Post-cholecystectomy Changes in the Common Bile Duct Diameter: A Comparative Ultrasound Study

Background Dilatation of the common bile duct (CBD) after cholecystectomy is frequently observed during follow-up imaging; however, its extent and clinical implications remain incompletely defined. Distinguishing physiological postoperative ductal enlargement from pathological dilatation is essential to avoid unnecessary diagnostic evaluation. This study aimed to compare CBD diameter in post-cholecystectomy patients with non-operated controls and to assess its association with time since surgery, age, and body mass index (BMI). Materials and methods This retrospective observational study included 165 adult patients who underwent abdominal ultrasound examination, comprising 91 post-cholecystectomy patients and 74 controls with an intact gallbladder. The CBD diameter was measured in the suprahilar segment. Group differences were evaluated using independent t-tests and chi-square tests. Logistic and linear regression analyses were used to assess predictors of CBD dilatation and continuous diameter change. All multivariable models were adjusted for age, sex, and BMI. Results CBD diameter was significantly greater in post-cholecystectomy patients compared with controls (6.61 mm vs. 4.56 mm; p < 0.001). Dilatation ≥7 mm occurred in 38.5% of post-cholecystectomy patients versus 5.4% of controls (p < 0.001), and prior cholecystectomy remained a strong independent predictor of dilatation after adjustment (aOR = 14.583; 95% CI: 4.449-47.807). Using a fixed ≥7 mm cutoff, increasing age was associated with lower odds of categorical CBD dilatation, whereas sex and BMI were not significant predictors. Linear regression analyses demonstrated a significant positive association between CBD diameter and both time elapsed since surgery and age, indicating gradual ductal enlargement over time. Marked dilatation (>10 mm) was uncommon and did not reach statistical significance in relation to cholecystectomy. Conclusion Cholecystectomy is associated with measurable and progressive enlargement of the CBD. While CBD diameter increases gradually with advancing age and postoperative duration, categorical dilation thresholds are more strongly influenced by surgical status than by age alone. Recognition of this expected postoperative anatomical pattern may help clinicians avoid unnecessary imaging and interventions in asymptomatic patients.