Seung Hong Choi, MD, Joon Koo Han, MD, Jeong Min Lee, MD, Kyoung Ho Lee, MD, Se Hyung Kim, MD, Jae Young Lee, MD and Byung Ihn Choi, MD
1
From the Department of Radiology and the Institute of Radiation Medicine, Seoul National
University College of Medicine, Clinical Research Institute, Seoul National University Hospital, 28 Yongon-dong, Chongno-gu, Seoul 110-744, Korea. Received May 2, 2004; revision requested July 14; revision received August 3; accepted September 23. Supported in part by the 2001 BK21 Project for Medicine, Dentistry, and Pharmacy. Address correspondence to J.K.H. (e-mail: hanjk@radcom.snu.ac.kr ).
TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References ABSTRACT PURPOSE: To evaluate retrospectively the use of multiphasic helical computed tomography (CT) to differentiate malignant and benign common bile duct (CBD) strictures in patients with only a focal CBD stricture and to determine predictors for this differentiation.
MATERIALS AND METHODS: Institutional review board approval and informed patient consent were not required. Fifty patients (35 men, 15 women; age range, 35–87 years; mean age, 61.6 years) with only a focal CBD stricture comprised the sample for this study (32 malignant and 18 benign strictures). The diagnosis of all malignant and five benign CBD strictures was confirmed by reviewing patients' surgical and pathology records; in 13 benign CBD strictures, the diagnosis was confirmed by means of clinical
features. Multiphasic CT findingswere analyzed with regard to the wall
thickness, location, length, and enhancement pattern of the involved CBD, the upstream CBD diameter, and other findings. CT features to identify benign and malignant CBD strictures were compared by means of univariate analysis and multivariable stepwise logistic regression analysis. RESULTS: Malignant strictures were longer (17.9 mm ± 6.6 [± standard deviation]) than benign strictures (8.9 mm ± 6.8) (P < .0001), and upstream CBD diameters were larger in malignant cases (22.0 mm ± 5.4) than in benign cases (17.8 mm ± 4.6) (P = .033). The involved wall thickness was more than 1.5 mm in 26 malignant cases and three benign cases (P < .0001). During both hepatic arterial and portal venous phases, greater enhancement than that in the normal CBD were more frequently
observed in malignantcases (in 27 and 30 patients for hepatic arterial and portal venous phase scans, respectively) than in benign cases (in two and three patients, respectively) (P < .0001). Results of multivariable stepwise logistic regression analysis showed that hyperenhancement of the involved CBD during the portal venous phase was the only variable that could be used to independently differentiate malignant from benign strictures.
CONCLUSION: Hyperenhancement of the involved CBD during the portal venous phase is the main factor distinguishing malignant from benign CBD strictures. © RSNA, 2005
TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS DISCUSSION References INTRODUCTION Cholangiocarcinoma is an adenocarcinoma that arises from the bile duct epithelium. It is usually classified as either intrahepatic or
extrahepatic. Cholangiocarcinoma typically manifests in one of three shapes: infiltrative, exophytic, or polypoid. Most extrahepatic
cholangiocarcinomas are of the infiltrative type and manifest as a focal stricture of the bile duct, whereas papillary carcinoma is occasionally reported to manifest as an intraductal polypoid mass (1–4). Benign common bile duct (CBD) strictures, which have several possible causes (eg, cholangitis, traumatic and postsurgical sequelae, chronic pancreatitis, and papillary stenosis), may mimic infiltrative cholangiocarcinoma (5). At cholangiography, typical malignant CBD strictures usually manifest as irregular strictures with a shouldered margin, whereas benign stenoses tend to have smooth borders with tapered margins (6). In addition,
computed tomographic (CT) findings, including thickeningand enhancement of involved CBD, extrabiliary manifestations such as lymph node
metastasis, and distant metastasis, enable malignant strictures to be differentiated from benign ones. However, it is well known that it is extremely difficult to differentiate benign from malignant CBD strictures on the basis of radiologic features alone, especially in patients with only a focal CBD stricture. Moreover, given the now widespread use of imaging studies in patients with jaundice, early detection of biliary stenosis is possible, and it is not rare to encounter patients with a focal CBD stricture that is difficult to characterize.
To our knowledge, no reports are available concerning the usefulness of helical CT for differentiating malignant from benign CBD strictures in a large population. Thus, the purpose of our study was to evaluate
retrospectively the use of multiphasic helical CT for differentiating malignant from benign CBD strictures in patients with only a focal CBD stricture and to determine predictors for this differentiation.
MATERIALS AND METHODS
TOP Patients and Reference Standard Diagnoses ABSTRACT A computerized search by one of the authors (S.H.C.) INTRODUCTION
of our hospital'sradiology and pathology files for MATERIALS AND METHODS the 4-year period from 1999 to 2002 revealed that 180 RESULTS patients were suspected of having a CBD stricture. DISCUSSION One hundred thirty patients were excluded from the References analysis by that author for one of the following
reasons: (a) a CT study had not beenperformed; (b) obstructive jaundice was not confirmed by means of laboratory testing and direct cholangiography; (c) the patient had undergone biliary
interventional procedures, such as biliary stent insertion, endoscopic
biliary drainage, or percutaneous transhepaticbiliary drainage, before the CT study; (d) the review of CT images or medical records revealed nodal or extrabiliary metastasis, acute or chronic pancreatitis, or biliary stones; or (e) pathology reports revealed exophytic or polypoid
cholangiocarcinoma of the CBD.
The remaining 50 patients with a malignant (n = 32) or a benign (n = 18) CBD stricture were included in our retrospective study. Their mean age was 61.6 years (age range, 35–87 years). The patients included 35 men (age range, 35–87 years; mean age, 61.8 years) and 15 women (age range, 38–74 years; mean age, 61.1 years). According to our hospital's
institutional review board, we were not required to have formal approval or informed patient consent for the limited and anonymous review of patient data required for this study.
All malignant CBD strictures were infiltrative cholangiocarcinomas. The diagnosis of all malignant CBD strictures and five of the 18 benign strictures was confirmed by reviewing patients' surgical and pathology records. All patients with a malignant stricture underwent a Whipple operation (n = 18) or pylorus-preserving pancreaticoduodenectomy (n = 14), one patient with a benign stricture underwent a Whipple operation, and four patients with benign strictures underwent CBD resection only. In 13 of 18 patients with benign CBD strictures, the diagnosis was confirmed
by means of clinical features. The diagnosticcriterion for a benign stricture was a stable condition during a follow-up period of more than 1 year after the endoscopic CBD biopsy (7,8); the median length of follow-up was 13.7 months (range, 12–20 months).
CT Scan Acquisition
In the 50 patients included in our study, CT examinations had been performed at our institution with a Somatom Plus-4 scanner (Siemens, Erlangen, Germany) (n = 24), a HiSpeed Advantage scanner (General Electric Medical Systems, Milwaukee, Wis) (n = 11), or an MX8000 four–detector
row scanner (Philips Medical Systems, Cleveland, Ohio) (n = 15). Each patient received 120 mL of a nonionic contrast material (iopromide, Ultravist 370; Schering Korea, Seoul, Korea) through an 18-gauge angiographic catheter inserted into a forearm vein. CT scans were routinely obtained with the patient in a supine position during full inspiration. The contrast material was injected at a rate of 3 mL/sec with an automatic power injector. Helical CT was performed with a
single–detector row scanner at the following parameters: detector collimation, 5 mm; table pitch, 1:1; and reconstruction intervals, 5 mm. When the MX8000 scanner was used, the parameters were as follows: detector
collimation, 2.5 mm; table speed, 20 mm/sec;section thickness, 3.2 mm; and reconstruction interval, 1.6 mm. Multiphasic helical CT scans were
obtained 30 seconds (hepatic arterial phase)and 70 seconds (portal venous phase) after initiation of the contrast material injection.
CT Scan Analysis
The CT scans acquired in the 50 patients were reviewed in consensus by two abdominal radiologists (J.M.L., 14 years of experience; S.H.K., 7 years of experience) who had no knowledge of the final radiologic or pathologic findings. All CT scans were reviewed on a picture archiving and communication system workstation (Marotech, Seoul, Korea). During analysis of the CT features, cases of malignant and benign strictures were randomly intermixed. The CBD was considered to be involved when the two radiologists encountered a narrow duct followed by a dilated proximal duct. CT findings were interpreted with regard to wall thickness, the location and length of the involved CBD, and the enhancement pattern of the involved
CBD wall during hepatic arterial and portalvenous phases. These were compared with the attenuation of the normal CBD wall, the maximum CBD diameter proximal to the site of the involved CBD, and the presence or absence of pancreatic duct dilatation, air in the biliary tree, and cholecystectomy. The maximum transverse thickness of the involved CBD wall was recorded, and a thick CBD wall was defined as wall thickening of more than 1.5 mm (9). The location of the involved duct was described as intrapancreatic, suprapancreatic, or supra- and intrapancreatic. The involved CBD length was calculated by observing a number of CT scans. CT numbers were obtained by means of region-of-interest cursors placed on all wall portions of the CBD lesion and on the dilated upstream CBD wall (J.M.L. or S.H.K.). These cursors were carefully placed to encompass as much of the CBD wall as possible and to avoid adjacent structures. Region-of-interest measurements for lesions were obtained for both hepatic arterial phase and portal venous phase CT scans by either author. In all cases, scans were later reviewed in consensus to ensure that region-of-interest measurements were obtained for each CBD lesion and for
the upstream CBD. The mean CT number was recorded for each measurement obtained. In all cases, the individual measurements were very close to the mean. A difference of more than 10 HU in mean CT numbers between the involved CBD wall and the upstream CBD wall was considered meaningful. Finally, the CT number of the involved CBD wall was compared with that of the normal upstream CBD wall, and the enhancement pattern of the involved CBD wall was classified as hyperenhanced, isoenhanced, or hypoenhanced in comparison with that of the normal CBD wall.
Histopathologic Findings
The histopathologic findings in patients with malignant CBD strictures were collected by one radiologist (S.H.C.) who reviewed the pathology
reports. The length of the involved duct was recorded, and its locationwas also classified as intrapancreatic, suprapancreatic, or supra- and intrapancreatic on the basis of the histopathologic findings. Statistical Analysis
The Kolmogorov-Smirnov test was used to determine whether values were normally distributed. Statistical differences in the CT features of malignant and benign strictures were analyzed with the 2 test, the Fisher exact test, or the Mann-Whitney U test. For malignant strictures, the paired Student t test and the McNemar test were used to assess differences between CT and histopathologic findings, and agreements between CT and histopathologic findings were assessed by calculating the statistic. A multivariable stepwise logistic regression model was used to determine the best predictors of a differential diagnosis between benign and malignant strictures (10). Thereafter, the probability of benign or malignant obstruction was calculated for each patient. With these data, we determined the diagnostic performance of CT for differentiating benign
from malignant obstruction. Significantdifferences were defined as those with P values less than .05. All statistical analyses were performed with the SPSS software package (version 10.0; SPSS, Chicago, Ill).
RESULTS
TOP Univariate Analysis ABSTRACT Table 1 summarizes the different CT features INTRODUCTION observed in patientswith a malignant or a benign CBD MATERIALS AND METHODS
stricture. The involved segmentsof malignant CBD RESULTS strictures were significantly longer (17.9 mm ± 6.6 DISCUSSION [mean ± standard deviation]) than those of benign References strictures (8.9 mm ± 6.8) (P < .0001). Maximum CBD
diameters measuredproximal to malignant strictures were also significantly larger (22.0 mm ± 5.4) than those measured proximal to benign strictures (17.8 mm ± 4.6) (P = .033). CBD stricture walls were considered thick (>1.5 mm) in 26 of 32 patients with a malignant
strictureand in three of 18 patients with a benign stricture, and this difference was also significant (P < .0001) (Figs 1, 2).
View this table: [in this window] [in a new window] TABLE 1. CT Findings in Malignant and Benign CBD Strictures
Figure 1a. Contrast material–enhanced transverse CT scans show infiltrative cholangiocarcinoma involving the supra- and intrapancreatic portion of the CBD in a 54-year-old man. (a) Hepatic arterial phase scan shows a dilated CBD with wall thickening (large arrow). The thickened wall is hyperattenuating relative to the
View larger version wall of the normal CBD. Dilated
(146K): intrahepatic ducts (small arrows) are [in this window] also seen. (b) Portal venous phase scan [in a new window] shows progressive enhancement of the [Download PPT slide] thickened CBD wall (large arrow) compared
with the hepatic arterial phase scan in
a. Dilated intrahepatic ducts (small
arrows) are seen. (c) Hepatic arterial phase scan obtained at the level of the pancreas shows thickening of the entire ductal wall (arrows) in the intrapancreatic portion of the CBD. The thickened wall shows hyperenhancement. (d) Portal venous phase scan shows thickening of the entire ductal wall (arrows) in the intrapancreatic portion of the CBD. The thickened wall shows more enhancement here than during the hepatic arterial phase.
Figure 1b. Contrast material–enhanced transverse CT scans show infiltrative cholangiocarcinoma involving the supra- and intrapancreatic portion of the CBD in a 54-year-old man. (a) Hepatic arterial phase scan shows a dilated CBD with wall thickening (large arrow). The thickened wall is hyperattenuating relative to the
View larger version wall of the normal CBD. Dilated
(151K): intrahepatic ducts (small arrows) are [in this window] also seen. (b) Portal venous phase scan [in a new window] shows progressive enhancement of the [Download PPT slide] thickened CBD wall (large arrow) compared
with the hepatic arterial phase scan in
a. Dilated intrahepatic ducts (small arrows) are seen. (c) Hepatic arterial phase scan obtained at the level of the pancreas shows thickening of the entire ductal wall (arrows) in the
intrapancreatic portion of the CBD. The thickened wall shows hyperenhancement. (d) Portal venous phase scan shows thickening of the entire ductal wall (arrows) in the intrapancreatic portion of the CBD. The thickened wall shows more enhancement here than during the hepatic arterial phase.
Figure 1c. Contrast material–enhanced transverse CT scans show infiltrative cholangiocarcinoma involving the supra- and intrapancreatic portion of the CBD in a 54-year-old man. (a) Hepatic arterial phase scan shows a dilated CBD with wall thickening (large arrow). The thickened wall is hyperattenuating relative to the
View larger version wall of the normal CBD. Dilated
(148K): intrahepatic ducts (small arrows) are [in this window] also seen. (b) Portal venous phase scan [in a new window] shows progressive enhancement of the [Download PPT slide] thickened CBD wall (large arrow) compared
with the hepatic arterial phase scan in
a. Dilated intrahepatic ducts (small arrows) are seen. (c) Hepatic arterial phase scan obtained at the level of the pancreas shows thickening of the entire ductal wall (arrows) in the
intrapancreatic portion of the CBD. The thickened wall shows hyperenhancement. (d) Portal venous phase scan shows thickening of the entire ductal wall (arrows) in the intrapancreatic portion of the CBD. The thickened wall shows more enhancement here than during the hepatic arterial phase.
Figure 1d. Contrast material–enhanced transverse CT scans show infiltrative cholangiocarcinoma involving the supra- and intrapancreatic portion of the CBD in a 54-year-old man. (a) Hepatic arterial phase scan shows a dilated CBD with wall thickening (large arrow). The thickened wall is hyperattenuating relative to the
View larger version wall of the normal CBD. Dilated
(151K): intrahepatic ducts (small arrows) are
[in this window] [in a new window] [Download PPT slide]
also seen. (b) Portal venous phase scan shows progressive enhancement of the thickened CBD wall (large arrow) compared with the hepatic arterial phase scan in a. Dilated intrahepatic ducts (small arrows) are seen. (c) Hepatic arterial phase scan obtained at the level of the pancreas shows thickening of the entire ductal wall (arrows) in the
intrapancreatic portion of the CBD. The thickened wall shows hyperenhancement. (d) Portal venous phase scan shows thickening of the entire ductal wall (arrows) in the intrapancreatic portion of the CBD. The thickened wall shows more enhancement here than during the hepatic arterial phase.
Figure 2a. Contrast-enhanced transverse CT scans show benign biliary stricture involving the intrapancreatic portion of the CBD in a 53-year-old man. (a, b) Scans obtained during the (a) hepatic arterial phase and (b) portal venous phase show dilatation of the intrapancreatic CBD (arrow). (c, d) Scans obtained during the
View larger version (c) hepatic arterial phase and (d) portal
(140K): venous phase show that the [in this window] intrapancreatic portion of the CBD [in a new window] (arrow) is not dilated and has no
[Download PPT slide] hyperattenuating portion compared with
the suprapancreatic CBD wall.
Figure 2b. Contrast-enhanced transverse CT scans show benign biliary stricture involving the intrapancreatic portion of the CBD in a 53-year-old man. (a, b) Scans obtained during the (a) hepatic arterial phase and (b) portal venous phase show dilatation of the intrapancreatic CBD (arrow). (c, d) Scans obtained during the
View larger version (c) hepatic arterial phase and (d) portal
(144K): venous phase show that the [in this window] intrapancreatic portion of the CBD [in a new window] (arrow) is not dilated and has no
[Download PPT slide] hyperattenuating portion compared with
the suprapancreatic CBD wall.
Figure 2c. Contrast-enhanced transverse CT scans show benign biliary stricture involving the intrapancreatic portion of the CBD in a 53-year-old man. (a, b) Scans obtained during the (a) hepatic arterial phase and (b) portal venous phase show dilatation of the intrapancreatic CBD (arrow). (c, d) Scans obtained during the
View larger version (c) hepatic arterial phase and (d) portal
(145K): venous phase show that the [in this window] intrapancreatic portion of the CBD [in a new window] (arrow) is not dilated and has no
[Download PPT slide] hyperattenuating portion compared with
the suprapancreatic CBD wall.
Figure 2d. Contrast-enhanced transverse CT scans show benign biliary stricture involving the intrapancreatic portion of the CBD in a 53-year-old man. (a, b) Scans obtained during the (a) hepatic arterial phase and (b) portal venous phase show dilatation of the intrapancreatic CBD (arrow). (c, d) Scans obtained during the
View larger version (c) hepatic arterial phase and (d) portal
(147K): [in this window] [in a new window] [Download PPT slide] venous phase show that the intrapancreatic portion of the CBD (arrow) is not dilated and has no hyperattenuating portion compared with the suprapancreatic CBD wall.
During the hepatic arterial phase, hyperenhancement of the involved CBD wall was observed in 27 (84.4%) of 32 patients with a malignant stricture and in two (11.1%) of 18 with a benign stricture (Fig 1). Isoenhancement or hypoenhancement of the CBD wall was seen in five (15.6%) of 32 patients with a malignant stricture and 16 (88.9%) of 18 with a benign stricture. During the portal venous phase, hyperenhancement of the CBD stricture wall was seen in 30 (93.8%) of 32 patients with a malignant stricture, including three patients whose stricture had shown isoenhancement and 27 whose stricture had shown hyperenhancement during the hepatic arterial phase (Fig 1). However, of 18 patients with a benign CBD stricture, two patients had hyperenhancement of the CBD stricture wall during both hepatic arterial and portal venous phases, and one had hyperenhancement only during the portal venous phase. Therefore, only three (16.7%) of 18 patients with a benign stricture demonstrated higher than normal ductal wall enhancement during the portal venous phase. The stricture wall showed
isoenhancement or hypoenhancementduring both hepatic arterial and portal
venous phases in the remaining15 patients (83.3%) (Fig 2). For both hepatic arterial phase and portal venous phase CT scans, the differences in enhancement patterns between benign and malignant stricture walls were significant (P < .0001).
Five (27.8%) of 18 patients with a benign CBD stricture and one (3.1%) of 32 patients with a malignant stricture underwent cholecystectomy, which is a significant difference in incidence (P < .001). No significant differences were found between malignant and benign CBD strictures with respect to stricture location (P = .35), the presence of air in the biliary tree (P = .319), or pancreatic duct dilatation (P = .188) (Table 1). CT-Histopathologic Correlation
The average length of malignant CBD strictures measured was 17.9 mm ± 6.6 at CT compared with 21.5 mm ± 9.3 at pathologic evaluation; this difference was not significant (P = .131). At CT, the malignant strictures
were categorized as suprapancreatic in fivepatients, intrapancreatic in 21, and supra- and intrapancreatic in six. At pathologic evaluation, the strictures were revealed as suprapancreatic in six patients,
intrapancreatic in 16, and supra- and intrapancreatic in 10. This difference was not significant (P = .18), with a value of 0.518 (P < .001)
(Table 2). The accuracy of CT with respect to malignant CBD stricture location was 72% (23 of 32 patients).
View this TABLE 2. Comparison of Malignant Stricture Site table: between CT and Pathologic Evaluation [in this window] [in a new window]
Multivariable Analysis and Diagnostic Performance
Univariate analysis showed several significant differences between
malignant and benign CBD strictures (Table 1). However, multivariable stepwise logistic regression analysis showed that a hyperenhancement pattern of the involved CBD wall during the portal venous phase was the only independently differentiating variable, with an odds ratio of 76.92 (95% confidence interval: 11.24, 500.00). Stricture length, ductal diameter proximal to a stricture, ductal thickness, hyperenhancement
pattern of the involved CBD wall during the hepatic arterial phase,and a history of cholecystectomy were close alternatives (10). When
diagnostic predictive values were calculated by using one variable,
enhancement pattern during the portal venous phase (hyperenhancement vs isoenhancement or hypoenhancement), a malignant stricture was correctly identified in 30 (93.8%) of 32 patients, and a benign stricture was correctly identified in 15 (83.3%) of 18 patients. Thus, the overall accuracy of CT was 90.0%, with correct classifications in 45 of the 50 patients.
DISCUSSION
TOP Evaluation of patients suspected of having a biliary ABSTRACT
tract obstructionhas conventionally involved a INTRODUCTION
variety of diagnostic imaging techniques.In our MATERIALS AND METHODS hospital, dual-phase CT is used as a major RESULTS diagnostic imaging modality for patients suspected DISCUSSION of having obstructive jaundice. The technique References provides good information about the presence of
biliaryobstruction and the degree of ductal
dilatation in such patients. The challenge for radiologists when
interpreting these CT images is to differentiate a malignant bile duct obstruction from a benign lesion. Since our institution is a tertiary
referral center, we havehad experience with many patients who have obstructive jaundice. On the basis of these experiences, we focused on patients who presented with biliary obstruction without any intra- or extrabiliary manifestation suggesting a malignant or a benign condition,
in whom it can be difficultto differentiate malignant from benign CBD strictures.
Although radiologic findings suggestive of malignant or benign CBD strictures have been reported, to our knowledge, most of these have
concerned conventional CT findings. However, a small number of reports have described the use of multiphasic helical CT findings for this
differentiation (1,5). The CT findings in benign biliary strictures, as documented in previous studies, include diffuse bile duct dilatation and an abrupt narrowing of the dilated duct (11), whereas infiltrative cholangiocarcinoma can be detected as focal wall thickening, usually with early or late enhancement or both, in addition to the same CT findings as seen in benign CBD strictures (3,12). However, the ability of CT to differentiate benign from malignant CBD obstruction has not been reported. Moreover, to our knowledge, the CBD is a common location for benign biliary strictures of different causes (13), which is one of the many difficulties
of differential diagnosis.
In our study, a malignant CBD stricture was characterized by strong
enhancement or high attenuation during the hepatic arterial or portalvenous phase, a wall thicker than 1.5 mm, and a longer involved segment and a more dilated duct proximal to the involved CBD than observed in cases of benign stricture. Patients who had undergone cholecystectomy were more frequently encountered among those with a benign CBD stricture. The results of our study correlated well with those of previous studies, which showed that malignant CBD strictures show hyperenhancement on
contrast-enhanced CT scans or magnetic resonance (MR) images, as well as a thickened wall and a relatively longer segment (1,2,6,12). In addition,
more than 80% of bile duct strictures occur after extrahepatic bile duct injury during cholecystectomy (14,15). The remaining strictures are attributable to other benign causes, such as infection, pancreatitis, stone passage, trauma, primary sclerosing cholangitis, ischemia, chemotherapy, or acquired immunodeficiency syndrome.
Multivariable stepwise logistic regression analysis showed that
enhancement pattern during the portal venous phase was the only variable that was independently predictive of a differential diagnosis, although we found a number of significant differences between malignant and benign CBD strictures with univariate analysis. In our study, the predictive value calculated by using a hyperenhancement pattern only during the
portal venous phase was 93.8% in patients with malignantCBD strictures (30 of 32 patients), 83.3% in those with benign strictures (15 of 18), and 90.0% overall (45 of 50 patients). CT is known to be more accurate for demonstrating the location and extent of the involved CBD than MR cholangiopancreatography and endoscopic retrograde
cholangiopancreatography (7). However, in the present study, CT had an accuracy of 75%, correctly demonstrating the location and extent of the stricture in 24 of 32 patients with malignant CBD stricture. We believe that CT evaluation of the extent of CBD cancer is sometimes limited by pancreatic enhancement, which can mask bile duct enhancement or microscopic infiltration by cholangiocarcinoma, the latter of which causes subtle changes in enhancement pattern.
The results of our study suggest that multiphasic CT is useful for
characterizing and revealing the locations of CBD strictures. Compared with MR imaging and endoscopic retrograde cholangiopancreatography, helical CT scanning is both faster and more readily available. Furthermore, the recently introduced multi–detector row CT technology produces
isotropic images and excellent temporal resolution, and CT angiographic or CT cholangiographic coronal or oblique sagittal multiplanar scans with the same spatial resolutions as transverse scans are therefore obtainable. Therefore, we expect that multi—detector row CT will play a major role in the diagnostic work-up of biliary stenosis.
Apart from the intrinsic limits of any retrospective study, several other limitations should be mentioned. First, this study lacked pathologic proof in some patients with a benign CBD stricture. However, clinical and imaging follow-up, along with consultations with patients' clinicians, provided no evidence of tumors at follow-up in patients presumed to have a benign CBD stricture. Second, because our patient population
represented a subset of all patients with biliary obstruction at our institution, the effects of selection bias must be considered. Third, the data used in the present study were acquired at section thicknesses
ranging from 2.5 to 5.0 mm, and the CBD is not exclusively perpendicular to the transverse plane. Thus, this study has a limitation with respect to the CT evaluation of the involved CBD length.
In conclusion, the results of our study show that certain findings (hyperenhancement during the hepatic arterial phase or portal venous phase, a stricture wall thicker than 1.5 mm, a longer involved segment, and a more dilated duct proximal to the involved CBD than in benign
stricture) are observed more frequently in malignant CBD strictures than in benign strictures. In particular, this study shows that a hyperenhancement pattern of the involved CBD wall during the portal venous phase is the main feature distinguishing malignant from benign CBD
strictures.
Abbreviations: CBD = common bile duct
Authors stated no financial relationship to disclose.
Author contributions: Guarantor of integrity of entire study, J.K.H.; Study concepts/study design or data acquisition or data
analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, S.H.C., K.H.L.; clinical studies, S.H.C., J.K.H., J.M.L., S.H.K., B.I.C.; statistical analysis, S.H.C., J.K.H., J.M.L., S.H.K., B.I.C.; manuscript editing, S.H.C., J.K.H., J.M.L., K.H.L., J.Y.L., B.I.C.
FOOTNOTES
References
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