British Journal of Radiology (2007) 80, e150-e154
© 2007 British Institute of Radiology
doi: 10.1259/bjr/50929809
Duplication of the extrahepatic bile duct with anomalous union of the pancreaticobiliary ductal system revealed by MR cholangiopancreatography
E Choi, BA
1,2
J H Byun, MD
1
B J Park, MD
1 and
M-G Lee, MD
1
1 Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Pungnap-2dong, Songpa-gu, 138-736 Seoul, Korea, 2 Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
Correspondence: Jae Ho Byun, MD, Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 388-1 Pungnap-2dong, Songpa-gu, 138-736 Seoul, Korea. E-mail: jhbyun{at}amc.seoul.kr
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Abstract
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MR cholangiopancreatography (MRCP) is a valuable, non-invasive tool for accurate examination of the biliary system. We report a case in which MRCP played a critical role in the diagnosis of a duplication of the extrahepatic bile duct with anomalous union of the pancreaticobiliary ductal system in a patient with hilar cholangiocarcinoma. This variant of a duplication of the extrahepatic biliary system has not been described previously in the literature.
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Introduction
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Congenital anomalies of the bile ducts are relatively common with a reported prevalence of 15% based on surgical studies [1]. Congenital doubling of the extrahepatic biliary tract, however, is extremely rare with discussion primarily limited to sporadic case reports. Duplication of the common bile duct, for instance, has been reported in only 24 individuals, according to a review of the western literature over a 500 year period up to 1986 [2]. The anomaly has also been associated with a high incidence of concomitant malformation of the pancreaticobiliary union, especially in cases where the accessory bile duct opens into the second portion of the duodenum or the pancreatic duct [3]. We present a unique variant of a duplication of an extrahepatic biliary system with anomalous arrangement of the pancreaticobiliary ductal union, visualized on MR cholangiopancreatography (MRCP), which has never, to our knowledge, been reported in the English literature.
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Case report
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A 72-year-old woman with a history of insulin-dependent diabetes and hypertension presented to our institution with a 2-day history of right upper quadrant abdominal pain, jaundice and generalized pruritus. The patient denied fever, chills, dyspnoea or any gastrointestinal symptoms. Physical examination revealed a soft, non-distended abdomen without any tenderness or peritoneal signs. Laboratory results indicated a cholestatic profile, including an alkaline phosphatase of 379 IU l–1 (normal 40–120 IU l–1), 
-glutamyl transferase value of 334 IU l–1 (normal 8–35 IU l–1) and a direct bilirubin of 15.8 mg dl–1 (normal 
0.5 mg dl–1). Liver function tests were slightly elevated ((AST 56 IU l–1; normal 40 IU l–1), (ALT 51 IU l–1; normal 40 IU l–1)). The serum level of carbohydrate antigen 19-9 (CA 19-9) was noted to be markedly elevated (3530 U ml–1; normal 0–37 U ml–1). CT examination (Figure 1a
) was performed using a 16-detector CT scanner (LightSpeed Ultra 16; GE Medical Systems, Milwaukee, WI) and showed diffuse dilatation of the intrahepatic bile ducts and an enhancing bile duct wall thickening in the hilar portion of both main right and left bile ducts, suggestive of a diagnosis of hilar cholangiocarcinoma [4]. Endoscopic retrograde cholangiopancreatography (ERCP) was subsequently performed (Figure 1b,c) and showed the presence of two extrahepatic bile ducts, with the medial bile duct of smaller diameter designated as the accessory extrahepatic bile duct, exhibiting both proximal hilar and distal communication. The main pancreatic and accessory extrahepatic bile duct create an early, superior junction and subsequently form a long common channel, which in turn joins the main extrahepatic bile duct to create a short common bile duct that drains into the duodenal major papilla (Figure 1c). With the understanding of hilar communication between the two extrahepatic bile ducts, the clinician inserted an endoscopic nasobiliary drainage (ENBD) tube for temporary therapeutic decompression. Further evaluation with MR cholangiopancreatography (MRCP) was subsequently performed on a 1.5 T clinical unit (Magnetom Avanto; Siemens, Erlangen, Germany) with a phased-array body coil. Two different MRCP sequences, thick-slab single-shot rapid acquisition with relaxation enhancement (RARE) (repetition time (TR)/echo time (TE) 4500/757; flip angle 180°) and maximum intensity projection (MIP) reconstruction of a free-breathing navigator triggered T2 weighted turbo spin-echo sequence with prospective acquisition correction (TR/TE 5515/671; flip angle 140°), were applied. Contrary to the ERCP finding of proximal hilar confluence of both extrahepatic bile ducts, oblique coronal, thick and thin MIP MRCP (Figure 1d–f) demonstrated clear radiographic evidence of cross-over of the extrahepatic bile ducts without any communication. With knowledge of this separation, the clinician performed a follow-up ERCP with insertion of two ENBD tubes to achieve sufficient biliary decompression prior to definitive treatment with a biliary stent and a percutaneous transhepatic biliary drainage tube (Figure 1g). Although the anatomy of the cystic duct was not visualized on ERCP and MRCP, the location of its distal insertion was presumed to be in an extrahepatic bile duct. Insertion of the cystic duct into the short common bile duct, however, is unlikely given that the proximity of the common bile duct to the site of contrast injection at ERCP would have certainly revealed any such communication. Careful, retrospective review of the CT scans revealed the presence of two extrahepatic bile ducts on CT (Figure 1h). We believe that it is most likely that the tumour originated from a single extrahepatic bile duct and subsequently extended to encase the second bile duct. Given the patient's advanced age and medical co-morbidities, the patient did not undergo surgery.
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Figure 1. A 72-year-old women with right upper quadrant pain, jaundice and generalized pruritus. (a) Contrast-enhanced CT image during the portal venous phase shows diffuse dilatation of the intrahepatic bile ducts and an enhancing wall thickening of the hilum (black arrow), representing hilar cholangiocarcinoma. (b) Initial endoscopic retrograde cholangiopancreatography (ERCP) image demonstrates duplication of the extrahepatic bile ducts with early junction (black arrow) between the medial, accessory bile duct and the main pancreatic duct (arrowheads) and subsequent formation of a long common channel (curved arrow). Proximal communication of both extrahepatic bile ducts (white thick arrow) with irregular luminal narrowing, representing cholangiocarcinoma, is also noted. Note that there is also communication between the accessory extrahepatic bile duct and a branch pancreatic duct (white thin arrow). (c) Initial ERCP image shows distal union (white arrow) of both extrahepatic bile ducts to form a short common bile duct. (d) Oblique coronal, thick-slab maximum intensity projection (MIP) MR cholangiopancreatography image from a free-breathing navigator triggered T2 weighted turbo spin-echo sequence with prospective acquisition correction (repetition time (TR)/echo time (TE) 5515/671; slice thickness 50 mm) demonstrates the absence of proximal communication between both extrahepatic biliary ducts. The abnormal arrangement of the pancreaticobiliary ductal union (curved arrow) and the long common channel (black arrow) are also noted. ) (e) Oblique coronal, thin-slab MIP MR cholangiopancreatography image from a free-breathing navigator triggered T2 weighted turbo spin-echo sequence with prospective acquisition correction (TR/TE 5515/671; slice thickness 5 mm) demonstrates better visualization of both proximal extrahepatic bile ducts, including the absence of communication at the intersection (white arrow). Note the distal communication and subsequent formation of a short common bile duct (black arrow). (f) Illustration shows a simplified representation of the anatomical anomaly of the biliary and pancreatic duct systems of the present case. (g) Follow-up ERCP image with insertion of two endoscopic nasobiliary drainage tubes (white arrow) shows clear separation of both extrahepatic bile ducts. (h) Axial contrast-enhanced CT scan caudal to (a) shows two extrahepatic bile ducts with enhancing bile duct wall thickening (arrows).
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Discussion
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The increased prevalence of biliary pathology, namely cholangitis, cholelithiasis and cholangiocarcinoma, seen in patients with pancreaticobiliary anomalies makes their early detection an important clinical goal [5]. Moreover, precise anatomic delineation of the biliary tree in such patients is critical for appropriate surgical planning and minimizing bile duct injury. Although ERCP represents the current gold standard, MRCP is an excellent non-invasive alternative that provides analogous anatomic information of the pancreaticobiliary ducts. The accuracy of MRCP in the diagnosis of anatomic variants of the biliary tract is well established [6, 7]. The present case not only reaffirms the utility of MRCP in the evaluation of biliary tree anomalies but also demonstrates how it may provide superior anatomical information of clinical import that may not be obtained with ERCP alone. Because ERCP is an operator-dependent, invasive technique associated with serious complications, including pancreatitis and duodenal perforation, MRCP is also preferred in the screening of biliary malignancies in high-risk patients with pancreaticobiliary malformations. The close association between cholangiocarcinoma and anomalous arrangement of the pancreaticobiliary ductal union, for example, is well demonstrated by our case [5]. The proximal location of the sphincter of Oddi relative to the pancreaticobiliary junction is believed to result in the continuous regurgitation of pancreatic juices into the bile duct, predisposing it to malignant change [1, 3]. In such cases, examination of the biliary tree with MRCP may be helpful in corroborating other associated congenital abnormalities, as well as evaluating any pathological change.
Owing to the unique nature of the anomaly in our present case and the wide variations of reported cases of extrahepatic biliary duplication, precise anatomical definition and classification posed a challenge. Although our case shared marked resemblance to the reported cases of double or duplication of common bile duct (DCBD), we refrain from classifying the anomaly of our case as such, given that the presumed definition of the "common bile duct" in the DCBD literature is defined as the duct that directly drains into the gastrointestinal tract irrespective of its proximal anatomy. Consequently, our case consists of a single, short common bile duct that is formed by the distal convergence of two long extrahepatic bile ducts. Since the cystic duct most likely does not drain into the short common bile duct, we can conclude that the common hepatic duct is absent.
The present case has marked similarities to a previously reported case of an accessory bile duct arising from the confluence of the right and left hepatic duct, which joins the pancreatic duct to form a long, common channel that drains separately from the main bile duct [8]. We emphasize that the present case differs with respect to the absence of communication between the right and left hepatic ducts and the formation of a short common channel described previously, resulting in single drainage into the papilla. Moreover, MRCP was useful in precisely delineating the biliary anatomy, in contradistinction to a previously reported case.
To allow inclusion of this rare anomaly into a classification scheme, we propose modification of the current classification of the DCBD proposed by Saito et al [9], which consists of four configuration types: (1) common bile duct with a septum within the lumen; (2) common bile duct which bifurcates with two independent drainages; (3) double biliary drainage without any direct communication; and (4) double biliary drainage with one or more communicating channels (Figure 2). A more generalized classification of double extrahepatic bile duct that would allow categorization of the present case requires addition of the following category: a single biliary drainage with or without one or more communication channels (Figure 2).
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Figure 2. Classification of double extrahepatic bile duct. Modified classification from Saito et al[9] and our new proposal of a fifth configuration type characterized by single drainage of two extrahepatic bile ducts. Type Va includes single drainage without any communication between two extrahepatic bile ducts, and Type Vb includes single drainage with one or more communication channels.
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The mechanism of such rare biliary anomalies has been a subject of much discussion, since Boyden and his colleagues first proposed that duplication of the biliary system, known to be a normal anatomical feature of reptiles, birds and fish, is present in early human embryogenesis and thereby represents primitive structures that regress with normal development [2, 10]. An early disruption of development, therefore, is believed to result in the persistence of an accessory extrahepatic duct. Since our case represents an incomplete duplication of the extrahepatic biliary system, we can logically infer that the disruptive event during organogenesis occurred relatively later than seen in cases of true duplication.
In conclusion, we illustrate the accurate MRCP-aided diagnosis of a very rare manifestation of a duplication of the extrahepatic bile ducts with concomitant anomalous union of the pancreaticobiliary ductal system in a patient with hilar cholangiocarcinoma. The case exemplifies how MRCP can provide detailed clinically significant anatomical information that may be overlooked on ERCP and thereby supports the increased use of MRCP in the routine evaluation of biliary anomalies.
Received for publication December 16, 2005.
Revision received March 20, 2006.
Accepted for publication April 10, 2006.
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References
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Abstract
Introduction
