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.

828 results found
Article

Foamy esophagus sign

Foamy esophagus is an appearance seen on a single contrast barium study in Candida esophagitis with associated scleroderma/achalasia (stasis). Pathology Pathophysiologic basis of the foamy esophagus is uncertain. Stasis is a predisposing factor. Foam is produced directly by the fungal organism...
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Focal hepatic hot spot sign

The focal hepatic hot spot sign can be seen on technetium 99m sulfur colloid scans of the liver and spleen. Radiographic features It occurs as a focal area of increased radiopharmaceutical uptake in the medial segment of the left hepatic lobe (segment IV) due to superior vena cava obstruction ...
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Fogging phenomenon

The fogging phenomenon is seen on non-contrast CT of the brain and represents a transient phase of the evolution of cerebral infarct where the region of cortical infarction regains a near-normal appearance.  {{youtube:http://www.youtube.com/watch?v=LuX3VV__2w0}} During the first week following...
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Football sign (pneumoperitoneum)

The football sign is seen in cases of massive pneumoperitoneum, where the abdominal cavity is outlined by gas from a perforated viscus. The median umbilical ligament and falciform ligament are sometimes included in the description of this sign, as representing the sutures. Which football is use...
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Fountain sign

The fountain sign is sonographic sign described in acute idiopathic scrotal edema (AISE). It refers to the appearance of the pattern of vascularity seen during transverse color Doppler sonography of the scrotum with both testes together1. In these transverse views in patients with AISE, marked ...
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Fragment-in-notch sign (knee)

The fragment-in-notch sign is closely related to, can be thought of as a failed, double PCL sign, in so far as it represents a meniscal fragment lying in the intercondylar notch, but not paralleling the posterior cruciate ligament (PCL).  Although both signs are most frequently seen in the sett...
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Frimann-Dahl sign

The Frimann-Dahl sign is a diagnostic sign demonstrated when three dense lines, representing the sigmoid walls, are seen converging to the site of obstruction in sigmoid volvulus and associated with empty rectal gas 1. History and etymology Johan Frimann-Dahl (1902-82) was a Norwegian Professo...
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Frostberg inverted 3 sign

Frostberg inverted 3 sign is a radiological sign seen on a barium examination where there is effacement and distortion of the mucosal pattern on the medial wall of the second part of the duodenum due to focal mass and local edema. It is most commonly associated with carcinoma of the head of the ...
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Fruit-inspired signs

There are many fruit-inspired signs in radiology: apple core sign (colon) apple core sign (femur) apple-peel intestinal atresia banana sign banana fracture berry aneurysm bunch of grapes sign lemon sign pear-shaped bladder strawberry gallbladder strawberry skull
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Funneling of the internal cervical os

Cervical funnelling is a sign of cervical incompetence and represents the dilatation of the internal part of the cervical canal and reduction of the cervical length. Greater than 50% funnelling before 25 weeks is associated with ~80% risk of preterm delivery. Radiographic features Good scanni...
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Funnel trachea

Funnel trachea is a colloquialism for a congenital long-segment intrathoracic tracheal stenosis.  The diameter of the trachea immediately below the cricoid is normal, and becomes progressively more stenotic caudally. The posterior, membranous portion of the trachea may be partially or completel...
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Gage sign

Gage sign is a V-shaped lucent defect at the lateral portion of the epiphysis and/or adjacent metaphysis. It is pathognomonic for Legg-Calve-Perthes disease. It may occur early in the disease and is one of the five indicators of a worse prognosis, which are: Gage sign  calcification lateral t...
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Galaxy sign (lungs)

The so-called galaxy sign, initially described as the sarcoid galaxy, represents a coalescent granuloma seen in a minority of patients with pulmonary sarcoidosis 1. The same appearance can be seen in tuberculosis 2,3. In other words, it represents a mass-like region composed of numerous smaller ...
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Garland triad

Garland triad, also known as the 1-2-3 sign or Pawnbrokers sign, is a lymph node enlargement pattern on chest radiographs which has been described in sarcoidosis: right paratracheal nodes right hilar nodes left hilar nodes Hilar lymphadenopathy is symmetrical and usually massive. These so-ca...
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Garrington sign (teeth)

Garrington sign is thickening of the periodontal ligament/membrane space of involved teeth in the setting of gnathic osteosarcoma. Symmetrical widening of the space can be seen early in the disease process due to infiltration of tumor cells. 
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Genu recurvatum

Genu recurvatum describes the malalignment or deformity of the knee joint with extension beyond neutral (i.e. hyperextension).  Pathology Genu recurvatum can be associated with subluxation or dislocation of the knee joint.  Etiology congenital arthrogryposis multiplex congenita congenital ...
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Geographic skull

A geographic skull is a radiographic appearance which is seen in eosinophilic granuloma (EG) and characterized by destructive lytic bone lesions, the edges of which may be bevelled, scalloped or confluent. See also geographic appearance
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Geyser sign (shoulder)

The geyser sign may occur in some cases of long-standing rotator cuff tear and advanced degenerative change of the shoulder.  Clinical presentation It may present as a pseudotumour above the AC joint. Pathology Chronic rotator cuff degenerative change and full-thickness tearing leads to inst...
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Ghon lesion

A Ghon lesion (sometimes called Ghon focus) represents a calcified tuberculous caseating granuloma (tuberculoma) and represents the sequelae of primary pulmonary tuberculosis infection. When associated with a calcified ipsilateral hilar node it is known as a Ranke complex. History and etymolog...
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Ghost meniscus

A ghost meniscus, also known as the empty meniscus sign, refers to a large radial tear that has completely transected the meniscus or, alternatively, previous meniscectomy. Radiographic features MRI On MRI knee when the slice plane is exactly in line with the meniscal tear this can produce ei...
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Ghost sign (cervical spine)

The ghost sign is a feature that has been described in a clay shoveler fracture as seen on the AP projection of a cervical spine radiograph. It is caused by the appearance of a "double spinous process" on C6 or C7 resulting from caudal displacement of the avulsed spinous process fragment, giving...
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Ghost sign (Charcot joint)

The ghost sign is seen when a Charcot joint is complicated by an osteomyelitis. It is most commonly seen in the setting of a diabetic foot.  It refers to the poor definition of the margins of a bone on a T1 weighted image, which reappears after contrast injection 1.
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Ghost vertebra

Ghost vertebra is a sign, that is generally used synonymously with bone-within-a-bone vertebra, and as such, the causes form a subset of those causing bone within a bone appearance 2: Thorotrast administration: bone within a bone appearance due to temporary growth arrest 1 stress line rickets...
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Ginkgo leaf sign (chest)

The ginkgo leaf sign of the chest, also referred as the ginkgo leaf sign of subcutaneous emphysema, is a radiograph appearance which is seen with extensive subcutaneous emphysema of the chest wall. Gas outlines the fibers of the pectoralis major muscle and creates a branching pattern that resemb...
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Girdlestone procedure

The Girdlestone procedure (also known as a femoral head ostectomy or Girdlestone resection arthroplasty) is an excision arthroplasty of the hip. The procedure inevitably results in limb shortening. Indications  peri-prosthetic infection aseptic loosening recurrent dislocation failed interna...
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Glenoid labrum ovoid mass sign

The glenoid labrum ovoid mass (GLOM) sign (seen on MRI) is useful when a torn anterior glenoid labrum retracts superiorly.  Seen typically on a T2 axial image through the glenohumeral joint as a low signal ovoid mass anterior to the glenoid labrum.  Sometimes this can be the only sign of a torn...
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Goblet sign (ureter)

The goblet sign, also known as the champagne glass sign, refers to the appearance of the ureter when it is focally dilated by an intraluminal mass. It is best seen when the ureter is opacified by retrograde contrast (retrograde ureterogram). Presence of this sign indicates the pathology to be ch...
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Golden arches sign (knees)

The Golden arches sign is a nuclear medicine sign often seen on bone scan in patients with total knee prosthesis. The femoral condylar prosthesis results in two central photopenic regions with two 'hot' arches formed around the periprosthetic region. This finding is non-specific and may sugges...
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Golden S-sign (lung lobe collapse)

The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden. Although typically seen with right upper lobe collapse, the S-sign can also be seen with the...
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Grey cortex sign (stress fracture)

The grey cortex sign was described as an early sign of stress (fatigue) fractures on plain radiographs and refers to subtle ill-definition/lucency of the cortex at the site of microfracture. However, plain radiography is insensitive (~25%, range 15-25%) for the detection of early-stage injuries....
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Griesinger sign (mastoid)

Griesinger sign, named after Wilhelm Griesinger, a German psychiatrist and neurologist (1817-1868) 3 refers to edema of the postauricular soft tissues overlying the mastoid process as a result of thrombosis of the mastoid emissary vein. It is a complication of acute otomastoiditis and may be ass...
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Gull-wing appearance (phalanges)

The gull-wing appearance (also known as seagull erosions) is seen in erosive osteoarthritis, typically on posteroanterior radiographs. The combination of cartilage space loss, central subchondral erosions, and marginal osteophyte proliferation results in a gull-wing appearance.
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Gut signature sign

The gut signature sign is an ultrasound term used to describe the appearance of the gastrointestinal wall. Radiographic features  Ultrasound The bowel wall has five layers, composed of alternating hyperechoic and hypoechoic appearances. Anatomically these layers are as follows (innermost to o...
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Guttman test (larynx)

The Guttman test is a clinical test relating to the function of the larynx. In normal subjects, frontal pressure on the thyroid cartilage lowers the tone of voice produced and lateral pressure produces a higher tone of voice. The opposite is true with paralysis of the cricothyroid muscle.
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Hematocrit effect

The hematocrit effect with fluid-fluid levels is the result by layering of heavier cellular elements of blood located dependent to a liquid supernatant. It can be seen on CT or MRI. It is most frequently seen in the setting of anticoagulation therapy or coagulopathy. See also signal flare phen...
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Hemorrhage exclusion sign (prostate)

The hemorrhage exclusion sign can be a useful MRI finding following prostate biopsy. Pathology The normal prostate produces high concentrations of citrate, which among other properties, acts as an anticoagulant 1. As tumor cells are dysfunctional, they will produce lower levels of citrate than...
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Hemosiderin cap sign

The hemosiderin cap sign refers to an MR imaging feature in some spinal tumors where a cap of T2 hypointense hemosiderin is above and/or below the tumor due to previous hemorrhage.  It is most often associated with spinal cord ependymomas (20-33% of cases) 1. It may also be seen in hemangioblas...
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Hair on end sign (mnemonic)

The hair on end sign refers to a radiographic appearance of the diploic space of the skull vault which results from a thickening of trabeculae as the diploic space expands. These trabeculae are perpendicular in orientation, interspersed by radiolucent marrow hyperplasia along the skull vault. I...
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Hairy kidney sign (Erdheim-Chester disease)

The hairy kidney sign refers to the soft tissue rind of perirenal infiltration seen on cross-sectional imaging studies in Erdheim-Chester disease, and is considered to be pathognomonic of this disease. The ‘‘hairy’’ description refers to the associated thickening of the bridging perirenal septa ...
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Hairy pleural plaque

Hairy pleural plaques are a manifestation of asbestos-related disease. They arise from the visceral pleura, typically from an interlobar fissure. The hairiness stems from short radially-oriented linear regions of fibrosis extending from the plaque into the adjacent lung parenchyma. Compared to ...
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Halo sign (chest)

The halo sign in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents hemorrhage. It is typically seen in angioinvasive aspergillosis. Pathology Histopathologically, it represents a focus of pulmona...
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Hampton hump

Hampton hump refers to a dome-shaped, pleural-based opacification in the lung most commonly due to pulmonary embolism and lung infarction (it can also result from other causes of pulmonary infarction (e.g. vascular occlusion due to angioinvasive aspergillosis). While a pulmonary embolism is expe...
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Hampton line

The Hampton line is a thin millimetric radiolucent line seen at the neck of a gastric ulcer in barium studies (profile view), indicating its benign nature. It is caused by a thin line of mucosa overhanging the ulcer's crater. History and etymology It was originally described by Aubrey Otis Ham...
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Hanging noose sign

Hanging noose sign in obstretric imaging is a rarely described but classical finding of a true umbilical cord knot. It demonstrates a transverse section of the umbilical cord surrounded by a loop of umbilical cord and changes in the pressure of the knot can be demonstrated with the fetal movemen...
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Harlequin eye deformity

The harlequin eye deformity may be seen in unilateral (plagiocephaly) or bilateral (brachycephaly) coronal suture synostosis, and refers to the elevation of the superolateral corner of the orbit. The term harlequin eye derives from the appearance of the eyes on a harlequin mask with their exagg...
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Harrison's sulcus

Harrison's sulcus or Harrison's groove refers to a groove at the lower end of the rib cage seen in young children / infants with abnormally weak bones (e.g. rickets) or chronic respiratory disease (e.g. severe asthma). The lower chest is drawn in with flaring of the rib margin. The exact cause i...
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Hatchet sign (ankylosing spondylitis)

Hatchet sign refers to the limited erosion of the lateral aspect of humeral head that produces a hatchet shaped deformity. This finding is typically associated with ankylosing spondylitis. In the absence of osteoporosis and presence of sclerosis this sign helps to differentiate it from rheumato...
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Hawkins sign (talus)

Hawkins sign describes subchondral lucency of the talar dome that occurs secondary to subchondral atrophy 6-8 weeks after a talar neck fracture 1. This indicates that there is sufficient vascularity in the talus, and is therefore unlikely to develop avascular necrosis later 2,3. Disruption of ...
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Haystack sign (pneumomediastinum)

The haystack sign on chest x-rays in pediatric patients is indicative of pneumomediastinum. The pediatric heart is surrounded above and below with gas, giving it an appearance of a haystack from Monet's paintings. 
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Head cheese sign (lungs)

The head cheese sign refers to a juxtaposition of regions with three different densities: ground glass opacities (high attenuation) mosaic attenuation pattern (low attenuation) normal lung tissue (normal attenuation) A mixed infiltrative (ground glass opacity) and obstructive (mosaic attenua...
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Heel pad sign

Increased heel pad thickness, also known as the heel pad sign, is seen in a number of conditions and relates to an increase in the soft-tissue thickness of the heel pad on lateral ankle radiographs.   The heel pad should normally be <21 mm. However, in certain situations, this is increased: ac...
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Hemithorax white-out (differential)

Complete white-out of a hemithorax on the chest x-ray has a limited number of causes. The differential diagnosis can be shortened further with one simple observation: the position of the trachea. Is it central, pulled or pushed from the side of opacification? Is there pulmonary volume loss or vo...
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Hennebert sign (inner ear)

The Hennebert sign describes a positive fistula test without clinical evidence of middle ear or mastoid disease. It is associated with congenital syphilis and may also be present in Ménière disease. It has been postulated that the vestibular stimulation is mediated by fibrous bands between foot...
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Hepatic edge sign

The hepatic edge sign is a radiographic sign of pneumoperitoneum seen on a supine plain abdominal radiograph. It is represented by a cigar-shaped pocket of free air in the subhepatic region, which tracks superomedial following the contour of the liver.
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Hide-bound sign (bowel)

The hide-bound bowel sign refers to an appearance on a barium study of the small bowel in patients with scleroderma. The sign describes the narrow separation between the valvulae conniventes which are of normal thickness despite dilatation of the bowel lumen.   Although the term hide-bound is u...
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High-attenuation crescent sign

The high attenuating crescent sign represents an acute hematoma within either the mural thrombus or the aneurysm wall, especially when detected on unenhanced CT scans. It is a specific sign of impending abdominal aortic aneurysm (AAA) rupture or so-called contained rupture. Pathology The hyper...
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Higoumenakis sign (clavicle)

Higoumenakis sign is the unilateral enlargement of the sternal end of the clavicle in patients with late congenital syphilis. Pathology Treponema pallidum becomes readily localized in the lymphatic spaces and may remain in the connective tissues without manifestation in childhood. Through mech...
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Hilum convergence sign

The hilum convergence sign is a useful chest radiograph sign to help distinguish a bulky hilum due to pulmonary artery dilatation from a juxtahilar mass/nodal enlargement.  If pulmonary artery branches are visible through the opacity and converge towards the waist of the heart (positive hilum c...
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Hilum overlay sign

The hilum overlay sign is useful in differentiating cardiac enlargement from a mediastinal mass. It refers to an abnormally dense hilum on frontal chest radiograph with preserved visualization of the hilar vessels.   If a mass arises from the hilum, the normal pulmonary vessels (interlobar arte...
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Hitchhiker thumb deformity

Hitchhiker thumb deformity refers to: flexion of the metacarpophalangeal joint and extension of the distal interphalangeal joint of the thumb It is used to both describe the appearance of the thumb on physical examination and also the corresponding radiographic appearance. It is similar to ho...
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Hockey stick sign (Creutzfeldt-Jakob disease)

The hockey stick sign refers to the hyperintense signal involving the pulvinar and dorsomedial thalamic nuclei bilaterally on FLAIR, in cases of variant Creutzfeldt-Jakob disease, which has the shape of a hockey stick. See also pulvinar sign (Creutzfeldt-Jakob disease) hockey stick sign (thyr...
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Hockey stick sign (thyroid hemiagenesis)

Hockey stick sign has been used to describe the appearance of the thyroid gland in cases of thyroid hemiagenesis, when investigated with 99m technetium pertechnetate thyroid scan 1. The unilateral lobe and isthmus make a shape reminiscent of a hockey stick.  See also hockey stick sign (Creutzf...
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Hoffman-Rigler sign (heart)

The Hoffman-Rigler sign is a sign of left ventricular enlargement inferred from the distance between the inferior vena cava (IVC) and left ventricle (LV).​ Radiographic features On a lateral chest radiograph, if the distance between the left ventricular border and the posterior border of IVC e...
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Hole within a hole sign

The hole within a hole sign or bevelled edge sign describes one classic appearance of lytic skull lesions in patients with eosinophilic granuloma. The bevelled edge of the defects indicates asymmetrical destruction of both inner and outer tables of the skull, giving the appearance of two overlap...
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Holly leaf sign

The holly leaf sign refers to the appearance of pleural plaques on chest x-rays. Their irregular thickened nodular edges are likened to the appearance of a holly leaf.
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Holman-Miller sign (maxillary sinus)

The Holman-Miller sign (also called the antral sign) is seen in juvenile nasopharyngeal angiofibroma; it refers to the anterior bowing of the posterior wall of the maxillary antrum as seen on a lateral skull radiograph or cross-sectional imaging 1,2. This is a non-specific sign that can be prod...
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Honda sign (sacrum)

The Honda sign (H sign / H pattern) is a term used to describe the appearances of bilateral sacral insufficiency fractures on a radioisotope bone scan. Radiographic features Sacral insufficiency fractures are usually vertically through the sacral alae, paralleling the sacroiliac joint, often w...
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Honeycombing (lungs)

Honeycombing is a CT imaging descriptor referring to clustered cystic air spaces (between 3-10 mm in diameter but occasionally as large as 2.5 cm) which are usually subpleural and basal in distribution. They can be subdivided into: microcystic honeycombing macrocystic honeycombing The walls o...
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Hot cross bun sign (pons)

The hot cross bun sign refers to the MRI appearance of the pons in a variety of neurodegenerative diseases.  T2 hyperintensity forms a cross on axial images through the pons, representing selective degeneration of pontocerebellar tracts. It has been described in 1: multiple system atrophy (MSA...
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Hot nose sign

The hot nose sign refers to increased perfusion in the nasal region on nuclear medicine cerebral perfusion studies in the setting of brain death. The absent or reduced flow in the internal carotid arteries is thought to lead to increased flow within the external carotid arteries and subsequent i...
Article

Howship-Romberg sign

The Howship-Romberg sign refers to obturator nerve neuropathy due to compression of the obturator nerve by an obturator hernia. Patients present with pain and paraesthesia along the inner aspect of the thigh, down to the knee. History and etymology Named after Moritz Heinrich Romberg (1795-187...
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H-shaped vertebra

H-shaped vertebrae, also known as Lincoln log vertebrae, are a characteristic finding of sharply delimited central endplate depression, classically seen in approximately 10% of patients with sickle-cell anemia, and results from microvascular endplate infarction (figure 1) 3. It may occasionally...
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Hummingbird sign (midbrain)

The hummingbird sign, also known as the penguin sign, refers to the appearance of the brainstem in patients with progressive supranuclear palsy (PSP).  The atrophy of the midbrain results in a profile of the brainstem (in the sagittal plane) in which the preserved pons forms the body of the bir...
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Humpback deformity of the scaphoid

Humpback deformity of the scaphoid results from volar angulation of the proximal and distal poles of the scaphoid in the setting of scaphoid fracture through the waist 1. The dorsal component forms a 'humpback' which can be palpated. It is important to identify as it can result in a progressive...
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Hurley stick ureters

Hurley stick ureters refers to the widening of the distal ureters with abnormal lateral and upward curvature instead of normal oblique intramural course in excretory urogram. The appearance of distal ureter resembles hurley stick used in the traditional Iris game of hurling. This is seen in blad...
Article

Hutchinson pupil

Hutchinson pupil is a fixed and dilated pupil caused by compression of the oculomotor nerve (CN III) as a result of uncal herniation. It should not be confused with any of the following: Hutchinson triad Hutchinson freckle Hutchinson teeth Hutchinson sign Hutchinson syndrome History and e...
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Hutchinson sign (disambiguation)

The Hutchinson sign can refer to two signs.  Hutchinson sign (ophthalmology) Relates to involvement of the tip of the nose from facial herpes zoster. It implies involvement of the external nasal branch of the nasociliary nerve (branch of the ophthalmic division of the trigeminal nerve) and thu...
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Hutchinson teeth

Hutchinson teeth are smaller and more widely spaced than normal and are notched on their biting surfaces. It is a sign of congenital syphilis and should not be confused with: Hutchinson triad Hutchinson pupil Hutchinson freckle Hutchinson sign Hutchinson syndrome History and etymology Na...
Article

Hutchinson triad

Hutchinson triad of congenital syphilis consists of: dental abnormalities interstitial keratosis deafness History and etymology Named after Sir Johnathan Hutchinson, English surgeon, ophthalmologist and pathologist (1828 - 1913). Hutchinson triad should not be confused with: Hutchinson pu...
Article

Hydatid cyst signs

There are several signs of hydatid cysts seen associated with hydatid disease: cumbo sign: air is seen between the pericyst and the laminated membrane of the cyst  serpent sign: internal rupture of the cyst with collapse of membranes of the parasite into the cyst water lily sign: endocyst flo...
Article

Hyoid elevation

Hyoid elevation on a modified barium swallow study indicates that the pharyngeal muscles are contracting appropriately. Radiographic features Modified barium swallow With real time fluoroscopy (or videofluoroscopy) during the act of swallowing, the larynx moves upward and forward when there i...
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Hyperattenuating ring sign in epiploic appandagitis

The hyperattenuating ring sign is a sign that has been described with epiploic appendagitis and refers to a hyperattenuating ring of visceral peritoneum surrounding an inflamed epiploic appendage 1. On CT it can be seen as a ring of soft tissue surrounding a region of fat attenuation adjacent to...
Article

Hypercontracting (nutcracker) esophagus

Hypercontracting (nutcracker) esophagus is a motility disorder of the esophagus. This condition is primarily diagnosed with manometry with high intra-esophageal pressure and normal peristalsis. Most patients will have a normal barium swallow.  Hypercontracting esophagus ("nutcracker esophagus")...
Article

Hyperdense MCA sign (brain)

The hyperdense MCA sign refers to focal increased density of the middle cerebral artery (MCA) on CT and is a direct visualization of thromboembolic material within the lumen. It is thus the earliest visible sign of MCA infarction as it is seen within 90 minutes after the event 1. It is the longi...
Article

Hypomelanotic macules

Hypomelanotic macules are otherwise known as ash-leaf spots due to their resemblance to Sorbus aucuparia, or mountain-ash, leaves. These macules have a strong association with tuberous sclerosis and are often multiple and present in the vast majority of individuals with the condition (up to 97% ...
Article

Ice cream cone sign (disambiguation)

The ice cream cone sign may refer to: the appearance of the head of malleus and the body and short process of the incus on axial CT scan: failure of this normal configuration suggests incudomalleolar dysarticulation the ball of the ice cream is formed by the head of the malleus and cone is for...
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Ice pick sign

The ice pick sign is a smooth tapered narrowing of the upstream pancreatic duct distal to the pancreatic lesion seen frequently in benign pancreatic lesions such as a focal autoimmune pancreatitis, this is due to the extrinsic narrowing of the duct secondary to periductal fibrosis and inflammati...
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Imaging psoas sign (spondylodiscitis)

The imaging psoas sign is an MRI finding specific for spondylodiscitis and is seen as T2 hyperintensity in the psoas major muscle. The sign has a high sensitivity (92%) and specificity (92%) for spondylodiscitis and in the clinical context of a suspected infective process of the spine supports c...
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Inanimate object inspired signs

Inanimate object inspired signs are numerous with many radiographic appearances likened to bottles, hooks, items of clothing, weapons etc.  They are listed below in the 'related articles' section. 
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Incomplete border sign

The incomplete border sign is useful to depict an extrapulmonary mass on chest radiograph. An extrapulmonary mass will often have a inner well-defined border and an ill-defined outer margin 1-3. This can be attributed to the inner margin being tangential to the x-ray beam and has good inherent ...
Article

Infundibulum sign (pituitary)

The infundibulum sign is helpful in distinguishing an empty pituitary sella from a cystic lesion of the pituitary region 1.  In the former, although the sella is enlarged, there is no mass as such and the pituitary infundibulum traverses the enlarged sella to its floor where residual pituitary ...
Article

Interface sign (HRCT chest)

The interface sign is a feature seen on HRCT chest imaging and refers to the presence of irregular interfaces at the margins of pulmonary parenchymal structures or the pleural surface of the lung. It suggests interstitial thickening.
Article

Interstitial line sign

The interstitial line sign is an ultrasound finding in interstitial ectopic pregnancy. It is an echogenic line from the mass to the endometrial echo complex. Reportedly it has high sensitivity (80%) and specificity (98%).

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