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...
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
interstitial ectopic pregnancy 1
normally implanted pregnancy in a
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...
In fetal sonographic assessment, an absent nasal bone is a feature which can sometimes be used as an adjunctive marker for fetal aneuploidy.
It is assessed on a midline sagittal view. In this section the nasal bone is often seen as a bright echogen...
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...
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...
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 ...
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...
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...
Andersson lesions refer to inflammatory involvement of the intervertebral discs by spondyloarthritis.
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.
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).
A thin stripe of flow is caused by decreased pressure and flow distal to the stenosis, whi...
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: ...
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.
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...
The anterior bronchus sign refers to the appearance of the anterior segmental bronchus of the upper lobes as seen on a frontal chest radiograph.
The anterior segment bronchus of the upper lobes courses anteriorly and laterally. When the orientation is predominantly anteriorly t...
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 ...
The antral nipple sign refers to redundant pyloric mucosa protruding into the gastric antrum and is seen in pyloric stenosis.
cervix sign of pyloric stenosis
target sign of pyloric stenosis
shoulder sign of pyloric stenosis
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...
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.
The appearance of the apple-core lesion of the colon also can be caused by other diseases...
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
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...
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...
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...
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...
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 ...
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.
Baastrup syndrome (also referred to as kissing spines) results from adjacent spinous processes in the lumbar spine rubbing against each other and resulting in hypertrophy and sclerosis with focal midline pain and tenderness relieved by flexion and aggravated by extension.
Backwash ileitis is seen in patients with ulcerative colitis (UC), where the entire colon is involved. In such cases the terminal ileum is oedematous.
Backwash ileitis extends contiguously backward from the cecum without skip regions. One source estimates it to occur in 6% of patients with UC, ...
The Ballet sign refers paralysis of voluntary movements of the eyeball with preservation of the automatic movements. Sometimes this sign is present with exophthalmic goitre and hysteria.
In renal imaging, the balloon on a string sign refers to the appearance on IVU in ureteropelvic junction obstruction. It is seen due to the high and eccentric point of exit of ureter from a dilated renal pelvis.
Bamboo spine is a radiographic feature seen in ankylosing spondylitis that occurs as a result of vertebral body fusion by marginal syndesmophytes. It is often accompanied by fusion of the posterior vertebral elements as well.
A bamboo spine typically involves the thoracolumbar and or lumbosacr...
The banana sign is one of the many notable fruit inspired signs.
It is seen on axial imaging through the posterior fossa of fetus and is associated with the Chiari II malformation. It describes the way the cerebellum is wrapped tightly around the brain stem as a result of spinal cord tethering ...
Bare orbit sign, is described as a characteristic appearance of orbit, where the innominate line is absent. The innominate line is a projection of the greater wing of the sphenoid, and its absence or destruction is responsible for this appearance.
It is the classical frontal radiograph sign of ...
Bat wing 4th ventricle sign refers to the morphology of the fourth ventricle in the Joubert anomaly and related syndromes. The absence of a vermis with apposed cerebellar hemispheres give the fourth ventricle an appearance reminiscent of a bat with its wings outstretched.
It is best demonstrate...
Bat's wing or butterfly pulmonary opacities refer to a pattern of bilateral perihilar shadowing. It is classically described on a frontal chest radiograph but can also refer to appearances on chest CT 3-4.
Bat's wing pulmonary opacities can be caused by:
Bayonet deformity is a term used to describe the shape of wrist in certain conditions:
hereditary multiple exostosis with pseudo-Madelung deformity
retarded bone growth of the distal ulna with outward bowing of radius with distal radioulnar joint subluxation
Beak sign in pyloric stenosis is one of the fluoroscopic (Barium meal) findings which is useful in the diagnosis of congenital hypertrophic pyloric stenosis.
Peak of Barium is seen entering into the narrowed and compressed pyloric channel with distal taperin...
The beak sign of arterial dissection represents a wedge of haematoma at the distal end of the false lumen. It is here that false lumen propagation is occurring. It manifests as an acute angle between the dissection flap and the outer wall. It may be filled with contrast enhanced blood (high atte...
The bear paw sign is seen in xanthogranulomatous pyelonephritis and refers to the cross-sectional appearance of the kidney which is said to resemble the paw of a bear. The renal pelvis is contracted whereas the calyces are dilated, mimicking the toe-pads of the paw.
Beck triad is a collection of three clinical signs associated with pericardial tamponade which is due to excess accumulation of fluid within the pericardial sac. The three signs are:
low blood pressure (weak pulse or narrow pulse pressure)
muffled heart sounds
raised jugular venous pressure ...
The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.
It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.
Bilateral adrenal gland hyperenhancement or intense adrenal enhancement may be a feature of hypotension and forms part of the CT hypoperfusion complex.
It has has been described in paediatric and small adult series or individual cases of haemorrhagic shock, pancreatitis, sepsis and trauma 1-3 b...
The bird-beak sign is used to refer to the tapering of the inferior oesophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the rat-tail sign.
The appearances although classically occurring in primary achalasia, can also occur in pseu...
The black turbinate sign refers to an area of non-enhancing mucosa on MRI in a patient with angioinvasive fungal sinus infection / rhinocerebral mucormycosis.
Mucormycosis is caused by fungi that include Mucor, Rhizopus, and Absidia species. It is seen in diabetic and immunocompromised patient...
The blade of grass sign (also called the candle flame sign) refers to the lucent leading edge in a long bone seen during the lytic phase of Paget disease of bone.
The blade of grass sign is characteristic of Paget disease of bone. This is akin to osteoporosis circumscripta cranii seen in the s...
Early haematoma growth is not uncommon in patients with intracerebral haemorrhage and is an independent predictor of poor functional outcome. In nonenhanced cranial CT the blend sign is defined as blending of a hypoattenuating area and a hyperattenuating region with a well-defined margin.
Bone within a bone is a descriptive term applied to bones that appear to have another bone within them. There are numerous causes including:
thoracic and lumbar vertebrae (in infants)
growth recovery lines (after infancy)
sickle cell disease / thalassaemia
autosomal dominant osteopet...
The boomerang sign refers to boomerang shaped splenial lesion (splenium of corpus callosum) which is seen as hyperintense lesion on T2-WI, FLAIR and DWI 1.
This sign can be seen in:
transient lesion in splenium
posterior reversible encephalopathy syndrome
diffuse axonal injury
The boomerang sign is defined as a small displaced flap from longitudinal horizontal type medial meniscal tear which is displaced inferiorly into the medial meniscotibial recess. The imaging diagnosis of this type of tear is crucial because it is normally hidden from surgeons eye during routine ...
Bouchard nodes are a clinical sign relating to bony nodules of the the proximal interphalangeal joints, and are much less common than Heberden nodes. They generally (but not always) correspond to palpable osteophytes.
They are sometimes painful, and are typically associat...
A bouquet of flowers appearance is a description given to the appearances of medullary sponge kidney on a traditional intravenous pyelogram (IVP) study. The ectatic distal collecting ducts contain the microcalcification typical of the disease. This is also known as a 'bunch of grapes' appearance...
Boutonniere deformity is one of the musculoskeletal manifestations of rheumatoid arthritis in the hand with:
flexion contracture of the proximal interphalangeal (PIP) joints
extension of the distal interphalangeal (DIP) joints
The buttonhole appears in the tendon which splays open. The appea...
A 'box-shaped' heart is a radiographic description given to the cardiac silhouette in some cases of Ebstein anomaly. The classic appearance of this finding is caused by the combination of the following features:
huge right atrium that may fill the entire right hemithorax
shelved appearance of ...
The bracket sign refers to a radiographic appearance seen with the tubulonodular variety of pericallosal lipoma. It reflects calcification seen at the periphery of the midline lipoma. It is best seen on coronal imaging, and historically was identified on frontal radiographs.
The breast within a breast sign refers to the common mammographic appearance of breast hamartomas (fibroadenolipomas). Since these benign lesions are well-circumscribed and contain a mixture of fibrous, glandular and fatty tissue (just like normal breast), it is not surprising that they appear v...
The bridging vessel sign refers to an appearance of vessels coursing from the uterus into an adjoining pelvic mass (a vascular bridge). This sign helps to differentiate a pedunculated subserosal uterine leiomyoma from other juxtauterine masses of ovarian, adnexal or bowel origin.
Colour and pow...
The bright dot sign refers to presence of a bright dot within a lesion which remains hyper-attenuating on arterial and portal venous phase CT, corresponding to early nodular enhancement seen on dynamic MRI of liver haemangioma.
This can be used as an indicator that the lesion in question is a ...
The bright rim sign in anterior-talofibular ligament injury refers to a sign seen on MRI. A cortical defect with a bright dot-like or curvilinear high-signal-intensity, usually in fibular attachment site, is seen on MRI. It has been described an indicator of ATFL injury 1.
bright rim ...
The bright rim sign has been described in DNETs and is seen, as the name so aptly describes, as a rim of high signal around the DNET on FLAIR sequences.
The bronchial cut off sign refers to the abrupt truncation of a bronchus from obstruction, which may be due to cancer, mucous plugging, trauma or foreign bodies. Typically, there is associated distal lobar collapse.
Bronchorrhoea is the expectoration of copious amounts of mucus from the lungs. It has been defined as production of more than 100ml of mucus in 24 hours, which is more than is usually seen in chronic lung disease (e.g. chronic bronchitis typically produces 25ml/24hrs) 2. It may be a feature of:
Brudzinski sign occurs in meningitis, where passive flexion of one leg causes flexion in the opposite leg. Passive flexion of the neck brings about flexion of the legs as well.
First described by Jósef Brudziñski (1874-1917), Paediatrician from Warsaw, Poland 2.
Bubbly consolidation describes internal or central lucencies which represent normal aerated lung lobule within infrarcted, consolidated, lung parenchyma. It is one of the unique imaging appearances of focal pulmonary haemorrhage or possibly pulmonary infarct secondary to pulmonary embolism.
The bulging fissure sign refers to lobar consolidation where the affected portion of the lung is expanded. It is now rarely seen due to the widespread use of antibiotics.
The most common infective causative agents are 1:
Klebsiella pneumoniae: Klebsiella pneumonia
There are many bull's eye signs, also referred to as target signs:
red bone marrow located in shaft of long bone with central yellow marrow on MRI
peripheral plexiform neurofibromas on MRI
intussusception: see target sign of intussusception
choledocholithiasis: see target sign of choledochol...
Bullet and bodkin sign is the appearance of the ureter when there is an abrupt transition in the ureteral caliber. Bullet in the name is represented by the dilated proximal ureteric segment which appears to be perched on the constricted / non dilated encased ureter which gives an appearance of a...
Bullet shaped vertebra refers to the anterior beaking of the vertebral body.
It is seen in the following conditions:
mucopolysaccharidosis (Morquio disease, Hurler disease)
weapons and munitions inspired signs
Bunch-of-grapes sign refers to the ultrasound appearance of multiple cystic spaces within the uterus as the result of hydropic swelling of trophoblastic villi within a hydatidiform mole.
This sign is also described in bronchiectasis where on plain radiograph, the dilated bronchi in approximatio...
Butterfly gliomas are a high grade astrocytoma, usually a glioblastoma (WHO grade IV), which crosses the midline via the corpus callosum. Other white matter commissures are also occasionally involved. The term butterfly refers to the symmetric wing like extensions across the midline.
Butterfly sign refers to the normal appearance of bilateral choroid plexuses on axial imaging of the fetal brain, commonly observed on the antenatal ultrasound. Its absence may suggest holoprosencephaly 1.
In the CNS, the term should not be mistaken by butterfly glioma, which is a glioblastoma ...
Butterfly vertebra is a type of vertebral anomaly that results from the failure of fusion of the lateral halves of the vertebral body because of persistent notochordal tissue between them.
an anterior spina bifida, with or without an anterior meninogocoele
can be part ...
A button sequestrum is a small sequestrum of devascularised bone surrounded by lucency. Although classically described in osteomyelitis and eosinophilic granuloma it is also occasionally seen in fibrosarcoma and lymphoma.
The C sign is an important radiological sign which may be seen on a lateral radiograph of ankle in those with a tarsal coalition (talocalcaneal coalition).
A continuous C-shaped arc is seen on a lateral ankle radiograph which is formed by the medial outline of the tal...
The caecal bar sign is a secondary sign in acute appendicitis. It refers to the appearance of inflammatory soft tissue at the base of the appendix, separating the appendix from the contrast-filled caecum.
The callosal angle has been proposed as a useful marker of patients with idiopathic normal pressure hydrocephalus (iNPH), helpful in distinguishing these patients from those with ex-vacuo ventriculomegaly (see hydrocephalus versus atrophy).
Ideally the angle should be measured on a cor...
The calyceal crescent sign (Dunbar's crescents) refers to the early IVP appearance of markedly dilated renal calyces. It is formed by early contrast opacification of the dilated collecting ducts and ducts of Bellini with the characteristic shape as a result of the associated enlarged calyces.
Cannonball metastases refer to large, well circumscribed, round pulmonary metastases that appear, well, like cannonballs. The French term "envolée de ballons" which translates to "balloons release" is also used to describe this same appearance.
Metastases with such an appear...
The Capp triad refers to the constellation of clinical and imaging findings in patients with spontaneous retropharyngeal haematomas, and consists of:
tracheal and oesophageal compression
anterior displacement of the trachea
subcutaneous bruising over the neck and anterior chest
The caput medusae sign, refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus.
The sign is seen on both CT and ...
The caput medusae sign is seen in patients with severe portal hypertension. It describes the appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen to join the systemic veins.
The appearance is reminiscent of Medusa, a gorgon of...
Cardiac chamber enlargement can be recognised by cardiac contour changes, new or different interfaces with adjacent lung, and/or displacement of adjacent mediastinal structures. These are discussed separately:
right atrial enlargement
right ventricular enlargement
left atrial enlargement
The Carman meniscus sign describes the lenticular shape of barium in cases of large and flat gastric ulcers, in which the inner margin is convex toward the lumen. It usually indicates a malignant ulcerated neoplasm; in cases of benign gastric ulcers, the inner margin is usually concave toward th...
Cartilage interface sign, also referred as "double cortex sign", refers to the sonographic presence of a thin markedly hyperechoic line at the interface between the normally hypoechoic hyaline articular cartilage of the humeral head and an abnormally hypoechoic supraspinatus tendon, du...
Caton-Deschamps index is a ratio that is used in everyday practice as well as in research to measure patellar height and allows the diagnosis of patella alta and patella baja.
Caton-Deschamps index is the ratio between the distance between the lower pole of the patella an...
Celery stalk metaphysis refers to a plain film appearance of the metaphyses in a number of conditions characterised by longitudinally aligned linear bands of sclerosis. They are seen in:
The celery stalk sign is a term given to the appearance of the anterior cruciate ligament which has undergone mucoid degeneration and has been likened to that of a celery stalk. Its low signal longitudinal fibers are separated from each other by higher signal mucinous material, best seen on T2 ...
The centipede sign is seen as engorged mesenteric vessels in case of acute sigmoid diverticulitis which gives an appearance similar to centipede 1.
The cervicothoracic sign, a variant of the silhouette sign, is believed to have been coined by Benjamin Felson. It helps to discern the anterior or posterior location of a mass in the superior mediastinum on frontal chest radiographs.
As the anterior mediastinum ends at the level of the clavic...
The cervix sign of pyloric stenosis describes indentation of the pylorus into the fluid-filled antrum, seen in pyloric stenosis.
antral nipple sign
target sign of pyloric stenosis
shoulder sign of pyloric stenosis
The champagne glass pelvis is a helpful sign in achondroplasia which the iliac blades are flattened, giving rise to a pelvic inlet and resembles a champagne glass. The acetabular angles are increased, and the sacrosciatic notch is small.
The Chang sign refers to the dilatation and abrupt change in calibre of the main pulmonary artery due to pulmonary embolism 1.
knuckle sign in pulmonary embolism
"Chasing the dragon" is a sign seen in toxic leukoencephalopathy caused by inhalation of heroin fumes.
Three stages are recognised:
cerebellar signs and motor restlessness
pyramidal and pseudobulbar signs
spasms, hypotonic paresis, and ultimately death
Cheerio sign in thoracic imaging relates to pulmonary nodules with a central lucent cavity as seen on CT. It is due to proliferation of (malignant or non-malignant) cells around an airway. They are so named because of their resemblance to the breakfast cereal, Cheerios 1-2.
The Cheerio sign pu...