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Psoas sign (abdominal x-ray)

The psoas sign is a classic non-specific finding on the abdominal radiograph, potentially representing retroperitoneal pathology. Normally on an abdominal radiograph, the lateral margins of both the psoas muscles are clearly visible due to adjacent fat. When the lateral edge of one, or both, ps...

Ptosis

Ptosis (or blepharoptosis) is a drooping or falling of the upper eyelid. Complete ptosis is due to complete oculomotor nerve palsy. Partial ptosis is due to a dysfunction of the sympathetic pathway leading to paralysis of Muller muscle. Note that facial nerve paralysis prevents screwing of the...

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...

Pulmonary plethora

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

Pulvinar sign (Creutzfeldt-Jakob disease)

The pulvinar sign refers to bilateral FLAIR hyperintensities involving the pulvinar thalamic nuclei. It is classically described in variant Creutzfeldt-Jakob disease. It is also described in other neurological conditions: Fabry disease: the hyperintense signal is seen on T1 rather than T2 bila...

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 Radi...

Putaminal rim sign

The putaminal rim sign, also known as the putaminal slit sign, is a relatively specific sign of multiple system atrophy - parkinsonism (MSA-P), and refers to a linear region of high signal surrounding the lateral aspect of the putamen at 1.5 T MRI on T2 weighted images or ADC map. Importantly th...

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 calcificati...

Quad sign

The quad sign is a static sonographic sign observed in pleural effusion. It consists of four lines representing the pleura, rib, fluid, and lung. Similar to the sinusoid sign, this sign has a high sensitivity and specificity for pleural effusion, which - when simple - is itself anechoic.

Raccoon eyes sign (base of skull fracture)

Raccoon eyes sign (or panda eyes in the UK and Ireland) is due to periorbital ecchymosis and is specific for base of skull fracture of the anterior cranial fossa. However it is not pathognomonic for trauma, and there are several rare causes described, including metastatic neuroblastoma, Kaposi ...

Rachitic rosary

Rachitic rosary refers to expansion of the anterior rib ends at the costochondral junctions and is most frequently seen in rickets as nodularity at the costochondral junctions. Differential diagnosis Other causes of this appearance include: scurvy: the costochondral junction is more angula...

Racing car sign (callosal dysgnesis)

The racing car sign refers to widely spaced lateral ventricles due to agenesis of the corpus callosum with intervening Probst bundles. Appearances on axial MRI or CT are reminiscent of a Formula One car seen from above, with the tyres represented by the widely-spaced frontal horns, and the dilat...

Radial bands sign

The radial bands sign refers to linear bands seen on MRI, radiating from the periventricular white matter to the subcortical region, thought to be specific for tuberous sclerosis 1,2. Pathology The exact pathogenesis of radial bands is uncertain, but they are thought to relate to dysfunction o...

Radiocapitellar line

The radiocapitellar line is one of the key lines used to assess alignment on the elbow radiograph. It is particularly useful in the pediatric setting. The rule A line drawn down the neck of the radius should intersect the capitellum. It is important to ensure that you draw the line down the ra...

Radiological signs (gastrointestinal tract)

Radiological signs are described across the disciplines of imaging, including the gastrointestinal tract. Fruit-inspired, nature-related, and more feature in the list of signs described for a wide array of pathology. How fascinating are the minds of radiologists work in describing pathology?

Raindrop skull

The raindrop skull appearance of calvarial multiple myeloma is the presence of multiple, well-defined lytic lesions (punched out lesions) of various size scattered throughout the skull. This term is applied as an analogy to rain hitting a surface and splashing, where it leaves a random pattern o...

Ranke complex

Ranke complex is seen in 'healed' primary pulmonary tuberculosis and consists of two components: Ghon lesion: calcified parenchymal tuberculoma ipsilateral calcified hilar node History and etymology Karl Ernest Ranke (1870-1926) was a German physician who developed the (now outdated) hypothe...

Rat bite erosions (gout)

Rat (or mouse) bite erosions are seen in gout and refer to punched out erosions with sclerotic and overhanging margins.

Rat-tail sign (esophagus)

The rat-tail sign is used to refer to the tapering of the inferior esophagus in achalasia. The same appearance (although it is difficult to see the similarity) is also referred to as the bird beak sign (esophagus).

Renal arterial cut-off sign

Renal arterial cut-off sign, as the name suggests, is an abrupt termination of the contrast-opacified lumen of the renal artery. It may or may not be associated with contrast extravasation. It is seen in a vascular injury, e.g. segmental or main renal artery thrombosis or occlusion.

Reverse bat wing pulmonary opacities

Reverse bat wing pulmonary opacities refer to peripheral opacities of the lungs, sparing the perihilar region. It is a relatively unusual appearance with a relatively narrow differential: chronic eosinophilic pneumonia organising pneumonia (formerly bronchiolitis obliterans with organising pne...

Reversed halo sign (lungs)

Reversed halo sign, also known as the atoll sign, is defined as central ground-glass opacity surrounded by denser consolidation of crescentic (forming more than three-fourths of a circle) or ring (forming a complete circle) shape of at least 2 mm in thickness. It was initially described on high-...

Reverse figure 3 sign

The reverse figure 3 sign (also known as the E sign) is seen on barium swallows in patients with a coarctation of the aorta and is the medial equivalent of the figure 3 sign seen on plain chest radiographs. It is formed by prestenotic dilatation of the ascending aorta, indentation of the coarcta...

Reverse target sign (cirrhotic nodules)

A reverse target sign is a potential ultrasound marker for cirrhotic nodules on ultrasound.It represents central iso-hyperechogenicity with surrounding hyperechoic rim. This sign is useful to differentiate metastases from cirrhotic nodules, conversely the target sign is seen with liver metastases.

Ribbon ribs deformity

Ribbon ribs deformity refers to the presence of thinned ribs on image studies. Such findings could be present in patients with neurofibromatosis type 1 due to the presence of multiple neurofibromas of intercostal nerves. This deformity is also described in osteogenesis imperfecta 1 Edwards s...

Rice grain calcification

Rice grain calcification is characteristic of infection with Taenia solium (cysticercosis); when the inflammatory response of the host kills the larval cysts (cysticerci), they undergo granulomatous change and become calcified. Radiographic features Ovoid flecks of calcification resembling gra...

Right posterior hepatic notch sign

The right posterior hepatic notch sign is a sharp indentation of the normally smooth posterior right hepatic lobe margin. It is associated with cirrhosis, although the mechanism is not entirely clear. It has been suggested that this may be an indication of relative caudate lobe hypertrophy and d...

Rigler notch sign

The Rigler notch sign refers to an indentation in the border of a solid lung mass, which is thought to represents a feeding vessel, thus suggesting the presence of a bronchial carcinoma 1. However, this sign is also observed in other conditions, including granulomatous infections, and its differ...

Rigler sign

The Rigler sign, also known as the double wall sign, is seen on a radiograph of the abdomen when the air is present on both sides of the intestine, i.e. when there is air on both the luminal and peritoneal side of the bowel wall. Pneumoperitoneum may be a result of perforation or, recent instru...

Rigler triad

Rigler triad consists of three findings seen in gallstone ileus: pneumobilia small bowel obstruction ectopic gallstone, usually in the right iliac fossa History and etymology It is named after Leo George Rigler, American radiologist (1896-1979) 1. Practical points Rigler triad should not ...

Rim sign in chronic hydronephrosis

The rim sign can be seen in association with chronic hydronephrosis. In patients with chronic hydronephrosis, in all forms of contrast-enhanced imaging of the obstructed kidney, enhancement may occur in the residual, but markedly atrophic, renal parenchyma, surrounding the dilated calyces and ...

Rim sign in pulmonary infarction

The rim sign in pulmonary infarction is seen on PET-CT with very mild peripheral continuous FDG uptake and the complete absence of central uptake. This is a different appearance to that seen in lung abscesses or necrotic tumors, whereby the peripheral FDG-avidity is marked. History and etymolog...

Rim sign in renal vascular compromise

Rim sign in renal vascular compromise is seen in major renal vascular compromise. It can be seen in: renal artery obstruction from embolism, thrombosis or dissection renal vein thrombosis acute tubular necrosis Radiographic features At contrast-enhanced CT or MRI, a thin (1-3 mm) rim of su...

Rim sign of avascular necrosis

The rim sign of avascular necrosis (AVN) comprises a high T2 or intermediate T1 signal line sandwiched between two low signal lines, and represents fluid between the sclerotic borders of an osteochondral fragment, and implies instability (stage III). The rim sign should not be confused with the...

Rind sign (bones)

The rind sign is used when a lesion is surrounded by a layer of thick, sclerotic reactive bone (i.e. a rind) and is suggestive of fibrous dysplasia. The classic rind sign is most commonly seen in the proximal femur.

Ring of fire sign (adnexa)

The ring of fire sign, also known as ring of vascularity, signifies a hypervascular lesion with peripheral vascularity on color or pulsed Doppler examination of the adnexa due to low impedance high diastolic flow 1. This sign can be seen in: corpus luteum cyst (more commonly) ectopic pregnancy

Rings and arcs calcification

Rings and arcs calcification is characteristic of chondroid lesions, such as enchondromas and chondrosarcomas. It is due to endochondral mineralisation of multiple hyaline cartilage nodules and is similar to popcorn calcification, which has rings and arcs on the background of more amorphous calc...

Ring shadow (disambiguation)

Ring shadows are radiographic signs seen on either chest x-rays or on upper gastrointestinal fluoroscopy: ring shadow (chest) ring shadow (abdomen)

Roberts sign

Roberts sign refers to the presence of a gas shadow within the heart or the greater vessels, in cases of fetal death in utero. It is a rare sign caused by postmortem blood degeneration, usually seen 1-2 days after death; and may be seen as early as 12 hours. History and etymology First describ...

Rokitansky nodule

A Rokitansky nodule or dermoid plug refers to a solid protuberance projecting from an ovarian cyst in the context of a mature cystic teratoma. It often contains calcific, dental, adipose, hair, and/or sebaceous components 1. This region has the highest propensity to undergo malignant transformat...

Rolling stone sign

The rolling stone sign refers to the presence of gallstones within the gallbladder that are mobile when the patient moves. Small gallstones can sometimes be difficult to diagnose due to the absence of posterior shadow artefact but the presence of a rolling stone sign increases the confidence of...

Romana sign (Chagas disease)

Romana sign, also known as chagoma, refers to periorbital swelling, palpebral edema and conjunctivitis seen 1-2 weeks following infection with Trypanosoma cruzi (causative agent in Chagas disease). Romana sign is associated with ipsilateral regional lymphadenopathy. History and etymology It...

Romanus lesion

The Romanus lesion represents an early finding in inflammatory spondyloarthropathies, such as ankylosing spondylitis and enteropathic arthritis, and appears as irregularity and erosion involving the anterior and posterior edges of the vertebral endplates 1. Healing response to these inflammatory...

Rosary sign (gallbladder)

The rosary sign is a CT finding in adenomyomatosis of the gallbladder. It is formed by the enhanced proliferative mucosal epithelium, with the intramural diverticula surrounded by the unenhanced hypertrophied muscle coat of the gallbladder. The rosary sign is similar to the pearl necklace sign.

Rose-thorn ulcers

Rose-thorn ulcers or rose-thorn appearance refers to deep penetrating linear ulcers or fissuring typically seen within stenosed terminal ileum with a thickened wall. They appear as thorn-like extraluminal projections on barium studies and this appearance is one of the typical signs of Crohn dise...

Rugger-jersey spine

Rugger-jersey spine describes the prominent subendplate densities at multiple contiguous vertebral levels to produce an alternating sclerotic-lucent-sclerotic appearance. This mimics the horizontal stripes of a rugby jersey. This term and pattern are distinctive for hyperparathyroidism. Pathol...

Saber-sheath trachea

Saber-sheath trachea refers to diffuse coronal narrowing of the intrathoracic portion of the trachea with the concomitant widening of the sagittal diameter. It is not uncommon and is pathognomonic for chronic obstructive pulmonary disease (COPD) 1. The sagittal:coronal diameter is over 2:1 2 a...

Saber sign in pneumobilia

The saber sign refers to a pattern of gas distribution seen in supine abdominal radiographs of patients with pneumobilia. A sword-shaped lucency is apparent in the right paraspinal region of the upper abdomen representing arching gas extending from the common bile duct into the left hepatic duc...

Sack of marbles sign

The sack of marbles sign refers to aggregations of multiple small globules of fat within a cyst mimicking marble spheres within a sack. They appear hyperechoic on ultrasound, fat attenuation on CT, and high signal on T1WI and T2WI on MRI. It is considered highly suggestive of a dermoid cyst 1.

Saddle pulmonary embolism

Saddle pulmonary embolism commonly refers to a large pulmonary embolism that straddles the bifurcation of the pulmonary trunk, extending into the left and right pulmonary arteries. If large enough, it can completely obstruct both left and right pulmonary arteries resulting in right heart failur...

Sail sign (elbow)

The sail sign on an elbow radiograph describes the elevation of the anterior fat pad to create a silhouette similar to a billowing spinnaker sail from a boat. It indicates the presence of an elbow joint effusion. The anterior fat pad is usually concealed within the coronoid fossa or seen parall...

Sail signs

There are numerous sails signs in radiology, where a normal structure is displaced or a pathology creates the appearance of a sail: elbow sail sign: the raised anterior fat pad on an elbow radiograph thymic sail sign: normal thymus on a pediatric chest radiograph spinnaker-sail sign (angel wi...

Salad oil sign

Salad oil sign, also referred to as the droplet sign, is characterized by small rounded high T2 signal foci within a breast implant on MRI studies and represents water droplets or small amounts of gas within the silicone. It also can be characterized as hypointense foci on the water-suppressed s...

Salt and pepper sign

The salt and pepper sign is used to refer to a speckled appearance of tissue. It is used in many instances, but most commonly on MRI. Please note that pathologists also use the term. Differential diagnosis Vascular tumors Used to describe some highly vascular tumors which contain foci of hemo...

Salt and pepper sign (skull)

Salt and pepper sign or pepper pot skull refers to multiple tiny well-defined lucencies in the calvaria caused by resorption of trabecular bone in hyperparathyroidism. There is a loss of definition between the inner and outer tables of the skull and a ground-glass appearance as well as spotty de...

Sandwich sign (Marchiafava-Bignami disease)

Sandwich sign of Marchiafava-Bignami disease is described as the appearance due to the involvement of central layers of the corpus callosum. T2 and FLAIR hyperintensities are seen in the central region of body and splenium of corpus callosum with sparing of peripheral dorsal and ventral layers ...

Sandwich sign (mesentery)

A sandwich sign, sometimes known as a hamburger sign, refers to a mesenteric nodal mass, either para-aortic or not, giving an appearance of a hamburger. Confluent lymphadenopathy on both sides of the mesenteric vessels gives rise to an appearance described as the sandwich sign 2. The sign is sp...

Sandwich vertebral body

Sandwich vertebral body is a radiologic appearance in which the endplates are densely sclerotic, giving the appearance of a sandwich. This term and pattern are distinctive for osteopetrosis. Differential diagnosis the sandwich vertebrae appearance resembles rugger-jersey spine but can be diffe...

Scalpel sign (spinal cord)

The scalpel sign has been recently described in dorsal thoracic arachnoid web on sagittal MRI spine studies. It relates to focal distortion of the thoracic cord, appearing anteriorly displaced. The enlarged dorsal CSF space mimics the profile of a surgical scalpel. It is helpful in distinguishi...

Scaphoid fat pad sign

The scaphoid fat pad or stripe sign is defined as obliteration or lateral displacement of the normal scaphoid fat pad. A positive sign usually indicates a scaphoid fracture, although it may also be associated with a radial styloid or proximal first metacarpal fracture. Is it best visualized on p...

Scimitar sign of cystic adventitial disease

Scimitar sign traditionally referred to a catheter angiographic appearance, although it can also be seen on MRA and CTA. It denotes lateral displacement and stenosis of the popliteal artery in patients with cystic adventitial disease.

Scottie dog sign (spine)

The Scottie dog sign refers to the normal appearance of the lumbar spine when seen on oblique radiographic projection. On oblique views, the posterior elements of the vertebra form the figure of a Scottie dog with: the transverse process being the nose the pedicle forming the eye the inferior...

Seatbelt sign (abdomen)

The seatbelt sign is both a clinical and radiological sign. It is simply the presence of bruising/abrasions in the distribution of a seatbelt (i.e. horizontal and/or diagonal) across the abdomen, chest and sometimes neck. A positive seatbelt sign, in combination with abdominal pain or tenderne...

Segond fracture

Segond fracture is an avulsion fracture of the knee that involves the lateral aspect of the tibial plateau and is very frequently (~75% of cases) associated with disruption of the anterior cruciate ligament (ACL). On the frontal knee radiograph, it may be referred to as the lateral capsular sign...

Sentinel clot sign

The sentinel clot sign is a useful CT finding for the evaluation of probable anatomic sites of hemorrhage. On CT, acute clotted hemorrhage typically has high attenuation (45 to 80 HU), whereas surrounding areas of acute non-clotted hemorrhage or more chronic hemorrhage have either lower attenua...

Sentinel loop

A sentinel loop is a short segment of adynamic ileus close to an intra-abdominal inflammatory process. The sentinel loop sign may aid in localising the source of inflammation. For example, a sentinel loop in the upper abdomen may indicate pancreatitis, while one in the right lower quadrant may ...

Septal bounce

Septal bounce is a sign of ventricular interdependence on echocardiography, cardiac CT, and cardiac MRI, manifested by paradoxical interventricular septal movement during early diastole (i.e. initial septal movement towards and then away from the left ventricle) seen mainly in constrictive peric...

Septal flash

Septal flash, also known as septal beaking, is a sign of interventricular dyssynchrony seen on echocardiography or cinematographic cardiac CT/MRI. It represents an abnormal rapid movement pattern of the interventricular septum during pre-ejection systole (i.e. isovolumic contraction): septal mo...

Septal lines in lung

Septal lines, also known as Kerley lines, are seen when the interlobular septa in the pulmonary interstitium become prominent. This may be because of lymphatic engorgement or edema of the connective tissues of the interlobular septa. They usually occur when pulmonary capillary wedge pressure rea...

Sergeant stripes sign (cerebellum)

The sergeant stripes sign refers to the oblique direction of the cerebellar tonsillar folia a feature sometimes visible in cases of Chiari I malformation on sagittal imaging. It is unclear which insignia this is meant to represent as the direction of the chevrons depends on nationality. For exam...

Seurat spleen

Seurat spleen is an angiographic appearance seen following blunt trauma to the spleen. Multiple small punctate regions of intraparenchymal contrast extravasation lead to a spotted appearance. History and etymology The term refers to a likeness between the angiographic appearance and the artwor...

Shading sign (endometrioma)

Shading sign is an MRI finding typically seen in an endometrioma. It may also be seen with some endometrioid tumors (e.g endometrioid carcinoma of the ovary) It helps to distinguish endometriomas from other blood-containing lesions (e.g. hemorrhagic corpus luteum cysts), with a sensitivity of 9...

Shagreen patch

A shagreen patch is a subepidermal collagenous connective tissue naevus, also known as a collagenoma, associated with tuberous sclerosis. The overlying skin may be discoloured with obvious pours, giving the appearance of orange peel. These lesions are most commonly found in the lumbosacral regio...

Shepherd crook deformity

A shepherd crook deformity refers to a coxa varus angulation of the proximal femur, classically seen in femoral involvement by fibrous dysplasia, although may be seen in other disorders such as Paget disease of bone and osteogenesis imperfecta. History and etymology The shape of the proximal f...

Shifting granuloma sign

Shifting granuloma sign refers to a shift in the location of a parenchymal lesion visible on prior films that may be seen in the presence of atelectasis. For example, this occurs when a calcified granuloma is present in a lung and a significant parenchymal collapse "shifts" it from one location...

Shiny corner sign (ankylosing spondylitis)

The shiny corner sign is a spinal finding in ankylosing spondylitis, representing reactive sclerosis secondary to inflammatory erosions at the superior and inferior endplates (corners on lateral radiograph) of the vertebral bodies which are known as Romanus lesions. Eventually, the vertebral bod...

Shmoo sign

Shmoo sign refers to the appearance of a prominent, rounded left ventricle and dilated aorta on a plain AP chest radiograph giving the appearance of Shmoo, a fictional cartoon character in the comic strip Li'l Abner, which first appeared in 1948. This sign is indicative of left ventricular enlar...

Shortening of the cervical canal

Shortening of the uterine cervical canal as the name implies refers to an abnormal shortening of the uterine cervical length. It is considered a sign of cervical incompetence during pregnancy and can lead to premature delivery. Pathology Etiology primary (i.e. congenital/idiopathic) secondar...

Shoulder sign of pyloric stenosis

The shoulder sign of pyloric stenosis is seen during barium examination and refers to the bulging of the hypertrophied pyloric muscle into the lumen of the antrum. It is closely related to the cervix sign of pyloric stenosis. See also cervix sign of pyloric stenosis target sign of pyloric s...

Shred sign (lungs)

Shred sign is a static sonographic sign observed in lung consolidation. The deeper border of consolidated lung tissue that makes contact with the aerated lung is shredded and irregular. This sign is not seen in massive translobar consolidation in which it is more difficult to appreciate the deep...

Sigmoid kidney

A sigmoid kidney is an uncommon variant of the horseshoe kidney. Whereas the typical horseshoe kidney is fused only at the lower poles, in a sigmoid kidney both the upper and the lower poles are fused 1.

Signal flare phenomenon

The signal flare phenomenon is a useful sign to identify active bleeding in a liquefied hematoma with hematocrit effect on dynamic CT scan images. When active arterial hemorrhage is present in a liquefied hematoma that has a hematocrit effect, a signal flare phenomenon may be seen as a linear, ...

Signet ring sign

The signet ring sign is seen in bronchiectasis when the dilated bronchus and accompanying pulmonary artery branch are seen in cross-section. The bronchus and artery should be the same size, whereas in bronchiectasis, the bronchus is markedly dilated. The signet ring analogy has also been applie...

Signs article structure

Signs are numerous in radiology and typically relate to a specific appearance or feature that is reminiscent of an object. The aim of a named sign is to help recognize or understand a specific imaging appearance (e.g. racing car sign of corpus callosal dysgenesis). The most important signs are t...

Signs of pulmonary embolus on chest radiography

There are several described signs of pulmonary embolus on chest radiography which are suggestive of this diagnosis. None are pathognomonic and need to be interpreted with caution with close regard to the clinical presentation. Chang sign Fleischner sign Hampton hump (strictly a sign of pulmon...

Silhouette sign (x-rays)

Silhouette sign is somewhat of a misnomer and in the true sense actually denotes the loss of a silhouette, thus, it is sometimes also known as loss of silhouette sign or loss of outline sign 4. The differential attenuation of x-ray photons by two adjacent structures defines the silhouette, e.g...

Sinusoid sign (ultrasound)

The sinusoid sign is a dynamic sonographic sign, present when respiratory variation decreaes the distance between the parietal and visceral pleura, when separated by a pleural effusion. Classically demonstrated in M-mode, the appearance of which the moniker is derived, it is specific for the ide...

Sitting duck appearance (jugular foramen)

The sitting duck appearance denotes the normal anatomical configuration of the jugular foramen: the head of the duck (pointing backwards on the right side) represents the anteromedial pars nervosa the body of the duck representing the pars vascularis

Sliding sign

The loss of the normal sliding sign is a dynamic sonographic sign performed during transvaginal ultrasound (TVS) of women with suspected pelvic peritoneal endometriosis. It indicates pouch of Douglas (POD) involvement and obliteration and is suggestive of deep infiltrating endometriosis (DIE). ...

Sliver sign (patella)

The sliver sign refers to a curvilinear intra-articular osteochondral fragment in the knee joint on conventional knee radiographs. In the context of acute knee trauma and in association with joint effusion this sign is highly predictive of a recent transient lateral patellar dislocation 1. Path...

Small bowel feces sign

The small bowel feces sign can be observed on abdominal CT scans. The sign has been described as a finding specific for small bowel obstruction or another severe small bowel abnormality (e.g. metabolic or infectious disease). While the reported prevalence of the sign in small bowel obstruction i...

Snake-eye appearance (spinal cord)

Snake-eye appearance refers to symmetric bilateral T1 hypointensity/T2 hyperintensity of the anterior horn of the grey matter on axial cervical MRI, evocative of a pair of snake's eyes. It can be seen in late phase CT myelography, an all but forsaken technique, where it is also known as fried e...

Snowcap sign (avascular necrosis)

Snowcap sign or snowcapping is defined as the appearance of dense sclerosis over the head of humerus or femur in cases of avascular necrosis as seen on plain radiographs, which resembles a snowcapped mountain.

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