6 with an estimated incidence of 1:1000-10,000 births.
It is often thought that they most frequently result from a tubal rupture ...
Abdominal hernias (herniae also used) may be congenital or acquired and come with varying eponyms. They are distinguished primarily based on location and content. 75-80% of all hernias are inguinal.
Content of the hernia is variable, and may include:
small bowel loops
mobile colon segments (s...
The role of dual energy CT is becoming increasingly more prevalent abdominal imaging due to the availability of scanners and increasing field of research.
Acute bowel ischemia
The addition of iodine maps and 40-keV monoenergetic images to standard single energy CT images was found to increase ...
The lateral view abdominal radiograph is a less common projection of the abdomen, it is different from the lateral decubitus view of the abdomen and looks more like a lateral lumbar spine view.
This projection is often requested as a useful problem-solving view that can complement ...
Abdominal migraine is a syndrome that presents as recurrent episodes of severe paroxysmal abdominal pain, coupled with vasomotor symptoms, nausea, and emesis that lasts for at least 1 hour 3. Historically it has tended to be a pediatric diagnosis, but it is now increasingly seen in adults. It is...
An opacity projecting over the abdomen has a broad differential. Possibilities to consider include:
ingested, e.g. coins, batteries, bones, etc
artifacts, e.g. object attached to the cloth of the patient like a safety pin or button
iatrogenic, e.g. hemostatic clips, gastric ba...
This mnemonic helps to remember the relative echogenicity of abdominal organs on ultrasound:
Darling Parents So Love Kids
From most to least echogenic:
K: kidneys (cortex)
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...
An abdominal paracentesis (plural: paracenteses), more commonly referred to as an ascitic tap, is a procedure that can be performed to collect peritoneal fluid for analysis or as a therapeutic intervention.
diagnostic: especially for newly-diagnosed ascites
determine etiology of a...
A mnemonic to remember the contraindications to abdominal paracentesis is:
C: coagulopathy (INR >2.0)
A: abdominal wall cellulitis
S: surgical abdomen (absolute contraindication) / severe thrombocytopenia (platelet count <50 x 103/μL)
I: intra-abdominal adhes...
Abdominal radiography can be useful in many settings. Before the advent of computed tomography (CT) imaging, it was a primary means of investigating gastrointestinal pathology and often allowed indirect evaluation of other abdominal viscera.
Although abdominal radiography has lower...
This is a basic article for medical students and other non-radiologists
Abdominal radiology curriculum for medical students is broadly split into content that refers to imaging (the test and findings) and conditions that are considered key for this stage of training.
Some non-abdominal conditi...
Abdominal surface anatomy can be described when viewed from in front of the abdomen in 2 ways:
divided into 9 regions by two vertical and two horizontal imaginary planes
divided into 4 quadrants by single vertical and horizontal imaginary planes
These regions and quadrants are of clinical imp...
Abdominal trauma is usually divided into blunt and penetrating trauma.
Findings of abdominal trauma
splenic trauma: most common
gastrointestinal tract (bowel) trauma:
proximal jejunum is most commonly affected by blunt trauma,...
Abdominal tuberculous can manifest in almost every abdominopelvic organ:
jejunal and ileal tuberculosis
Abdominal wall injuries comprise a set of injuries of the abdominal wall and include different forms of muscle injuries, traumatic hernias and injuries to the subcutaneous tissue. They are often overshadowed by the attention to associated “more severe” abdominal visceral injuries.
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where D refers to the assessment of dense structures such as the bones and areas of calcification.
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review:
A: air - where it should and shouldn't be
B: bowel - position, size and wall thickness
D: dense st...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where A refers to the assessment of the presence and location of air.
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where X refers to the assessment of external objects and artifacts.
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where B refers to the assessment of the bowel loops.
stomach, small bowel and...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where O refers to the assessment of the intra-abdominal organs and soft tissues.
This is a basic article for medical students and other non-radiologists
Abdominal radiographs can be a useful examination, but you need to think about the question you are asking before getting the test. Before the advent of computerized tomography (CT) imaging, it was a primary means of invest...
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...
The abducens nerve is the sixth cranial nerve. It courses from its nucleus located in the dorsal pons to its innervation of the lateral rectus muscle and can be divided into four parts:
nucleus and intraparenchymal portion
cavernous sinus portion
Abducens nerve palsy, or sixth nerve palsy, results in weakness of the ipsilateral lateral rectus muscle.
Patients present with horizontal diplopia with an inability to abduct the ipsilateral eye, thereby resulting in an esotropia (nasal deviation of the eye).
The abducent or abducens nucleus is a small motor nucleus in the pons for the abducens nerve.
The nucleus is located in the paramedian dorsal lower pons in the floor of the fourth ventricle lateral to the medial longitudinal fasciculus. The nucleus forms a longitudinal paramedian...
The abductor digiti minimi (ADM) muscle is on the lateral side of the foot and contributes to the large lateral plantar eminence on the sole.
origin: lateral and medial processes of calcaneal tuberosity, and band of connective tissue connecting calcaneus with base of the fifth metatars...
The abductor digiti minimi muscle overlies the opponens digiti minimi muscle, within the hypothenar eminence, and is one of the intrinsic muscles of the hand. Occasionally an accessory abductor digiti minimi muscle of the hand is present.
origin: pisiform, pisohamate ligament, and tend...
The abductor hallucis muscle forms the medial margin of the foot and contributes to a soft tissue bulge on the medial side of the sole.
origin: medial process of calcaneal tuberosity
insertion: medial side of base of proximal phalanx of great toe
action: abducts and flexes great toe ...
The abductor pollicis brevis muscle is a thin subcutaneous muscle located laterally in the thenar eminence of the hand, and is one of the intrinsic muscles of the hand.
origin: mainly from the flexor retinaculum
few fibers originate from the tubercles of scaphoid and trapezium and ten...
The abductor pollicis longus (APL) muscle is found in the deep layer of the posterior compartment of the forearm. As it descends, it becomes superficial and passes under the extensor retinaculum and through the 1st extensor compartment of the wrist before attaching distally. It is one of the ext...
Abernethy malformations are rare vascular anomalies of the splanchnic venous system. They consist of congenital portosystemic shunts and result from persistence of the embryonic vessels.
Type I malformations are thought to occur only in females, while type II have a male predomin...
The ABER position relates to MR arthrography of the shoulder joint and is a mnemonic for ABduction and External Rotation.
In this position, labral tears are made conspicuous by tightening the inferior glenohumeral labroligamentous complex (which are also the most important glenohumeral ligament...
Aberrant arachnoid granulations, also known as arachnoid pits, are arachnoid granulations that penetrated the dura but failed to migrate normally in the venous sinus. They are most often located in the greater wing of the sphenoid bone and may be seen in idiopathic intracranial hypertension. Occ...
Aberrant internal carotid artery is a variant of the internal carotid artery and represents a collateral pathway resulting from involution of the normal cervical portion (first embryonic segment) of the internal carotid artery 5.
There is consequent enlargement of the usually sma...
Aberrant left pulmonary artery, also known as pulmonary sling, represents an anatomical variant characterized by the left pulmonary artery arising from the right pulmonary artery and passing above the right main bronchus and in between the trachea and esophagus to reach the left lung. It may lea...
Aberrant right subclavian arteries (ARSA), also known as arteria lusoria, are among the commonest aortic arch anomalies.
The estimated incidence is 0.5-2%.
They are often asymptomatic, but around 10% of people may complain of tracheo-esophageal symptoms, a...
Aberrations in the Normal Development and Involution of the breast (ANDI) is an overarching term used to describe a wide spectrum of benign breast disease. As the name suggests, it is based on the theory that most of the encountered benign breast disorders are aberrations in the normal developme...
Abnormal bowel wall attenuation patterns on CT scan can be grouped under five categories:
water halo sign
fat halo sign
The first three patterns are seen on contrast studies.
It is defined as uniform enhancement of th...
A mnemonic used for abnormal collection of barium anywhere in the body:
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.
Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situ...