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.

60 results found
Article

Pancake brain

Pancake brain, is the classical sign of alobar holoprosencephaly. It is due to fusion of the cerebral hemispheres leaving a single ventricle in its center. It is the most severe form of holoprosencephaly. It is associated with multiple facial abnormalities. See also pancake vertebra vegetable...
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Panda sign

The humble panda has a few signs to its name: panda sign of the midbrain panda sign of sarcoidosis See also animal and animal produce inspired signs
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Panda sign of sarcoidosis

The panda sign of sarcoidosis is a gallium-67 citrate scan finding. It is due to bilateral involvement of parotid and lacrimal glands in sarcoidosis, superimposed on the normal uptake in the nasopharyngeal mucosa. The presence of perihilar adenopathy adds the lambda distribution of increased up...
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Panda sign of the midbrain

The panda sign in neuroimaging refers to the appearance of the midbrain, when the red nucleus and substantia nigra are surrounded by high T2 signal. It is classically seen in Wilson disease, although whenever the white matter is diffusely abnormal in the region a similar appearance will be perc...
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Panzerherz

Panzerherz (or armoured heart) is a term used to describe the appearance of the heart in calcified constrictive pericarditis. The pericardium becomes circumferentially thickened with calcification, limiting the ability of the heart to contract. The rim of dense calcification describes how the h...
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Papilloedema

Papilloedema is essentially an ophthalmoscopic diagnosis and refers to swelling of the optic disc. The MRI appearance relates to the dural anatomy of the optic nerve, which is continuous with the subarachnoid space, thereby allowing increased intracranial pressure (ICP) to be transmitted to the ...
Article

Parrot beak tear of meniscus

A parrot beak meniscal tear is a type of oblique meniscal tear which is connected in one plane and and displaced in the other plane. Its appearance on axial images is curved like a crescent and is likened to that of a parrot's beak. The tear gap has a curved V-shape.  Some authors advise that t...
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Pear-shaped bladder

Pear-shaped (or tear-drop-shaped) bladder is one whose normal round or ovoid shape has been extrinsically compressed to resemble a pear. The pear may be inverted or upright, depending on how the excess pelvic tissue compresses the bladder. Pathology Aetiology Causes of a pear-shaped bladder i...
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Pearl necklace sign

The pearl necklace sign occurs in adenomyomatosis of the gallbladder, on both oral cholecystograms and MRCP. It represents the contrast / fluid-filled intramural mucosal diverticula (Rokitansky-Aschoff sinuses); lined up, these are reminiscent of pearls on a necklace. It is synonymous with the C...
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Peg like tonsils

Peg like tonsils refer to CT or MR appearances of pointed cerebellar tonsils on sagittal scans.  The may help distinguish tonsillar ectopia from a Chiari 1 malformation.
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Pelvic tear drop

The pelvic tear drop (also known as U-figure) is a radiographic feature seen on pelvic x-rays and results from the the end-on projection of a bony ridge running along the floor of the acetabular fossa. This was shown to be the case by demonstrating that sawing away this bony plate made the feat...
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Penumbra sign

The penumbra sign represents a rim of vascularized granulation tissue around a bone abscess cavity that has a higher T1 signal intensity than the cavity itself 1.  It should not be confused with the ischaemic penumbra of cerebral infarction.  The penumbra is isointense to muscle on T1, enhance...
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Pepperpot skull

Pepperpot skull is occasionally used in place of salt and pepper skull to describe the typical radiographic appearance of multiple small radiolucent lesions of the skull vault. This is clasically seen in hyperparathyroidism2, and is occasionally used (inaccurately) to describe the raindrop skul...
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Peri-bronchial cuffing

Peri-bronchial cuffing refers to a radiographic (usually plain film but sometimes CT) descriptive term to describe hazyness around a bronchus or large bronchiole seen end on (plain film). When viewed tangentially this can give the appearance of a tram line 3. It is sometimes described as a "...
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Pericardial calcification

Pericardial calcification (PC) usually occurs in patients with a history of pericarditis.  Pathology Causes uraemia previous trauma or prior pericarditis later sequelae of rheumatic heart disease malignant pericardial involvement (e.g. mediastinal teratoma) On chest radiography, location ...
Article

Perilymphatic fistula

A perilymphatic fistula (PLF) (also known as a labyrinthine fistula) is a pathologic communication between the fluid-filled space of the inner ear and the air-filled space of the middle ear, most commonly occurring at either the round or oval window. The primary manifestations of perilymphatic...
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Perinephric stranding

Perinephric stranding refers to the appearance of oedema within the fat of the perirenal space on CT or MRI. While a degree of symmetric bilateral perinephric stranding is common, particularly in the elderly, asymmetric or unilateral perinephric stranding is an important sign of renal inflammati...
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Periportal halo

Periportal halo or periportal collar sign is a zone of low attenuation seen around the portal vein on contrast enhanced CT. Periportal halos may occur around the central portal veins or their peripheral branches.  Pathology Aetiology This sign is seen when there is fluid accumulation or dilat...
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Perirenal cobweb

Perirenal cobwebs is the presence of prominent perinephric septae. It is best appreciated on CT images. Pathology The cobweb is considered to be due to engorged venous collaterals or due to edema and fluid extravasation into the perirenal space 1. Perirenal cobwebs may be seen in many benign ...
Article

Phantom calyx

Phantom calyx is a calyx which fails to fill with contrast admist a well opacified remainder of pyelocalyceal system. It refers to an intrarenal process which has infilterated and caused obliteration of the involved collecting system element. It may be seen in: tumour: especially transitional ...
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Phemister triad

The triad of Phemister refers to three features seen classically with tuberculous arthropathy: juxta-articular osteopaenia/osteoporosis peripheral osseous erosions gradual narrowing of joint space
Article

Phrygian cap

Phrygian caps are the most common congenital anatomic variant of the gallbladder. It denotes folding of the fundus back upon the gallbladder body and is asymptomatic with no pathological significance. Radiographic findings A Phrygian cap may be identified in ultrasound, multiphase CT/MRI or in...
Article

Picture frame vertebral body

Picture frame vertebral body is a radiologic appearance in which the cortex of the vertebral body is thickened. This sign is seen in a patient with Paget disease.  This is a result of disorganized new cortical bone formation after excessive osteoclastic activity causes the resorption of normal ...
Article

Piece of pie sign

The piece of pie sign refers to an abnormal triangular appearance of the lunate on an PA image of the wrist indicating lunate dislocation or perilunate dislocation 1-2. A lateral image will help differentiate whether there is lunate or perilunate dislocation with lunate dislocation demonstrating...
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Pine cone bladder

A pine cone bladder or christmas tree bladder is a cystogram appearance in which the bladder is elongated and pointed with thickened trabeculated wall. It is typically seen in severe neurogenic bladder with increased sphincter tone (detrusor sphincter dyssynergia) due to suprasacral lesions (abo...
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Pistol grip deformity of the hip

The pistol grip deformity is considered a typical radiographic sign of cam-type femoro-acetabular impingement. The shape of the proximal femur is reminiscent of a flintlock pistol known from old pirate movies. History and etymology It was first described by Stulberg and co-workers in 1975 1.
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Pitt pit

Pitt pit refers to an oval or round lucency in the anterosuperior aspect of the femoral neck, just distal to the articular surface. It represents a herniation of synovium or soft tissues into the bone through a cortical defect, hence the alternate name synovial herniation pit. They are usually a...
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Pleural mouse

A pleural mouse (also known as a fibrin body), is a 1-2 cm mobile rounded clump of fibrin left over after resolution of a pleural effusion.
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Pneumothorax in supine projection

A pneumothorax does not display classical signs when a patient is positioned supine for a chest radiograph. Instead, the pneumothorax may be demonstrated by looking for the following signs: relative lucency of the involved hemithorax deep, sometimes tongue-like, costophrenic sulcus: deep sulcu...
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Pneumothorax: ultrasound

Pneumothorax is a serious potential consequence of blunt thoracic trauma and, if misdiagnosed, it may quickly become life-threatening. For a discussion on epidemiology, clinical presentation, pathology, and treatment and prognosis please see the main pneumothorax article.  Radiographic feature...
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Polka-dot sign

Polka dots refer to a clothing pattern consisting of equally sized and spaced filled circles. It is generally confined to more playful attire e.g. bathing suits and lingerie 1.  In medical imaging, this pattern can be found on transverse CT (white on black) or MR (black on white) sections of th...
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Polo mint sign

The polo mint sign is a description given to a venous thrombosis on contrast enhanced CT imaging.  When viewed in the axial plane, a thin rim of contrast persists around a central filling defect due to thrombus. This gives an appearance like that of the popular mint sweet, the polo, also referre...
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Popcorn calcification

Popcorn calcification refers to amorphous calcifications often with rings and arcs that resemble popped corn kernels. This type of calcification may be seen in many radiological settings including 1: chondroid lesions (e.g enchondroma, chondrosarcoma) fibrous dysplasia pulmonary hamartomas d...
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Popcorn calcification within the breast

Popcorn calcification in the breast is the classical description for the calcification seen in involuting fibroadenomas, which as the name suggests has a pop corn like appearance.  Pathology A fibroadenoma in the long run may degenerate and calcify. Initially there are a few punctate periphera...
Article

Porcelain gallbladder

Porcelain gallbladder refers to extensive calcium encrustation of the gallbladder wall. The term has been used to emphasise the blue discoloration and brittle consistency of the gallbladder wall at surgery. Often an incidental finding on multiple different modalities, CT can be used to confirm t...
Article

Porcelain left atrium

Porcelain left atrium (or coconut left atrium) is a term used when a large part of or the entire left atrial wall becomes calcified. It can occur as a rare consequence of endocarditis (with underlying rheumatic heart disease). It has also been described in the setting of end stage renal disease ...
Article

Positive carpal sign

The positive carpal sign is a useful radiographic sign for the diagnosis of Turner's syndrome in association with the other musculoskeletal manifestation. Radiographic features Abnormality in the shape of the proximal carpal row in the dorsopalmar radiographs of the wrist and hand (taken in th...
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Positive metacarpal sign

In the metacarpal sign, a line drawn along the heads of the 4th and 5th metacarpals will intersect the head of the 3rd metacarpal if shortening is present. The shortened 4th metacarpal is the key to the sign. The sign is positive in up to 9.6% of normal individuals 3. It is however seen in a va...
Article

Positive PCL line sign

Positive PCL line sign is an indirect sign of anterior cruciate ligament (ACL) tear based on secondary changes of the posterior cruciate ligament (PCL) on MRI images. A line tangent to the upper border of the PCL should normally intersect medullary cavity of the distal femur, if it does not, it ...
Article

Posterior fat pad sign

The posterior fat pad sign is the visualisation of a lucent crescent of fat located in olecranon fossa on true lateral view of elbow joint with the elbow flexed at a right angle, and it indicates an elbow joint effusion. Normally, the posterior fat pad will not be seen on this view.  In an appr...
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Posterior pituitary bright spot

The posterior pituitary bright spot (PPBS) is a MRI feature of the normal pituitary gland. It refers to the intrinsically high T1 signal of the posterior pituitary thought to be from the storage of vasopressin, which has a T1-shortening effect 2. It is important to note that a posterior pituita...
Article

Powers ratio

Powers ratio is a measurement of the relationship of the foramen magnum to the atlas, used in the diagnosis of atlanto-occipital dissociation injuries. The ratio, AB/CD, is measured as the ratio of the distance in the median (midsagittal) plane between the: basion (A) and the posterior spinola...
Article

Prévost sign

The Prévost sign refers to deviation of the eyes away from the hemiparesis in acute cortical hemiparetic stroke. Therefore, the eyes are deviated towards the involved hemisphere and may be exaggerated when the head is turned in the same direction. It is most pronounced with non-dominant hemisphe...
Article

Pronator quadratus sign

The pronator quadratus sign can be an indirect sign of distal forearm trauma. It relies on displacement of the fat pad that lies superficial to the pronator quadratus muscle. Radiographic appearance Plain radiograph On lateral wrist radiographs, the pronator fat pad normally appears a thin ra...
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Pseudo gallbladder sign

Pseudo gallbladder sign  is a sonographic feature that can be seen in some children with biliary atresia  Radiographic features Ultrasound Appears as a cystic structure seen in the liver which is confused with gallbladder in few cases of biliary atresia. In these patients it is an important f...
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Pseudo vein sign

The pseudo vein sign can occur with active gastrointestinal bleeding where contrast extravasation during angiography may have a curvilinear appearance as it pools in the gastric rugae or mucosal folds of bowel, mimicking the appearance of a vein. However, contrast in the “pseudo-vein” persists ...
Article

Pseudo-omphalocoele

Pseudo-omphalocoele is the spurious sonological appearance giving an impression of an anterior abdominal wall defect. Radiographic features Ultrasound Pseudo-omphalocoele may be seen in: scanning errors where there is a deformation of fetal abdomen by transducer pressure and the image is bei...
Article

Pseudo-subarachnoid haemorrhage

Pseudo-subarachnoid haemorrhage is a sign related to apparent increased attenuation within the basal cisterns which simulates a true subarachnoid haemorrhage (SAH). Pathology Causes and associations The most common cuase is cerebral oedema where there is a decrease in parenchymal attenuation ...
Article

Pseudocalculus sign

A pseudocalculus sign is a term coined to describe a mimic of a distally impacted common bile duct stone on MRCP and CT cholangiography.  It results from the forceful contraction of ampulla of Vater with secondary pouting into the lower end of the CBD. This impression is superiorly rounded and ...
Article

Pseudocavitation of a lung lesion

Pseudocavitation has been described as a well recognised feature of  adenocarcinoma in situ / minimally invasive adenocarcinoma - (bronchoalveolar carcinoma) of lung. It refers to the central bubble-like low density region seen within a pulmonary nodule on CT.
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Pseudodysraphism

A pseudodysraphism refers to the splayed  appearance of a normal spine created due to excessive craniocaudal angulation during sonographic evaluation. This can erroneously lead to the diagnosis of a spinal neural tube defect.
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Pseudogestational sac

A pseudogestational sac is the idea that a small amount of intrauterine fluid in the setting of a positive pregnancy test and abdominal pain could be erroneously interpreted as a true gestational sac in ectopic pregnancy. The sign was originally reported before the use of endovaginal ultrasound...
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Pseudokidney of intussusception

The pseudokidney of intussusception refers to the longitudinal ultrasound appearance of the intussuscepted segment of bowel. The fat containing mesentary which is dragged into the intussusception, containing vessels, is reminiscent of the renal hilum, with the renal parenchyma formed by the oe...
Article

Pseudopneumomediastinum

Pseudopneumomediastinum is the false impression, usually on a chest X-ray, of pneumomediastinum. Correctly identifying pneumomediastinum is important, but making the diagnosis in error may lead to further unnecessary investigation and possible treatment. Causes include: Mach bands superimpose...
Article

Puff of smoke sign

The puff of smoke sign describes the characteristic angiographic appearance of tiny abnormal intracranial collateral vessel networks in moyamoya disease. Progressive narrowing of the supraclinoid internal carotid arteries and circle of Willis vessels results in extensive small collateral arteria...
Article

Pulmonary plethora

Pulmonary plethora is a term used to describe the appearances of increased pulmonary perfusion on chest radiographs. It is commonly used in paediatric radiology.  Pathology Usually a left-to-right shunt of 2:1 is required for pulmonary plethora to occur 2,3. Increased pulmonary perfusion occur...
Article

Pulvinar sign

The pulvinar sign refers to bilateral FLAIR hyperintensities involving the pulvinar thalamic nuclei. It is classically described in variant Creutzfeldt-Jakob disease (vCJD). It is also described in other neurological conditions: Fabry disease (although the hyperintense signal is seen on T1WI) ...
Article

Punctate microcalcification within the breast

Punctate microcalcifications in the breast are defined as calcific opacities < 0.5 mm in diameter seen within the acini of a terminal duct lobular unit. Pathology Associations fibrocystic changes skin calcification skin talc rarely in DCIS (punctate, clustered, segmentally distributed) ...
Article

Putaminal rim sign

The putaminal rim sign, also known as putaminal slit sign,  is a relatively specific sign of multiple system atrophy - parkinsonism (MSA-P), and refers to a linear region of high T2 signal surrounding the lateral aspect of the putamen at 1.5T MRI. Importantly this appearance can be seen in norma...
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Putty kidney

A putty kidney refers to a pattern of renal calcification associated with renal tuberculosis conventionally described on plain radiography. Calcification characteristically is very homogeneous and ground glass like, representing calcified caseous tissue 3-4. Premkumar et al labelled calcificatio...

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