Age-Associated Differences in Ductal Involvement in Biliary Lithiasis: A Consecutive MRCP Cohort Study

Background: Magnetic resonance cholangiopancreatography (MRCP) enables non-invasive assessment of biliary lithiasis, duct caliber, and associated anatomical findings. Although age-dependent reference limits for common bile duct (CBD) diameter have been described, the relationships among age, gallbladder stone morphology, ductal anatomy, and CBD stones remain incompletely characterized in consecutive radiology cohorts. This study assessed age-associated MRCP patterns and imaging features associated with CBD stones. Methods: We retrospectively analyzed 242 consecutive MRCP examinations performed for biliary indications. Recorded variables included age, sex, gallbladder and CBD stone characteristics, CBD diameter, intrahepatic bile duct (IHBD) dilatation, CBD tortuosity, cystic duct morphology, periampullary diverticulum, microlithiasis, and associated pancreatobiliary findings. Ordered trend tests, group comparisons, correlation analyses, ROC analysis, and a parsimonious multivariable logistic model were used. Model 2 included six predictor parameters for 65 CBD-stone events (10.8 events per variable) and was internally validated with 2000 bootstrap resamples. Results: The cohort had a median age of 63 years (IQR 49-73), and 135 patients (55.8%) were female. GB stones were present in 211 patients (87.2%), and CBD stones in 65 (26.9%). Across ordered age strata, GB stone prevalence decreased (p = 0.006), whereas CBD stone prevalence increased (p = 0.038); CBD diameter and IHBD severity also increased with age (both p < 0.001). CBD-positive patients had larger CBD diameters than CBD-negative patients (median 10.0 vs. 6.5 mm, p < 0.001). In Model 2, CBD diameter was the strongest independent imaging correlate of CBD stones (OR 1.567 per 1 mm, 95% CI 1.310-1.873; p < 0.001), whereas age was not independently associated after adjustment (p = 0.781). CBD diameter alone achieved an AUC of 0.853; Model 2 achieved an AUC of 0.896 and an optimism-corrected AUC of 0.884. Conclusions: Older age groups showed greater ductal involvement and larger CBD caliber in this consecutive MRCP cohort. CBD diameter was the strongest imaging correlate of CBD stones, while age and CBD diameter provided overlapping information in the adjusted model. These findings describe an observational MRCP pattern and require external validation.