The common bile duct (CBD) was measured in 600 ultrasound studies. In normal patients the mean width of the CBD increased from 2.8 mm in the age group 20 years or younger to 4.1 mm in patients 71 years of age or older. The mean width of the CBD for all age groups in normal cases was 3.4 (range 2 to 11 mm). In presence of cholelithiasis the mean width of the CBD was 4.5 mm (range 2 to 15 mm). There was no further increase of the CBD after cholecystectomy (mean width 4.6 mm, range 2 to 12 mm). The CBD in patients with hepatocellular disease was wider than normals (mean 4.4 mm) and markedly increased in patients with pancreatic disease (mean 6.2 mm, range 2 to 21 mm) due to obstruction in several cases.
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].
1 Demonstrator, Department of Anatomy, College of Medicine & Sagore Dutta Hospital, Kolkata, India.
We studied a total of 200 subjects; wherein an equal proportion belonged to either sex. The study subjects belonged to the age group 18-85 years of age; the mean age was 34.5 years (SD 13.24 years). A majority of the participants belonged to the age group 18-25 years. The mean age for males was 35.8 years while that for females was 33.1 years. This difference in ages was not statistically significant.
We did not find any statistically significant correlation of common bile duct diameter with sex. This finding was similar to other studies by Niederau et al., , Admassie , Reinus et al., , Adibi and Givechian , Brogna et al.,  and El Sharkawy E et al., .
Aim: Study was conducted to obtain data on sonographically measured diameters of common bile duct in a series of normal Rajasthani population and to measure its correlation with age, sex and anthropometry.
With the development of high resolution scanners, the luminal diameters of the common bile duct can be assessed accurately. The normal internal diameter of the common bile duct on ultrasonography is 6 mm . Different opinions regarding the size of the common bile duct have been revealed in literature.
Socio-demographic details related to age, sex and place of residence were recorded for each subject. The ultrasonographic findings with regard to common bile duct diameter were obtained. In order to reduce observer bias, the same expert radiologist was involved in conducting ultrasonography for all subjects. A 3.5 megahertz (MHz) transducer was used. The common bile duct was identified through its association with the portal vein in the long axis of the gallbladder. At this location the common bile duct and hepatic artery appear as two smaller circles anterior to the portal vein, giving an appearance of a face with two ears – also called a ‘Mickey Mouse’ sign. With the indicator directed toward the patient’s right, the right ear is the common bile duct and the left ear, the hepatic artery.
Mean and standard deviation of common bile duct diameter by age group
2 Associate Professor, Department of Anatomy, Mahatma Gandhi Medical College and Hospital, Jaipur, India.
Poupon R, Rosmorduc O, Boelle PY, et al. Genotype-phenotype relationships in the low-phospholipid-associated cholelithiasis syndrome: a study of 156 consecutive patients. Hepatology. 2013 Sep. 58(3):1105-10. [Medline].
Gurusamy K, Sahay SJ, Burroughs AK, Davidson BR. Systematic review and meta-analysis of intraoperative versus preoperative endoscopic sphincterotomy in patients with gallbladder and suspected common bile duct stones. Br J Surg. 2011 Jul. 98(7):908-16. [Medline].
Dan DV, Harnanan D, Maharaj R, Seetahal S, Singh Y, Naraynsingh V. Laparoscopic cholecystectomy: analysis of 619 consecutive cases in a Caribbean setting. J Natl Med Assoc. 2009 Apr. 101(4):355-60. [Medline].