The mean diameter observed in our study was 4.1 mm with a standard deviation of 1.01 mm. This was similar to that reported by Parulekar  in his study on 200 normal subjects. Mesenas et al., , reported a higher mean diameter of 5 mm (SD 1.9 mm). In a study in Korea, Park et al.,  reported the average diameter of the common bile duct was 6.7 mm. Other studies have reported lower mean diameters at less than 4 mm [9–11].
Height was measured using a stadiometer with a sensitivity of 0.1 centimeter. The weighing scale with a sensitivity of 0.1 kg was used to measure weight. Chest circumference was measured using a measuring tape over light clothing and while breathing normally. In the males, the measurement was made at the widest point of the chest; in the females, the measurement was made at the level of the nipples with the measuring tape held horizontally. The circumference at the transpyloric plane was measured at a level midway between the suprasternal notch (at the upper border of manubrium between the sternal heads of sternomastoid muscles) and the symphysis pubis (at the lower end of median line). Circumference at the umbilicus was obtained by measuring the abdominal circumference using measuring tape at the level of the umbilicus. Circumference at the hip was measured with the measuring tape positioned around the maximum circumference of the buttocks.
Statistical Analysis: Univariable analysis with measures of frequency and standard deviation and bivariable analysis using correlation.
1 Demonstrator, Department of Anatomy, College of Medicine & Sagore Dutta Hospital, Kolkata, India.
In order to assess the association between common bile duct diameter and anthropometric measurements, both of which were continuous variables, correlation was used.
The mean diameter of common bile duct was observed to be 4.1 mm (SD 0.95 mm) for males and 4.0 mm (SD 1.07 mm) for females. This difference was tested by applying independent samples t -test. The t value was 0.86, which was not found to be statistically significant (p = 0.38).
The mean diameters of the common bile duct in the three locations were: proximal, 4.0 mm (SD 1.02 mm); middle, 4.1 mm (SD 1.01 mm); and distal, 4.2 mm (SD 1.01 mm). The overall mean for all measures was 4.1 mm, with a standard deviation of 1.01 mm. All the three diameters were highly correlated and statistically significant (p-value<0.001). While the lower limit of common bile duct diameter among the normal subjects was 2.0 mm, the upper limit was found to be 7.9 mm. However, 95% of the study participants showed a common bile duct diameter of < 6 mm.
Results: Mean age of study subjects was 34.5 years (Range 18-85 years). Mean diameters of the common bile duct in the three locations were: proximal, 4.0 mm (SD 1.02 mm); middle, 4.1 mm (SD 1.01 mm); and distal, 4.2 mm (SD 1.01 mm) and overall mean for all measures 4.1 mm (SD 1.01 mm). Average diameter ranged from 2.0 mm to 7.9 mm, with 95 percent of the subjects having a diameter of less than 6 mm. We observed a statistically significant relation of common bile duct with age, along with a linear trend. There was no statistically significant difference in common bile duct diameter between male and female subjects. The diameter did not show any statistically significant correlation with any of the anthropometric measurements.
It is an established fact that variations exist in the anthropometric features of various populations, races and regions . Studies have suggested correlation between different kinds of body builds and diseases. However, despite technological advancements, the association of anthropometric measurements with the diameters of common bile duct has remained controversial.
The relationship to ‘pathology’ seen on imaging to ‘disease’ and
clinical symptoms is interesting. Gallstones are common and an incidence
in excess of 10% in the population is described. It is common to find
gallstones in an otherwise asymptomatic patient. My policy is to tell
patients that they have gallstones even if they have no symptoms, however
I am always concerned that patients will then develop symptoms. I am
always surprised how patients can have significant radiological pathology
and have so few symptoms. The patient had obvious gallstones, a thickened
gallbladder wall, biliary dilatation and many CBD stones and yet had only
itching with a history of itching. The story of painless jaundice would be
more suggestive of pancreatic malignancy or a drug reaction rather than
Her pancreas was seen to be swollen. The enlargement of the pancreas
may have various causes and if a biliary stone is lodged in the distal
CBD then the patient may develop pancreatitis. With aging, the pancreas
becomes more echogenic and atrophic on ultrasound.
Her initial presentation was during a consultation made by her
husband. Her symptoms seem relatively minor yet the biochemistry results
are quite abnormal indicating a pattern of obstructive jaundice. Her
ultrasound findings are dramatic with stones seen in the gallbladder and
in the lower common bile duct (CBD). Ultrasound is the first-line
investigation for the gallbladder and biliary tree. The ultrasound scan
should be available with only a short wait for more urgent cases. This
patient should be prioritised for an urgent scan appointment.
Her biliary tree is dilated with both intrahepatic and extrahepatic
biliary dilatation. Her CBD measured 11 mm. This is a pathologically
dilated CBD. In over 95% of young normal subjects the common bile duct
measures less than 4mm. In the presence of gallstones the CBD can measure
up to 7mm without implying obstruction. The CBD can also dilate in the
elderly secondary to degeneration in the ductal wall and reach diameters
of up to 9mm. The CBD can also change in size physiologically in relation
to meals. In this patient there were gallstones readily visible in the
lower CBD on ultrasound. A diameter of the CBD of over 10mm is definitely
abnormal and will suggest the presence of stones in the CBD. In assessing
the CBD for stones, if ductal stones are seen then stones are present. If
CBD stones are not seen then this does not mean that they are absent since
there is a significant rate of false negative results, partly related to
the presence of obscuring gas in the duodenum.
The appearances of the liver are unexplained. Ultrasound is good for
assessing focal liver disease. A common abnormal pattern is the
geographical echogenic appearance seen in fatty change of the liver.
I am a commentator on this interactive case and will receive an honorarium from the BMJ. I am a radiologist working in the same hospitals that the patient attended.