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.

40 results found
Article

Atoll sign - liver MRI

The atoll sign in hepatic imaging has been described when a liver lesion shows a peripheral rim of high T2 signal intensity with the center of the lesion appearing isointense to the background of non-cirrhotic liver on T2WI mimicking an atoll. It is considered a characteristic sign of an inflamm...
Article

Bright dot sign - atypical liver haemangioma

The bright dot sign refers to presence of a bright dot within a lesion which remains hyper-attenuating on arterial and portal venous phase CT, corresponding to early nodular enhancement seen on dynamic MRI of liver haemangioma.  This can be used as an indicator that the lesion in question is a ...
Article

Caput medusae sign - developmental venous anomalies

The caput medusae sign, refers to developmental venous anomalies of the brain, where a number of veins drain centrally towards a single drain vein. The appearance is reminiscent of Medusa, a gorgon of Greek mythology, who was encountered and defeated by Perseus. The sign is seen on both CT and ...
Article

Caput medusae sign - portal hypertension

The caput medusae sign is seen in patients with severe portal hypertension. It describes the appearance of distended and engorged paraumbilical veins, which are seen radiating from the umbilicus across the abdomen to join the systemic veins.  The appearance is reminiscent of Medusa, a gorgon of...
Article

Cottage loaf sign

The cottage loaf sign occurs as a result of a right-sided diaphragmatic rupture with partial herniation of the liver through the diaphragmatic defect. The herniated component is separated by a waist at the diaphragm from the larger intra-abdominal component. This shape is reminiscent of a cottag...
Article

Courvoisier sign

Courvoisier sign or Courvoisier-Terrier's sign states that in a patient with painless jaundice and an enlarged gallbladder (or right upper quadrant mass), the cause is unlikely to be gallstones and therefore presumes the cause to be an obstructing pancreatic or biliary neoplasm until proven othe...
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Double barrel sign

Double barrel sign is an imaging appearance of two lumens adjacent to each other. It can be seen in: dilated bile duct adjacent to portal vein double barrel aorta: aortic dissection double barrel oesophagus: oesophageal dissection
Article

Double duct sign

The double duct sign refers to the presence of simultaneous dilatation of the common bile and pancreatic ducts. Being an anatomical sign it can be seen on all modalities that can visualise the region, including: MRI, CT, ultrasound and endoscopic retrograde cholangiopancreatography (ERCP).  The...
Article

Double target sign of hepatic abscess

The double target sign is a characteristic imaging feature of liver abscess demonstrated on contrast enhanced CT scans, in which a central, fluid-filled low attenuation lesion is surrounded by a high attenuation inner rim and a low attenuation outer ring1-2 . The inner ring (abscess membrane) d...
Article

Duct penetrating sign

The duct-penetrating sign is a radiographic sign which can be useful in differentiating between focal pancreatitis (inflammatory pancreatic mass ) from pancreatic carcinoma. Best description of positive sign is visualisation of a mass penetrated by an unobstructed pancreatic duct makes focal pa...
Article

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 ...
Article

Intrahepatic arterioportal shunt

Intrahepatic arterioportal shunts represent abnormal flow between the portal venous system and a hepatic arterial system within the liver. They can be a reversible cause of portal hypertension. Clinical presentation Clinical features will depend on size and other underlying pathology. Small sh...
Article

Light bulb sign - hepatic haemangioma

The light bulb sign of a hepatic haemangioma is a feature than can be seen on MRI imaging with a classic hepatic haemangioma. This refers to marked hyperintensity seen on heavily T2 weighted sequences that has been likened to a glowing light bulb. See also light bulb sign - shoulder light bul...
Article

Mercedes-Benz sign (gallbladder)

In the gallbladder the Mercedes-Benz sign describes a star-shaped pattern of gas-fissuring within gallstones initially described on an abdominal radiograph 2. Fissures, usually fluid-filled, are present in close to 50% of gallstones. Less than half of these fissured gallstones contain some amou...
Article

Nodule-in-nodule appearance: liver

In hepatic imaging, a nodule-in-nodule appearance represents foci of abnormal arterial enhancement within a liver lesion, in cases of a liver regenerative nodule with a focus of hepatocellular carcinoma or high-grade dysplastic nodule. It is so called because of the nodular arterial enhancement ...
Article

Nubbin sign

Nubbin sign (also called as cystic duct sign) is an important sign in a HIDA scan (cholescintigraphy using iminodiacetic acid analogues) that may be seen in cases of gallbladder neck obstruction. The "nubbin" refers to a small amount of radiotracer activity in the cystic duct, with abs...
Article

Nutmeg liver

A nutmeg liver appearance is due to a perfusion abnormality of the liver usually as result of hepatic venous congestion. When hepatic veins are congested, contrast is prevented from diffusing through the liver in a normal manner. This results in a mottled pattern of contrast enhancement in the a...
Article

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...
Article

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...
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

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

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...
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

Reverse target sign: cirrhotic nodules

A reverse target sign is a potential ultrasound marker for cirrhotic nodules on ultrasound.It represents central iso-hyperechogenecity with surrounding hyperechoic rim .This sign is useful to differentiate metastases from cirrhotic nodules where target sign is seen in liver metastases.
Article

Rigler triad

Rigler triad consists of three findings seen in gallstone ileus: pneumobilia small bowel obstruction gallstone, usually in the right iliac fossa Rigler triad should not be confused with Rigler sign or the Hoffman-Rigler sign. History and etymology It is named after Leo George Rigler, Ameri...
Article

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...
Article

Rosary sign

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.
Article

Saber sign in pneumobilia

The saber sign refers to a pattern of gas distribution seen in supine 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 duct.  This i...
Article

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...
Article

Sonographic halo sign

Sonographic halo sign is used in a number of situations. They include: hypoechoic halo sign in liver metastases: used in hepatobiliary imaging, is a concerning feature for malignant lesion if the lesion is a hyperechoic liver lesion 1,3 ultrasound halo in angiolymphoid hyperplasia with eosinop...
Article

Sonographic Murphy sign

Sonographic Murphy sign (SMS) is defined as maximal abdominal tenderness from pressure of the ultrasound probe over the visualised gallbladder 1,2. SMS is a sign of local inflammation around the gallbladder along with right upper quadrant pain, tenderness or mass 2. It is one of the most impor...
Article

Starry sky appearance on ultrasound

A "starry sky appearance" refers to a sonographic appearance of the liver parenchyma in which there are bright echogenic dots throughout a background of decreased liver parenchymal echogenicity. Although usually associated with acute hepatitis, this sign has been found to have poor sen...
Article

Strawberry gallbladder

Strawberry gallbladder refers to the surface appearance (not shape) of the mucosa of the gallbladder due to multiple small collections of triglycerides and cholesterol esters within the lamina propria of the gallbladder wall.  Strawberry gallbladder represents diffuse cholesterolosis and is a c...
Article

Target sign of choledocholithiasis

The target sign of choledocholithiasis is a finding seen on contrast enhanced CT and comprises: central density within the bile duct: stone surrounding low density: bile or mucosa
Article

Target sign of tuberculosis

The target sign of tuberculosis refers to the bull's-eye appearance of some parenchymal tuberculomas involving the brain (see: CNS tuberculosis) and solid abdominal organs (see: hepatic and splenic tuberculosis) on cross-sectional imaging.  Radiographic features CT central nidus of calcificat...
Article

Tensile gallbladder fundus sign

The tensile gallbladder fundus sign is positive when the gallbladder fundus is seen to bulge into, and distort, the anterior abdominal wall and is a feature of acute cholecystitis. It is particularly useful as an early sign of the condition on CT as it has around a 75% sensitivity and 95% speci...
Article

Three line sign

The three line sign refers to an MRI term that describes the appearance of roundworm Ascaris lumbricoides within the CBD lumen which appears as two hypointense lines representing the worm walls and hyperintense center which represents the worm gut. See also biliary ascariasis
Article

Triangular cord sign

The triangular cord sign is a triangular or tubular echogenic cord of fibrous tissue seen in the porta hepatis at ultrasonography and is relatively specific in the diagnosis of  biliary atresia1,2. This sign is useful in the evaluation of infants with cholestatic jaundice, helping for the diffe...
Article

Turtle back sign

Turtle back sign, also referred as tortoise shell appearance, represents a very characteristic pattern of the schistosomiasis cirrhotic liver in which calcified fibrotic septa are seen aligned perpendicular to the liver capsule resembling the turtle's carapace. 
Article

Wheels within wheels sign

This sign is seen in USG of patient with the hepatic candidiasis and described as central hypoechoic area (necrosis containing fungi) surrounded by an echogenic zone (inflammatory cells). Differs from bull’s-eye sign for reverse echogeniticity, as it consists a central echogenic nidus surrounde...

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