Reference Value for The Diameter of The Common Bile Duct and Pancreatic Duct on MRCP: Based on Age and Gender

Abstract

Background: Magnetic Resonance Cholangiopancreatography (MRCP) is a non-invasive imaging modality widely used to visualize the biliary and pancreatic ductal systems. Accurate interpretation of duct diameters is essential for identifying pathology; however, reference values may vary across populations. Limited regional data exists for asymptomatic individuals in Western Uttar Pradesh, India. Objective: To determine normative reference values for the diameters of the common bile duct (CBD) and main pancreatic duct (MPD) using MRCP, and to assess the influence of age, gender, and cholecystectomy status on these measurements. Methods: A cross-sectional observational study was conducted on 100 asymptomatic adults aged 20–70 years using 1.5 Tesla MRCP. CBD and MPD diameters were measured and analyzed across age groups, gender, and surgical history. Statistical analysis included t-tests, ANOVA, and Pearson’s correlation. Results: CBD diameter showed a significant positive correlation with age (r = 0.67, p < 0.001) and was significantly higher in post-cholecystectomy patients (mean = 7.51 mm) compared to non-operated individuals (mean = 6.29 mm, p < 0.001). MPD diameters exhibited a mild age-related increase (r = 0.32) but were unaffected by gender or surgery. No significant gender differences were observed for either duct. Conclusion: Age and cholecystectomy significantly influence CBD diameter, while MPD remains relatively stable. These findings provide essential region-specific reference data for MRCP interpretation in Indian populations, minimizing diagnostic errors related to physiological ductal dilation.

Keywords

MRCP, Common Bile Duct, Pancreatic Duct, Duct Diameter, Age-related Changes, Cholecystectomy, Biliary System, Normative Values, India, Diagnostic Radiology

Introduction

Interpretation:

• There was a highly significant difference in CBD diameter based on cholecystectomy status (p < 0.001), confirming physiological post-operative duct dilation.
• No significant difference in MPD diameter was observed between the two groups (p = 0.9489), reaffirming the anatomical independence of the pancreatic duct from gallbladder surgery.

DISCUSSION

The present study was undertaken to establish normative reference values for the common bile duct (CBD) and main pancreatic duct (MPD) diameters using Magnetic Resonance Cholangiopancreatography (MRCP) in a population of asymptomatic adults from Western Uttar Pradesh, India. The results demonstrate a clear and statistically significant correlation between advancing age and increasing CBD and MPD diameters, consistent with previously reported global and regional findings. One of the most prominent findings of this study is the positive correlation between age and CBD diameter. The mean CBD diameter increased from 5.70 mm in the 20–39-year group to 7.40 mm in the 60–70-year group. This trend is well supported in the literature. For instance, Peng et al. (2015) demonstrated a linear increase in CBD diameter with age at a rate of approximately 0.033 mm per year, suggesting age-related atrophy of periductal tissues and diminished smooth muscle tone as potential physiological mechanisms [5]. Similar findings were reported by Mehta et al. (2024), who proposed adjusted CBD cut-offs of up to 8.5 mm in elderly Indian populations to account for physiological dilation [10]. These results highlight the importance of using age-adjusted reference values to prevent false-positive diagnoses of biliary obstruction. The effect of cholecystectomy on CBD diameter was also highly significant in this study, with a mean diameter of 7.51 mm in post-cholecystectomy individuals compared to 6.29 mm in those with intact gallbladders (p < 0.001). This finding supports existing evidence that removal of the gallbladder alters bile dynamics, resulting in compensatory dilation of the CBD. Chawla et al. (2010) and Kratzer et al. (2015) both documented similar post-operative dilation, with reported diameters often exceeding 7 mm in otherwise asymptomatic patients [8,9]. The current findings reaffirm that post-cholecystectomy CBD dilation should not be immediately considered pathological in the absence of other clinical or biochemical abnormalities. In contrast, MPD diameters remained relatively stable across cholecystectomy status and showed only a modest increase with age (r = 0.32). The highest mean MPD diameter observed in this study was 2.44 mm in the 60–70-year group, which falls within the established normal range. This observation aligns with findings from Wang et al. (2019), who concluded that MPD diameter increases with age to a lesser extent than the CBD and typically remains under 3 mm in healthy individuals. Similarly, Conwell et al. (2014) noted that MPD diameters beyond 3.5 mm in the pancreatic head or 2 mm in the tail may indicate pathology, supporting the conclusion that age-related MPD changes are usually clinically insignificant [3]. Regarding gender differences, this study found no statistically significant variations in either CBD or MPD diameters between male and female participants. While female participants showed a slightly higher mean CBD diameter (6.69 mm vs. 6.32 mm in males), the difference did not reach statistical significance. These results are consistent with those reported by Kim et al. (2022) and Lin et al. (2022), both of whom found minimal or no impact of gender on ductal diameters, emphasizing that uniform diagnostic thresholds across sexes may be appropriate for duct measurements in most clinical scenarios [2,13]. Furthermore, the moderate correlation between CBD and MPD diameters (r = 0.45) may suggest a shared physiological response or parallel anatomical variation, although no causality can be inferred. It does, however, highlight the importance of interpreting both ducts concurrently on MRCP, especially in cases where a double-duct sign raises suspicion of malignancy [12]. In this study, none of the participants presented with concurrent pathological dilation, reinforcing the assumption that ductal widening in asymptomatic individuals is likely physiological when within population-adjusted norms. The findings of this study are consistent with other regional investigations. For example, Rodrigues et al. (2022) and Shrestha et al. (2021) reported age-related increases in CBD and MPD diameters in South Indian and Nepalese populations respectively, and both emphasized the need for localized reference values due to ethnic, dietary, and physiological differences [4,11]. This study adds to the growing body of evidence from South Asia supporting population-specific MRCP standards rather than reliance on Western norms, which may lead to overdiagnosis and unnecessary interventions in local populations.

CONCLUSION

This study establishes that the diameter of the common bile duct (CBD) increases significantly with age and following cholecystectomy, whereas the main pancreatic duct (MPD) remains relatively stable across different ages and is unaffected by surgical status. No significant differences were observed between male and female participants for either duct. These findings highlight the importance of using age- and surgery-adjusted reference values during MRCP interpretation to distinguish physiological changes from pathological dilatation. The normative data generated from this Western Uttar Pradesh cohort provides valuable population-specific benchmarks that can enhance diagnostic accuracy and prevent unnecessary investigations in asymptomatic individuals.                                          

REFERENCE

1. Goldfinger J, Lim AK, Hamilton G, et al. The evolving role of MRCP in hepatobiliary imaging: A 30-year perspective. Br J Radiol. 2020;93(1107):20200382.
2. Kim E, Lee JM, Park JH, et al. Normative MRCP reference values for biliary and pancreatic duct diameters in a healthy Korean population. Asian Radiol J. 2022;13(1):22–30.
3. Conwell DL, Lee LS, Yadav D, et al. American Pancreatic Association Practice Guidelines in Chronic Pancreatitis: Evidence-based report on diagnostic guidelines. Pancreas. 2014;43(8):1143–1162.
4. Rodrigues D, Thomas B, Nair S, et al. MRCP-based assessment of ductal dimensions in South Indian adults: impact of age and cholecystectomy. South Asian J Radiol. 2022;9(4):203–210.
5. Peng R, Wang Q, Yang J, et al. Age-related changes in common bile duct diameter: an MRCP-based study. BMC Med Imaging. 2015;15(1):19.
6. Wang Q, Peng R, Zhang X, et al. Pancreatic duct size in relation to age and gender: an MRCP-based study in healthy adults. Pancreas. 2019;48(7):913–920.
7. Takahashi Y, Matsumoto K, Sano T, et al. Age- and gender-specific reference values for bile duct and pancreatic duct diameters using MRCP in Japan. J Gastroenterol Hepatol. 2022;37(5):834–841.
8. Chawla A, Bosco JJ, Lim TC, et al. Radiological manifestations of post-cholecystectomy syndrome. J Gastrointest Surg. 2010;14(4):679–684.
9. Kratzer W, Haenle MM, Schneider D, et al. Effect of cholecystectomy on the diameter of the common bile duct: an ultrasonographic study. Ultrasound Int Open. 2015;1(2):E58–E61.
10. Mehta S, Arora A, Joshi A, et al. Establishing MRCP-based normative data for biliary and pancreatic duct diameters in North India. Indian J Radiol Imaging. 2024;34(1):44–51.
11. Shrestha S, Karki S, Sharma R, et al. Normative reference values for common bile duct and pancreatic duct diameters by MRCP in healthy Nepalese adults. Nepal Med Coll J. 2021;23(3):201–207.
12. Fragaki M, Kosmidou M, Theodosiou D, et al. Clinical relevance of incidental common bile duct dilatation and the double duct sign: a retrospective MRCP analysis. Eur J Gastroenterol Hepatol. 2025;37(2):145–152.
13. Lin Z, Zhang J, Han Y, et al. MRCP-based evaluation of ductal diameters in relation to age, sex, and BMI: a multicenter Chinese study. Chinese Med Imaging. 2022;40(3):203–212.