Indian J Gastroenterol

DOI 10.1007/s12664-013-0371-9

ORIGINAL ARTICLE

An analysis of biliary anatomy according to different

classification systems
Pranjal Deka & Mahibul Islam & Deepti Jindal &
Niteen Kumar & Ankur Arora & Sanjay Singh Negi

Received: 22 January 2013 / Accepted: 28 July 2013

# Indian Society of Gastroenterology 2013

Abstract considers most clinically relevant variations pertinent to

Purpose Variations in biliary anatomy are common, and dif- hepatobiliary surgery.
ferent classifications have been described. These classification
systems have not been compared to each other in a single
Keywords Bile ducts . Cholecystectomy . Injury . Surgical
cohort. We report such variations in biliary anatomy on mag-
anatomy
netic resonance cholangiopancreatography (MRCP) using six
different classification systems.
Methods In 299 patients undergoing MRCP for various indica-
tions, biliary anatomy was classified as described by Couinaud Introduction
(1957), Huang (1996), Karakas (2008), Choi (2003), Champetier
(1994), and Ohkubo (2004). Correlation with direct cholangiog- Precise demonstration of vascular and biliary anatomy, includ-
raphy and vascular anatomy was done. Bile duct dimensions ing anatomical variations, is an essential step when contem-
were measured. Cystic duct junction and pancreaticobiliary duc- plating surgical, radiologic, or endoscopic intervention in the
tal junction (PBDJ) were classified. liver and biliary tract [1, 2]. Prior delineation of the anatomy
Results Normal biliary anatomy was noted in 57.8 %. The helps in tailoring the proposed intervention and thereby helps
most common variants were Couinaud type D2, Choi type improve outcomes and reduce complications [3]. A successful
3A, Huang type A1, Champetier type a, Ohkubo types D and biliary drainage (endoscopic or percutaneous transhepatic)
J, and Karakas type 2a. The Ohkubo classification was the most depends to a large extent on proper delineation of the biliary
appropriate; 3.1 % of right ducts and 6.3 % of left ducts with anatomy. Similarly, liver resections for benign and malignant
variant anatomy could not be classified using the Ohkubo diseases require precise knowledge of the vascular and biliary
classification. There was a good agreement between MRCP anatomy. With advances in living donor and split liver trans-
and direct cholangiography (ĸ=0.9). Anomalous PBDJ was plantation, the relevant anatomy has implications on both
noted in 8.7 %. Variant biliary anatomy was not associated with donor and recipient safety [4].
gender (p=0.194) or variant vascular anatomy (p=0.24). Biliary anatomy has been studied by different methods
Conclusion Although each classification system has its merits such as corrosion cast studies [5], dissection of autopsy spec-
and demerits, some anatomical variations cannot be classified imens [6], and imaging studies such as endoscopic retrograde
using any of the previously described classifications. The cholangiography (ERC), magnetic resonance cholangiogra-
Ohkubo classification system is the most applicable as it phy (MRC), computed tomography (CT) cholangiography,
and intraoperative cholangiography [1, 7, 8]. Among all these
methods, MRC is noninvasive and is associated with minimal
P. Deka : M. Islam : D. Jindal : N. Kumar : S. S. Negi (*)
patient safety issues. Therefore, MRC is probably the ideal
Department of HPB Surgery, Institute of Liver and Biliary Sciences, method for delineating biliary anatomy prior to an invasive
D-1, Vasant Kunj, New Delhi 110 070, India procedure [9].
e-mail: drsanjaynegi@gmail.com There have been several reports describing biliary and vas-
cular anatomy of the liver and biliary tract in both diseased and
A. Arora
Department of Radiology, Institute of Liver and Biliary Sciences, healthy individuals [1, 8, 10]. However, most of these reports
D-1, Vasant Kunj, New Delhi 110 070, India have focused on the right hepatic duct and its variations. In the
 Indian J Gastroenterol

only study from India, the study group comprised patients Length and diameter of the main portal vein, left portal
undergoing ERC for various indications [11]. vein, and right portal vein were also measured. In addition,
The purpose of this study is to review our data with respect wherever possible, the length of the right hepatic duct (RHD),
to biliary anatomy and its variations in patients undergoing left hepatic duct (LHD), and common channel were measured.
MRC and to assess the applicability of different classification The following parameters were also measured: distance be-
systems with respect to our patient population. tween the segment 4 duct and segments 2–3 duct junctions,
distance between the hilar confluence and cystic duct inser-
tion, and distance between the hilar confluence and insertion
Materials and Methods of an accessory duct. The diameters of CBD, common hepatic
duct (CHD), RHD, LHD, accessory duct, main pancreatic
After approval from the Institutional Ethics Committee, we duct, and common channel were measured.
carried out a retrospective analysis of our database of patients Anomalous pancreaticobiliary ductal junction was classi-
undergoing magnetic resonance cholangiopancreatography fied as types I, II, or III [22]. The junction of cystic duct with
(MRCP) for various indications from 2009 to 2011. CT and CHD was classified as angular, parallel, or spiral [29].
direct cholangiography images, where available, were also All continuous data are presented as median (range). Cat-
reviewed. Patients who had a dilated biliary system or in whom egorical variables are compared using Fischer's exact test. The
poor quality images rendered interpretation of segmental biliary ĸ statistic was used to measure an agreement between MRCP
anatomy difficult were excluded from the final analysis. and direct cholangiography with respect to variant biliary
MRCP studies were performed on the 3-Tesla Signa HDxt anatomy. All statistical analyses were carried out using the
MR scanner (GE Medical Systems, USA). The phased array Microsoft Excel for Windows (Redmond, USA). P<0.05 was
TORSOPA coil was used to improve the signal reception. considered statistically significant.
Baseline-unenhanced axial sequences were acquired through
the liver with a slice thickness of 5 mm at 1-mm intervals,
including breath hold in- and out-phase T1 weighted sequence
and T2 single-shot fast spin echo (SSFSE) with and without Results
fat suppression. The 2D fast imaging employing steady-state
acquisition (FIESTA) sequences were performed in axial and Between June 2009 and August 2011, 400 patients underwent
coronal planes through the liver with slice thickness of 3 mm MRCP at Institute of Liver and Biliary Sciences, New Delhi.
and at 0.5-mm intervals. The 3D MRCP images were obtained Of these, 101 (25.2 %) patients were excluded from the
using respiration-triggered heavily T2-weighted sequence present analysis due to generalized dilatation of the biliary
(FRFSE-XL) in axial and coronal planes with contiguous thin system and/or poor image quality leading to inadequate inter-
sections (1.4 mm/0.7 overlap). T2 SSFSE with breath hold in pretation of the biliary anatomy. The indications of MRCP in
thick slabs of 40 mm in coronal oblique planes at 20° incre- the 299 patients who form the study group are summarized in
ments keeping the common bile duct (CBD) as the center of Table 1. Of the 299 patients analyzed, 133 (44.4 %) were
rotation was also performed. The imaging parameters used for female. The median age of the patients was 40 years (range 9–
SSFSE sequences were as follows: time of repetition (TR) 82 years).
2,100 ms, time to echo (TE) 80.1 ms, slab thickness 0.5 mm, In 22 patients, intraoperative cholangiography was also
field of view (FOV) 38 cm, and matrix 288×192. The imaging done. Thirty patients underwent ERCP for various indications.
parameters used for FIESTA sequences were as follows: TR Thus, direct cholangiography was available in 52 patients
4.7 ms, TE 2.1 ms, slab thickness 3 mm, FOV 35 cm, flip (17.4 %). There was a good agreement between the results
angle 70, and matrix 224×352. All source images were inde-
pendently reviewed by two surgeons and a radiologist, and in
case of any discrepancy, a consensus was arrived at. Table 1 Indication of
MRCP (n=299) Indication n (%)
Intrahepatic biliary anatomy was classified according to
different classification systems as proposed by Couinaud, Stone disease 72 (24)
Huang, Choi, Champetier, Karakas, and Ohkubo. The details Chronic pancreatitis 31 (10.3)
of these different classification schemes have been described Acute pancreatitis 18 (6)
in detail previously [1, 8, 10, 12–14]. Donor for liver transplant 56 (18.7)
Arterial anatomy was classified as proposed by Michels Evaluation of pain abdomen 53 (17.7)
et al. [15]. Portal venous anatomy was classified as proposed Chronic liver disease 37 (12.3)
by Varotti et al. [16]. Hepatic venous anatomy was classified Percentages may not add Obstructive jaundice 25 (8.3)
according to three different classification systems proposed by to 100 due to the effect of Liver mass 7 (2.3)
Nakamura et al., Marcos et al., and Kawasaki et al. [17–19]. rounding
Indian J Gastroenterol

of MRCP and direct cholangiography with respect to variant patients underwent a contrast-enhanced CT scan for various
biliary anatomy (ĸ=0.9). One hundred and nine (36.4 %) reasons.
Biliary anatomy was classified according to different clas-
Table 2 Classification of biliary anatomy according to different classifi- sification systems as shown in Table 2. Classification of
cation systems biliary anatomy according to Couinaud's and Ohkubo's clas-
sification systems is shown in Figs. 1 and 2, respectively.
Classification system Type N (%) Classification not
applicable, N (%) Variant biliary anatomy was not related to sex (38.5 % in
males vs. 46.6 % in females; p=0.194). An accessory duct
Couinaud [12] A 173 (57.8) 10 (3.3) was present in 42 (14 %) patients. All accessory ducts origi-
B 24 (8) nated from the right ductal system. Among all the different
C1 9 (3) classification systems, the Ohkubo classification was the most
C2 20 (6.6) applicable in this study population as the percentage of un-
D1 52 (17.4) classified variants was least with this classification, and both
D2 1 (0.3) right and left ductal systems could be classified. However,
E1 1 (0.3)
E2 2 (0.6)
F 7 (2.3)
Huang et al. [1] A1 173 (57.8) 23 (7.7)
A2 24 (8)
A3 52 (17.4)
A4 20 (6.6)
A5 7 (2.3)
Karakas et al. [13] K1 47 (15.7) 30 (11.1)
K2a 126 (42.1)
K2b 24 (8)
K3a 51 (17)
K3b 1 (0.3)
K4 20 (6.6)
Choi et al. [8] 1 173 (57.8) 15 (5)
2 24 (8)
3A 52 (17.4)
3B 20 (6.6)
3C 7 (2.3)
4 3 (1)
5A 5 (1.6)
5B 0
6 0
Champetier et al. [14] a 54 (18) 102 (34.1)
b 26 (8.7)
c 96 (32.1)
d 21 (7)
e 0
Ohkubo et al. [10] (right duct) A 93 (31.1) 9 (3.1)
B 26 (8.7)
C 54 (18)
D 96 (32.1)
E 21 (7)
F 0
G 0
Ohkubo et al. [10] (left duct) H 232 (77.6) 19 (6.3)
I 21 (7)
J 24 (8)
K 3 (1)
Fig. 1 Classification of biliary anatomy according to Couinaud [12]
 Indian J Gastroenterol

Table 3 Anatomical parameters (n=299)

Parameter n Not Mean Median Range (mm)

measurable

CHD length 296 3 22.05 21.88 2.32 to 57.89

CHD diameter 296 3 4.14 3.64 1.77 to 10.73
RHD length 290 101 10.06 8.57 1.29–33.09
RHD diameter 290 101 2.59 2.33 1.17–6.43
LHD length 290 3 7.83 6.83 1.2–30.36
LHD diameter 290 3 2.92 2.73 1.39–7.83
Diameter of 42 8 2.03 1.98 0.89 to 3.97
accessory duct
Distance from 42 0 8.16 12.83 1.09 to 27.07
confluence to
accessory duct
insertion
Diameter of CBD at 296 3 4.61 4.01 0.07 to 12.14
upper end
Diameter of CBD at 294 5 2.88 2.73 1.3 to 6.93
lower end
Diameter of MPD 288 11 2.01 1.99 0.98 to 4.56
Length of common 243 56 5.1 4.13 1.45 to 38.43
channel
Diameter of common 240 59 2.21 2.11 1.09 to 4.87
channel near the
Fig. 2 Classification of biliary anatomy according to Ohkubo et al. [10] ampulla
MPV length 260 39 55.25 55.46 9.82 to 90.31
MPV diameter 260 39 11.7 11.5 7.23 to 21.3
even this classification could not be applied in 3.1 % (right RPV length 272 27 15.01 13.94 5.56 to 43
ductal system) and 6.3 % (left ductal system) of cases. Eight RPV diameter 272 27 9.68 9.65 5.86 to 20.46
patients had two or more segment 4 ducts, and in these LPV length 259 40 21.1 22.24 9.55 to 31.19
patients, the Ohkubo classification could not be applied. LPV diameter 259 40 9.2 9.06 4.51 to 14.4
The cystic duct junction with the CHD was classified as
CHD common hepatic duct, RHD right hepatic duct, LHD left hepatic
angular in 206 patients (68.9 %), parallel in 50 (16.7 %), and
duct, CBD common bile duct, MPD main pancreatic duct, MPV main
spiral in 28 (9.3 %). Classification was not possible in 15 portal vein, RPV right portal vein, LPV left portal vein
(5 %) patients.
Anomalous pancreaticobiliary ductal junction was present
in 26 (8.7 %) patients. Eight patients (30.7 %) had Komi type I Classification of arterial anatomy is shown in Fig. 3. Table 4
anomalous pancreaticobiliary ductal junction (APBDJ), 14 shows the comparison of arterial anatomy with previous studies.
patients (53.8 %) had Komi type II APBDJ, and 4 patients Portal venous anatomy was classified as type 1 in 264 patients
(15.3 %) had Komi type III APBDJ. Seven of the 26 patients (88.3 %), type 2 in 14 (4.7 %), and type 3 in 6 (2 %). Classifi-
(26.9 %) with APBDJ had an associated choledochal cyst. cation was not possible in 15 (5 %) patients. Fifty-five percent of
Table 3 shows the imaging measurements of various pa- patients with portal vein (PV) variations had an associated vari-
rameters pertaining to the biliary and portal venous system. ation of biliary anatomy in contrast to 40 % of patients with
Right hepatic duct dimensions were not measurable in 101 normal PV anatomy having a variation in biliary anatomy
patients, corresponding to Ohkubo types B, C, E, and G. Left (p=0.24). Classification of hepatic venous anatomy according
hepatic duct dimensions were not measurable in three patients, to different classification systems is shown in Table 5.
corresponding to Ohkubo type K.
The distance between the segment 4 duct and segments 2–3
duct junctions was measured. In 232 patients with Ohkubo Discussion
type H anatomy and 3 patients with type K anatomy, this
distance ranged from 1.72 to 40 mm (median 9.42 mm). In Numerous reports have described the variations in the anato-
24 patients with Ohkubo type J anatomy, where the segment 4 my of the intrahepatic bile ducts [1–3, 5, 7, 8, 10, 11]. These
duct joins the segment 3 duct, this distance ranged from 1.59 variations are clinically important when performing surgical
to 15.2 mm (median 7.3 mm). In 21 patients with Ohkubo or radiological interventions pertaining to the biliary tree for a
type I anatomy (trijunction), this distance was not measurable. wide range of benign and malignant conditions. With rapid
Indian J Gastroenterol

Fig. 3 Classification of arterial

anatomy according to Michels
[15]

Table 4 Anatomical variants of

hepatic artery according to Michels type Kishi et al. 2010 [28] Lopez-Andujar et al. Sahani et al. 2004 [27] Present study
Michels' classification [15] (all 2007 [26]
figures in percentages) n=361 n=1,081 n=? n=79

I 68.6 70 55 64.5
II 10.2 9.7 10 19
III 6.9 7.8 11 3.8
IV 4.2 3.1 1 3.8
V 4.7 3.9 8 6.3
Others (VI–X) 5.1 4.0 17 2.5
 Indian J Gastroenterol

Table 5 Classification of hepatic venous anatomy. Values are n (%) Using the classification system proposed by Choi et al.,
Classification Type 1 Type 2 Type 3 Unclassified variations in anatomy compared well with a previous study
from India, wherein the most common variants were types 3A
Nakamura and Tsuzuki 185 (61.8) 22 (7.3) 4 (1.3) 88 (29.4) and 2 [11]. Type 7 that is an unclassified or complex variation
[17] was seen in 5 % of patients, higher than that reported else-
Marcos et al. [18] 137 (45.8) 51 (17) 24 (8) 87 (29)
where [8, 11, 23]. A major drawback with the Choi classifi-
Kawasaki et al. [19] 40 (13.3) 167 (55.8) 2 (0.6) 90 (30.1)
cation is that only type 6 considers variations pertaining to the
left ductal system. More importantly, the Choi classification
does not consider variations in the drainage of segment 4 duct
strides being made in imaging techniques, preoperative road which is relevant to left-sided liver resections. Cysticohepatic
mapping of the biliary anatomy has come to play a significant ducts, which correspond to type 3C in the Choi classification,
part in surgical planning. This is all the more relevant in have been reported in 1 % to 2 % patients [14, 21]. Recogni-
evaluation of donors for live donor liver transplantation [8, tion of this variant is especially important in laparoscopic
10]. cholecystectomy. Type 3C was present in 2.3 % of our pa-
Previous studies have reported anatomical variants detect- tients. The Choi classification was based on intraoperative
ed by different imaging modalities such as endoscopic retro- cholangiography in donors of liver transplantation. In that
grade cholangiography [11], magnetic resonance cholangiog- study, the length of the right hepatic duct ranged from 2.4 to
raphy [7], and intraoperative cholangiography [8] and also by 30 mm, and in 34 % of donors, the RHD was <10 mm [8]. In
corrosion cast studies [5] on autopsy specimens. The study the present study, RHD length ranged from 1.2 to 33 mm, with
populations in these reports are variable. Most recent reports 56 % of the study population with measurable RHD having
have focused on liver donors. A prospective liver donor is RHD length of <10 mm.
essentially a healthy individual and, hence, is a representative Using the Huang classification, type A1 was seen in 57.8 %,
of the general population. A few reports have also analyzed and the 7.7 % could not be classified into any of the five types,
the relationship between variations in biliary and vascular which is higher than the 5.4 % incidence of unclassified type in
anatomy [10, 28]. a previous study on MRC in donors for liver transplantation
The present study included all consecutive patients under- [25]. An interesting concept proposed by Karakas et al. [13] is
going MRCP, irrespective of the indication. MRCP is a safe that a trifurcation anatomy (Huang type A2) could be subdi-
and noninvasive imaging modality with few contraindica- vided into two types from a surgical perspective. According to
tions, and hence, the possibility of selection bias for the this classification, they considered close proximity (<1 cm)
purpose of inclusion of patients for such a study is minimized. between the right posterior sectoral duct (RPSD) insertion and
The study population includes healthy individuals and pa- the primary confluence as a subtype of Huang type A2, and this
tients with or without biliary disease. led to the prevalence of Huang type A1 decreasing to 27 %
A major drawback with previous studies is that classifica- from 55 %. If this concept is applied to our study population,
tion of anatomical variants was done using a single classifica- wherein the distance between RPSD insertion and the primary
tion scheme [3, 11, 13, 24, 25]. In the only other study from confluence ranged from 1.29 to 33.09 mm, the prevalence of
this country, a diseased population was studied using a single Huang type A1 (ie. Karakas type K1) decreased from 57.8 % to
classification system [11]. In this study, we have classified 17.5 %. Karakas type K2a (ie. <1 cm distance between RPSD
biliary anatomy of the right hemiliver according to the classi- insertion and the primary confluence) was seen in 46.8 %.
fication systems proposed by Couinaud, Choi, Huang, Therefore, in our population, we can expect up to 55.7 % of
Karakas, Ohkubo, and Champetier and of the left hemiliver individuals to have a ductal anatomy such that two ducts would
according to the classification scheme proposed by Ohkubo be obtained in a right lobe graft for living donor liver transplan-
et al. [1, 8, 10, 12–14]. tation. This has significant implications for biliary complica-
The most common type of biliary anatomy Couinaud type 1 tions in recipients.
was present in 57.8 % of patients. The Couinaud classification On analyzing biliary anatomy using the Ohkubo classifi-
does not take into account accessory ducts unlike the Choi cation, the most common type was type D (32.1 %) followed
classification. Previous studies have shown accessory ducts in by type A (31.1 %). This is in contrast to previous reports
2 % to 6 % patients [8]. Fourteen percent of our study popula- which show that Ohkubo type A is the most common type
tion had accessory ducts, and the significance of this would not [10]. With respect to the left hepatic duct and its branches,
have been recognized if classification systems other than that of Ohkubo type H was the most common (77.6 %). An important
Couinaud were not applied. Delineation of accessory ducts is drawback of the Ohkubo classification is that when two or
important in the context of liver resections and biliary drainage. more segment 4 ducts are present and drain separately into the
Excluded accessory ducts are a source of bile leak and/or left ductal system, classification is not possible. This was the
segmental cholangitis depending on the clinical scenario. case in eight of our patients. This specific aspect was studied
Indian J Gastroenterol

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