Imaging tests of the liver, gallbladder, and biliary tract include ultrasonography, radionuclide scanning, computed tomography (CT), magnetic resonance imaging (MRI), endoscopic retrograde cholangiopancreatography (ERCP), percutaneous transhepatic cholangiography, operative cholangiography, and simple x-rays.
(See also Overview of the Liver and Gallbladder Overview of the Liver and Gallbladder Located in the upper right portion of the abdomen, the liver and gallbladder are interconnected by ducts known as the biliary tract, which drains into the first segment of the small intestine... read more .)
Ultrasonography Ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more uses sound waves to provide images of the liver, gallbladder, and bile ducts. Transabdominal ultrasonography is better for detecting structural abnormalities affecting just certain parts of the liver, such as tumors, than for abnormalities that affect the entire liver uniformly, such as cirrhosis Cirrhosis of the Liver Cirrhosis is the widespread distortion of the liver's internal structure that occurs when a large amount of normal liver tissue is permanently replaced with nonfunctioning scar tissue. The scar... read more (severe scarring of the liver) or fatty liver Fatty Liver Fatty liver is an abnormal accumulation of certain fats (triglycerides) inside liver cells. People with fatty liver may feel tired or have mild abdominal discomfort but otherwise have no symptoms... read more (excess fat in the liver). It is the least expensive and safest technique for creating images of the gallbladder and bile ducts.
Using ultrasonography, a doctor can readily detect gallstones Gallstones Gallstones are collections of solid material (predominantly crystals of cholesterol) in the gallbladder. The liver can secrete too much cholesterol, which is carried with bile to the gallbladder... read more in the gallbladder. Ultrasonography of the abdomen can distinguish whether jaundice Jaundice in Adults In jaundice, the skin and whites of the eyes look yellow. Jaundice occurs when there is too much bilirubin (a yellow pigment) in the blood—a condition called hyperbilirubinemia. (See also Overview... read more (a yellowish discoloration of the skin and the whites of the eyes) is caused by obstructed bile ducts or by malfunctioning liver cells. If ultrasonography shows bile ducts that are dilated (widened), the cause is typically obstruction. Ultrasonography also provides guidance when doctors insert a needle to obtain a tissue sample for biopsy of the liver Biopsy of the Liver Doctors can obtain a sample of liver tissue during exploratory surgery, but more often they obtain a sample by inserting a hollow needle through the person's skin and into the liver. This type... read more .
A type of ultrasonography called Doppler ultrasonography Doppler ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more can show blood flowing through the blood vessels of the liver. Doppler ultrasonography can detect blockages in the liver's arteries and veins, particularly the portal vein, which brings blood from the intestines to the liver. Doppler ultrasonography can also detect the effects of high blood pressure within the portal vein (a condition called portal hypertension Portal Hypertension Portal hypertension is abnormally high blood pressure in the portal vein (the large vein that brings blood from the intestine to the liver) and its branches. Cirrhosis (scarring that distorts... read more ). Endoscopic ultrasonography uses a tiny probe on the tip of an endoscope that is passed through the mouth into the stomach and the first segment of the small intestine (duodenum), bringing the probe closer to the liver and its surrounding organs.
Radionuclide (radioisotope) scanning Radionuclide Scanning In radionuclide scanning, radionuclides are used to produce images. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more uses a substance containing a radioactive tracer that, when injected intravenously, collects in a particular organ. The radioactivity is detected by a gamma-ray camera, which is positioned over the upper abdomen and is attached to a computer that generates an image. A liver scan uses a radioactive substance that collects in liver cells.
Cholescintigraphy (hepatobiliary scintigraphy or scan), another type of radionuclide imaging, follows the movement of a radioactive substance as it is secreted from the liver and passes into the gallbladder and through the bile ducts into the duodenum (the first segment of the small intestine). This technique can detect a blocked cystic duct (the tube that joins the gallbladder to the major bile duct—see figure View of the Liver and Gallbladder View of the Liver and Gallbladder Located in the upper right portion of the abdomen, the liver and gallbladder are interconnected by ducts known as the biliary tract, which drains into the first segment of the small intestine... read more ). Such a blockage indicates acute inflammation of the gallbladder (cholecystitis Cholecystitis Cholecystitis is inflammation of the gallbladder, usually resulting from a gallstone blocking the cystic duct. Typically, people have abdominal pain, fever, and nausea. Ultrasonography can usually... read more ).
Computed tomography Computed Tomography (CT) In computed tomography (CT), which used to be called computed axial tomography (CAT), an x-ray source and x-ray detector rotate around a person. In modern scanners, the x-ray detector usually... read more (CT) provides excellent images of the liver. It is particularly useful for detecting tumors. It can also detect collections of pus (abscesses) and some disorders that affect the entire liver uniformly, such as a fatty liver Fatty Liver Fatty liver is an abnormal accumulation of certain fats (triglycerides) inside liver cells. People with fatty liver may feel tired or have mild abdominal discomfort but otherwise have no symptoms... read more (excess fat in the liver).
Magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI) can detect certain liver disorders, such as hepatitis Overview of Hepatitis Hepatitis is inflammation of the liver. (See also Overview of Acute Viral Hepatitis and Overview of Chronic Hepatitis.) Hepatitis is common throughout the world. Hepatitis can be Acute (short-lived) read more , hemochromatosis Hemochromatosis Hemochromatosis is a hereditary disorder that causes the body to absorb too much iron, causing iron to build up in the body and damage organs. In the United States, over 1 million people have... read more , and fatty liver disease Fatty Liver Fatty liver is an abnormal accumulation of certain fats (triglycerides) inside liver cells. People with fatty liver may feel tired or have mild abdominal discomfort but otherwise have no symptoms... read more , that affect all areas of the liver uniformly. MRI shows blood flow, providing information about blood vessel disorders.
MRI technology can also provide images of the bile ducts and nearby structures, using a technique called magnetic resonance cholangiopancreatography (MRCP). The images produced are as good as those produced by more invasive tests, in which a contrast agent is directly injected into the biliary and pancreatic ducts. Unlike CT, MRI tests do not involve exposure to x-rays, though they are more expensive than CT and take longer.
Endoscopic retrograde cholangiopancreatography (ERCP) involves passing an endoscope (a flexible viewing tube) through the mouth, esophagus, and stomach into the duodenum. A thin tube is then inserted through the endoscope into the biliary tract. Doctors inject a radiopaque contrast agent through the tube into the biliary tract, and, at the same time, x-rays are taken of the biliary tract and pancreatic duct.
ERCP is occasionally used simply to see the biliary tract structures, although doctors usually prefer MRCP when available because it is just as good and is safer. However, unlike other diagnostic tests, ERCP allows doctors to do biopsies and certain treatments because an endoscope is used during the procedure. For example, with the endoscope, a stone in a bile duct can be removed, or a tube (stent) can be inserted to bypass a bile duct blockage caused by cancer. With ERCP, complications (such as inflammation of the pancreas [pancreatitis Overview of Pancreatitis Pancreatitis is inflammation of the pancreas. The pancreas is a leaf-shaped organ about 5 inches (about 13 centimeters) long. It is surrounded by the lower edge of the stomach and the first... read more ] or bleeding) occur about 1% of the time. If a treatment is done during ERCP, such complications can occur more often.
Understanding Endoscopic Retrograde Cholangiopancreatography
Percutaneous transhepatic cholangiography involves inserting a long needle through the skin into the liver and then injecting a radiopaque contrast agent into a bile duct in the liver, using ultrasonography for guidance. The x-rays clearly reveal the biliary tract, particularly any blockage within the bile ducts. Like endoscopic retrograde cholangiopancreatography Endoscopic Retrograde Cholangiopancreatography Imaging tests of the liver, gallbladder, and biliary tract include ultrasonography, radionuclide scanning, computed tomography (CT), magnetic resonance imaging (MRI), endoscopic retrograde cholangiopancreatography... read more (ERCP), percutaneous transhepatic cholangiography is used more often for treatment or biopsy than to obtain images of the biliary tract. Complications of percutaneous transhepatic cholangiography, such as bleeding and internal damage, make it a less desirable method than ERCP, except in special circumstances.
Operative cholangiography involves the injection of a radiopaque contrast agent directly into the ducts of the biliary tract during gallbladder surgery. X-rays then reveal clear images of the biliary tract. This test is used only occasionally, when other, less invasive tests do not provide enough information.