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Diagnostic Pitfalls of MR Cholangiopancreatography in the Evaluation of the Biliary Tract and Gallbladder

¹ Department of Radiology, Kurashiki Central Hospital, Miwa 1-1-1, Kurashiki 710-8602, Japan

View larger version (90K): [in a new window]   Figure 1a.  Nonvisualized gallbladder cancer due to MIP postprocessing. (a) Multisection MR cholangiopancreatogram shows only minimal deformity of the gallbladder (arrow). No filling defect is seen. (b) Coronal source image reveals gallbladder cancer as a filling defect with a multinodular surface (arrows). (c) Single-section MR cholangiopancreatogram shows gallbladder cancer as an irregularly shaped filling defect (arrows).

View larger version (79K): [in a new window]   Figure 1b.  Nonvisualized gallbladder cancer due to MIP postprocessing. (a) Multisection MR cholangiopancreatogram shows only minimal deformity of the gallbladder (arrow). No filling defect is seen. (b) Coronal source image reveals gallbladder cancer as a filling defect with a multinodular surface (arrows). (c) Single-section MR cholangiopancreatogram shows gallbladder cancer as an irregularly shaped filling defect (arrows).

View larger version (49K): [in a new window]   Figure 1c.  Nonvisualized gallbladder cancer due to MIP postprocessing. (a) Multisection MR cholangiopancreatogram shows only minimal deformity of the gallbladder (arrow). No filling defect is seen. (b) Coronal source image reveals gallbladder cancer as a filling defect with a multinodular surface (arrows). (c) Single-section MR cholangiopancreatogram shows gallbladder cancer as an irregularly shaped filling defect (arrows).

View larger version (99K): [in a new window]   Figure 2a.  Respiratory motion artifact. (a) Multisection MR cholangiopancreatogram shows the biliary tree (solid arrows) and main pancreatic duct (arrowheads) as discontinuous and duplicated. Gallstones (open arrows) in the gallbladder are not well delineated due to MIP reconstruction artifact. (b) Single-section MR cholangiopancreatogram shows the CBD, main pancreatic duct (arrowheads), and multiple gallstones (arrows) more clearly than multisection MR cholangiopancreatography (cf a). Note the pancreatic cysts (*) and dilated right renal pelvis (+).

View larger version (111K): [in a new window]   Figure 2b.  Respiratory motion artifact. (a) Multisection MR cholangiopancreatogram shows the biliary tree (solid arrows) and main pancreatic duct (arrowheads) as discontinuous and duplicated. Gallstones (open arrows) in the gallbladder are not well delineated due to MIP reconstruction artifact. (b) Single-section MR cholangiopancreatogram shows the CBD, main pancreatic duct (arrowheads), and multiple gallstones (arrows) more clearly than multisection MR cholangiopancreatography (cf a). Note the pancreatic cysts (*) and dilated right renal pelvis (+).

View larger version (75K): [in a new window]   Figure 3a.  Overestimation of ductal narrowing. (a) Multisection MR cholangiopancreatogram demonstrates biliary obstruction at the junction of the common hepatic duct (CHD) (solid arrow) and accessory right hepatic duct (open arrow) due to invasion of gallbladder neck cancer. Note the conical deformity of the gallbladder (arrowheads). (b) Endoscopic retrograde cholangiopancreatogram reveals that the CHD (arrow) is severely stenotic but not completely obstructed.

View larger version (141K): [in a new window]   Figure 3b.  Overestimation of ductal narrowing. (a) Multisection MR cholangiopancreatogram demonstrates biliary obstruction at the junction of the common hepatic duct (CHD) (solid arrow) and accessory right hepatic duct (open arrow) due to invasion of gallbladder neck cancer. Note the conical deformity of the gallbladder (arrowheads). (b) Endoscopic retrograde cholangiopancreatogram reveals that the CHD (arrow) is severely stenotic but not completely obstructed.

View larger version (101K): [in a new window]   Figure 4a. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (131K): [in a new window]   Figure 4b. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (113K): [in a new window]   Figure 4c. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (96K): [in a new window]   Figure 5a. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (111K): [in a new window]   Figure 5b. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (111K): [in a new window]   Figure 5c. Figures 4, 5. (4) Pseudostenosis due to signal loss caused by a surgical clip used in cholecystectomy. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow). The appearance of the stenosis resembles that of a bile duct tumor. No dilatation of the upstream biliary tree is seen. (b) Drip-infusion cholangiogram reveals three surgical clips (arrowheads) near the normal CHD. (c) Drip-infusion cholangiographic computed tomographic (CT) scan also shows no stenosis of the CHD (arrow) close to the surgical clip (arrowhead). (5) Pseudo-obstruction due to signal void caused by a surgical clip used in gastrectomy. (a) Multisection MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Although the obstruction resembles a bile duct tumor or stone, no dilatation of the upstream bile duct is seen. (b) Transaxial fat-suppressed T2-weighted MR image reveals a large, round signal void (arrowheads) close to the gallbladder. (c) Drip-infusion cholangiographic CT scan reveals a metallic surgical clip (open arrows) at the duodenal bulbs, corresponding to the center of the signal void on the transaxial T2-weighted image (cf b). Note the high attenuation of the CBD (solid arrow) and intrahepatic bile duct.

View larger version (113K): [in a new window]   Figure 6a.  Pseudo-obstruction caused by a surgical clip used in gastrectomy. (a) Single-section fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow) and main pancreatic duct (arrowhead) due to signal loss caused by a surgical clip. A pancreatic cyst is also seen (*). (b) Single-section non–fat-suppressed MR cholangiopancreatogram reveals a normal-appearing CBD. No obstruction is seen. (c) Contrast material–enhanced CT scan demonstrates a metallic surgical clip (white arrow) at the duodenal bulbs, close to the CBD (black arrow).

View larger version (114K): [in a new window]   Figure 6b.  Pseudo-obstruction caused by a surgical clip used in gastrectomy. (a) Single-section fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow) and main pancreatic duct (arrowhead) due to signal loss caused by a surgical clip. A pancreatic cyst is also seen (*). (b) Single-section non–fat-suppressed MR cholangiopancreatogram reveals a normal-appearing CBD. No obstruction is seen. (c) Contrast material–enhanced CT scan demonstrates a metallic surgical clip (white arrow) at the duodenal bulbs, close to the CBD (black arrow).

View larger version (116K): [in a new window]   Figure 6c.  Pseudo-obstruction caused by a surgical clip used in gastrectomy. (a) Single-section fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow) and main pancreatic duct (arrowhead) due to signal loss caused by a surgical clip. A pancreatic cyst is also seen (*). (b) Single-section non–fat-suppressed MR cholangiopancreatogram reveals a normal-appearing CBD. No obstruction is seen. (c) Contrast material–enhanced CT scan demonstrates a metallic surgical clip (white arrow) at the duodenal bulbs, close to the CBD (black arrow).

View larger version (82K): [in a new window]   Figure 7a. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (86K): [in a new window]   Figure 7b. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (114K): [in a new window]   Figure 7c. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (138K): [in a new window]   Figure 8a. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (147K): [in a new window]   Figure 8b. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (159K): [in a new window]   Figure 8c. Figures 7, 8. (7) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal bulb. (a) Multisection fat-suppressed MR cholangiopancreatogram shows false obstruction of the middle CBD (arrow). Note the signal void resulting from gas in the duodenal bulb (arrowheads). (b) Multisection non–fat-suppressed MR cholangiopancreatogram reveals no false obstruction of the middle CBD. Note that the signal void resulting from gas in the duodenal bulb (arrowhead) appears much smaller than at multisection fat-suppressed MR cholangiopancreatography (cf a). (c) Intraoperative cholangiogram obtained during cholecystectomy reveals a normal CBD. (8) Pseudo-obstruction due to susceptibility artifact from gas in the duodenal diverticulum. (a) Multisection MR cholangiopancreatogram shows false obstruction of the lower CBD resembling a gallstone or ampullary tumor (arrow). Note the slight dilatation of the main pancreatic duct. (b) Endoscopic retrograde cholangiopancreatogram reveals a large duodenal diverticulum (arrow) and anomalous union of the CBD and main pancreatic duct (arrowhead). No obstruction of the lower CBD is seen. (c) Contrast-enhanced CT scan shows gas forming an air-fluid level in the duodenal diverticulum (arrow).

View larger version (76K): [in a new window]   Figure 9.  Anatomic relationship between the extrahepatic bile duct and splanchnic arteries. Illustration shows the gastroduodenal artery coursing immediately anterior to the CBD. Note that the cystic, right hepatic, and gastroduodenal arteries abut the extrahepatic bile duct. (Adapted and reprinted, with permission, from reference 21.)

View larger version (136K): [in a new window]   Figure 10a.  Pseudo-obstruction due to pulsatile compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false obstruction of the CHD resembling bile duct cancer or a biliary stone (arrow). No dilatation of the upstream biliary tree is seen. (b) Coronal source image for contrast-enhanced three-dimensional MR angiography reveals a dilated right hepatic artery (solid arrowheads) traversing the CHD (arrows) posteriorly. Note that the right hepatic artery is dilated to supply a hepatocellular carcinoma (open arrowheads).

View larger version (152K): [in a new window]   Figure 10b.  Pseudo-obstruction due to pulsatile compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false obstruction of the CHD resembling bile duct cancer or a biliary stone (arrow). No dilatation of the upstream biliary tree is seen. (b) Coronal source image for contrast-enhanced three-dimensional MR angiography reveals a dilated right hepatic artery (solid arrowheads) traversing the CHD (arrows) posteriorly. Note that the right hepatic artery is dilated to supply a hepatocellular carcinoma (open arrowheads).

View larger version (101K): [in a new window]   Figure 11a.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false obstruction of the CHD (arrow). (b, c) Coronal non–fat-suppressed, heavily T2-weighted MR images (b obtained anterior to c) show a tubular structure traversing the CHD posteriorly (arrowheads). The tubular structure proved to be the right hepatic artery at double-phase helical CT (not shown).

View larger version (86K): [in a new window]   Figure 11b.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false obstruction of the CHD (arrow). (b, c) Coronal non–fat-suppressed, heavily T2-weighted MR images (b obtained anterior to c) show a tubular structure traversing the CHD posteriorly (arrowheads). The tubular structure proved to be the right hepatic artery at double-phase helical CT (not shown).

View larger version (100K): [in a new window]   Figure 11c.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false obstruction of the CHD (arrow). (b, c) Coronal non–fat-suppressed, heavily T2-weighted MR images (b obtained anterior to c) show a tubular structure traversing the CHD posteriorly (arrowheads). The tubular structure proved to be the right hepatic artery at double-phase helical CT (not shown).

View larger version (104K): [in a new window]   Figure 12a.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow) with no dilatation of the upstream biliary tree. A small stone appears as a filling defect in the lower CBD (arrowhead). (b) Coronal non–fat-suppressed, heavily T2-weighted MR image shows a tubular structure traversing the CHD posteriorly (arrows). A small stone is seen in the lower CBD (arrowhead). (c) Contrast-enhanced CT scan shows the right hepatic artery (arrow) crossing the posterior aspect of the CHD (arrowhead). (d) Endoscopic retrograde cholangiopancreatogram shows no stenosis of the CHD.

View larger version (125K): [in a new window]   Figure 12b.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow) with no dilatation of the upstream biliary tree. A small stone appears as a filling defect in the lower CBD (arrowhead). (b) Coronal non–fat-suppressed, heavily T2-weighted MR image shows a tubular structure traversing the CHD posteriorly (arrows). A small stone is seen in the lower CBD (arrowhead). (c) Contrast-enhanced CT scan shows the right hepatic artery (arrow) crossing the posterior aspect of the CHD (arrowhead). (d) Endoscopic retrograde cholangiopancreatogram shows no stenosis of the CHD.

View larger version (139K): [in a new window]   Figure 12c.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow) with no dilatation of the upstream biliary tree. A small stone appears as a filling defect in the lower CBD (arrowhead). (b) Coronal non–fat-suppressed, heavily T2-weighted MR image shows a tubular structure traversing the CHD posteriorly (arrows). A small stone is seen in the lower CBD (arrowhead). (c) Contrast-enhanced CT scan shows the right hepatic artery (arrow) crossing the posterior aspect of the CHD (arrowhead). (d) Endoscopic retrograde cholangiopancreatogram shows no stenosis of the CHD.

View larger version (135K): [in a new window]   Figure 12d.  Pseudo-obstruction due to compression by the right hepatic artery. (a) Multisection MR cholangiopancreatogram shows false stenosis of the CHD (arrow) with no dilatation of the upstream biliary tree. A small stone appears as a filling defect in the lower CBD (arrowhead). (b) Coronal non–fat-suppressed, heavily T2-weighted MR image shows a tubular structure traversing the CHD posteriorly (arrows). A small stone is seen in the lower CBD (arrowhead). (c) Contrast-enhanced CT scan shows the right hepatic artery (arrow) crossing the posterior aspect of the CHD (arrowhead). (d) Endoscopic retrograde cholangiopancreatogram shows no stenosis of the CHD.

View larger version (93K): [in a new window]   Figure 13a.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows multiple filling defects (arrows) simulating stones in the dilated CBD. Note the bifurcation anomaly of the main pancreatic duct (arrowhead). (b) Coronal source image also shows multiple filling defects in the CBD (arrows). (c) Transaxial fat-suppressed T2-weighted MR image shows air bubbles (arrows) floating ventrally to the bile and producing air-fluid levels in the CBD and gallbladder.

View larger version (79K): [in a new window]   Figure 13b.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows multiple filling defects (arrows) simulating stones in the dilated CBD. Note the bifurcation anomaly of the main pancreatic duct (arrowhead). (b) Coronal source image also shows multiple filling defects in the CBD (arrows). (c) Transaxial fat-suppressed T2-weighted MR image shows air bubbles (arrows) floating ventrally to the bile and producing air-fluid levels in the CBD and gallbladder.

View larger version (98K): [in a new window]   Figure 13c.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows multiple filling defects (arrows) simulating stones in the dilated CBD. Note the bifurcation anomaly of the main pancreatic duct (arrowhead). (b) Coronal source image also shows multiple filling defects in the CBD (arrows). (c) Transaxial fat-suppressed T2-weighted MR image shows air bubbles (arrows) floating ventrally to the bile and producing air-fluid levels in the CBD and gallbladder.

View larger version (85K): [in a new window]   Figure 14a.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows filling defects in the dilated lower CBD (arrow) and CHD (arrowhead) resembling CBD stones. (b, c) Transaxial heavily T2-weighted MR images demonstrate the filling defects more clearly. The filling defect in the CHD represents gas floating ventrally to the bile (arrowhead in b), whereas that in the lower CBD is a real stone that is sinking and surrounded by hyperintense bile (arrow in c). (d, e) Unenhanced CT scans reveal pneumobilia of the CHD (arrowhead in d) and a soft-tissue-density stone in the lower CBD (arrow in e).

View larger version (104K): [in a new window]   Figure 14b.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows filling defects in the dilated lower CBD (arrow) and CHD (arrowhead) resembling CBD stones. (b, c) Transaxial heavily T2-weighted MR images demonstrate the filling defects more clearly. The filling defect in the CHD represents gas floating ventrally to the bile (arrowhead in b), whereas that in the lower CBD is a real stone that is sinking and surrounded by hyperintense bile (arrow in c). (d, e) Unenhanced CT scans reveal pneumobilia of the CHD (arrowhead in d) and a soft-tissue-density stone in the lower CBD (arrow in e).

View larger version (103K): [in a new window]   Figure 14c.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows filling defects in the dilated lower CBD (arrow) and CHD (arrowhead) resembling CBD stones. (b, c) Transaxial heavily T2-weighted MR images demonstrate the filling defects more clearly. The filling defect in the CHD represents gas floating ventrally to the bile (arrowhead in b), whereas that in the lower CBD is a real stone that is sinking and surrounded by hyperintense bile (arrow in c). (d, e) Unenhanced CT scans reveal pneumobilia of the CHD (arrowhead in d) and a soft-tissue-density stone in the lower CBD (arrow in e).

View larger version (132K): [in a new window]   Figure 14d.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows filling defects in the dilated lower CBD (arrow) and CHD (arrowhead) resembling CBD stones. (b, c) Transaxial heavily T2-weighted MR images demonstrate the filling defects more clearly. The filling defect in the CHD represents gas floating ventrally to the bile (arrowhead in b), whereas that in the lower CBD is a real stone that is sinking and surrounded by hyperintense bile (arrow in c). (d, e) Unenhanced CT scans reveal pneumobilia of the CHD (arrowhead in d) and a soft-tissue-density stone in the lower CBD (arrow in e).

View larger version (116K): [in a new window]   Figure 14e.  Pneumobilia simulating CBD stones. (a) Multisection MR cholangiopancreatogram shows filling defects in the dilated lower CBD (arrow) and CHD (arrowhead) resembling CBD stones. (b, c) Transaxial heavily T2-weighted MR images demonstrate the filling defects more clearly. The filling defect in the CHD represents gas floating ventrally to the bile (arrowhead in b), whereas that in the lower CBD is a real stone that is sinking and surrounded by hyperintense bile (arrow in c). (d, e) Unenhanced CT scans reveal pneumobilia of the CHD (arrowhead in d) and a soft-tissue-density stone in the lower CBD (arrow in e).

View larger version (131K): [in a new window]   Figure 15a.  Nonvisualized gallstone at the gallbladder neck. (a) Multisection MR cholangiopancreatogram shows heterogeneously hypointense bile in the gallbladder, which has a hyperintense wall (arrows). These findings suggest acute cholecystitis with debris formation. (b) On a coronal source MR image, an impacted gallstone at the neck of the gallbladder can barely be detected (arrowheads). The gallstone is not surrounded by hyperintense bile. * = hypointense debris. (c) Coronal source MR image shows the gallbladder wall as inflamed and hyperintense (arrows). * = hypointense debris.

View larger version (118K): [in a new window]   Figure 15b.  Nonvisualized gallstone at the gallbladder neck. (a) Multisection MR cholangiopancreatogram shows heterogeneously hypointense bile in the gallbladder, which has a hyperintense wall (arrows). These findings suggest acute cholecystitis with debris formation. (b) On a coronal source MR image, an impacted gallstone at the neck of the gallbladder can barely be detected (arrowheads). The gallstone is not surrounded by hyperintense bile. * = hypointense debris. (c) Coronal source MR image shows the gallbladder wall as inflamed and hyperintense (arrows). * = hypointense debris.

View larger version (100K): [in a new window]   Figure 15c.  Nonvisualized gallstone at the gallbladder neck. (a) Multisection MR cholangiopancreatogram shows heterogeneously hypointense bile in the gallbladder, which has a hyperintense wall (arrows). These findings suggest acute cholecystitis with debris formation. (b) On a coronal source MR image, an impacted gallstone at the neck of the gallbladder can barely be detected (arrowheads). The gallstone is not surrounded by hyperintense bile. * = hypointense debris. (c) Coronal source MR image shows the gallbladder wall as inflamed and hyperintense (arrows). * = hypointense debris.

View larger version (120K): [in a new window]   Figure 16a.  Nonvisualized gallbladder due to iodinated contrast material. (a) Multisection MR cholangiopancreatogram performed immediately after endoscopic retrograde cholangiopancreatography demonstrates neither the gallbladder nor the CBD. Note the areas of hyperintensity surrounding the biliary tree and pancreas (solid arrowheads), suggestive of peripancreatic edema and exudate due to acute pancreatitis caused by endoscopic retrograde cholangiopancreatography. Note also the minimal dilatation of the main pancreatic duct (open arrowheads). (b) Transaxial fat-suppressed T2-weighted MR image shows a thin layer of hyperintense bile (arrows) floating on hypointense fluid (*) in the gallbladder. Note that the pancreatic parenchyma is hyperintense relative to the hepatic parenchyma. Peripancreatic exudate is seen as areas of hyperintensity surrounding the pancreas (arrowheads). (c) Transaxial fat-suppressed T1-weighted MR image reveals a hyperintense gallbladder (*) and CBD (arrow) due to the presence of iodinated contrast material. (d) Unenhanced CT scan reveals hyperattenuating iodinated contrast material in the gallbladder (*) and CBD (arrow).

View larger version (132K): [in a new window]   Figure 16b.  Nonvisualized gallbladder due to iodinated contrast material. (a) Multisection MR cholangiopancreatogram performed immediately after endoscopic retrograde cholangiopancreatography demonstrates neither the gallbladder nor the CBD. Note the areas of hyperintensity surrounding the biliary tree and pancreas (solid arrowheads), suggestive of peripancreatic edema and exudate due to acute pancreatitis caused by endoscopic retrograde cholangiopancreatography. Note also the minimal dilatation of the main pancreatic duct (open arrowheads). (b) Transaxial fat-suppressed T2-weighted MR image shows a thin layer of hyperintense bile (arrows) floating on hypointense fluid (*) in the gallbladder. Note that the pancreatic parenchyma is hyperintense relative to the hepatic parenchyma. Peripancreatic exudate is seen as areas of hyperintensity surrounding the pancreas (arrowheads). (c) Transaxial fat-suppressed T1-weighted MR image reveals a hyperintense gallbladder (*) and CBD (arrow) due to the presence of iodinated contrast material. (d) Unenhanced CT scan reveals hyperattenuating iodinated contrast material in the gallbladder (*) and CBD (arrow).

View larger version (119K): [in a new window]   Figure 16c.  Nonvisualized gallbladder due to iodinated contrast material. (a) Multisection MR cholangiopancreatogram performed immediately after endoscopic retrograde cholangiopancreatography demonstrates neither the gallbladder nor the CBD. Note the areas of hyperintensity surrounding the biliary tree and pancreas (solid arrowheads), suggestive of peripancreatic edema and exudate due to acute pancreatitis caused by endoscopic retrograde cholangiopancreatography. Note also the minimal dilatation of the main pancreatic duct (open arrowheads). (b) Transaxial fat-suppressed T2-weighted MR image shows a thin layer of hyperintense bile (arrows) floating on hypointense fluid (*) in the gallbladder. Note that the pancreatic parenchyma is hyperintense relative to the hepatic parenchyma. Peripancreatic exudate is seen as areas of hyperintensity surrounding the pancreas (arrowheads). (c) Transaxial fat-suppressed T1-weighted MR image reveals a hyperintense gallbladder (*) and CBD (arrow) due to the presence of iodinated contrast material. (d) Unenhanced CT scan reveals hyperattenuating iodinated contrast material in the gallbladder (*) and CBD (arrow).

View larger version (108K): [in a new window]   Figure 16d.  Nonvisualized gallbladder due to iodinated contrast material. (a) Multisection MR cholangiopancreatogram performed immediately after endoscopic retrograde cholangiopancreatography demonstrates neither the gallbladder nor the CBD. Note the areas of hyperintensity surrounding the biliary tree and pancreas (solid arrowheads), suggestive of peripancreatic edema and exudate due to acute pancreatitis caused by endoscopic retrograde cholangiopancreatography. Note also the minimal dilatation of the main pancreatic duct (open arrowheads). (b) Transaxial fat-suppressed T2-weighted MR image shows a thin layer of hyperintense bile (arrows) floating on hypointense fluid (*) in the gallbladder. Note that the pancreatic parenchyma is hyperintense relative to the hepatic parenchyma. Peripancreatic exudate is seen as areas of hyperintensity surrounding the pancreas (arrowheads). (c) Transaxial fat-suppressed T1-weighted MR image reveals a hyperintense gallbladder (*) and CBD (arrow) due to the presence of iodinated contrast material. (d) Unenhanced CT scan reveals hyperattenuating iodinated contrast material in the gallbladder (*) and CBD (arrow).