BACKGROUND: Common Bile duct (CBD) measurement is a crucial aspect in the evaluation of the biliary tree. Whether the CBD undergoes any compensatory change in diameter after laparoscopic cholecystectomy or laparoscopic common bile duct exploration is still up for discussion. The aim of this study was to investigate CBD diameter changes after laparoscopic cholecystectomy (LC) and laparoscopic common bile duct exploration (LCBDE) on magnetic resonance cholangiopancreatography (MRCP). MATERIALS AND METHODS: Our retrospective study is divided into 2 sections. The first part assessing CBD diameter changes after laparoscopic cholecystectomy due to gallstones or gallbladder polyps, involved 85 patients, who underwent MRCP procedures. These patients aged between 30 and 85 were divided into an interval LC group (group A, n=56) and a remote LC group (group B, n=29). In group A, the common CBD diameters were measured at their widest portions on MRCP obtained before and after laparoscopic cholecystectomy. Measurements of the CBD diameters were repeated on MRCP obtained twice after the surgery in group B.Section 2 consisted of 38 patients who had choledocholithiasis and were treated with laparoscopic CBD exploration and T-tube placement. These patients aged 26 to 86 formed the interval LCBDE group (group C). The CBD widest diameters were measured on MRCP before LCBDE and after T-tube cholangiography for these individuals.Patients in groups A and C were further divided into 5 and those in group B into 4 age-related subgroups to facilitate statistical analysis. The Pearson correlation test was performed to find any relationship between CBD diameters and age in groups A and B. Paired sample T test was used to compare the significant difference between the 2 sets of CBD diameters in each study group and their subgroups. RESULTS: In the interval LC group, the post-LC mean CBD diameter was significantly wider when compared with the preoperative mean diameter ( P <0.05). There was a significant difference between the first and second post-LC means CBD diameter in the remote LC group ( P <0.05). In group C, the mean CBD diameter measured on T-tube cholangiography after LCBDE was significantly smaller than the preoperative dilated mean diameter ( P <0.05). CONCLUSIONS: This study demonstrated significant dilation occurring in the common bile duct diameter after laparoscopic cholecystectomy. Furthermore, our remote LC group also supported that claim by showing significant dilation between the first and second post-cholecystectomy CBD diameter values. And lastly, our interval LCBDE sample's initial dilation of the CBD diameters was reduced after surgery and stone extraction.