Download Common and Rare Variants of the Biliary Tree: Magnetic

J Radiol Sci 2012; 37: 59-67
Common and Rare Variants of the Biliary Tree: Magnetic
Resonance Cholangiographic Findings and Clinical
Implications
Sin-Yi Lyu1 Kuang -Tse Pan1,2 Sung -Yu Chu1,2 Ming -Yi Hsu1,2 Chien-Ming Chen1,2 Chien-Fu Hung1,2
Jeng -Hwei Tseng1,2
Department of Medical Imaging and Intervention1, Chang Gung Memorial Hospital Linkou Medical Center, Taoyuan, Taiwan
College of Medicine and School of Medical Technology2, Chang Gung University, Taoyuan, Taiwan
Abstract
With increasing complexity and prevalence of hepatobiliary surgery (eg. Hepatic resection and liver transplantation), accurate preoperative evaluation of the biliary anatomy is essential to ensure safe and successful hepatic
surgery. Magnetic resonance cholangiography (MRC) is a safe, non-invasive diagnostic imaging technique, with
added value of imaging postprocessing, allows accurate identification of biliary anatomy. The purpose of this paper
is to document the epidemiology of biliary variation of Taiwanese population, to demonstrate imaging features of
the common and rare anatomical variation of biliary tree by using MRC and to emphasize its implications on major
hepatic surgery.
Despite improvements in hepatic surgical techniques,
biliary complication remains a major cause of morbidity
and mortality, and accurate diagnosis is crucial for treatment planning. Thus, a detailed knowledge of the hepatic
anatomy is a prerequisite for successful, complication-free
liver surgeries [1-4]. Presurgical planning with detailed
anatomy is a key component of liver surgeries, including
transplantation, tumor resection, and laparoscopic hepatobiliary surgeries [2]. Magnetic resonance imaging is
an accurate and noninvasive technique for evaluating the
hepatic vascular and biliary anatomy, is devoid of ionizing
radiation and is safe for patients who are allergic to iodinated
contrast agents [5]. The purposes of this study were to use
Magnetic resonance cholangiography (MRC) to investigate
the anatomical variants of biliary tracts in Taiwanese population, to demonstrate imaging features of these common
and rare biliary variants and to stress its implications for
liver surgery.
Material and Method
Patient
This was a retrospective single-institution study that
was approved by our institutional review board. In our
hospital, a total of 476 living related liver transplantation
donors received conventional T2 MRC examination for
pre-operative evaluation over a 45-month period (from
April 2006 to December 2009). Due to suboptimal imaging
quality, 14 patients (3%) were excluded from this study. A
total of 462 patients were enrolled for evaluation (age range,
17-58 years, mean 31.4; 233 male, 229 female).
MRC protocol
All MRC were obtained with a 1.5T scanner (GE, Signa
Excite). Morphine (0.04 mg/kg body weight) was given
intravenously prior to the examination to improve imaging
quality of the biliary tree. Our protocol includes one set of
Correspondence Author to: Jeng-Hwei Tseng
Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital Linkou Medical Center, Taoyuan, Taiwan
No. 5, Fu-Shin Street, Kueishan, Taoyuan 333, Taiwan
J Radiol Sci June 2012 Vol.37 No.2
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biliary tract variation in taiwanese
2D coronal thick slice fast spin echo (FSE) MRC (relaxation
time/echo time = 4000 ms/ 901.1 ms) and a second set of
3D oblique coronal thin slice fast spin echo T2-weighted
image MRC (relaxation time/echo time = 5454.6 ms/ 551.4
ms, spatial resolution = 0.66mm × 0.66 mm × 2.8 mm).
Post-processing of the image data was performed to reconstruct maximum intensity projection (MIP) images and
multiplanar reformatted images (MPR).
Normal biliary tract anatomy
The normal biliary drainage system is parallel to the
portal venous supply. The right posterior segmental duct
(RPSD) draining the posterior segments (VI and VII) join
the right anterior segmental duct (RASD) draining the
anterior segments (V and VIII) to form the right hepatic
duct (RHD). The right posterior segmental duct is almost
horizontal, but the right anterior segmental duct tends to be
more vertical. The right posterior segmental duct usually
runs posterior to the right anterior segmental duct and fuses
to form the right hepatic duct. The left hepatic duct (LHD) is
formed by segmental tributaries the drain segments II–IV.
The common hepatic duct is formed by fusion of the right
hepatic duct and left hepatic duct. The bile duct draining
the caudate lobe usually joins the origin of the left or right
hepatic duct.
Biliary tract variation
Common variations of the biliary tract were divided
into 7 types according to Yoshida classification [6]: Type 1
(Fig. 1), union of the right anterior segmental duct (RASD)
Figure 1
Figure 1. MRCP and drawing illust ration show t y pe 1 biliar y t ract
variation: union of the right anterior
segmental duct (RASD) and the right
posterior segmental duct (RPSD) to
form a right intrahepatic duct.
Figure 2
Figure 2. MRCP and drawing illust ration show t y pe 2 biliar y t ract
variation: union of the right anterior
segmental duct (RASD), right posterior segmental duct (RPSD), and left
intrahepatic duct (LHD) to form a
trifurcation.
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biliary tract variation in taiwanese
and the right posterior segmental duct (RPSD) to form a
right hepatic duct (RHD); Type 2 (Fig. 2), union of the
rRASD, RPSD, and left hepatic duct (LHD) to form a triple
confluence; Type 3 (Fig. 3), the RPSD draining directly into
the LHD; Type 4 (Fig. 4), the RPSD draining into common
hepatic duct (CHD); Type 5 (Fig. 5), union of the RPSD, left
superior segmental duct (LSSD) and left inferior segmental
duct (LISD) to form a trifurcation; Type 6 (Fig. 6), union
of the RASD, RPSD and LSSD as a triple confluence and
the LISD draining into the CHD; Type 7 (Fig. 7), the LISD
draining into the CHD. There are several rare variants with
accessory ducts which were not included in the Yoshida
classification were grouped into type 8 (Fig. 8-13).
Results
All of the 462 patients with visualization of the third
order branches of the intrahepatic ducts on MRC were
selected for analysis. In this study, normal biliary duct
anatomy was present in 65.8% of patients. Drainage of the
right posterior segment into the left hepatic duct before its
confluence with the right anterior segmental duct was the
most common anatomic variant of the biliary system (type
3, 13.0%). Another common variant of main hepatic biliary
branching was the so-called triple confluence (type 2, 9.1%),
which is characterized by simultaneous emptying of the
right posterior segmental duct, right anterior segmental duct,
and left hepatic duct into the common hepatic duct. These
variants at the level of the confluence become important in
Figure 3
Figure 3. MRCP and drawing illustration show type 3 biliary tract variation: the right anterior segmental duct
(RASD) draining directly into the left
intrahepatic duct (LHD).
Figure 4
Figure 4. MRCP and drawing illustration show type 4 biliary tract variation: the right posterior segmental duct
(RPSD) draining into common hepatic
duct.
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biliary tract variation in taiwanese
Figure 5
Figure 5. MRCP and drawing illust ration show t y pe 5 biliar y t ract
variation: union of the right posterior
segmental duct (RPSD), left superior
segmental duct (LSSD) and left inferior segmental duct (LISD) to form a
trifurcation.
Figure 6
Figure 6. MRCP and drawing illust ration show t y pe 6 biliar y t ract
variation: a union of the right anterior segmental duct (RASD), right
posterior segmental duct (RPSD) and
left superior segmental duct (LSSD)
as a trifurcation and the left inferior
segmental duct (LISD) draining into
the common hepatic duct.
Figure 7
Figure 7. MRCP and drawing illustration show type 7 biliary tract variation:
the left inferior segmental duct (LISD)
draining into the common hepatic
duct.
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biliary tract variation in taiwanese
Table 1. Incidence of common and rare biliary variation
Anatomic
variation
Our series
(n=462)
Choi et al [4]
2003 (n=188)
Puente al. [13]
1983 (n=3845)
Masayuki Ohkubo al. [15]
2004 (n=165)
Type 1 (%)
65.8
63
57.6
65
Type 2 (%)
9.1
10
11
Type 3 (%)
13.0
11
12.9
12
Type 4 (%)
8.9
6
6.5
5
Others (%)
3.2
10
12
5
13
Figure 8
Figure 8. MRCP and drawing illustration show one rare biliary tract variation: the right posterior segmental duct
(RPSD) draining into the left intrahepatic duct (LHD) inferiorly
patients who are considered as potential donors for right
hepatic lobe transplantation. The proportions of these 8
types of biliary tract variation are listed with respect to
type classification (Table 1): type 1: 307 cases (65.8%); type
2: 42 cases (9.1%); type 3: 60 cases (13%); type 4: 41 cases
(8.9%); type 5-8: 15 cases (3.2%).
Discussion
According to a literature review, the incidence of the
typical pattern of biliary system has been reported to be
57%-72% [7-19]. With the increasing complexity and prevalence of hepatobiliary surgeries (eg, transplantation surgery
and hepatic resection), a detailed preoperative evaluation of
the hepatic vascular and biliary anatomy is mandatory to
minimize postoperative morbidity [4].
Determination of biliary anatomy can be performed
preoperatively by endoscopic retrograde cholangiography (ERC), intraoperative cholangiography (IOC),
conventional T2 MRC, contrast enhanced T1 MRC and
J Radiol Sci June 2012 Vol.37 No.2
multi-detector row computed tomography cholangiography (CTC). ERC is able to provide precise evaluation
of the biliary tract with the best imaging quality. ERC,
however, is associated with certain risks, including postERC pancreatitis, biliary tract injury and duodenal perforation [19]. Intraoperative cholangiography (IOC) can be
challenging, time consuming and injurious. IOC is rarely
performed in our institution, which stress the importance
and necessity of accurate and safe methods for preoperative evaluation of the biliary tree anatomy.
MRC has potential as a noninvasive, non-biohazardous diagnostic modality for pre-operation evaluation [5]. The basic concept is that heavily T2-weighted
images demonstrate high signal intensity from structures
containing static fluid. The limitation of this conventional
MRC technique has been inadequate depiction of the
biliary tract, especially in nondilated ducts [4]. In our
study, Morphine was used for increasing the frequency and
amplitude of basal contractions of the sphincter of Oddi.
Reduced outflow of bile and pancreatic juice and distension
of biliary tract was also noted as an effect of Morphine.
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biliary tract variation in taiwanese
Figure 9
Figure 9. MRCP and drawing illustration show one rare biliary tract variation: bilateral IHDs form a trifurcation
respectively.
Figure 10
Figure 10. MRCP and drawing illustration show one rare biliary tract
variation: one accessory hepatic duct
draining into CHD.
Figure 11
Figure 11. MRCP and drawing illustration show one rare biliary tract
variation: LISD draining into RASD
and the RPSD draining into CHD.
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However, we must note the adverse effects of Morphine,
such as miosis, dizziness, nausea, vomiting, bowel ileus and
respiratory depression. During this study, two patients were
sent to emergency room due to hypotension and another 14
patients complained minor side effects (e.g., nausea, dizziness and skin rash). Poor visualization of biliary tree on T2
MRC was encountered in 3% of our patients even with the
help of Morphine. Other imaging modalities are needed for
these patients with poor distention of bile ducts.
The usefulness of CTC using intravenous injection of
contrast medium has been shown to provide much better
spatial resolution than other indirect cholangiography.
Previous studies have reported that CTC enables significantly better biliary tract visualization than conventional
T2-weighted or contrast enhanced T1-weighted MRC either
alone or in combination [20]. CTC is minimally invasive
and simple to perform. The image data enable visualization
of the biliary tract anatomy, as well as the relationship
between biliary tract and hepatic vasculature, and the data
are easily reformatted into 3D displays [21]. However, the
contrast medium is currently not available in Taiwan.
The hepatocyte-specific contrast agents, gadolinium
benzyloxypropionictetraacetate (Gd-BOPTA) and gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid
(Gd-EOB-DTPA) were developed to improve the detection
and characterization of focal liver lesions at MR imaging.
The injected contrast medium is taken up into the functional
hepatocyte and is excreted via the biliary system. Because
of this property, hepatocyte-specific contrast agent has the
potential to be a biliary contrast agent. When combined with
T2-weighted MR cholangiography, both Gd-EOB-DTPA
and Gd-BOPTA enhanced MR imaging could be effective
in evaluation of biliary anatomy. In patient with suboptimal
imaging quality T2-WI MRC, hepatocyte-specific contrast
Figure 12
Figure 12. MRCP and drawing illustration show one rare biliary tract
variation: accessory segmental left
IHD draining into CHD.
Figure 13
Figure 13. MRCP and drawing illustration show one rare biliary tract
variation: S4 segmental IHD draining
into CHD directly.
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agent enhanced T1-WI MRC should be considered as an
alternative. However, hepatospecific contrast medium
enhanced MRC itself has several limitations, including:
high cost, limited availability, the potential risk of contrastinduced adverse reactions, and long examination times [10].
Sufficient knowledge and detailed anatomic demonstration before hepatobiliary surgery are mandatory to
avoid formidable complications, which might lead to
biliary cripple and/or mortality, if not adequate corrected.
For example, for those with Yoshida classification 3
who undergo left hepatectomy, his or her right posterior
segmental branch might be erroneously ligated without
proper biliary reconstruction, if this biliary anomaly is
not well recognized preoperatively. Further, for those with
Yoshida classification 4 who undergo laparoscopic cholecystectomy, the right posterior segmental branch might be
mistaken as cystic duct and erroneously divided. Of note,
the type 3 and type 4 occurred in 13% and 8.9%, respectively, of our patients surveyed by MRCP, which therefore
represent an important issue for hepatobiliary surgeons.
Furthermore, there are several rare biliary tract variations,
such as aberrant (Fig. 13) and accessory hepatic ducts (Fig.
10, 12). An aberrant hepatic duct is the only hepatic duct
draining a particular hepatic segment, whereas an accessory duct is an additional hepatic duct draining the same
area of the liver. An aberrant right hepatic duct, which
occurs in 3.2%–18.0% of patients, drains part of the right
lobe of the liver directly into the extrahepatic hepatic tract
[4]. The aberrant duct may undergo accidental transection
or ligation during cholecystectomy, and complications may
therefore occur. These complications include formation of a
biliary fistula, biloma, sepsis, pain, and repetitive episodes
of cholangitis. Increasing demand for liver transplantation with a concomitant shortage of cadaveric livers had
increased the prevalence of living donor living transplantation (LDLT) [21]. Right-lobe LDLT is expected to provide
advantages over left-lobe LDLT in terms of graft size. In
order to obtain full benefits of a larger graft volume of the
right-lobe LDLT, it is therefore essential to avoid the surgical
complications associated with increased anatomical variations [22-25]. The surgical complications are classified into
early and late complications. Early complications include
periductal bile leakage with resultant edema, fibrosis or
secondary stricture, and ischemia. Bile duct strictures are
the most common late complications and may develop a few
months or many years after surgery [26].
Conclusion
The incidence of biliary tract variation in our study
has been measured to be similar as previous studies. Preoperative imaging of the biliary branching pattern remains
the only method to diagnose and treat problems posed by
variantions in biliary anatomy [27]. MRC offers a reliable
66
and non-invasive visualization of the biliary tract, enabling
the surgical approach to be planned and adapted to prevent
an injury of a variant of the hepatic duct confluence.
Reference
1.Van Thiel DH, Wright HI, Fagiuoli S, Caraceni P, Rodriguez-Rilo H. Preoperative evaluation of a patient for
hepatic surgery. J Surg Oncol Suppl 1993; 3: 49-51
2.Ozeki Y, Uchiyama T, Katayama M, Sugiyama A,
Kokubo M, Matsubara N. Extended left hepatic trisegmentectomy with resection of main right hepatic vein
and preservation of middle and inferior right hepatic
veins. Surgery 1995; 117: 715-717
3.Fan S, Lo C, Liu C, Yong BH, Chan JK, Ng IO. Safety
of donors in live donor liver transplantation using right
lobe grafts. Arch Surg 2000; 135: 336-340
4.Catalano OA, Singh AH, Uppot RN, Hahn PF, Ferrone
CR, Sahani DV. Vascular and Biliary Variants in the
Liver: Implications for Liver Surgery. RadioGraphics
2008; 28: 359-378
5.Song GW, Lee SG, Hwang S, et al. Preoperative evaluation of biliary anatomy of donor in living donor liver
transplantation by conventional nonenhanced magnetic
resonance cholangiography. Transpl Int 2007; 2: 167-173
6.Yoshida J, Chijiiwa K, Yamaguchi K, Yokohata K,
Tanaka M. Practical classification of the branching
types of the biliary tree: an analysis of 1094 consecutive
direct cholangiograms. J Am Coll Surg 1996; 182: 37-40
7.Huang TL, Cheng YF, Chen CL, Chen TY, Lee TY.
Variants of the bile ducts: clinical application in the
potential donor of living-related hepatic transplantation.
Transplant Proc 1996; 28: 1669-1670
8.Mortele KJ, Ros PR. Anatomic variants of the biliary
tree: MR cholangiographic findings and clinical applications. AJR Am J Roentgenol 2001; 177: 389-394
9.Jin WC, Tae KK, Kyoung WK, et al. Anatomic variation
in intrahepatic bile ducts: an analysis of intraoperative
cholangiograms. Korean J Radiol 2003; 4: 85-90
10.Lee CM, Chen HC, Leung TK, Chen YY. Magnetic
resonance cholangiopancreatography of anatomical
variants of the biliary tree in Taiwanese. J Formos Med
Assoc 2004; 103: 155-159
11.Kim MH, Sekijima J, Lee SP. Primary intrahepatic
stones. Am J Gastroenterol 1995; 90: 540-548
12.Kim HJ, Kim MH, Lee SK, et al. Normal structure,
variations and anomalies of the pancreaticobiliary ducts
of Koreans: a nationwide cooperative prospective study.
Gastrointest Endosc 2002; 55: 889-896
13.Turner MA, Fulcher AS. The cystic duct: normal
anatomy and disease processes. Radiographics 2001;
21: 3-22
J Radiol Sci June 2012 Vol.37 No.2
biliary tract variation in taiwanese
14.Champetier J, Letoublon C, Alnaasan I, Charvin B.
The cystico-hepatic ducts: surgical implications. Surg
Radiol Anat 1991; 13: 203-211
15. Hamlin JA. Biliary ductal anomalies. In: Berci G,
Hamlin JA, eds. Operative Biliary Radiology, 1st edn.
Baltimore. Williams &Wilkins 1981: 110-116
16.Reid SH, Cho SR, Shaw CI, Turner MA. Anomalous
hepatic duct inserting into the cystic duct. AJR Am J
Roentgenol 1986; 147: 1181-1182
17.Park CH, Cho HJ, Kwack EY, Choi CS, Kang IW, Yoon
JS. Intrahepatic biliary duct anatomy and its variations.
J Korean Radiol Soc 1991; 27: 827-831
18.Puente SG, Bannura GC. Radiological anatomy of the
biliary tract: variations and congenital abnormalities.
World J Surg 1983; 7: 271-276
19.Masayuki O, Masato N, Junichi K, et al. Surgical
anatomy of the bile ducts at the hepatic hilum as applied
to living donor liver transplantation. Ann Surg 2004;
239: 82-86
20.Yeh BM, Breiman RS, Taouli B, Qayyum A, Roberts JP,
Coakley FV. Biliary tract depiction in living potential
liver donors: comparison of conventional MR, mangafodipir trisodium–enhanced excretory MR, and multi–
detector row CT cholangiography—initial experience.
Radiology 2004; 230: 645-651
21.Hashimoto M, Itoh K, Shibata T, Okada T, Okuno
Y, Hino M. Evaluation of biliary abnormalities with
64-channel multidetector CT. Radiographics 2008; 28:
119-134
J Radiol Sci June 2012 Vol.37 No.2
22.Marcos A, Ham JM, Fisher RA, Olzinski AT, Posner
MP. Surgical management of anatomical variations of
the right lobe in living donor liver transplantation. Ann
Surg 2000; 231: 8241
23.Liu CL, Fan ST, Lo CM, et al. Operative outcomes of
adult-to-adult right lobe live donor liver transplantation:
a comparative study with cadaveric whole-graft liver
transplantation in a single center. Ann Surg 2006; 243:
404
24.Lo CM, Fan ST, Liu CL, et al. Lessons learned from one
hundred right lobe living donor liver transplants. Ann
Surg 2004; 240: 151
25.Ikegami T, Soejima Y, Taketomi A et al. Hilar Anatomical Variations in Living-Donor Liver Transplantation
Using Right-Lobe Grafts. Dig Surg 2008; 25: 117-123
26.Hoeffel C, Azizi L, Lewin M, et al. Normal and pathologic Features of the Postoperative Biliary Tract at
3D MR Cholangiopancreatography and MR Imaging.
RadioGraphics 2006; 26: 1603-1620
27.Fragulidis G, Marinis A, Polydorou A, et al. Managing
injuries of hepatic duct confluence variants after major
hepatobiliary surgery: An algorithmic approach. World
J Gastroenterol 2008; 19: 3049-3053
67