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Recognition of pseudolesions of the liver at computed tomography (CT) is important because of their close resemblance to primary liver cancers or metastases. Two types of pseudolesion in the noncirrhotic liver include that due to transient extrinsic compression, typically caused by ribs or the diaphragm, and that due to a "third inflow" of blood from other than the usual hepatic arterial and portal venous sources: the cholecystic, parabiliary, or epigastric-paraumbilical venous system. Although the location of both types of pseudolesion are characteristic, their appearances at CT during arterial portography and CT during selective angiography vary from nonenhanced low-attenuation areas to well-enhanced high-attenuation areas, depending on the amount and timing of the inflow and presence or absence of focal metabolic alteration of the hepatocytes. Radiologists need to understand the underlying mechanism of these pseudolesions to better recognize the wide range of their appearances at CT.

In patients with intraductal mucin-producing tumors of the pancreas, filling defects are indicative of malignancy. Diffuse main pancreatic duct dilatation greater than 15 mm (main duct type), or any main pancreatic duct dilatation (branch duct type), is strongly associated with malignancy.

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OBJECTIVE. The aim of thisretrospective studywasto clarify whetherMR cholangiopan creatography (MRCP) isa suitablereplacement for ERCP in evaluation of thecholedochal cyst. MATERIALSAND METHODS. Sixteenpatients(six adultand 10pediatric)with chole dochal cysts underwent MRCP using a half-Fourier acquisition single-shot turbo spin-echo se quence. Extent of the cyst. defects within the biliary tree, and presence or absence of the anomalous junction of the pancreaticobiliary duct were evaluated. Findings were compared with those of ERCP.RESULTS. MRCP betterdefinedthe proximalbiliary tree thandid ERCP in two patients. Defectswithin the biliary tree were diagnosedcorrectlyon MRCP in eight patients;however, two defects within the distal common bile duct were missed in pediatric patients. The presence of the anomalous junction of the pancreaticobiliary duct was revealed accurately by MRCP in all adult patients but was revealed accurately in only four of the 10 pediatric patients.CONCLUSION. MRCP appearsto offer diagnosticinformationthat is equivalentto that of ERCP for assessment ofcholedochalcystsin adults.In pediatricpatients, MRCP shouldnot replace ERCP; however, MRCP can play an important role as a noninvasive examination and shouldbe considered a first-choiceimagingtechniquefor evaluationof choledochal cysts.