A filling defect is a general term used to refer to any abnormality on an imaging study which disrupts the normal opacification (filling) of a cavity or lumen. The opacification maybe physiological, for example, bile in the gallbladder or blood in a dural venous sinus, or maybe due to the instal...
A fistula (plural: fistulae) is an abnormal connection between two epithelial surfaces such as between hollow organs, skin or vessels. Conventionally, the name of a specific fistula type is a combination of the two organs
For discussions of specific fistulae please refer to individual articles....
Flash filling hepatic hemangiomas, also known as flash filling hepatic venous malformations, are a type of atypical hepatic hemangioma, which due to its imaging features often raises the concern of a malignant process rather than a benign one.
It is important to note that accordin...
Focal fatty sparing of the liver is the localized absence of increased intracellular hepatic fat, in a liver otherwise fatty in appearance i.e. diffuse hepatic steatosis. Recognition of this finding is important to prevent the erroneous belief that the region of sparing is itself a mass.
Focal gallbladder wall thickening is an imaging finding that includes both benign and malignant etiologies.
gallbladder carcinoma: look for infiltration into adjacent organs, metastases, lymphadenopathy, bile duct dil...
Focal gas collection in right upper quadrant on plain radiographs can occur from a number of pathologies. Things to consider are:
enterobiliary fistula: common types include cholecystoduodenal fistula and cholecystocolic fistula. It may occur with:
gallstone ileus (being most common) 3
The focal hepatic hot spot sign can be seen on technetium 99m sulfur colloid scans of the liver and spleen, as well as CT studies.
It occurs as a focal area of increased radiopharmaceutical uptake in the medial segment of the left hepatic lobe (segment IV) due to superior...
Focal hepatic steatosis, also known as focal fatty infiltration, represents small areas of liver steatosis. In many cases, the phenomenon is believed to be related to the hemodynamics of a third inflow.
Essentially the same as those that contribute to diffuse hepatic steatosis:
Focal hypodense hepatic lesions on a non-contrast CT scan can result from a number of pathological entities, including:
biliary hamartoma: von Meyenberg complexes 2
hepatoma/hepatocellular carcinoma (HCC)
Focal nodular hyperplasia (FNH) is a regenerative mass lesion of the liver and the second most common benign liver lesion (most common is a hemangioma). Many FNHs have characteristic radiographic features on multimodality imaging, but some lesions may be atypical in appearance. Focal nodular hyp...
Focused Assessment with Sonography for Trauma (FAST) scan is a point-of-care ultrasound examination performed at the time of presentation of a trauma patient.
It is invariably performed by a clinician, who should be formally trained, and is considered as an 'extension' of the trauma clinical a...
The Frey procedure is a type of pancreaticojejunostomy designed to treat chronic pancreatitis.
The fundamental technique is similar to the Puestow procedure, with a lateral incision of the pancreatic duct from an anterior approach, and then a side-to-side anastomosis between the pancreas and a ...
Gadoxetate disodium (also known by the tradenames PrimovistTM and EovistTM) is a hepatospecific paramagnetic gadolinium-based contrast agent, used exclusively in MRI liver imaging. Its chief use is in hepatic lesion characterization, i.e. assessing focal liver lesions identified on other imaging...
The gallbladder is a pear-shaped musculomembranous sac located along the undersurface of the liver. It functions to accumulate and concentrate bile between meals.
The normal adult gallbladder measures from 7-10 cm in length and 3-4 cm in transverse diameter 6. The ga...
Gallbladder adenomas are uncommon gallbladder polyps that, although benign, have a premalignant behavior.
As the distinction of adenomas and intracholecystic papillary-tubular neoplasms (ICPN) is not entirely clear, with important overlap between both entities, some authors have p...
Agenesis of the gallbladder describes the rare congenital absence of the gallbladder.
overall incidence is estimated <0.1% (range 0.04-0.1%)
reported 3:1 female predominance of symptomatic cases
equivalent gender distribution in autopsy cases
Gallbladder carcinoma is a term referring to primary epithelial malignancies arising from the gallbladder, in which the great majority (90%) are adenocarcinomas and the remainder are squamous cell carcinomas. They are more prevalent in elderly women and, in most cases, are only symptomatic when ...
Gallbladder cholecystoses are conditions characterized by the accumulation of cholesterol (and other fats) in the gallbladder. There are two main forms:
adenomyomatosis: mucosal hyperplasia with growth toward the muscular layer - thickened muscular layer. Cholesterol accumulation is intralumina...
Gallbladder duplication is a rare anatomic anomaly characterized by the presence of an accessory gallbladder. There is no increased risk for malignancy or calculi compared to a single gallbladder.
Prevalence is estimated at 1 in 4000 live births 3.
Gallbladder dysfunction, or functional gallbladder disorder, refers to biliary pain due to motility disturbance of the gallbladder without gallstones, biliary sludge, microlithiasis or microcrystals. The disorder has previous been known by several other names, including gallbladder dyskinesia, g...
Gallbladder empyema (suppurative cholecystitis 1) is an uncommon complication of cholecystitis and refers to a situation where the gallbladder lumen is filled and distended by purulent material (pus).
There is an increased incidence in those with diabetes mellitus 2 and/or advance...
Gallbladder ghost triad is a term used on ultrasound studies when there is a combination of three gallbladder features on biliary atresia:
atretic gallbladder, length less than 19 mm
irregular or lobular contour
lack of smooth/complete echogenic mucosal lining with an indistinct wall
Gallbladder hydrops or mucocele 5 refers to marked dilatation of the gallbladder due to chronic obstruction of the cystic duct resulting in accumulation of sterile non-pigmented mucin.
Abdominal pain with palpable gallbladder without any signs of infection. In an asymptom...
Gallbladder inflammatory polyps are a benign subtype of gallbladder polyps, representing ~10% of all polyps. They appear as a result of chronic inflammation (chronic cholecystitis).
For further details, please refer to the parental article on gallbladder polyps.
Gallbladder malignancy (or gallbladder cancer) is relatively uncommon. The commonest histopathological type is carcinoma.
gallbladder adenocarcinoma: most common 1
gallbladder squamous cell carcinoma
gallbladder neuroendocrine carcinoma
gallbladder sarcoma: ve...
Gallbladder metastases are rare and usually represent an advanced and end-stage of malignancy. Malignant melanoma and gastric carcinoma account for the most common primary malignancies to see metastases to the gallbladder, in the Western and Asian societies, respectively.
Gallbladder perforations are a serious complication of acute cholecystitis and represent an advanced stage of the disease. They tend to occur in an elderly and/or comorbid demographic and carry higher rates of morbidity and mortality.
Symptoms and clinical signs are varia...
Gallbladder polyps are elevated lesions on the mucosal surface of the gallbladder. The vast majority are benign, but malignant forms are seen.
On imaging, although they may be detected by CT or MRI, they are usually best characterized on ultrasound as a non-shadowing and immobile polypoid ingro...
Gallbladder sludge, also known as biliary sand, biliary sediment, or thick bile, is a mixture of particulate matter and bile, normally seen as a liquid-liquid level in the gallbladder on ultrasound, corresponding to the precipitate of bile solutes.
The term biliary microlithiasis ...
Gallbladder triplication is an extremely rare anomaly. There are three types of gallbladder triplication are described according to the number of cystic duct and their insertion:
Three gallbladders and three cystic ducts which unite to form a common cystic duct before joining the common bile du...
Gallbladder volvulus is a relatively rare condition in which there is a rotation of the gallbladder around the axis of the cystic duct and artery.
Symptoms are non-specific, however right upper quadrant pain and vomiting are similar to biliary colic. Laboratory evaluation...
Gallbladder wall cholesterolosis is a type of cholecystosis, therefore, results from the accumulation of cholesterol esters and triglycerides in the macrophages within the gallbladder wall (cf. adenomyomatosis, where cholesterol accumulation is intraluminal). It is a benign condition that may oc...
Thickening of the gallbladder wall, usually considered >3 mm, is a non-specific sign of various conditions.
Gallbladder wall thickening can be caused by inflammatory, benign, and malignant etiologies. Pseudothickening caused by the normal postprandial state of the contracted gallblad...
This is a basic article for medical students and other non-radiologists
Gallstone disease represents a group of conditions that are linked to, or caused by, gallstones. These stones are formed from sludge in the gallbladder and may range from millimeters in diameter to several centimeters. 90% ...
Gallstone ileus is an uncommon cause of a mechanical small bowel obstruction. It is a rare complication of chronic cholecystitis 7 and occurs when a gallstone passes through a fistula between the gallbladder and small bowel before becoming impacted at the ileocecal valve.
Gallstone pancreatitis refers to pancreatitis caused by gallstones, specifically distal choledocholithiasis. Gallstones are the cause for 35-40% of acute pancreatitis but this number has a wide regional variance.
Gallstone pancreatitis has a higher incidence in women (compared to...
Gallstones, also called cholelithiasis, are concretions that may occur anywhere within the biliary system, most commonly within the gallbladder.
Gallstones (cholelithiasis) describe stone formation at any point along the biliary tree. Specific names can be given to gallstones depe...
Gangrenous cholecystitis is the most common complication of acute cholecystitis, affecting ~15% (range 2-30%) of patients.
systemic inflammatory response syndrome 5
Gastric varices are an important portosystemic collateral pathway, occurring in ~20% of patients with portal hypertension. They are considered distinct from esophageal varices in that they have a propensity to hemorrhage at comparatively lower portal pressures 1, and are also associated with hig...
Gastrinomas are the second most common pancreatic endocrine tumor and the most common type in the setting of multiple endocrine neoplasia type I (MEN I).
Most gastrinomas are sporadic, although some are seen in the setting of multiple endocrine neoplasia type I (MEN I). In general...
The gastroduodenal artery (GDA) is a terminal branch of the common hepatic artery which mainly supplies the pylorus of the stomach, proximal duodenum, and the head of the pancreas. Due to its proximity to the posterior wall of the first part of the duodenum, the gastroduodenal artery is one of t...
Causes of generalized increase in hepatic echogenicity include:
diffuse fatty change
cirrhosis: and/or coarsening
chronic hepatitis 3: and/or coarsening
diffuse infiltration or deposition
glycogen storage disease
Causes of generalized reduction of liver echogenicity on ultrasound include:
diffuse malignant infiltration
generalized increase in liver echogenicity
hepatic attenuation on CT
Geographic appearance is a term used in imaging, and other clinical fields (e.g. histopathology) to describe lesions with a well-circumscribed margins with adjacent tissues. The term derives from the somewhat similar appearance of the outline of countries on a map or the clear demarcation forme...
Giant hepatic hemangiomas, also known as giant hepatic venous malformations, are relatively uncommon non-neoplastic vascular lesions of the liver, which can be strikingly large and mimic tumors.
It is important to note that according to newer nomenclature, these lesions are known ...
Gilbert syndrome is a hereditary condition which can result in jaundice.
It results in intermittent unconjugated hyperbilirubinemia in the absence of hepatocellular disease or hemolysis. Uridine diphosphate-glucuronyl transferase activity is reduced resulting in indirect hyperbilirub...
Glisson's capsule is the external fibrous layer that envelops liver lobules.
Right upper quadrant pain can be caused by distension of Glisson's capsule 3. This can be caused by several processes, including a hematoma or a mass.
History and etymology
It is named after Franc...
Glucagonomas are pancreatic endocrine tumors that secrete glucagon. Most lesions are malignant.
They are very rare with an incidence of ~0.000005% or less than 1 case per 20 million. Equal incidence in middle-aged men and women.
Accounts for 1% of all the neuroendocrine tumors a...
Glycogen storage disease (GSD) refers to a number of syndromes which are characterized by a defect in synthesis, metabolism or storage of glycogen.
There are many types of GSD:
type I: von Gierke disease
type II: Pompe disease
type III: Cori or Forbes disease
type IV: Andersen di...
Glycogen storage disease type II, also known as Pompe disease or acid maltase deficiency disease, is an inherited lysosomal storage disorder characterized by abnormal glycogen accumulation within lysosomes. It is a multisystem disorder involving the heart, skeletal muscle and liver. It is caused...
Granulomatous hepatitis refers to an inflammatory liver disease associated with granuloma formation in the liver. These can be caseating or non-caseating.
It can be associated with a wide variety of conditions, which most commonly includes
sarcoidosis: hepatic manifest...
The greater pancreatic artery, also known as the pancreatica magna artery, is a branch of the splenic artery that supplies the pancreatic tail and body.
It arises approximately two thirds the way along the splenic artery and descends a short distance to run to the left along the posterior margi...
Gullo syndrome, also known as benign pancreatic hyperenzymemia, is characterized by the abnormal elevation of the serum levels of most or all of the pancreatic enzymes without any evidence of underlying pancreatic pathology. It is a diagnosis of exclusion made when all other laboratory assays an...
Abdominal complications of hematopoietic stem cell transplantation can occur early (0-100 days) or late (>100 days) post-transplant.
bacterial infections, e.g. pseudomembranous colitis
fungal infections, often affecting the esophagus or as hepatic/splenic microabscesses
Hemobilia refers to the presence of blood in the biliary tree.
The classical clinical triad, only seen in ~50% of cases, consists of:
melena (i.e. upper gastrointestinal bleeding)
iatrogenic: surgical or percutaneous proced...
Hemochromatosis is an iron overload disorder characterized by a progressive increase in total body iron stores and deposition of iron in some non-reticuloendothelial system (RES) body organs which results in some instances in organ dysfunction.
This article focus on the general principles of he...
Hemorrhagic cholecystitis refers to an inflammatory process of the gallbladder, complicated by hemorrhage into the lumen.
The presenting features may mimic non-hemorrhagic acute cholecystitis, with right upper quadrant pain being a dominant feature. If the blood is passe...
Hemorrhagic pancreatitis is characterized by bleeding within or around the pancreas, and is usually considered a late sequela of acute pancreatitis.
Hemorrhage can occur in patients with severe necrotizing pancreatitis or as a result of pancreatic pseudoaneurysm rupture when it const...
HELLP syndrome is a pregnancy-related condition and is an abbreviation for:
elevated liver enzymes and
It is considered a severe and life-threatening form of pre-eclampsia although it can occur without co-existing pre-eclampsia.
The estimated inciden...
Hepar lobatum carcinomatous, also known as pseudocirrhosis of the liver, is a rare form of metastatic liver disease. It is most often secondary to invasive ductal and lobular breast cancer. It was, however, first described in tertiary syphilis. The exact pathogenesis is unclear, and both direct ...
Hepascore is a biochemical severity scoring system based on liver function tests in predicting the extent of liver fibrosis/cirrhosis in patients with hepatitis C infection. Hepascore may also be applicable to other liver diseases and is being trialed for fatty liver disease and hepatitis B infe...
Hepatic abscesses, like abscesses elsewhere, are localized collections of necrotic inflammatory tissue caused by bacterial, parasitic, or fungal agents.
The frequency of individual infective agents as causes of liver abscesses are intimately linked to the demographics of the affe...
Hepatic adenomas, also referred to as hepatocellular adenomas, are benign, generally hormone-induced, liver tumors. The tumors are usually solitary, have a predilection for hemorrhage, and must be differentiated from other focal liver lesions.
The incidence of hepatic adenomas is ...
Hepatic adenomatosis is the presence of numerous, more than 10 and up to 50, hepatic adenomas. It is a rare disorder, best characterized with MRI.
Patients with hepatic adenomatosis do not necessarily have the classic risk factors associated with the development of hepatic adenoma...
Hepatic adrenal rest tumors (HART), previously been termed primary hypernephroma of the liver or hypernephroid carcinoma of the liver, are very rare liver tumors with histology similar to adrenocortical carcinoma.
It tends to occur in younger patients and there is no recognized g...
Hepatic amyloidosis refers to the extracellular deposition of amyloid in the parenchyma sinusoids or vessel walls. Liver involvement in amyloidosis is uncommon.
It can be primary or secondary and it typically occurs as diffuse infiltration 2.
There is amyloid deposition in liver p...
Hepatic angiomyolipoma (HAML) is an uncommon benign hamartomatous hepatic mass lesion, containing blood vessel (angioid), smooth muscle (myoid) and mature fat (lipoid) components. There is an association with tuberous sclerosis, although this is less strong than for renal AMLs.
Hepatic angiosarcoma is a rare malignancy but is still the third most common primary liver tumor. They have a variable appearance on both CT and MRI, reflecting the pleomorphic histological nature. Prognosis is very poor, with survival uncommon beyond one year from diagnosis.
The resistive index (RI) is the commonest Doppler parameter used for hepatic arterial evaluation. The usual range in normal, as well as post-transplant individuals, is between 0.55 and 0.8.
It is measured by:
Resistive index (RI) = (peak systolic velocity - end-diastolic velocity)/peak systoli...
The hepatic artery proper, also known as the proper hepatic artery (PHA), is the continuation of the common hepatic artery after it gives off the gastroduodenal artery. Just prior to the porta hepatis it divides into the left and right hepatic arteries.
The hepatic artery...
Hepatic attenuation on CT, reflected by Hounsfield values, depends on a combination of factors including the presence or absence, as well as the phase, of IV contrast administration.
Allowing for all these factors, the mean unenhanced attenuation value is around 55 HU 4.
Hepatic capsular retraction is an uncommon finding that is defined as loss of the normal liver contour due to focal flattening/irregularity or concavity. It is related to several benign and malignant pathologies.
The list of differential diagnoses associated with hepatic...
The following mnemonics can be used as reminders of the causes of hepatic capsular retraction:
C: cholangiocarcinoma (intrahepatic)
T: treated hepatic metastasis or hepatocellular carcinoma
C: cirrhosis with confluent hepatic fibrosis
H: hemangioma (es...
Hepatic carcinosarcoma is a very rare tumor that is defined by mixed histological features.
This tumor has also been referred to as malignant mixed tumor, spindle cell carcinoma, pseudosarcoma or sarcomatoid carcinoma 1,2.
Hepatic carcinocarcinoma contain a mixture of...
Hepatic encephalopathy (HE), also known as portosystemic encephalopathy (PSE), refers to a spectrum of neuropsychiatric abnormalities occurring in patients with liver dysfunction and portal hypertension. It results from exposure of the brain to excessive amounts of ammonia.
Hepatic epithelioid hemangioendothelioma (HEHE) is a rare, low to intermediate grade malignant hepatic vascular tumor.
There may be a greater female incidence (with reported male-to-female ratio, 3:2), with peak incidence thought to be around 30-40 years old.
Hepatic hemangiomas or hepatic venous malformations are the most common benign vascular liver lesions. They are frequently diagnosed as an incidental finding on imaging, and most patients are asymptomatic. From a radiologic perspective, it is important to differentiate hemangiomas from hepatic m...
Hepatic haemangiomatosis is a condition in which the are multiple hemangiomas affecting the liver.
When the lesions are spread throughout the liver, then this is termed diffuse hepatic haemangiomatosis.
giant liver hemangioma 2
Hepatic hemosiderosis, or hepatic iron overload, refers to the deposition of hemosiderin in the liver.
Hepatic iron overload can be in the form of 7:
In the absence of genetic he...
Hepatic hydatid disease is a parasitic zoonosis caused by the Echinococcus tapeworm. In the liver, two agents are recognized as causing disease in humans:
For a general discussion, and links to other system-specific manifestations, please r...
Hepatic hydrothorax (HH) is an uncommon manifestation of cirrhosis with ascites. It is one of the pulmonary complications of cirrhosis with portal hypertension.
It is characterized by formation of pleural effusions usually greater than 500 mL, in patients with portal hypertension without any o...
Hepatic infarction is an extremely rare situation because the liver has a dual blood supply from the hepatic artery and portal vein. Hepatic infarction can occur when there is both hepatic arterial and portal vein flow compromise but most cases are due to acute portal venous flow compromise 11.
Hepatic inflammatory pseudotumors (IPT), also known as xanthogranulomas or plasma cell granulomas of the liver, are rare benign hepatic lesions.
Most common in young adults with males affected more than females 7.
Etiology is unknown 7.
Hepatic leiomyosarcomas are rare primary malignant tumors derived from smooth muscle cells in the liver.
Hepatic leiomyosarcoma is rare 1. An equal sex distribution and a broad age range (5 months-66Y) has been reported. Some have suggested an associated with AIDS 2.
Hepatic lipomas are uncommon benign lesions of the liver.
As with lipomas elsewhere in the body, hepatic lipomas are marginated masses that are composed of mature adipocytes without evidence of cellular atypia.
Hepatic lymphangiomas are a rare benign condition that corresponds to focally dilated lymphatic channels in the liver.
For a general discussion on this topic, please refer to the parental article on lymphatic malformations.
Most cases are asymptomatic.
Hepatic lymphoma is a term given to any form of hepatic involvement with lymphoma. This can be broadly divided into:
secondary hepatic involvement with lymphoma: most common by far, many tend to be non-Hodgkin lymphoma (NHL) 1
primary hepatic lymphoma: extremely rare
Risk factors f...
Hepatic mesenchymal hamartomas are uncommon benign hepatic lesions which are mostly seen in children under the age of 2. Some authors consider them to be developmental anomalies rather than cystic neoplasia 9,12.
Hepatic mesenchymal hamartomas typically occur in children and neon...
Hepatic metastases are 18-40 times more common than primary liver tumors 6. Ultrasound, CT, and MRI are all useful for detection of hepatic metastases and evaluation across multiple post-contrast CT series, or MRI pulse sequences are necessary.
The demographics of patients with l...
Hepatic myeloid sarcomas, also referred to as hepatic granulocytic sarcoma or hepatic chloromas, are rare neoplasms comprised of myeloid precursor cells happening in the liver. They are a unique presentation of acute myeloid leukemia (AML).
Please refer to the main article on myeloid sarcoma/c...
Hepatic myelolipoma is a rare, benign fat-containing lesion of the liver, usually asymptomatic and found incidentally. Its diagnosis by imaging remains difficult because of a lack of pathognomonic signs. The definite diagnosis is by resection or biopsy.
Hepatic myelolipomas are ...
Primary hepatic neuroendocrine tumors (carcinoids) is an extremely rare type of neuroendocrine tumor, with somewhere between 60-90 cases reported in the literature. Metastatic neuroendocrine tumor from the gastrointestinal tract to the liver is far more common.
Hepatic osteodystrophy is an often forgotten metabolic bone disease seen in patients with chronic liver disease, in particular cirrhosis, primary biliary cholangitis, and primary sclerosing cholangitis.
Cirrhotic patients have increased risk factors for developing osteoporosis such as hypogonad...