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.

615 results found
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Splenic hamartoma

Splenic hamartomas are very rare lesions commonly found incidentally on imaging. They are most often solitary but may be present as multiple nodules in patients with tuberous sclerosis or Wiskott-Aldrich syndrome. Terminology  The recently-described sclerosing angiomatoid nodular transformatio...
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Splenic hydatid infection

Splenic hydatid infection is a rare form of hydatid disease, and isolated splenic involvement is even less common. For a general discussion, and for links to other system-specific manifestations, please refer to the article on hydatid disease.  Epidemiology Splenic hydatid disease has been re...
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Splenic infarction

Splenic infarction is a result of ischemia to the spleen, and in many cases requires no treatment. However, identification of the cause of infarction is essential.   Epidemiology Splenic infarcts can occur due to a number of processes, involving either arterial supply, the spleen itself or the...
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Splenic peliosis

Splenic peliosis is an unusual benign disorder characterized by the presence of irregular cystic blood-filled cavities. Clinical presentation Most patients are asymptomatic although very rarely patient can present with spontaneous organ rupture. Associations Recognized associations include ...
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Splenic steal syndrome

Splenic steal syndrome is a possible complication after liver transplantation. In this syndrome, blood flows preferentially from the celiac artery into the splenic artery and the hepatic artery is relatively hypoperfused as a result. This complication can threaten a liver transplant's survival. ...
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Splenomegaly

Splenomegaly refers to enlargement of the spleen. The upper limit of normal adult splenic length is traditionally cited at 12 cm, but lengths upwards of 14 cm can be seen in normal, taller males 7. Massive splenomegaly is variably defined, including when the spleen is 5 standard deviations abov...
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Splenorenal shunt

A splenorenal shunt refers to an abnormal collateral portosystemic communication between the splenic vein and the left renal vein. It is one of the features of portal hypertension. See also portosystemic shunts
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Splenosis

Splenosis is one type of ectopic splenic tissue (the other being accessory spleen). It is an acquired condition and is defined as autoimplantation of one or more focal deposits of splenic tissue in various compartments of the body. Abdominal splenosis is seen after abdominal trauma or surgery (...
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Starry sky appearance (disambiguation)

Starry sky appearance is a radiological sign used to describe the appearance of the liver on two different imaging modalities: starry sky appearance (ultrasound) starry sky appearance (MRI) starry sky artifact (MRI)
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Starry sky appearance (MRI)

Starry sky appearance on MRI refers to the appearance of small innumerable T2 hyperintense bile duct hamartomas and biliary microhamartomas, scattered throughout the T2 hypointense hepatic parenchyma, which resembles a “starry sky”. The high T2 signal lesions represent Von Meyenburg complexes se...
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Starry sky appearance (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 sensitivity and...
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Stauffer syndrome

Stauffer syndrome is paraneoplastic nephrogenic hepatomegaly. It most commonly occurs in the setting of renal cell carcinoma, and is the enlargement of the liver without hepatic metastases. It is a cause of cholestasis and cholestatic jaundice.  History and etymology It is named after Maurice ...
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Strasberg classification of bile duct injury

The Strasberg classification of bile duct injury is a widely used system to anatomically define these injuries by location 1.  Classification type A: injury to the cystic duct or from minor hepatic ducts draining the liver bed type B: occlusion of the biliary tree, commonly aberrant right hep...
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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 (gallbladder wall cholesterolosis).  Strawberry gallbladder represents...
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Subvesical bile ducts

Subvesical/subvesicular bile ducts are variants of the biliary tree, and knowledge of these are important because they account for a significant portion of post-cholecystectomy bile leaks.  Terminology Cholecystohepatic ducts (usually segment V to the gallbladder) are commonly known as bile du...
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Superior pancreaticoduodenal artery

The superior pancreaticoduodenal artery is a branch of gastroduodenal artery that supplies the duodenum and pancreas. Gross anatomy Superior pancreaticoduodenal artery arises after branching off from gastroduodenal artery. It divides into anterior and posterior divisions which supply the pylor...
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Supradiaphragmatic liver

Supradiaphragmatic liver has been reported as a very rare variant in liver morphology.  In this variant, liver tissue extends into the right hemithorax through an opening in the right hemidiaphragm. The tissue is connected to the right hepatic lobe by a pedicle. In one report, the caudate lobe ...
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Syphilis

Syphilis is the result of infection with the gram negative spirochete Treponema pallidum, subspecies pallidum. It results in a heterogeneous spectrum of disease with many systems that can potentially be involved, which are discussed separately.  Epidemiology Despite the discovery of penicillin...
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Tamoxifen-induced reversible hepatic steatosis

Tamoxifen is an important anti-estrogen agent used for the treatment of hormone receptor-positive breast cancer and it may induce reversible hepatic steatosis. This is usually transient and may occasionally be associated with hepatic dysfunction. It only rarely leads to cirrhosis 1. Epidemiolog...
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Target sign (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
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Target sign (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 Ultrasound hypoechoic nodules ...
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Tc99m IDA (iminodiacetic acid) analogs

Tc99m IDA (iminodiacetic acid) analogs are hepatobiliary agents in nuclear medicine, used in cholescintigraphy. These include: Tc99m-DISIDA: diisopropyl IDA, aka Hepatolite Tc99m-Mebrofenin: trimethyl bromo IDA, aka Choletec Tc99m-PIPIDA: paraisopropyl iminodiacetic acid The use of IDA alon...
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Tc-99m sulfur colloid

Technetium-99m sulfur colloid is one of the technetium radiopharmaceuticals. Characteristics photon energy: 140 keV physical half-life: 6 hours biological half-life normal distribution: liver: 85% spleen: 10% bone marrow: 5% excretion: hepatic target organ: liver, spleen pharmacokinet...
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Technetium agents

Technetium agents based on the technetium-99m (Tc-99m) radioisotope are frequently used agents in medical imaging. A radiopharmaceutical labeled with Tc-99m constitutes a coordination complex in which ligands bond to a central atom of Tc-99m by coordinate covalent bonds 4 . The radioactive tech...
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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...
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Third inflow

Third inflow refers to anatomical variants leading to an additional venous inflow to the liver apart from the usual dual blood supply (portal vein and hepatic artery). They tend to be associated with parenchymal pseudolesions (focal hyperenhancement on post-contrast imaging, focal fat infiltrati...
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Thorotrast

Thorotrast is a suspension of radioactive thorium dioxide first produced in Germany in 1928 and used as a contrast agent until the 1950s. Its principal use was for cerebral angiography: 90% of the estimated 50,000-100,000 patients treated received it for this purpose. Umbrathor was another thori...
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Three line sign (common bile duct)

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
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TIPS evaluation

TIPS evaluation is useful to ensure that the shunt is working properly and that no stenosis has occurred within the stent. Ultrasound is often used as a first-line modality. Radiographic features Ultrasound The normal TIPS should show color Doppler flow throughout its length. The in-stent vel...
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Todani classification of bile duct cysts

The Todani classification of bile duct cysts divides choledochal cysts into five groups. Classification Type I See: type I choledochal cyst account for 80-90% of all bile duct cysts characterized by fusiform dilation of the extrahepatic bile duct a subclassification has been proposed Ia: ...
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Transcatheter arterial chemoembolisation

Transarterial chemoembolisation therapy (TACE) is a localized method of administrating chemotherapy directly to a liver tumor via a catheter study. The chemoembolic agent may be delivered via a mixture with LipiodolⓇ, known as conventional TACE, or as an injection of drug-eluting beads (DEB-TACE...
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Transient hepatic attenuation differences

Transient hepatic attenuation differences (THAD) lesions refer to areas of parenchymal enhancement visible during the hepatic artery phase on helical CT. They are thought to be a physiological phenomenon caused by the dual hepatic blood supply. Occasionally, they may be associated with hepatic t...
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Transient hepatic intensity difference

Transient hepatic intensity differences (THIDs) are a phenomenon observed on MRI imaging of the liver. They are considered a direct equivalent to transient hepatic attenuation differences (THADs) noted on CT. They may be focal or nonfocal. Pathology Focal lesions A focal THID lesion can arise...
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Transjugular intrahepatic portosystemic shunt

Transjugular intrahepatic portosystemic shunt (TIPS) is a treatment for portal hypertension in which direct communication is formed between a hepatic vein and a branch of the portal vein, thus allowing some proportion of portal flow to bypass the liver. The target portosystemic gradient after TI...
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Transverse pancreatic artery

The transverse pancreatic artery, also known as the inferior pancreatic artery, is a branch of the splenic artery that supplies the pancreatic tail and body. It arises from the proximal splenic artery and descends a short distance to run to the left along the posterior margin of the pancreas ne...
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Triangular cord sign (biliary atresia)

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 for the diagnosis of biliary atresia 1,2. This sign is useful in the evaluation of infants with cholestatic jaundice, helping in the diffe...
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T tube cholangiogram

T-tube cholangiograms are a fluoroscopic study performed in the setting of hepatobiliary disease.  This technique has been largely superseded by MRCP and ERCP. Typically a T-shaped tube is left in the common bile duct at the time of surgery (e.g. cholecystectomy) and allows for exploration of t...
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Turtleback sign

Turtleback sign, also referred as tortoise shell appearance, represents a characteristic appearance of chronic hepatic schistosomiasis in which dystrophic calcifications within a polygonal network of fibrous septae are seen in the periphery, often perpendicular to the liver capsule, resembling t...
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Type I choledochal cyst

Type I choledochal cysts appear as a fusiform or cystic dilatation of the extrahepatic biliary system (common bile duct +/- common hepatic duct). Epidemiology Although uncommon in Western countries (1:100,000 to 1:150,000), they are the most common type of biliary cyst. Their prevalence may be...
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Tyrosinemia type 1

Tyrosinemia type 1 is an autosomal recessive disorder of metabolic origin. Progressive renal tubular defects and hepatocellular carcinoma are the primary manifestations. Epidemiology More common in Turkey, India and Europe. Clinical presentation Presentation is typically in the first few mon...
Article

Ultrasound appearances of liver metastases

Ultrasound appearance of liver metastases can have bewildering variation, and the presence of hepatic steatosis can affect the sonographic appearance of liver lesions. Radiographic features Ultrasound Patterns do exist between ultrasound appearance of the liver metastases and the likely prima...
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Ultrasound-guided biopsy

Ultrasound-guided biopsy is one form of image-guided biopsy, typically performed by a radiologist. It is the most common form of image-guided biopsy, offering convenience and real-time dynamic observation with echogenic markers on cannulae allowing for precise placement. It can potentially be u...
Article

Umbilical vein

The umbilical vein is the conduit for blood returning from the placenta to the fetus until it involutes soon after birth. The umbilical vein arises from multiple tributaries within the placenta and enters the umbilical cord, along with the (usually) paired umbilical arteries. Once it enters the...
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Undifferentiated embryonal sarcoma of the liver

Undifferentiated embryonal sarcomas of the liver are rare, aggressive, and malignant liver tumors encountered in the pediatric population.  Epidemiology Approximately 90% of cases occur in patients under 15 years of age, most commonly between 6 and 10 years of age, but some cases have been rep...
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US abdomen (summary)

This is a basic article for medical students and other non-radiologists Ultrasound abdomen is one of the tests that is commonly used in the assessment of patients with abdominal pain. It is particularly useful for the assessment of solid organs and fluid-filled structures. Reference article T...
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Variant hepatic arterial anatomy

Variation in hepatic arterial anatomy is seen in 40-45% of people. Classic branching of the common hepatic artery from the celiac artery, and the proper hepatic artery into right and left hepatic arteries to supply the entire liver, is seen in 55-60% of the population.  Terminology An accessor...
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Ventriculogallbladder shunt

Ventriculogallbladder shunts are a rare form of cerebrospinal fluid diversion, used when a ventriculoperitoneal shunt is not possible (e.g. intra-abdominal adhesions, peritonitis). Differential diagnosis a ventriculoperitoneal shunt in a right upper quadrant CSFoma See also ventriculoperiton...
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Vicarious contrast media excretion

Vicarious contrast media excretion (VCME) is defined as excretion of intravascularly-administered water-soluble contrast media in a way other than via normal renal excretion. The most common vicarious excretion of water-soluble contrast material is via the liver, resulting in increased bile dens...
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Wall-echo-shadow sign (ultrasound)

The wall-echo-shadow sign (also known as WES sign) is an ultrasonographic finding within the gallbladder fossa referring to the appearance of a "wall-echo-shadow": a curvilinear hyperechogenic line representing the gallbladder wall a thin hypoechoic space representing a small amount of bile a...
Article

Wandering spleen

Wandering spleen is a rare condition in which the spleen migrates from its usual anatomical position, commonly to the lower abdomen or pelvis. Epidemiology Wandering spleen is rare, with a reported incidence of <0.5%. Diagnosis is most commonly made between ages 20 and 40 years and is more co...
Article

Water-lily sign (hydatid cyst)

The water-lily sign, also known as the camalote sign, is seen in hydatid infections when there is detachment of the endocyst membrane which results in floating membranes within the pericyst that mimic the appearance of a water lily. It is classically described on plain radiographs (mainly chest...
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Wheel within a wheel sign (hepatic candidiasis)

The wheel within a wheel sign describes one of several possible ultrasound findings of hepatic candidiasis. The finding consists of a round lesion with three layers corresponding to the following histopathological changes 2: peripheral hypoechoic area (fibrosis) middle hyperechoic area (inflam...
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Whipple triad

Whipple triad is the clinical presentation of pancreatic insulinoma and consists of: fasting hypoglycemia (<50 mg/dL) symptoms of hypoglycemia immediate relief of symptoms after the administration of IV glucose History and etymology The triad and also the Whipple procedure were both named a...
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Wilson disease

Wilson disease, also known as hepatolenticular degeneration, is a rare autosomal recessive disorder of copper metabolism affecting multiple systems.  Epidemiology Wilson disease is commonly found in Japan. It affects 1 in 30,000-40,000 individuals 12. 1 in 90 individuals are a heterozygous car...
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Wilson disease (hepatobiliary manifestations)

Hepatobiliary manifestations of Wilson disease vary largely from fatty changes to cirrhosis and occasionally fulminant hepatic necrosis. They result from accumulation of copper in the liver. For a general discussion of the underlying condition, please refer to the article Wilson disease.  Epid...
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Wirsungocele

Wirsungocele refers to a cystic dilatation of the pancreatic duct of Wirsung, which is the portion of ventral duct between the dorsal-ventral junction and major duodenal papilla. It is believed to be analogous to a choledochocele and santorinicele. Clinical presentation It may be an incidental...
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Xanthogranulomatous cholecystitis

Xanthogranulomatous cholecystitis (XGC) is an uncommon inflammatory disease of the gallbladder that may be difficult to differentiate from malignancy, both on imaging and pathologically. It is characterized by the presence of multiple intramural nodules. Epidemiology It is seen predominantly i...

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