Age-Related Variation in the Diameter of the Common Bile Duct and Its Association With Anthropometric Parameters: An Ultrasonographic Study in an Eastern Indian Cohort.

Introduction The common bile duct (CBD) is a key structure in bile transport and lipid digestion, and its diameter is an important parameter for diagnosing biliary pathology. However, normal reference values vary across populations owing to differences in age, body size, sex, and imaging modalities. This study aimed to establish baseline CBD diameter ranges and evaluate their relationships with demographic and anthropometric variables in an Eastern Indian cohort. Methods A cross-sectional, hospital-based study was conducted at the College of Medicine and Sagore Dutta Hospital, Kolkata, and included 315 adults evenly distributed by sex and stratified into five age groups (18-25, 26-35, 36-45, 46-55, and >55 years). Participants with hepatobiliary or systemic diseases were excluded. CBD diameters were measured ultrasonographically at three anatomical levels (porta hepatis, mid-duct, and distal pancreatic head) using a standardized protocol. Anthropometric data (height and weight) were recorded, and statistical analyses included analysis of variance (ANOVA), correlation tests, and multiple regression. Results The results indicated a progressive, age-related increase in CBD diameter, from 3.1 mm in the youngest group to 4.4 mm in participants aged ≥55 years. One-way ANOVA confirmed that age was a statistically significant predictor (p<0.05). Body weight demonstrated a moderate positive correlation with CBD size (r≈0.36), whereas height showed only a weak correlation (r≈0.09). The mean diameter was slightly higher in male patients (3.2 mm) than in female patients (3.1 mm); however, this difference was not statistically significant. Multivariate regression revealed that age exerted the strongest influence on CBD diameter, followed by weight, whereas height and sex had minimal impact. The model explained 46% of the total variance. Conclusion In conclusion, the diameter of the CBD increased significantly with age and moderately with weight, whereas sex and height were not independent determinants. These findings highlight the need for age-adjusted normative reference values to improve diagnostic accuracy and reduce the misinterpretation in biliary imaging of physiological dilation as being pathological.