tailieunhanh - Chapter 043. Jaundice (Part 7)

Cholestatic Conditions When the pattern of the liver tests suggests a cholestatic disorder, the next step is to determine whether it is intra- or extrahepatic cholestasis (Fig. 43-1). Distinguishing intrahepatic from extrahepatic cholestasis may be difficult. History, physical examination, and laboratory tests are often not helpful. The next appropriate test is an ultrasound. The ultrasound is inexpensive, does not expose the patient to ionizing radiation, and can detect dilation of the intra- and extrahepatic biliary tree with a high degree of sensitivity and specificity. The absence of biliary dilatation suggests intrahepatic cholestasis, while the presence of biliary dilatation indicates extrahepatic. | Chapter 043. Jaundice Part 7 Cholestatic Conditions When the pattern of the liver tests suggests a cholestatic disorder the next step is to determine whether it is intra- or extrahepatic cholestasis Fig. 43-1 . Distinguishing intrahepatic from extrahepatic cholestasis may be difficult. History physical examination and laboratory tests are often not helpful. The next appropriate test is an ultrasound. The ultrasound is inexpensive does not expose the patient to ionizing radiation and can detect dilation of the intra- and extrahepatic biliary tree with a high degree of sensitivity and specificity. The absence of biliary dilatation suggests intrahepatic cholestasis while the presence of biliary dilatation indicates extrahepatic cholestasis. False-negative results occur in patients with partial obstruction of the common bile duct or in patients with cirrhosis or primary sclerosing cholangitis PSC where scarring prevents the intrahepatic ducts from dilating. Although ultrasonography may indicate extrahepatic cholestasis it rarely identifies the site or cause of obstruction. The distal common bile duct is a particularly difficult area to visualize by ultrasound because of overlying bowel gas. Appropriate next tests include CT magnetic resonance cholangiography MRCP and endoscopic retrograde cholangiopancreatography ERCP . CT scanning and MRCP are better than ultrasonography for assessing the head of the pancreas and for identifying choledocholithiasis in the distal common bile duct particularly when the ducts are not dilated. ERCP is the gold standard for identifying choledocholithiasis. It is performed by introducing a side-viewing endoscope perorally into the duodenum. The ampulla of Vater is visualized and a catheter is advanced through the ampulla. Injection of dye allows for the visualization of the common bile duct and the pancreatic duct. The success rate for cannulation of the common bile duct ranges from 80-95 depending on the operator s experience. Beyond its .