Aims: To understand the significance of the CBD, it is essential to be aware of the normal variations in CBD diameter.

Materials and Methods: Referred patients aged 18 years and above who were coming for abdominal ultrasonography were included. Detailed history, including age, gender, and complaints as noted in a semi-structured pro forma after obtaining informed consent. Data analysis was performed using Microsoft Excel spread sheet, and statistical analysis was conducted using Statistical Package for the Social Sciences (SPSS version 11.5) software. Mean, standard deviation, percentage and range were calculated for descriptive statistics

Results: Among the total 145 participants 60 (41.4%) were male and 85 (58.6%) were female, with a male to female ratio of 0.7:1. The age of the participants ranged from 18 years and above with mean age of 47.94±18.02 years. The mean age of the male and female participants was 53.35±19.36 and 44.12±16.06 years, respectively. The mean CBD diameter was found to be 4.74±1.14 mm. The normal range of CBD diameter was 2.30 mm to 7.50 mm. The mean and standard deviation of the common bile duct diameter in males and females were 4.91±1.03 mm and 4.62±1.21 mm respectively. The mean common bile duct diameter in males was slightly higher than in females but was not found to be statistically significant (P=0.123).

Conclusions: The mean CBD diameter in males and females was four point nine one and four point sixty two millimetres respectively, showing that males had a slightly larger CBD diameter than females. However, an independent t-test showed no significant difference in mean diameter between genders. The mean CBD diameter in different age groups showed a gradual increase with age, and a significant increase occurred after the age of sixty one.