DOI: 10.1148/rg.281075058
RadioGraphics 2008;28:119-134
© RSNA, 2008
Evaluation of Biliary Abnormalities with 64-Channel Multidetector CT1
Mariko Hashimoto, MD,
Kyo Itoh, MD,
Kazuna Takeda, MD,
Toyomichi Shibata, MD,
Tomohisa Okada, MD,
Yoshishige Okuno, MD, and
Megumu Hino, MD
1 From the Department of Radiology, Kobe City General Hospital, 4–6, Minatojima-Nakamachi, Chuou-ku, Kobe 650-0046, Japan. Presented as an education exhibit at the 2006 RSNA Annual Meeting. Received March 29, 2007; revision requested April 30; final revision received July 20; accepted August 7. All authors have no financial relationships to disclose.
Address correspondence to M.H. (e-mail: hasimari-1101{at}hotmail.co.jp).
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Abstract
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Precise preoperative assessment of the vascular and biliary anatomy is important in ensuring the safety of hepatobiliary surgical procedures, including laparoscopic cholecystectomy, living donor liver transplantation, and tumor resection of the liver. Endoscopic retrograde cholangiography and percutaneous transhepatic cholangiography clearly depict the biliary anatomy but are considered invasive procedures. Magnetic resonance cholangiopancreatography is noninvasive but sometimes fails to depict the normal intrahepatic bile ducts. Multidetector computed tomography (CT) has contributed greatly to the evaluation of the normal anatomy, anatomic variants, and disease extent in this setting. With 64-channel multidetector CT, high-resolution three-dimensional images can be reconstructed from isotropic data with a 0.625-mm section thickness. Because of its capacity for thin-section scanning and multiplanar reformation, 64-channel multidetector CT cholangiography can clearly demonstrate the biliary anatomy, a variety of anatomic variants, and the extent of disease—information that is indispensable for successful hepatobiliary surgery.
© RSNA, 2008
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Introduction
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Recently developed surgical procedures include laparoscopic cholecystectomy and living donor liver transplantation. Laparoscopic cholecystectomy has proved to be a remarkable surgical advance, but like all surgical procedures, it can lead to complications, including bile duct injury and biliary leakage (1). A growing demand for liver transplantation with a concomitant shortage of cadaveric livers has increased the prevalence of living donor liver transplantation. Ensuring the safety of donors is critical, and strict evaluation has been suggested (2); therefore, more detailed information regarding the biliary anatomy is indispensable, since incorrect information could cause severe complications.
Multiple modalities can depict the normal biliary anatomy, including percutaneous transhepatic cholangiography, endoscopic retrograde cholangiopancreatography (ERCP), and magnetic resonance (MR) cholangiopancreatography. Some of these modalities require invasive procedures and are not easy options.
Modern multidetector computed tomography (CT) is a new diagnostic imaging tool that allows multiplanar reformation. In particular, the isotropic data generated with 64-channel multidetector CT have increased the understanding of clinical anatomy and various abnormalities. Schroeder et al (3) performed studies with four-row multidetector CT and concluded that the inherent noninvasiveness and achievable spatial resolution of multidetector CT cholangiography is valuable in the preoperative assessment of the biliary anatomy of potential living liver donors. CT cholangiography performed with 64-channel multidetector CT scanners could provide much more information regarding the biliary tree and its abnormalities.
In this article, we discuss and illustrate the advantages and limitations (side effects of meglumine iotroxate, poor hepatic function) of 64-channel multidetector CT performed with the intravenous injection of biliary contrast agents. In addition, we review the normal biliary anatomy and a variety of anatomic variants. We also describe the imaging features of various relevant benign conditions (cholecystitis and cholelithiasis, adenomyomatosis, cholesterol polyps, choledochal cysts, anomalous junction of the pancreatic duct and common bile duct [CBD]), malignancies (gallbladder carcinoma, bile duct carcinoma, cholangiocellular carcinoma), and postoperative states.
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Sixty-four–Channel Multidetector CT
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Multidetector CT remains the most commonly used technique for imaging patients with suspected abdominal abnormalities. It allows the rapid acquisition of multiphase data sets and continuous raw data for detailed reconstruction into three-dimensional (3D) images. The advent of 64-channel multidetector CT has allowed additional high-resolution 3D images to be reconstructed from the isotropic data. This modality has been used to great advantage in various applications, including cardiovascular, neurovascular, gastrointestinal, and hepatobiliary imaging. In cardiovascular imaging, 64-channel multidetector CT has yielded isotropic data of the coronary arteries, whereas in gastrointestinal imaging, virtual navigation and computer-generated simulation have permitted internal viewing through body cavities and hollow viscera.
In the hepatobiliary system, choosing an appropriate therapy requires complete preoperative staging to determine resectability. Sixty-four–channel multidetector CT is a powerful tool that allows the depiction of tumors and surrounding structures. Its high-resolution images show the anatomic relationships of vessels and neighboring structures, thus providing reliable "road maps" that are helpful during surgery.
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Imaging Indications
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ERCP, MR cholangiopancreatography, ultrasonography (US), and multidetector CT cholangiography each have their own advantages and disadvantages (Table 1). Eracleous et al (4) concluded that multisection helical CT cholangiography provides high-resolution images of the biliary tree and allows functional and kinetic evaluation of the liver.
On the basis of the data shown in Table 1, we consider the indications of CT cholangiography to be as follows:
- Screening for cholelithiasis. Are there any stones in the intrahepatic bile ducts or the CBD?
- Preoperative screening. Is there any anatomic variation of the biliary tree? What is the relationship between the cystic duct and the extrahepatic bile duct?
- Detection of postoperative complications or traumatic biliary injury. Is there any extravasation from the injured biliary duct? How long is the remnant cystic duct?
- Screening for other biliary abnormalities (eg, gallbladder adenomyomatosis, cholesterol polyps, congenital abnormalities).
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Imaging Techniques
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CT scans were obtained on a 64–channel helical CT scanner (LightSpeed VCT; GE Healthcare, Milwaukee, Wis) with the following parameters: 0.5 seconds per rotation, 5-mm collimation, pitch of 0.984:1, and tube current of 120 kV per 300–400 mAs.
Transverse 0.625-mm-thick sections were reformatted into thin-section coronal images, maximum-intensity-projection (MIP) images, and volume-rendered (VR) images.
An intravenous drip infusion of 100 mL of meglumine iotroxate (Biliscopin; Schering, Berlin, Germany) was administered for 50 minutes as a biliary contrast agent 40–60 minutes prior to scanning. This biliary agent has been approved in some countries, including Japan, and has been used for tomographic cholangiography.
A paging method was used to observe the continuous raw data displayed on the workstation. Supplementary multiplanar reformatted images were also generated.
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Normal Anatomy
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The right and left hepatic ducts collect bile from the liver, and the common hepatic duct unites with the cystic duct just superior to the duodenum. The mucous membrane of the gallbladder has a low honeycomb surface, whereas the mucous membrane of the sinuous cystic duct forms a spiral fold (5).
CT cholangiography of the normal biliary ducts clearly demonstrates the intrahepatic and extrahepatic ducts, the gallbladder, and the duodenum (Fig 1). When these structures are not well enhanced, the possibility of biliary abnormalities should be considered. In patients with normal liver function, the contrast material is excreted primarily via the hepatobiliary system and, to a lesser degree, via the kidneys.
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Figure 1a. VR (a) and axial (b) CT cholangiographic images obtained in a 65-year-old woman with normal liver function clearly demonstrate the intra- and extrahepatic ducts, the gallbladder, and the duodenum (white arrow in b). A small amount of contrast material has been excreted via the kidneys (black arrows in b) as well as the hepatobiliary system.
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Figure 1b. VR (a) and axial (b) CT cholangiographic images obtained in a 65-year-old woman with normal liver function clearly demonstrate the intra- and extrahepatic ducts, the gallbladder, and the duodenum (white arrow in b). A small amount of contrast material has been excreted via the kidneys (black arrows in b) as well as the hepatobiliary system.
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Variations in Intrahepatic Biliary Anatomy
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It is essential for both the radiologist and the surgeon to have precise knowledge of the patient’s anatomy prior to hepatobiliary surgery. For example, in cases of anomalous insertion of the cystic duct, mistaking the cystic duct for the bile duct can result in iatrogenic injury. Similarly, a lack of awareness of biliary variations can cause complications in living donor liver transplantation or liver dissection. The structure of the biliary tree is classified according to the relationship between the hepatic segmental ducts and the cystic duct, and a variety of studies have described biliary duct anomalies (2,6–10). CT cholangiography clearly demonstrates the various anatomic patterns, which are classified according to a classification scheme developed by Yoshida et al (6) (Fig 2) and are shown in Figures 3–9.
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Figure 2. Anatomic variants as classified by Yoshida et al (6). A = right anterior duct, C = cystic duct, L = left hepatic duct, P = right posterior duct, R = right hepatic duct. When the branches come off at different levels, a hyphen is inserted between the appropriate letters. For example, "A-PL" indicates that the first branch from below is A (right anterior duct) and that the next branches are P (right posterior duct) and L (left hepatic duct) at the same level. The percentage of cases in which each variant is seen in shown in parentheses or brackets. (Reprinted, with permission, from reference 6.)
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Figure 3a. APL pattern in a 75-year-old man. Posterior (a) and right superior (b) CT cholangiograms show the left hepatic duct, the right anterior hepatic duct (white arrow in a), and the right posterior hepatic duct (black arrow in a) entering the common hepatic duct at the same level.
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Figure 3b. APL pattern in a 75-year-old man. Posterior (a) and right superior (b) CT cholangiograms show the left hepatic duct, the right anterior hepatic duct (white arrow in a), and the right posterior hepatic duct (black arrow in a) entering the common hepatic duct at the same level.
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Figure 5. VR image obtained in a 56-year-old man shows the right posterior inferior branch (large arrow) and the right posterior superior branch (small arrow) draining separately into the right anterior hepatic duct.
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Figure 6a. P-AL/P-C-AL pattern in a 47-year-old man. (a, b) Anterior (a) and posterior (b) VR images clearly depict the cystic duct (arrow) draining into the common hepatic duct between the right anterior and right posterior hepatic ducts. (c) Coronal thin-section image clearly depicts stones in the CBD.
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Figure 6b. P-AL/P-C-AL pattern in a 47-year-old man. (a, b) Anterior (a) and posterior (b) VR images clearly depict the cystic duct (arrow) draining into the common hepatic duct between the right anterior and right posterior hepatic ducts. (c) Coronal thin-section image clearly depicts stones in the CBD.
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Figure 6c. P-AL/P-C-AL pattern in a 47-year-old man. (a, b) Anterior (a) and posterior (b) VR images clearly depict the cystic duct (arrow) draining into the common hepatic duct between the right anterior and right posterior hepatic ducts. (c) Coronal thin-section image clearly depicts stones in the CBD.
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Figure 7a. A-PL/AC pattern in a 61-year-old woman. MIP (a) and VR (b) images demonstrate the right posterior hepatic duct draining into the left hepatic duct, and the cystic duct (arrow in b) entering the right anterior hepatic duct. The MIP image reveals a calcified stone (arrow in a) in the fundus of the gallbladder that is obscured on the VR image.
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Figure 7b. A-PL/AC pattern in a 61-year-old woman. MIP (a) and VR (b) images demonstrate the right posterior hepatic duct draining into the left hepatic duct, and the cystic duct (arrow in b) entering the right anterior hepatic duct. The MIP image reveals a calcified stone (arrow in a) in the fundus of the gallbladder that is obscured on the VR image.
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Figure 8a. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 8b. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 8c. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 8d. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 8e. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 8f. Biliary anomaly in a 79-year-old woman with a portal venous anomaly and deviation of the ligamentum teres to the right. (a–c) Contiguous contrast material–enhanced CT scans show anterior branches (arrow in a and b) arising from the umbilical portion of the portal vein. (d) CT cholangiogram demonstrates a collapsed gallbladder (arrow). (e) Portal venogram also shows the anomaly depicted in a–c. (f) VR CT cholangiographic image demonstrates the anomalous biliary tree. B2 = left superior segmental duct, B3 = left inferior segmental duct, B4 = medial segmental duct, B5 = anterior inferior segmental duct, B6a and B6b = branches of the posterior inferior segmental duct, B7 = posterior superior segmental duct, B8 = anterior superior segmental duct.
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Figure 9a. Gallbladder stones in a 43-year-old man. (a) CT cholangiogram reveals multiple stones in the gallbladder. (b) VR cholangiographic image demonstrates the origin of the cystic duct, with the right posterior duct (arrow) draining into the left hepatic duct (A-PL pattern).
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Figure 9b. Gallbladder stones in a 43-year-old man. (a) CT cholangiogram reveals multiple stones in the gallbladder. (b) VR cholangiographic image demonstrates the origin of the cystic duct, with the right posterior duct (arrow) draining into the left hepatic duct (A-PL pattern).
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In patients with the P-AL/P-C-AL pattern (Fig 6), misidentification of the right posterior hepatic duct as a cystic duct at laparoscopic cholecystectomy could result in injury to the hepatic duct. Similar iatrogenic injury could also occur with other cystic duct patterns, including A-PL/AC patterns (Fig 7).
There is no one bile duct variation that excludes a person from being a living donor; however, to avoid potential complications to both donors and recipients, unusual patterns of intrahepatic duct connection may require modification of both the cutting plane during graft retrieval and the pattern of ductoenteral anastomosis (8).
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Benign Biliary Conditions
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Cholecystitis and Cholelithiasis
Acute cholecystitis is the most common cause of acute pain in the right upper quadrant and occurs in approximately one-third of patients with gallstones (11). In most cases, the condition is due to calculous obstruction of the gallbladder neck or cystic duct, leading to increased intraluminal pressure and distention of the gallbladder.
US is the modality of choice for the detection of stones and the evaluation of inflammation. US is also superior to CT for the initial imaging assessment of biliary disease (12). In addition, it has high sensitivity and accuracy (>95%) in the detection of gallstones (13). At our institution, CT cholangiography is used for the preoperative evaluation of the biliary anatomy.
At CT cholangiography, gallbladder stones can be seen as defects when the gallbladder is filled with contrast material (Fig 9); however, calcified stones can be obscured by the contrast material, and impacted stones or decreased biliary function results in poor contrast material uptake (Fig 10).
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Figure 10a. Cholecystitis in a 58-year-old man. CT cholangiograms demonstrate a stone in the gallbladder neck (a) and thickening of the gallbladder wall. The impacted stone prevents the filling of the gallbladder with contrast material (b), which does, however, fill the bile ducts.
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Figure 10b. Cholecystitis in a 58-year-old man. CT cholangiograms demonstrate a stone in the gallbladder neck (a) and thickening of the gallbladder wall. The impacted stone prevents the filling of the gallbladder with contrast material (b), which does, however, fill the bile ducts.
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In a study by Laing et al (14), eight of nine proximal CBD stones (89%) and 16 of 23 distal CBD stones (70%) were visualized at US. If US findings are equivocal, CT cholangiography is performed. Stones in the CBDs can also be seen as defects. To identify calcified stones, the window level setting must be modified; these stones are often seen more clearly on thin-section axial or coronal images than on MIP or VR images. At our institution, axial and coronal images are obtained with standard window settings (width/level = 400/40), although these settings are sometimes changed; for example, a setting of 1000/200 is used to visualize calcified stones.
Adenomyomatosis
Adenomyomatosis is now recognized as a common condition of the gallbladder wall and is seen in up to 8.7% of cholecystectomy specimens (15). There are three types of adenomyomatosis: localized (or fundal), segmental, and diffuse. Localized adenomyomatosis is the most common and manifests as a well-formed mass in the gallbladder fundus. Segmental adenomyomatosis is characterized by focal circumferential wall thickening in the gallbladder wall. Diffuse adenomyomatosis is characterized by diffuse wall thickening with intramural diverticula that appear as cystic spaces within the wall.
Adenomyomatosis is seen on US images as focal or diffuse gallbladder wall thickening. The US hallmark of adenomyomatosis is a V-shaped or "comet tail" reverberation artifact that is seen emanating from small echogenic foci in the gallbladder wall (16). This artifact is created by sound reverberating from the material within the diverticula.
At MR cholangiopancreatography, the Rokitansky-Aschoff sinuses manifest as "pearl necklace gallbladder," a finding that is typical of adenomyomatosis (Fig 11).
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Figure 11a. Adenomyomatosis in a 23-year-old woman. (a) Contrast-enhanced CT scan shows edematous thickening of the gallbladder wall and marked enhancement of the inner layer. (b) MR cholangiopancreatogram shows pearl necklace gallbladder, a finding that is typical of adenomyomatosis. (c) CT cholangiogram reveals biliary reflux to the main pancreatic duct (arrow), a finding that indicates anomalous union of the pancreatic duct and the main pancreatic duct uncontrolled by the sphincter of Oddi. (d) VR image shows the cystic duct joining the common hepatic duct at a higher level near the bifurcation (arrow).
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Figure 11b. Adenomyomatosis in a 23-year-old woman. (a) Contrast-enhanced CT scan shows edematous thickening of the gallbladder wall and marked enhancement of the inner layer. (b) MR cholangiopancreatogram shows pearl necklace gallbladder, a finding that is typical of adenomyomatosis. (c) CT cholangiogram reveals biliary reflux to the main pancreatic duct (arrow), a finding that indicates anomalous union of the pancreatic duct and the main pancreatic duct uncontrolled by the sphincter of Oddi. (d) VR image shows the cystic duct joining the common hepatic duct at a higher level near the bifurcation (arrow).
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Figure 11c. Adenomyomatosis in a 23-year-old woman. (a) Contrast-enhanced CT scan shows edematous thickening of the gallbladder wall and marked enhancement of the inner layer. (b) MR cholangiopancreatogram shows pearl necklace gallbladder, a finding that is typical of adenomyomatosis. (c) CT cholangiogram reveals biliary reflux to the main pancreatic duct (arrow), a finding that indicates anomalous union of the pancreatic duct and the main pancreatic duct uncontrolled by the sphincter of Oddi. (d) VR image shows the cystic duct joining the common hepatic duct at a higher level near the bifurcation (arrow).
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Figure 11d. Adenomyomatosis in a 23-year-old woman. (a) Contrast-enhanced CT scan shows edematous thickening of the gallbladder wall and marked enhancement of the inner layer. (b) MR cholangiopancreatogram shows pearl necklace gallbladder, a finding that is typical of adenomyomatosis. (c) CT cholangiogram reveals biliary reflux to the main pancreatic duct (arrow), a finding that indicates anomalous union of the pancreatic duct and the main pancreatic duct uncontrolled by the sphincter of Oddi. (d) VR image shows the cystic duct joining the common hepatic duct at a higher level near the bifurcation (arrow).
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CT cholangiography cannot depict the Rokitansky-Aschoff sinuses as clearly as MR cholangiopancreatography or US. Axial and coronal images reveal wall thickening (Fig 11).
Cholesterol Polyps
Cholesterol polyps of the gallbladder represent approximately one-half of all polypoid lesions in the gallbladder and have no malignant potential (17,18). They are typically found in patients who are being evaluated for epigastric distress and right upper quadrant pain.
Cholesterol polyps can be seen as defects at CT cholangiography (Fig 12) and can be misdiagnosed as stones. Polyps that stick to the upper wall are easily diagnosed because stones tend to settle in the bottom of the gallbladder. Polyps are generally diagnosed at US, with CT cholangiography playing a complementary role.
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Figure 12a. Cholesterol polyp in a 35-year-old woman. (a) CT cholangiogram demonstrates a small defect in the fundus of the gallbladder (arrow), a finding that indicates a small polyp. (b) On a VR image, the polyp is obscured, as is sometimes the case on MIP or VR images.
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Figure 12b. Cholesterol polyp in a 35-year-old woman. (a) CT cholangiogram demonstrates a small defect in the fundus of the gallbladder (arrow), a finding that indicates a small polyp. (b) On a VR image, the polyp is obscured, as is sometimes the case on MIP or VR images.
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Choledochal Cysts
According to a modification of the Alonso-Lej classification scheme (19) by Todani et al (20), there are five discrete types of biliary cysts with many variations (Table 2).
The following distribution of choledochal cyst types has been reported: type I, 77% of cases; type II, 1.2%; type III, 1.4%; and type IV (IVa and IVb), 18.9% (21). Choledochal cysts are frequently accompanied by an anomalous junction of the pancreatic duct and CBD.
CT cholangiography is valuable for confirming the diagnosis, whereas MIP and VR images allow an appreciation of the 3D structure (Fig 13).
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Figure 13a. Choledochal cyst (Todani type IVa) with dilatation of the intrahepatic bile ducts and CBD in an 81-year-old man. (a) CT cholangiogram shows calcified stones (arrows) in the left inferior and medial segmental ducts. (b) VR image does not demonstrate the left inferior and medial segmental ducts because the impacted stones prevent enhancement of the ducts with contrast material.
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Figure 13b. Choledochal cyst (Todani type IVa) with dilatation of the intrahepatic bile ducts and CBD in an 81-year-old man. (a) CT cholangiogram shows calcified stones (arrows) in the left inferior and medial segmental ducts. (b) VR image does not demonstrate the left inferior and medial segmental ducts because the impacted stones prevent enhancement of the ducts with contrast material.
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Anomalous Junction of the Pancreatic Duct and CBD
Anomalous junction of the pancreatic duct and CBD can take a number of forms, most of which are considered normal variants and are of no clinical significance (22). Pancreatic ducts are sometimes visualized at CT cholangiography, a finding that indicates the presence of reflux (Fig 14).
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Figure 14. Malunion of the pancre-aticobiliary ducts and inflammatory stenosis of the CBD in a 45-year-old woman. VR CT cholangiographic image shows stenosis of the middle portion of the CBD. Visualization of the pancreatic ducts (arrows) indicates the presence of reflux into these ducts with malunion.
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Biliary Malignancies
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Gallbladder Carcinoma
Gallbladder carcinoma is highly lethal because anatomic factors promote early local spread. The ease with which this tumor invades the liver and surrounding structures (including the biliary tree) contributes to its high mortality rate. The cross-sectional imaging patterns of gallbladder carcinoma have been described as a mass replacing the gallbladder in 40%–50% of cases, focal or diffuse gallbladder wall thickening in 20%–30%, and an intraluminal polypoid mass in 15%–25% (23–26). Although contrast-enhanced CT and MR imaging play important roles in the diagnosis of tumor spread and metastases, they do not always allow exact assessment of the invaded area because it is sometimes unclear whether the enhancement indicates invasion. The invaded area manifests with poor enhancement at CT cholangiography (Fig 15); therefore, CT cholangiography has the potential to be useful for the evaluation of tumor spread.
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Figure 15a. Gallbladder carcinoma in a 73-year-old woman. (a) Contrast-enhanced CT scan demonstrates invasion of the liver by a gallbladder tumor. (b) CT cholangiogram reveals a poorly enhanced area (arrows), a finding that indicates invasion of the liver parenchyma, which does not secrete bile.
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Figure 15b. Gallbladder carcinoma in a 73-year-old woman. (a) Contrast-enhanced CT scan demonstrates invasion of the liver by a gallbladder tumor. (b) CT cholangiogram reveals a poorly enhanced area (arrows), a finding that indicates invasion of the liver parenchyma, which does not secrete bile.
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Bile Duct Carcinoma (Extrahepatic Cholangiocarcinoma)
Malignant strictures usually manifest as areas of narrowing with proximal bile duct dilatation.
MIP and VR CT cholangiographic images help accurately identify the site of obstruction and the length of the stricture (Fig 16). In addition, CT cholangiography is less invasive than ERCP. Satisfactory enhancement is difficult to achieve in patients with severe obstructive jaundice because deteriorated hepatobiliary function prevents enhancement of the biliary system.
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Figure 16a. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16b. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16c. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16d. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16e. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16f. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Figure 16g. Bile duct carcinoma in an 84-year-old woman. (a–f) Contiguous coronal (a–c) and axial (d–f) CT cholangiograms demonstrate dilatation of the CBD and intrahepatic ducts. A large duodenal diverticulum is seen compressing the lower portion of the CBD. (g) VR image also reveals dilatation of the biliary tract. These findings may lead to a misdiagnosis of Lemmel syndrome, a biliary obstructive disease that is caused by a periampullary duodenal diverticulum. However, the circumferential stenosis of the CBD in this case suggests the possibility of carcinoma.
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Cholangiocellular Carcinoma
Cholangiocellular carcinomas, many of which occur in noncirrhotic livers, are classified into two types: hilar cholangiocarcinoma and peripheral cholangiocarcinoma.
Types of hepatic duct obstruction caused by hilar cholangiocarcinoma have been classified by Bismuth and Corlette (27) as follows: type I, non-obstructed primary confluence; type II, obstruction limited to primary confluence; type III, obstructed primary confluence with extension to the secondary confluence of the right (type IIIa) or left (type IIIb) hepatic duct; and type IV, obstructed secondary confluence of both the right and left hepatic ducts.
Type IV hilar cholangiocarcinoma classically manifests as segmental dilatation and nonunion of the right and left hepatic ducts at the porta hepatis (28–30). Dilatation of the intrahepatic bile ducts is clearly seen at CT cholangiography (Fig 17).
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Figure 17. Cholangiocellular carcinoma (hilar type IV) in a 78-year-old man. VR CT cholangiographic image clearly depicts tumor involvement of the common hepatic bile duct and the proximal portion of the right and left hepatic ducts. Tumor spread was confirmed at ERCP.
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Peripheral type cholangiocarcinomas manifest as low-attenuation tumors at contrast-enhanced CT. These lesions may infiltrate the biliary ducts and cause isolated intrahepatic duct dilatation. This feature was observed in 31% of cases of peripheral cholangiocarcinoma in a study by Wibulpolprasert and Dhiensiri (31) and in only 2% of hepatocellular carcinomas in a study by Lee et al (32). CT cholangiography is used to obtain anatomic information prior to surgery and is also useful in identifying segments with deteriorated hepatobiliary function when investigating regions of poor enhancement (Fig 18).
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Figure 18a. Cholangiocellular carcinoma (peripheral type) in a 72-year-old woman. (a) Contrast-enhanced CT scan reveals a solid tumor in the lateral segment of the left lobe with dilatation of the peripheral bile ducts. (b) CT cholangiogram does not demonstrate the dilated bile ducts. The lateral segment of the left lobe manifests as a poorly enhanced area (arrows) due to the segmental deterioration of hepatobiliary function.
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Figure 18b. Cholangiocellular carcinoma (peripheral type) in a 72-year-old woman. (a) Contrast-enhanced CT scan reveals a solid tumor in the lateral segment of the left lobe with dilatation of the peripheral bile ducts. (b) CT cholangiogram does not demonstrate the dilated bile ducts. The lateral segment of the left lobe manifests as a poorly enhanced area (arrows) due to the segmental deterioration of hepatobiliary function.
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Postoperative States
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Typically, the length of the cystic duct remnant that is retained at cholecystectomy is clearly observed at CT cholangiography (Fig 19). This modality is valuable in detecting retained stones within the remnant that may cause recurrent pain (Fig 19). MIP and VR images may obscure the stones; therefore, it is necessary to check the thin-section images using the paging method.
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Figure 19a. (a) Coronal CT cholangiogram (0.625-mm section thickness) obtained in a 63-year-old woman with abdominal pain who had previously undergone cholecystectomy clearly depicts stones in the remnant cystic duct. It was difficult to determine at US whether these stones were in the cystic duct or the extrahepatic bile duct. (b) VR image shows the exact length of the remnant cystic duct. Stones are sometimes obscured on VR images; thus, it is important to check the thin-section images carefully by using the paging method.
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Figure 19b. (a) Coronal CT cholangiogram (0.625-mm section thickness) obtained in a 63-year-old woman with abdominal pain who had previously undergone cholecystectomy clearly depicts stones in the remnant cystic duct. It was difficult to determine at US whether these stones were in the cystic duct or the extrahepatic bile duct. (b) VR image shows the exact length of the remnant cystic duct. Stones are sometimes obscured on VR images; thus, it is important to check the thin-section images carefully by using the paging method.
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Endoscopic sphincterotomy is a technique that was developed relatively recently to examine and treat abnormalities of the bile ducts, pancreas, and gallbladder. Pneumobilia is a common sequela of procedures such as endoscopic sphincterotomy and ductoenteric anastomosis and often manifests as air in the bile ducts at CT cholangiography. In contrast, MR cholangiopancreatography is not useful for differentiating pneumobilia from intrahepatic stones.
Biliary leakage is sometimes detected at CT cholangiography following liver surgery (Fig 20).
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Figure 20a. Biliary leakage in a 51-year-old male liver donor following transplantation. (a) CT cholangiogram demonstrates extrahepatic leakage of contrast material around the liver. (b) Oblique thin-section image shows the exact point of leakage from the stump of the caudate branch (arrow).
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Figure 20b. Biliary leakage in a 51-year-old male liver donor following transplantation. (a) CT cholangiogram demonstrates extrahepatic leakage of contrast material around the liver. (b) Oblique thin-section image shows the exact point of leakage from the stump of the caudate branch (arrow).
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Limitations of CT Cholangiography
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Side Effects of Meglumine Iotroxate
Rashes and nausea are common side effects of meglumine iotroxate. Very rarely, anaphylactic shock has been reported. Among 157 patients, we found three (1.9%) who complained of nausea or rashes. None of these 157 patients experienced severe side effects such as anaphylactic shock.
Poor Hepatic Function
Poor hepatic function results in poor enhancement of the biliary system (Fig 21), with contrast material being excreted via the kidneys rather than the biliary system. It is difficult to generate MIP and VR images in these patients due to poor enhancement. CT cholangiography clearly demonstrates obstructed bile ducts, despite the elevated bilirubin level; however, in patients with jaundice caused by hepatocellular dysfunction, only a small amount of contrast material is excreted into the bile, resulting in poor enhancement of the biliary tree. This poor enhancement sometimes produces a sharp contrast between areas of good and poor biliary function within the liver.
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Figure 21. Severe liver cirrhosis with massive ascites in a 76-year-old woman. The patient’s serum bilirubin level was high (2.4 mg/dL). CT cholangiogram shows poor enhancement of the gallbladder and common hepatic duct. The biliary contrast material has been excreted via the kidneys rather than the biliary system.
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The biliary tree may be insufficiently demonstrated in patients with proteinuria, since this biliary contrast material combines with serum protein and will be excreted to a greater extent by the kidneys. We found no such cases in our study.
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Conclusions
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A variety of modalities are used to evaluate hepatobiliary diseases, including 64-channel multidetector CT cholangiography, which has become an important diagnostic modality in this setting. With its capacity for thin-section scanning and multiplanar reformation, 64-channel multidetector CT cholangiography can clearly demonstrate the biliary anatomy and the extent of disease. The information provided by CT cholangiography is indispensable for successful hepatobiliary surgery.
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Acknowledgments
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We wish to thank Kotaro Morita, RT, Takashi Utsunomiya, RT, and Yuki Okada, RT, for their technical assistance in preparing this article.
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Footnotes
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Abbreviations: CBD = common bile duct, ERCP = endoscopic retrograde cholangiopancreatography, MIP = maximum intensity projection, VR = volume-rendered, 3D = three-dimensional
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Abstract
Introduction
