A variety of diagnostic tests help doctors assess disorders of the liver, gallbladder, and biliary tract (the ducts that connect the liver and gallbladder and that transport bile). Among the most important are a group of blood tests known as liver function tests. However, the term is somewhat misleading because most such tests do not test the metabolic or bile-secreting functions of the liver. Rather, they detect inflammation of or damage to the liver. Such blood tests represent a noninvasive way to screen for the presence of liver disease (for example, hepatitis in blood donations) and to measure the severity and progress of liver disease and its response to treatment.
Depending on the suspected problem, a doctor may also order certain imaging tests, such as ultrasonography, computed tomography (CT), or cholangiography of the bile ducts using magnetic resonance imaging (MRI) or x-rays. Also, a doctor may take a sample of liver tissue for examination under a microscope, a procedure called a liver biopsy.
Ultrasonography uses sound waves (see see Common Imaging Tests: Ultrasonography) to provide images of the liver, gallbladder, and bile ducts. Transabdominal ultrasonography is better for detecting structural abnormalities, such as tumors, than for diffuse abnormalities, such as cirrhosis (severe scarring of the liver) or fatty liver (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 in the gallbladder. Ultrasonography of the abdomen can distinguish whether jaundice (a yellowish discoloration of the skin and the whites of the eyes) is caused by bile duct obstruction or by liver cell malfunction. If ultrasonography shows ducts that are dilated (widened), the cause is obstruction. Ultrasonography also provides guidance when inserting a needle to obtain a tissue sample for biopsy. A type of ultrasounography, called Doppler ultrasonography, can show blood flow in 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 intestine to the liver. Doppler ultrasonography can also detect the effects of high blood pressure in the portal vein (portal hypertension). Endoscopic ultrasonography uses a tiny probe on the top 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) imaging (see see Common Imaging Tests: Radionuclide Scanning) uses a substance containing a radioactive tracer that, when injected intravenously into the body, 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. This technique can detect a blocked cystic duct (which joins the gallbladder to the major bile duct). Such a blockage indicates acute inflammation of the gallbladder (cholecystitis—see Tumors of the Liver: Hepatic Granulomas).
Computed tomography (CT−see see Common Imaging Tests: Computed Tomography) provides excellent images of the liver. It is particularly useful for detecting tumors. It can also detect collections of pus (abscesses) and some diffuse disorders, such as a fatty liver (excess fat in the liver).
Magnetic resonance imaging (MRI−see see Common Imaging Tests: Magnetic Resonance Imaging) can detect diffuse liver disorders, such as hepatitis, hemochromatosis, and Wilson's disease, which affect all areas of the liver about equally. 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 dye 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 to perform.
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. A radiopaque dye is injected through the tube into the biliary tract, and x-rays are taken of the biliary tract and pancreatic duct. ERCP is occasionally used simply to see the biliary tract structures, although MRCP is usually preferred 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. For example, 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] or bleeding) occur about 1% of the time. If a treatment is done during ERCP, such complications can occur more often.
Percutaneous transhepatic cholangiography involves inserting a long needle through the skin into the liver and then injecting a radiopaque dye into a bile duct in the liver, using ultrasound for guidance. The x-rays clearly reveal the biliary tract, particularly any blockage within the bile ducts. Like 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 dye 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. Operative cholangiography is more difficult when the gallbladder surgery is being performed via laparoscopy (using a flexible viewing tube and surgical instruments inserted through tiny abdominal incisions).
Simple x-rays of the abdomen usually cannot detect disorders of the liver, gallbladder, or biliary tract.
Biopsy of the Liver
A liver specimen can be obtained during exploratory surgery but is more often obtained by inserting a hollow needle through the skin and into the liver. Before this procedure, called percutaneous liver biopsy, is performed, the skin is anesthetized. Ultrasound is usually used to locate the liver and guide the needle to biopsy any abnormal area. Liver biopsy can be performed as an outpatient procedure. After the specimen is obtained, the person remains in the outpatient department for 3 to 4 hours because of a small risk of complications, such as tearing (laceration) of the liver. If the liver is torn, bleeding into the abdomen may occur. If severe, bleeding can lead to shock. Because bleeding can start up to 15 days after the biopsy, the person is instructed to stay within an hour's drive of the hospital during that period. These complications, though infrequent, can cause serious problems; 1 of 10,000 people die as a result of the procedure. Mild pain in the upper right abdomen, sometimes extending to the right shoulder, is common after a liver biopsy and is usually relieved by analgesics.
In transvenous liver biopsy, a catheter is inserted into a neck vein, threaded through the heart, and placed into one of the hepatic veins that drain the liver. A needle on the tip of the catheter is then inserted through the wall of the vein into the liver. This procedure is less likely to injure the liver than is percutaneous liver biopsy. It is especially useful in people who bleed easily, a complication of severe liver disease.
Liver biopsy can detect information about the liver that may not be evident from other tests. It is commonly used to detect excess fat in the liver (fatty liver), chronic liver inflammation (chronic hepatitis), metabolic liver diseases such as Wilson's disease (an excess of copper) and hemochromatosis (iron overload), complications following liver transplantation, and cancer that has spread to the liver.
Last full review/revision October 2006 by Eldon A. Shaffer, MD