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.

528 results found
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Simple hepatic cyst

Simple hepatic cysts are common benign liver lesions and have no malignant potential. They can be diagnosed on ultrasound, CT, or MRI. Epidemiology Simple hepatic cysts are one of the commonest liver lesions, occurring in ~2-7% of the population 1,2. There may be a slight female predilection. ...
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Solid and hollow abdominal viscera

The solid abdominal viscera (singular: viscus) is a collective term for those internal organs of the upper abdomen that are primarily solid in nature, namely the liver, pancreas, spleen, adrenals, and kidneys. It is used in contradistinction to the hollow abdominal viscera, which includes, the s...
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Solid pseudopapillary tumor of the pancreas

Solid pseudopapillary tumors (SPT) of the pancreas are rare (usually benign) pancreatic tumors. Terminology The tumor has been referred to with multiple different names, including: solid pseudopapillary tumor (SPT) of the pancreas solid pseudopapillary neoplasm (SPN) solid pseudopapillary e...
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Somatostatinoma

Somatostatinomas are a rare type of neuroendocrine tumor. They may represent around 1% of all gastro-entero-pancreatic endocrine neoplasms. Clinical presentation Presentation can be variable. Patients with functional stomatostatinomas may present with an "inhibitory syndrome" which is a triad ...
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Sonographic halo sign

Sonographic halo sign is used in a number of situations. They include: hypoechoic halo sign (also known as target or bull's eye sign) in liver metastases: used in hepatobiliary imaging, is a concerning feature for malignant lesion if the lesion is a hyperechoic liver lesion 1,2 ultrasound halo...
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Sonographic Murphy sign

Sonographic Murphy sign is defined as maximal abdominal tenderness from pressure of the ultrasound probe over the visualized gallbladder 1,2. It is a sign of local inflammation around the gallbladder along with right upper quadrant pain, tenderness and/or a mass 2. It is one of the most importa...
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Spindle cell hepatocellular carcinoma

Spindle cell hepatocellular carcinoma, also called sarcomatoid hepatocellular carcinoma, is a rare variant of hepatocellular carcinoma (HCC). These patients are reported to have low or normal AFP levels, otherwise risk factors and clinical presentation are similar to typical hepatocellular carci...
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Splenic abscess

Splenic abscesses, like abscesses elsewhere, are localised collections of necrotic inflammatory tissue caused by bacterial, parasitic or fungal agents. They uncommonly affect the spleen due to its efficient reticuloendothelial system phagocytic activity and, consequently, are more likely seen in...
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Splenic artery aneurysm

Splenic artery aneuryms are the commonest visceral arterial aneurysm formation as well as the 3rd commonest abdominal aneurysm (after the aorta and iliac vessels). Aneurysms are usually saccular in configuration and they can either be in the form of a true aneurysm (much more common) or as a pse...
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Splenic brucellosis

Brucellosis is a common zoonosis, which is particularly prevalent in Mediterranean countries. It produces a multisystemic illness that can present with a broad spectrum of clinical manifestations and complications 1. This article is focusing on the splenic involvement by brucellosis. For genera...
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Splenic calcification

Splenic calcifications can occur is various shapes and forms and can occur from a myriad of aetiological factors. The usual calcification observed in radiographs are the multiple, miliary form presenting numerous small rounded densities averaging from three to five millimeters in diameter where...
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Splenic cyst

Splenic epithelial cysts, also referred as splenic epidermoid cysts or primary splenic cysts, are unilocular fluid lesions with thin and smooth walls and no enhancement. They represent ~20% of cysts found in the spleen, and are usually an innocuous incidental imaging finding. Note that most (~8...
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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 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 is a term which refers to enlargement of the spleen. The normal adult splenic length upper limit is usually around 12-15 cm. It can also be helpful to know how to calculate splenic index, volume and mass by CT and MR techniques. Massive splenomegaly is a term used when the spleen we...
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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 one or more focal deposits of splenic tissue in various compartments of the body. Abdominal splenosis is seen after abdominal trauma or surgery (e.g...
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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 the liver without hepatic metastases. It is a cause of cholestasis and cholestatic jaundice.  History and etymology It is named after Maurice H. ...
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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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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. The radioactive technetium radiotracer can be chelated to a number of different compounds to create specific radiopharmaceuticals and optimise the functional imaging of various stru...
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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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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. Basic principles Thorotra...
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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 localised 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 tu...
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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 fluroscopic 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 th...
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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. It is considered pathognomonic for...
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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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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...
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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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Veins of Sappey

Veins of Sappey are small veins around the falciform ligament that drain the venous blood from the anterior part of the abdominal wall directly into the liver. This flow dilutes the portal perfusion at these sites, causing hepatic pseudolesions. Gross anatomy The superior vein of Sappey drains...
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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 material excretion

Vicarious contrast material excretion (VCME) defines excretion of water-soluble contrast material in a way other than via normal renal secretion.  The most common vicarious excretion of water-soluble contrast material is via the liver, resulting in increased bile density seen in the gallbladder...
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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...
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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...
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Water-lily sign (hydatid cyst)

The water-lily 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 X-ray) when the collapsed membran...
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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. Clinical presentation Clinical presentat...
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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 choledochocele and santorinicele. Clinical presentation It may be an incidental f...
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Xanthogranulomatous cholecystitis

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

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