This study evaluated whether MRCP-measured CBD diameter can function as a practical triage parameter in symptomatic post-cholecystectomy patients. Our findings indicate that ductal caliber was the most discriminative radiologic parameter within this cohort for identifying biliary pathology, with a threshold of ≥8 mm demonstrating robust diagnostic performance. In contrast, correlations between structural MRCP findings and endoscopic abnormalities were generally modest, underscoring that while mucosal and papillary changes are common, they do not provide the same level of stratification value as ductal measurements.

Our cohort’s symptom profile—abdominal pain predominating, followed by dyspepsia/bloating—mirrors prior syntheses reporting substantial rates of persistent or de novo pain and dyspeptic complaints after cholecystectomy [2,4]. Practical guidance emphasizes a broad differential that spans biliary and non-biliary drivers [4], consistent with the dual structural–mucosal signal we observed.

The moderate correlation between endoscopic papillary changes and suspected Oddi dysfunction fits contemporary descriptions of functional biliary disorders under Rome IV [9,10] and the clinical ambiguity highlighted by Kegnæs et al.—namely overlapping symptomatology, imperfect noninvasive markers, and the need to avoid indiscriminate invasive testing [8]. Our finding that Oddi dysfunction was not an independent predictor of ductal dilatation in multivariable modeling supports the view that papillary/functional abnormalities contribute variably to the structural phenotype and should be interpreted in context rather than used as solitary triggers for ERCP [8,9,10]. The high prevalence of mucosal inflammation in our cohort likely reflects the broad and pragmatic endoscopic categorization used in routine clinical practice. This category may encompass nonspecific gastritis, bile reflux-related changes, and age-related incidental findings that are common in older populations. Although statistically significant correlations with CBD diameter were observed, their clinical magnitude should be interpreted cautiously.

These findings are consistent with prior meta-analytic and comparative studies that establish MRCP as a high-accuracy modality for evaluating ductal pathology [11,14,15,16]. In this context, ductal measurements provide objective structural information that may complement clinical assessment and guide further diagnostic steps. Given the procedural risks associated with ERCP, invasive intervention should remain indication-driven rather than routine, particularly in the absence of clear obstructive findings. It should be emphasized that diagnostic performance metrics, including ROC-derived thresholds, were calculated within the MRCP subgroup (n = 45). As such, these estimates may be subject to spectrum bias and should not be interpreted as universally generalizable across the broader PCS population. The identified ≥8 mm threshold should therefore be viewed as exploratory and context-dependent rather than definitive.

It is important to recognize that comprehensive contemporary evaluation of PCS extends beyond MRCP and upper endoscopy alone. EUS has been shown to provide high sensitivity for detecting microlithiasis, small retained stones, distal CBD lesions, and ampullary pathology that may not be visualized on MRCP, particularly in patients with persistent biliary-type symptoms [18,21]. In addition, hepatobiliary scintigraphy remains a noninvasive method for functional assessment of biliary drainage and may contribute to the evaluation of suspected sphincter of Oddi dysfunction within the broader Rome IV framework [8,9]. These modalities were not systematically incorporated in our retrospective cohort. Therefore, the proposed diagnostic framework should be interpreted as an imaging-centered pathway derived from available data rather than a complete representation of all real-world diagnostic strategies in PCS.

In contemporary clinical practice, evaluation of PCS is typically multidisciplinary and stepwise, incorporating symptom characterization, laboratory testing, transabdominal ultrasonography, cross-sectional imaging, EUS when microlithiasis or distal pathology is suspected, and functional testing in selected cases. Our study does not attempt to redefine this comprehensive pathway; rather, it examines how MRCP-derived ductal measurements relate to endoscopic findings within the subset of imaged patients. Therefore, the present analysis should be interpreted as contributing one structural component within a broader diagnostic framework rather than representing a complete clinical algorithm.

It is important to acknowledge that the definition of post-cholecystectomy CBD dilatation remains controversial. Several studies have reported that CBD diameter may increase physiologically after cholecystectomy, with proposed upper limits ranging from 7 mm to 10 mm depending on age, imaging modality, and population characteristics [11,20]. Age-related ductal enlargement and adaptive remodeling following gallbladder removal further complicate interpretation of a single numerical threshold [9,20]. Therefore, the ≥7 mm definition used in our study reflects a commonly applied imaging reference rather than an absolute pathological boundary. Importantly, the ≥8 mm cut-off derived from ROC analysis in this symptomatic cohort may assist in risk stratification within similar clinical settings and should not be interpreted as a universal definition of abnormality. Clinical context and associated findings remain essential in interpreting ductal caliber.

Although we observed a large odds ratio linking stricture with dilatation, the association was not statistically significant—likely a function of low stricture frequency and wide confidence intervals. This pattern is compatible with imaging-focused literature showing that while strictures often co-occur with dilated ducts, they do not consistently emerge as independent predictors once other factors are modeled [20,21]. In clinical terms, strictures signal a relevant subset requiring targeted therapy, but they may not drive population-level prediction.

An additional noteworthy finding was the relatively high proportion of radiologically detected postoperative complications (39.7%), including biloma, localized collections, and suspected infectious changes. While not all such findings were clinically significant, their presence underscores the heterogeneity of PCS presentations and highlights the importance of comprehensive imaging assessment. Management was individualized according to imaging and clinical severity, ranging from conservative monitoring and antibiotic therapy in stable cases to percutaneous drainage or endoscopic intervention when indicated. Although postoperative complications were not independent predictors of biliary dilatation in multivariable analysis, their detection remains clinically relevant, as early identification may prevent progression to more severe outcomes.

The inclusion of postoperative complications within the PCS framework warrants clarification. PCS is widely described as a heterogeneous clinical entity encompassing both biliary and non-biliary causes of persistent or new-onset symptoms following cholecystectomy [24,25]. Persistent symptoms may arise from functional disorders, retained stones, ductal injury, or other postoperative sequelae, reflecting the broad etiological spectrum of PCS [5]. Management-oriented studies comparing laparoscopic and endoscopic strategies for choledocholithiasis further illustrate that postoperative biliary findings and complications may overlap clinically with PCS presentations [26,27]. In addition, adaptive ductal enlargement following cholecystectomy has been documented, complicating strict diameter-based definitions of abnormality [28].

Within this broader clinical context, early or delayed postoperative complications—such as biloma, localized collections, or bile duct injury—may manifest with PCS-type symptoms, even though their underlying mechanisms differ from functional biliary disorders. We therefore considered radiologically detected postoperative complications within the symptomatic PCS spectrum, as they represent clinically relevant causes of post-cholecystectomy complaints. However, some authors advocate for a narrower definition of PCS limited to functional or obstructive etiologies, distinguishing it from discrete surgical complications [24,25]. This conceptual variability should be acknowledged when interpreting prevalence estimates and comparing studies.

From a practical perspective, ductal caliber can assist in stratifying patients who may benefit from further biliary evaluation. In contrast, the high prevalence of mucosal abnormalities highlights the importance of complementary endoscopic assessment. Given the procedural risks associated with ERCP, a stepwise evaluation strategy remains appropriate in symptomatic patients [11,12,14,19].

Prospective studies integrating standardized symptom scales, quantitative MRCP metrics (e.g., ductal caliber indexed to age/body size), and functional testing (manometry or secretin-MRCP) could refine thresholds and disentangle causal pathways in PCS. Prospective comparative studies would be valuable to assess whether MRCP-informed diagnostic sequencing influences procedure rates, diagnostic timelines, and patient-centered outcomes.

Compared with prior reports that have primarily focused on imaging accuracy (e.g., MRCP versus ERCP for choledocholithiasis) or symptom-oriented clinical guidance without systematic cross-modal linkage [4,8,12,14,20], our study explores the relationship between MRCP findings and contemporaneous upper endoscopic observations within a symptomatic PCS cohort. Rather than proposing a fundamentally new diagnostic construct, these findings provide exploratory data on cross-modal concordance (e.g., ductal caliber and mucosal changes) and suggest that structural ductal metrics may contribute to structured clinical assessment when interpreted alongside endoscopic findings [4,9,10]. These observations should be viewed as complementary to the existing literature on MRCP performance and ERCP selectivity [11,12,14] rather than as a replacement for comprehensive multimodal evaluation strategies.

This study has some limitations. First, its retrospective, single-center design may limit generalizability and introduce selection bias. Second, sphincter of Oddi dysfunction was not confirmed by manometry, and classification relied on descriptive endoscopic and radiologic impressions, which may have led to misclassification. Formal interobserver variability analysis for CBD measurements was not performed, which may affect measurement reproducibility. Third, the low number of biliary stricture events resulted in wide confidence intervals and limited statistical precision. Fourth, the absence of a non-symptomatic comparator group precludes assessment of background rates of ductal dilatation or mucosal abnormalities in asymptomatic post-cholecystectomy patients. Finally, the very high prevalence of mucosal inflammation reduced multivariable separability for this variable and therefore it was not retained in the primary adjusted model. An additional limitation relates to the absence of systematic preoperative endoscopic evaluation. Although alternative luminal causes were excluded at the time of post-cholecystectomy assessment, we cannot exclude the possibility that some mucosal abnormalities detected on EGD represented pre-existing gastrointestinal pathology rather than de novo PCS-related changes. Furthermore, EUS and functional biliary testing were not systematically incorporated into this retrospective cohort, although these modalities play an important role in contemporary PCS evaluation, particularly when MRCP findings are inconclusive.

Structural and mucosal abnormalities were frequently observed in this cohort; however, ductal measurements provided the most consistent stratification signal for biliary pathology. Age-related ductal enlargement likely contributed to observed variation, supporting the need for contextual interpretation of CBD measurements in post-cholecystectomy patients.

Overall, our findings suggested that an MRCP-informed component may be incorporated into structured diagnostic frameworks in similar clinical contexts. A schematic representation of this proposed pathway is provided in Figure 6. Prospective multicenter studies incorporating standardized symptom scales, quantitative MRCP metrics, and functional testing will be essential to validate these findings and refine patient-centered triage strategies.