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 edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

26 results found
Article

Abnormal bowel wall attenuation patterns

Abnormal bowel wall attenuation patterns on CT scan can be grouped under five categories: white enhancement gray enhancement water halo sign fat halo sign black attenuation The first three patterns are seen on contrast studies. White enhancement It is defined as uniform enhancement of th...
Article

Abnormally eccentric gestational sac

An eccentrically located gestational sac towards the fundus of uterus is the normal sonographic appearance; however an abnormally eccentric gestational sac on ultrasound may be apparent due to a number of causes They include interstitial ectopic pregnancy 1 normally implanted pregnancy in a  ...
Article

Absent bow tie sign

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 medal and lateral menisci appear as low signal bow-tie-shaped structures between the femoral condyles and tibial plateaux. As the no...
Article

Absent nasal bone

In fetal sonographic assessment, an absent nasal bone is a feature which can sometimes be used as an adjunctive 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

Accordion sign

The accordion sign is seen on CT examinations of the abdomen and refers to the similarity between the thickened oedematous wall of pseudomembranous colitis to that of an accordion. The appearance arises as a result of oral contrast being trapped between oedematous haustral folds and pseudomembra...
Article

Ace-of-spades sign

Ace-of-spades sign refers to the pathognomonic configuration of the left ventricle as seen in apical hypertrophy 1-3. It consists of marked ventricular wall thickening at the apex resulting in cavity narrowing at the apex with a relatively normal appearance of the mid-ventricular to basal wall a...
Article

Air bronchogram

Air bronchogram refers to the phenomenon of air-filled bronchi (dark) being made visible by the opacification of surrounding alveoli (grey/white). It is almost always caused by a pathologic airspace/alveolar process, in which something other than air fills the alveoli. Air bronchograms will not ...
Article

Air crescent sign

An air crescent sign describes the crescent of air that can be seen in invasive aspergillosis, semi-invasive aspergillosis or other processes that cause pulmonary necrosis. It usually heralds recovery and is the result of increased granulocyte activity. In angioinvasive fungal infection, the no...
Article

Air trapping

Air trapping in chest imaging refers to retention of excess gas (“air”) in all or part of the lung, especially during expiration, either as a result of complete or partial airway obstruction or as a result of local abnormalities in pulmonary compliance. It may also sometimes be observed in norma...
Article

Andersson lesion

Andersson lesions refer to inflammatory involvement of the intervertebral discs by spondyloarthritis. Epidemiology Rheumatic spondylodiscitis is a non-infectious condition that has been shown to occur in about 8% of patients with ankylosing spondylitis, as detected at radiography. Pathology ...
Article

Angiographic string sign

The angiographic string sign, also known as the carotid string sign, refers to the thin string of intravenous contrast material distal to a stenotic focus in the internal carotid artery (ICA).  Mechanism A thin stripe of flow is caused by decreased pressure and flow distal to the stenosis, whi...
Article

Animal and animal produce inspired signs

Animal and animal produce inspired signs may sound a little silly, but the radiology literature is replete with signs, some more fanciful than others. Fish and seafood fish vertebra (also known as codfish vertebra): biconcave vertebrae as seen in osteoporosis fishtail deformity of the elbow: ...
Article

Ankle tear drop sign

Ankle tear drop sign is one of the radiological signs of an ankle joint effusion. It represents the presence of fluid in the inferior part of anterior compartment of ankle . Pathology Causes trauma gout rheumatoid arthritis synovitis infectious arthritis Radiographic appearance Plain ra...
Article

Anteater nose sign

The anteater nose sign refers to an anterior tubular prolongation of the superior calcaneus which approaches or overlaps the navicular on a lateral radiograph of the foot. This fancifully resembles the nose of an anteater and is an indication of calcaneonavicular coalition 1-2.  History and ety...
Article

Anterior bronchus sign

The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph. Normal anatomy The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly t...
Article

Anterior tibial translocation sign

The anterior tibial translocation sign or anterior drawer sign (also known as anterior translation of tibia) is seen in cases of complete rupture of the anterior cruciate ligament, and refers to anterior translocation (anterior tibial subluxation) of the tibia relative to the femur of more than ...
Article

Antral nipple sign

The antral nipple sign refers to redundant pyloric mucosa protruding into the gastric antrum and is seen in pyloric stenosis. See also cervix sign of pyloric stenosis target sign of pyloric stenosis shoulder sign of pyloric stenosis
Article

Antral pad sign

An antral pad sign is a feature seen on a spot radiograph of the upper gastrointestinal tract obtained with orally administered contrast material. It refers to the the extrinsic impression or indentation on the postero-inferior aspect of the antrum. The impression is generally arcuate and smooth...
Article

Apple core sign - colon

The apple core sign, also known as a napkin ring sign (bowel), is most frequently associated with constriction of the lumen of the colon by a stenosing annular colorectal carcinoma. Differential diagnosis The appearance of the apple-core lesion of the colon also can be caused by other diseases...
Article

Apple core sign - femur

The apple core sign has been used to describe the circumferential erosion of the femoral neck seen in synovial chondromatosis. Although this is the most common process that may lead to an apple core erosion of the femoral neck, this has also been observed with: pigmented villonodular synovitis ...
Article

Apple-peel intestinal atresia

Apple-peel intestinal atresia, also known as type IIIb or Christmas tree intestinal atresia, is a rare form of small bowel atresia in which the duodenum or proximal jejunum ends in a blind pouch and the distal small bowel wraps around its vascular supply in a spiral resembling an apple peel. Oft...
Article

Arcuate sign

The arcuate sign is often a subtle but important finding on knee x-rays and represents an avulsion fracture of the proximal fibula at the site of insertion of the arcuate ligament complex, and is usually associated with cruciate ligament injury (~90% of cases) 2. The fracture fragment is attache...
Article

Arrowhead sign

The arrowhead sign refers to the focal caecal thickening centered on the appendiceal orifice, seen as a secondary sign in acute appendicitis. The contrast material in the cecal lumen assumes an arrowhead configuration, pointing at the appendix.   The arrowhead sign is applicable only when enter...
Article

Atoll sign - liver MRI

The atoll sign in hepatic imaging has been described when a liver lesion shows a peripheral rim of high T2 signal intensity with the center of the lesion appearing isointense to the background of non-cirrhotic liver on T2WI mimicking an atoll. It is considered a characteristic sign of an inflamm...
Article

Atrial escape

Atrial escape refers to a chest x-ray sign of massive left atrial enlargement and is an exaggerated version of the double density sign.   Normally, the right border of the left atrium is not visible. As it enlarges it forms a distinct border projecting through the right heart shadow, medial to ...
Article

Aubergine sign

The aubergine sign (also known as egg-plant sign or deformity) is a clinical sign of a fractured penis. Haemorrhage beyond the tunica albuginea produces swelling and bruising of the penis simulating the appearance of an aubergine.  

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