If there is no suggestion of biliary obstruction, screening studies should be performed to evaluate the potential causes of hepatocellular dysfunction; based on clinical suspicion confirmation of the diagnosis is usually made by liver biopsy
Serologic tests for viral hepatitis (most com mon)
Measurement of antimitochondrial antibod ies (for primary biliary cirrhosis).
Measurement of antinuclear anti-smooth muscle (sm), and liver-kidney microsomal (LKM) antibodies (for autoimmune hepatitis).
Serum levels of iron, transferrin, and ferritin (for hemochromatosis).
Serum levels of ceruloplasmin (for Wilson's disease).
Measurement of alpha-1-antitrypsin activity (for alpha-1-antitrypsin deficiency).
When obstruction of the biliary tree is suspected, an imaging study is indicated to differentiate extrahepatic and intrahepatic causes of cholestatic jaundice. The imaging tests which can be used include abdominal ultrasonography, CT of the abdomen, endoscopic retrograde cholangiopancreatography (ERCP), MRI and percutaneous transhepatic cholangiography (PTC)
Ultrasonography _ US can also demonstrate cholelithiasis and is exceedingly sensitive for gallbladder stones; however, common duct stones may not be well seen since gas in the duodenum can obscure visualization of the distal common duct. The advantages of US are that it is noninvasive, portable, and relatively inexpensive and must be considered the initial procedure of choice.
Helical CT scan
Conventional computed tomography (CT) and US are equally effective for the recognition of obstruction and identification of the level of obstruction. However, helical (spiral) CT has improved the accuracy of CT and may emerge as the preferred technique for hepatobiliary imaging
Endoscopic retrograde cholangiopancreatography
ERCP is more expensive than US and CT and, as an invasive maneuver, is associated with a mortality rate of around 0.2% and complications such as bleeding, cholangitis, and pancreatitis (3 percent)
Magnetic resonance cholangiopancreatography
Magnetic resonance cholangiopancreatography (MRCP) is a potential alternative to ERCP. MRCP is as accurate as ERCP for detecting choledocholithiasis. Stones larger than 4 mm are readily seen but these cannot be differentiated from other filling defects such as blood clots, tumor, sludge, or parasites
MRCP is expensive, it eventually replace diagnostic ERCP. However, it is unlikely to replace US as the initial imaging test in the diagnostic evaluation of jaundice; ERCP is preferred in the patient with cholangitis because it permits therapeutic drainage of the obstruction.
Percutaneous transhepatic cholangiography Percutaneous transhepatic cholangiography requires passage of a needle through the skin into the hepatic parenchyma and advancement into a peripheral bile duct. Injection of contrast media provides close to 100 percent sensitivity and specificity for the diagnosis of biliary tract obstruction . It is similar to ERCP in cost and morbidity and may be particularly useful when the level of obstruction is proximal to the common hepatic duct or ERCP is precluded for anatomic reasons. However, it may be technically limited in the absence of dilatation of the intrahepatic ducts.
Choice of imaging procedure In most instances, abdominal US and less often spiral CT is considered to be the screening procedure of choice for the diagnosis of obstructive jaundice of unknown etiology based upon the clinical circumstances.
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