Visualization of the Biliary Tree



Oral cholecystography (OCG), the time-honored method for imaging the gallbladder, involves the oral administration of an iodinated compound, which is concentrated in the gallbladder, fol­lowed 12 hours later by a radiograph of the gall­bladder. The technique identifies most gallstones in patients with a functioning gallbladder. How­ever, in many patients with chronic cholecystitis, and in all patients with a serum bilirubin greater than 2 mg/dl, the gallbladder will not opacify. US is more sensitive (> 98 per cent verus 90 per cent) in detecting gallstones and is replacing the OCG in many centers.

Bile ducts and disorders involving them are well seen only when contrast material is used to fill them. Contrast may be injected into the biliary tree from the upstream side via a thin (23-gauge) needle introduced percutaneously into the he­patic parenchyma (percutaneous transhepatic cholangiogram, PTC) or from below via a small catheter placed endoscopically into the papilla of Vater (endoscopic retrograde cholangiopancrea­tography, ERCP, see page 289). Table 37-3 com­pares these two procedures, both of which pro­vide an excellent view of the biliary tree, although PTC is generally preferred for intrahepatic bile duct lesions and ERCP for extrahepatic duct le­sions.