Imaging Tests

Imaging Tests:

• Ultrasound: An abdominal ultrasound can test for many liver conditions, including cancer, cirrhosis, or problems from gallstones.

• CT scan (computed tomography): A CT scan of the abdomen gives detailed pictures of the liver and other abdominal organs.

• Liver biopsy: A liver biopsy is most commonly done after another test, such as a blood test or ultrasound, indicates a possible liver problem.

• Liver and spleen scan: This nuclear scan uses radioactive material to help diagnose a number of conditions, including abscesses, tumors, and other liver function problems.

Liver function tests

Common tests that are used to see how well the liver is working. This is called liver function. Tests include:

•Albumin

•Alpha-1 antitrypsin

•ALP

•ALT

•AST

•Gamma-glutamyl transpeptidase (GGT)

•Prothrombin time

•Serum bilirubin

•Urine bilirubin

IMAGING TESTS

Ultrasonography uses sound waves (see 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.

Liver and Gallbladder Scan

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 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 Hepatic Granulomas).

Computed tomography (CT−see 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).

Understanding Endoscopic Retrograde Cholangiopancreatography

In endoscopic retrograde cholangiopancreatography (ERCP), a radiopaque dye is introduced through an endoscope (a flexible viewing tube), which is inserted into the mouth and through the stomach into the duodenum (the first segment of the small intestine). The radiopaque dye is injected into the biliary tract just past the sphincter of Oddi. The dye then flows back up the biliary tract and often shows the pancreatic ducts. Surgical instruments can also be used with the endoscope, allowing a doctor to remove a stone in a bile duct or insert a tube (stent) to bypass a bile duct blocked by scarring or cancer.

Magnetic resonance imaging (MRI−see Magnetic Resonance Imaging) can detect diffuse liver disorders, such as hepatitis, hemochromatosis, and Wilson's disease, which affect all areas of the liver about

...