Available online at www.sciencedirect.com
Journal of the Chinese Medical Association 75 (2012) 384e388
www.jcma-online.com
Original Article
The diameter of the common bile duct in an asymptomatic Taiwanese
population: Measurement by magnetic resonance cholangiopancreatography
Tom Chen a, Ching-Ruei Hung b, Ay-Chiao Huang a, Jiunn-Ming Lii a, Ran-Chou Chen b,*
b
a
Department of Radiology, Taipei City Hospital, Taipei, Taiwan, ROC
Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan, ROC
Received September 26, 2011; accepted February 26, 2012
Abstract
Background: Magnetic resonance cholangiopancreatography (MRCP) is a popular modality for evaluation of the biliary tract, yet there is no data
on the normal common bile duct (CBD) size of the average Taiwanese adult. This study attempts to establish a reference range for CBD diameter
for the Taiwanese population.
Methods: Over a 2-year period, all adults who underwent abdominal magnetic resonance imaging for health screening were recruited into the
study. Patients with a prior history of hepatobiliary surgery and other significant morbidity were not included. Patients who were found to have
abnormal liver function test results or abnormal imaging findings were also excluded from the study. After the patients fasted for a minimum of 8
hours, MR imaging was performed with a 1.5 T MR imager using a phased-array coil. Breath-hold thick slab single-shot turbo spin echo (ssTSE
BH) projections were obtained, and these were used for CBD and portal vein diameter (PVD) measurement by workstation software. Initial
recruitment included 265 patients, of which 66 were excluded due to abnormal liver function tests, seven more were excluded due to excess
imaging artifacts or incomplete CBD visualization, and five were excluded due to other abnormal blood tests. This yielded a final study group of
187 patients between the ages of 21 and 78 years, which comprised 69 women and 118 men.
Results: The mean CBD diameter is 4.6 mm, with a range from 1.76 to 10.49 mm. CBD diameters are significantly different in patients both
younger and older than 65 years of age ( p < 0.05), and are not significantly related to gender, serum glucose level, cholesterol level, hepatitis
status and PVD.
Conclusion: Our study showed that the average CBD diameter for an asymptomatic Taiwanese adult is 4.6 mm, with an upper limit of 10.49 mm.
CBD diameter is only significantly correlated with age. This is a useful reference in today’s clinical setting where MRCP are commonly
performed for evaluation of suspected biliary tract disease.
Copyright Ó 2012 Elsevier Taiwan LLC and the Chinese Medical Association. All rights reserved.
Keywords: adult; biliary tract; common bile duct; MRI; Taiwan
1. Introduction
Over the years, modern medical imaging technology has
helped medical practitioners become proficient in the assessment of biliary pathology, thereby better enabling more
precise measurement of the biliary tract. Because a dilated
* Corresponding author. Dr. Ran-Chou Chen, Department of Radiology,
Taipei City Hospital Heping Branch, 33, Section 2, Chun Hua Road, Taipei
100, Taiwan, ROC.
E-mail address: [email protected] (R.-C. Chen).
common bile duct suggests obstructive causes which may
require invasive imaging or remedial procedures, an accurate
CBD size reference range should be available. A plethora of
published literature exists regarding the normal size of the
common bile duct (CBD),1e7 and these range from the
cadaveric measurements, operative cholangiograms, and
endoscopic retrograde cholangio-pancreatography (ERCP) to
sonography, and, more recently, multi-detector-row computed
tomography (MDCT).
Since its introduction in 1991, MR imaging of the biliary
tract has underwent a progressive evolution.8 Today, magnetic
1726-4901/$ - see front matter Copyright Ó 2012 Elsevier Taiwan LLC and the Chinese Medical Association. All rights reserved.
http://dx.doi.org/10.1016/j.jcma.2012.06.002
T. Chen et al. / Journal of the Chinese Medical Association 75 (2012) 384e388
resonance cholangiopancreatography (MRCP) is one of the
diagnostic mainstays for assessment of biliary tract abnormalitydespecially those involving obstruction. Many
consider MR imaging to be the non-invasive “gold standard”
imaging for evaluation of biliary pathology,9,10 and it is
commonly performed first to determine the necessity of
subsequent invasive procedures such as ERCP.
Despite the prevalence of MRCP as a first-line modality of
biliary pathology,9 a search of the literature available revealed
no formal study that specifically documented normal CBD
diameter as measured by MRCP. Consequently, the lack of
a reference range may lead to over- or underdiagnosis of
biliary dilatation.
The purpose of this study was to evaluate the diameters of
CBD in asymptomatic Taiwanese patients using MRCP, and
determine the normal size range for this population. In addition, we also attempted to evaluate the relationship between
CBD diameter and other variables, in order to see if there is
a significant relationship between them.
2. Methods
2.1. Patients
During the period of January 2005 to December 2006, we
recruited for our study all asymptomatic individuals who
underwent abdominal MRI for health screening and who had
not undergone prior hepatobiliary surgery. The institutional
review board approved this retrospective study and the
informed consent requirement was waived.
We recorded the patients’ age, sex, medical history, list of
medications including substances of abuse, fasting blood sugar
level, total serum cholesterol, liver function tests, and hepatitis
status. Any positive history of myocardial infarction, cerebrovascular accident, biliary disease, pancreatic disease, hepatic
disease, or substance abuse precluded the individual from
joining the study group. Individuals with abnormal liver function
tests (total bilirubin, AST, ALT) or abnormal MRI findings such
as biliary stones or chronic cholecystitis were also subsequently
excluded from the study, thus preventing any individuals with
known potential biliary pathology from joining the study.
The initial recruitment group included 265 participants.
Seven were excluded due to excess image artifacts or
incomplete CBD visualization, five due to incomplete blood
test results, and 66 due to abnormal liver function tests. None
were excluded due to actual biliary abnormality found by
MRI. The final study population consisted of 187 patients
between 21 and 78 years of age (mean age of 51 years) and
included 69 (37%) women and 118 (63%) men.
385
spin-echo (TSE) T2-weighted images were acquired using the
following parameters without and with fat saturation: TR,
2500 ms; TE, 100 ms; TSE factor, 23; matrix, 256 256. Dual
phase T1-weighted images were obtained within one breath
hold using: TR, 210 ms; TE ¼ 2.3 and 4.6 ms; slices thickness,
8 mm; gap, 0.8 mm; flip. Breath-hold thick slab single-shot
turbo spin echo (ssTSE BH) projections were also acquired,
and these were used for the actual CBD measurement. The
parameters of the ssTSE BH sequence were as follows: TR,
8000 ms; effective TE, 850 ms; turbo factor, 128; flip angle,
90 ; slice thickness, 30e40 mm; field of view, 250 mm;
matrix, 256 205; acquisition time, 8 seconds. The entire
pancreaticobiliary tree was included in all images. The same
pulse sequence was repeated to acquire four to six projections
of the pancreaticobiliary system from different angles.
Measurements of the CBD diameters were performed
independently by an experienced radiological technologist
(with 11 years of experience with MR techniques, A.C.H.) and
an experienced radiologist (7 years of experience, T.C.).
Coronal ssTSE BH images at 4-6 different angular planes were
reviewed, and the one with well-demonstrated CBD and main
pancreatic duct with the least superimposed artifacts was used
for measurement. A magnification factor of 2.0 was used to
ensure precise delineation of the biliary duct margins. The
widest diameter of CBD was measured perpendicular to their
long axis using the electronic caliper provided by the picture
archiving and communications system (Centricity PACS, RA
600 v6.1, GE Medical Systems, Milwaukee, Wisconsin, USA)
(Fig. 1). Portions of CBD with superimposed artifacts from the
stomach, small intestines, and cystic ducts were avoided. The
anteroposterior diameters of portal vein anterior to inferior
vena cava were measured using the same method with PACS
electronic caliper, in T2-weighted images.
2.3. Statistical analysis
Statistical analysis was performed using SPSS (SPSS for
Windows, version 15.0, SPSS Inc, Chicago, IL, USA). The
2.2. Imaging
MR imaging was performed on patients after an overnight
fast, which translated to at least 8 hours prior to the MR
examination. Abdominal MR imaging was performed with 1.5
T MR imagers (GyroScan, Philips Medical Systems, the
Netherlands) using phased-array coils. Axial and coronal turbo
Fig. 1. Measurement of CBD diameter by placing electronic caliper at the
widest visible portion of CBD.
386
T. Chen et al. / Journal of the Chinese Medical Association 75 (2012) 384e388
recorded maximal CBD diameters were then analyzed against
age, gender, blood sugar, and cholesterol using Student t-test.
The CBD diameters were also analyzed against the presence
of hepatitis B and C antigens using ANOVA. CBD diameters
were analyzed against portal vein diameters using the Pearson
correlation.
Interobserver agreement was assessed with Pearson’s
correlation coefficient and paired t-test. Multiple linear
regressions were used to confirm the relationships between
CBD diameters and these variables. A p value < 0.05 was
considered statistically significant.
3. Results
The mean CBD diameter of 187 patients obtained by
Reader 1 was 4.6 mm (1.8 mm), with a range of
1.76e10.49 mm. The mean CBD diameter observed by
Reader 2 is 5.0 mm (1.7 mm), with a range of
2.42e11.65 mm. The mean portal vein diameters obtained by
Reader 1 and 2 are 8.13 mm (1.8 mm) and 8.14 mm
(1.8 mm), respectively (Table 1). There was excellent
interobserver agreement between Reader 1 and Reader 2’s
measurements of CBD and portal vein diameter (Pearson
correlation coefficients ¼ 0.89 and 0.90, p < 0.0001).
The mean CBD diameter for females was slightly larger
than that of males (4.8 1.7 mm vs. 4.5 1.8 mm), although
this lacks statistical significance ( p < 0.05). CBD diameter is
directly proportion to age ( p < 0.05), when patients are
divided into two groups using 65 years as the cut-off age.
When patient age is subdivided into decades, further analysis
reveals that there is a somewhat linear relationship between
CBD size and age in decades (R2 ¼ 0.62, Fig. 2). However
other variables such as fasting blood sugar levels, serum
cholesterol, presence of hepatitis B or C, and portal vein
diameters show no statistically significant effect on the CBD
diameter. The results are summarized in Table 1.
Fig. 2. CBD diameter versus patient age.
4. Discussion
Most recently, MRCP is the principle diagnostic modality
that determines if ERCP is neededdespecially when ultrasound findings are equivocal.9 The decision to perform ERCP
depends on whether an organic abnormality or an abnormal
dilation could be demonstrated. To prove the presence of
abnormal dilatation there needs to be a reference range, with
diameters exceeding its upper limit deemed abnormal.
Our results show that the average CBD diameter as
measured by MRCP is 4.6 mm 1.8 mm, with a range of
1.97e10.49 mm. Compared to the results of available research
papers using other imaging modalities, it is well within the
reported range. Jonson et al11 showed that the average diameter in patients with normal cholangiography was 5.9 mm. By
using ultrasound measurement, Kaim et al12 found that
Table 1
CBD diameters and its relations with different parameters.
Patient CBD diameter
Gender*
Age* (y)
Serum glucose* (mg/dL)
Total
cholesterol* (mg/dL)
Hepatitis status**
Portal vein diameter***
*Student t-test.
**ANOVA.
***Pearson Correlation Coefficient.
CBD ¼ common bile duct.
Reader 1
Reader 2
Female
Male
<65
S65
&110
>110
&200
>200
Negative
HBVþ
HCVþ
Continuous
variable
Number
Mean (mm)
Standard deviation
187
4.6
5.0
4.8
4.5
4.4
6.0
4.6
4.5
4.5
4.7
4.5
4.5
4.8
8.13
1.8
1.7
1.7
1.8
1.7
2.6
1.8
1.5
1.6
2
1.8
2
1.8
1.8
69
118
176
11
167
20
100
87
157
25
5
187
p
0.226
0.008
0.855
0.512
0.909
0.785
T. Chen et al. / Journal of the Chinese Medical Association 75 (2012) 384e388
asymptomatic patients without prior biliary surgery had
a mean CBD diameter of 6.2 mm. Horrow et al13 also analyzed
258 asymptomatic patients’ routine ultrasounds, and found
mean CBD diameters are 3.9 mm. The sonographic analysis of
the Iranian population presented by Adibi’ et al14 revealed an
average CBD diameter of 3.72 mm. Park et al15 measured 398
Koreans’ CBD diameter using multi-detector row CT, and
found the average diameter to be 6.7 mm. Our finding that the
average Taiwanese patients’ CBD of 4.6 mm as measured by
MRI is well within the range of currently reported rangevalues of normal CBD diameter, and appears to be unrelated
to the race of the patients. It is also unique in that this is the
only study that used MRCP to measure the CBD range of
healthy individuals.
The reason that average CBD diameter reported in available medical literature varies is complex, and, most likely,
multi-factorial. One possible source of this discrepancy is the
fact that the CBD cross-section is oval in shape when distended,16 which can affect its measurement when using
different modalities. For example, ultrasound measurement of
CBD measures anterioreposteriorly (AP), whereas other
cross-sectional imaging such as CT or MR enable measurement of the largest diameter. Another source of variation is the
depth of inspiration, which Wachsberg found can result in
changes of CBD diameter.17
Other factors that may have affected CBD diameters have
been investigated. However, few factors except for age have
proven to consistently affect CBD measurements. Kialian
et al.18 observed that the longitudinal smooth muscle bands
and its intervening connective tissues fragments with
increasing age are accompanied by loss of reticulo-endothelial
network of the ductal wall, and suggest this may be the
mechanism behind the age-related biliary dilatation. Most
authors support the proposition that age is significantly related
to CBD diameter,19e21 although the nature of the relationship
is still debated. Some believe that there is a linear relationship
between CBD diameter and gradual advancement in age,19,20
while others consider the relationship indirect,15 or that it
only dilates after the age of 65.22 Our findings also suggest
that there is a significant difference ( p ¼ 0.008) between CBD
diameters of patients younger and older than 65 years of age,
with patients older than 65 years having significantly larger
CBD diameter. When patients’ age is further divided into
decades, a trend becomes apparent: as patients’ age increases
from the third to the eighth decade of life, the average CBD
diameters also increase in an approximately linear fashion.
This trend can be summarized by the equation CBD
size ¼ 0.65 age (in decades) þ 1.52, with R2 ¼ 0.62. This
corresponds closely to what Wu et al.19 proposed: that CBD
diameter increase by 1 mm per decade.
Previous studies suggest that gender has no significant
effect on CBD diameter,6 and our studies also support this
observation ( p ¼ 0.23). Elevated blood sugar and cholesterol
levels are known to be risk factors for saturated bile and
gallstone formation,23 and although viral hepatitis in general is
not directly related to biliary dilatation, in rare circumstances
it can result in cholestasis and biliary dilatation.24 Hepatitis B
387
and C are also endemic in Taiwan with a high prevalence rate.
However, our results suggest that none of these are significantly related to CBD diameter ( p ¼ 0.86, 0.51 and 0.91,
respectively). Adibi et al.14 assert that there is a statistically
significant relationship between portal vein and CBD diameter, although our results suggest the opposite. This could
either be due to the intrinsic differences between MR and
sonography measurements or variances in the study
populations.
There are some limitations to this retrospective study. First,
medications such as morphine, calcium antagonists, and
nitroglycerine can cause CBD dilatation.25 Although our
screening questionnaires did specifically ask for list of medications from the study participants, including substances of
abuse such as alcohol and other drugs, patients may have
intentionally omitted drugs of abuse such as heroin. While this
study cohort does contain a wide range of patient age, there is
an insufficient number of patients at either end of the spectrum, which may lead to some statistical bias.
In conclusion, our study shows that the average CBD
diameter of the Taiwanese population measured by MRCP is
4.6 mm, with an upper limit of 10.5 mm. CBD diameter is
significantly larger in patients older than 65 years of age, and
increases proportionally by age for each subsequent decade of
life. Otherwise no significant association was found with
gender, blood sugar level, cholesterol level, viral hepatitis, and
portal vein diameter. This can serve as a useful reference tool
when medical professionals are faced with clinical decisions
involving biliary obstruction and the need for further investigation or intervention.
References
1. Co CS, Shea Jr WJ, Goldberg HI. Evaluation of common bile duct
diameter using high resolution computed tomography. J Comput Assist
Tomogr 1986;10:424e7.
2. Niederau C, Muller J, Sonnenberg A, Scholten T, Erckenbrecht J,
Fritsch WP, et al. Extrahepatic bile ducts in healthy subjects, in patients
with cholelithiasis, and in postcholecystectomy patients: a prospective
ultrasonic study. J Clin Ultrasound 1983;11:23e7.
3. Burrell MI, Zeman RK, Simeone JF, Dachman AH, McGahan JP,
VanSonnenberg E, et al. The biliary tract: imaging for the 1990s. AJR Am
J Roentgenol 1991;157:223e33.
4. Cohen SM, Kurtz AB. Biliary sonography. Radiol Clin North Am
1991;29:1171e98.
5. Parulekar SG. Ultrasound evaluation of common bile duct size. Radiology
1979;133:703e7.
6. Mahour GH, Wakim KG, Ferris DO. The common bile duct in man: its
diameter and circumference. Ann Surg 1967;165:415e9.
7. Karvonen J, Kairisto V, Gronroos JM. The diameter of common bile duct
does not predict the cause of extrahepatic cholestasis. Surg Laparosc
Endosc Percutan Tech 2009;19:25e8.
8. Sodickson A, Mortele KJ, Barish MA, Zou KH, Thibodeau S,
Tempany CM. Three-dimensional fast-recovery fast spin-echo MRCP:
comparison with two-dimensional single-shot fast spin-echo techniques.
Radiology 2006;238:549e59.
9. Shanmugam V, Beattie GC, Yule SR, Reid W, Loudon MA. Is magnetic
resonance cholangiopancreatography the new gold standard in biliary
imaging? Br J Radiol 2005;78:888e93.
10. Park MS, Kim TK, Kim KW, Park SW, Lee JK, Kim JS, et al.
Differentiation of extrahepatic bile duct cholangiocarcinoma from
388
11.
12.
13.
14.
15.
16.
17.
T. Chen et al. / Journal of the Chinese Medical Association 75 (2012) 384e388
benign stricture: findings at MRCP versus ERCP. Radiology
2004;233:234e40.
Jonson M. Width of the common bile duct before and after morphine
studied by cholegraphy. Acta radiol 1960;53:345e52.
Kaim A, Steinke K, Frank M, Enriquez R, Kirsch E, Bongartz G, et al.
Diameter of the common bile duct in the elderly patient: measurement by
ultrasound. Eur Radiol 1998;8:1413e5.
Horrow MM, Horrow JC, Niakosari A, Kirby CL, Rosenberg HK. Is age
associated with size of adult extrahepatic bile duct: sonographic study.
Radiology 2001;221:411e4.
Adibi A, Givechian B. Diameter of common bile duct: what are the
predicting factors? J Res Med Sci 2007;12:121e4.
Park JS, Lee DH, Jeong S, Cho SG. Determination of diameter and
angulation of the normal common bile duct using multidetector computed
tomography. Gut Liver 2009;3:306e10.
Wachsberg RH, Kim KH, Sundaram K. Sonographic versus endoscopic
retrograde cholangiographic measurements of the bile duct revisited:
importance of the transverse diameter. AJR Am J Roentgenol
1998;170:669e74.
Wachsberg RH. Respiratory variation of extrahepatic bile duct diameter
during ultrasonography. J Ultrasound Med 1994;13:617e21.
18. Kialian GP, Aznaurian AV. The age-related characteristics of the muscular
layer of the common bile duct in man. Morfologiia 1995;108:10e2.
19. Wu CC, Ho YH, Chen CY. Effect of aging on common bile duct diameter:
a real-time ultrasonographic study. J Clin Ultrasound 1984;12:473e8.
20. Bachar GN, Cohen M, Belenky A, Atar E, Gideon S. Effect of aging on
the adult extrahepatic bile duct: a sonographic study. J Ultrasound Med
2003;22:879e82. quiz 83e5.
21. Kim HJ, Kim MH, Lee SK, Seo DW, Kim YT, Lee DK, et al. Normal
structure, variations, and anomalies of the pancreaticobiliary ducts of
Koreans: a nationwide cooperative prospective study. Gastrointest Endosc
2002;55:889e96.
22. Weinstein BJ, Weinstein DP. Biliary tract dilatation in the nonjaundiced
patient. AJR Am J Roentgenol 1980;134:899e906.
23. Stokes CS, Krawczyk M, Lammert F. Gallstones: environment, lifestyle
and genes. Dig Dis 2011;29:191e201.
24. Lim HL, Lau GK, Davis GL, Dolson DJ, Lau JY. Cholestatic hepatitis
leading to hepatic failure in a patient with organ-transmitted hepatitis C
virus infection. Gastroenterology 1994;106:248e51.
25. Economou G, Ward-McQuaid JN. A cross-over comparison of the effect
of morphine, pethidine, pentazocine, and phenazocine on biliary pressure.
Gut 1971;12:218e21.