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.

45 results found
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H-shaped vertebra

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

The haematocrit effect with fluid-fluid levels is the result by layering of heavier cellular elements of blood located dependent to liquid supernatant may be seen on CT or MRI. It is most frequently seen in the setting of anticoagulation therapy or coagulopathy. See also signal flare phenomenon
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Haemosiderin cap sign

The haemosiderin cap sign refers to an MR imaging feature in some spinal tumours where a cap of T2 hypointense haemosiderin is above and/or below the tumour due to previous haemorrhage.  It is most often associated with spinal cord ependymomas, being seen in 20-33% of these cases 1. The sign ho...
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Hair on end sign

The hair on end sign refers to a radiographic appearance on a skull which results from a periosteal reaction manifesting as perpendicular trabeculations interspersed by radiolucent marrow hyperplasia along the skull vault. It is classically described with plain skull radiographs although can als...
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Hairy pleural plaques

The so-called hairy pleural plaque, are a manifestation of asbestos related disease. They arises 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...
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Halo sign (chest)

The halo sign (HS) in chest imaging is a feature seen on lung window settings (typically HRCT), ground glass opacity surrounding a pulmonary nodule or mass and represents haemorrhage. It is typically seen in angioinvasive aspergillosis. Pathology Histopathologically, it represents a focus of p...
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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 artery embolism ...
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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.
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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 fetus movemen...
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Harlequin eye deformity

The harlequin eye deformity may seen in unilateral (plagiocephaly) or bilateral (brachycephaly) coronal suture synostosis, and refers to the elevation of the superolateral corner of the orbit.
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Harrison's sulcus

Harrison's sulcus 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 is controversial altho...
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Hatchet sign of 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 rheumat...
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Hawkins sign

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

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

Head cheese, believe it or not, is not a cheese and is often not made of head. It is in fact a type of terrine, with bits of meat scavenged from various parts of various animals (including the head) usually from a calf or pig. It has a heterogeneous mosaic pattern, ranging from light to dark. T...
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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 < 21mm. However, in certain situations, this is increased: ...
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Hemithorax white-out

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? Trachea pulled toward the opacifie...
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Hennebert sign

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 Meniere disease. It has been postulated that the vestibular stimulation is mediated by fibrous bands between foo...
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Hidebound bowel sign

The hidebound 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 hidebound is use...
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High-attenuation crescent sign

The high attenuating crescent sign represents an acute haematoma 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 hype...
Article

Higoumenakis sign

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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Hill-Sachs lesion

Hill-Sachs lesions are a posterolateral humeral head compression fracture, typically secondary to recurrent anterior shoulder dislocations, as the humeral head comes to rest against the anteroinferior part of the glenoid. It is often associated with a Bankart lesion of the glenoid. Pathology I...
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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 mass/nodal enlargement. In the former, pulmonary vessels can be seen to converge and join a dilated pulmonary artery.  The sign was first described by Benjami...
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Hilum overlay sign

The hilum overlay sign refers to an appearance on frontal chest radiographs of patients with a mass projected at the level of the hilum which is in fact either anterior or posterior to the hilum. When a mass arises from the hilum, the pulmonary vessels are in contact with the mass and as such t...
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Hitchhiker thumb deformity

Hitchhiker thumb deformity refers to: flexion of the MCP and extension of distal interphalangeal joint of the thumb It is similar to how a person would normally angulate and hold out the thumb with the intension to hitchhike. It is one of the musculoskeletal manifestations of rheumatoid arthr...
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Hockey stick sign

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 (vCJD), which has the shape of a hockey stick. The hockey stick sign is also used sometimes to describe thyroid hemi...
Article

Hoffman-Rigler sign

The Hoffman-Rigler sign is a sign of left ventricular enlargement where an approximation of the distance between the inferior vena cava (IVC) and left ventricle is used.​ Radiographic features On a lateral chest radiograph, if the distance between the left ventricular border and the posterior ...
Article

Hole within a hole sign

The hole within a hole sign or (bevelled edge sign) is described with patient with eosinophilic granulomas. A bevelled edge of the defects indicates destruction of the two tables (e.g. of the skull) to a differing degree (more at the inner table), resulting in a formation of two different lucent...
Article

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

The Holman-Miller sign (also called antral sign) is seen in juvenile nasopharyngeal angiofibroma. The anterior bowing of the posterior wall of the maxillary antrum which is seen on lateral skull film or cross-sectional imaging 1-2. This is a nonspecific sign that can be produced by any slowly g...
Article

Honda sign

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

Honeycombing

Honeycombing refers to the computed tomographic (CT) manifestation of diffuse pulmonary fibrosis (usual interstitial pneumonia). The Fleischner Society definition is clustered cystic air spaces (between 3-10mm in diameter but occasionally as large as 2.5 cm) which are usually subpleural and basa...
Article

Hot cross bun sign

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...
Article

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

Howship-Romberg sign refers to obturator nerve neuropathy due to compression of it, by an obturator hernia. Patients present with pain and paresthesia along the inner aspect of the thigh, down to the knee.
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Hummingbird sign

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...
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's triad Hutchinson freckle Hutchinson teeth Hutchinson's sign Hutchinson syndrome History a...
Article

Hutchinson sign

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 nasal branch of the nasociliary nerve (branch of the ophthalmic division of the trigeminal nerve) and thus raises ...
Article

Hutchinson teeth

Hutchinson’s 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's triad Hutchinson pupil Hutchinson freckle Hutchinson's sign Hutchinson syndrome History and etymolo...
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's triad should not be confused with: Hutchinson ...
Article

Hydatid cyst signs

There are several signs in hydatid cyst are seen in 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 parasite into the cyst spin sign/whirl sign: deta...
Article

Hyoid elevation

Hyoid elevation is an indication on a modified barium swallow study that the pharyngeal muscles are contracting appropriately. Radiographic findings Modified barium swallow With real time fluoroscopy (or videofluoroscopy) during the act of swallowing, the larynx moves upward and forward when ...
Article

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 a inflammed epiploic appendix 1. On CT it can be seen as a ring of soft tissue surrounding a region of fat attenuation adjacent to ...
Article

Hypercontracting (nutcracker) oesophagus

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

Hyperdense MCA sign

The hyperdense MCA sign refers to the appearance of the middle cerebral artery (MCA) on CT. It has been associated with poor outcome, although this is by no means established 5. Radiographic features There is increased attenuation of the proximal portion of the MCA and it is often associated w...

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