S357 Colonic Transit Time: A Forgotten Modality–A Systematic Narrative Review

Introduction: Functional constipation (FC) imposes a significant burden worldwide. Accurate subtyping—normal transit constipation (NTC), slow transit constipation (STC), and dyssynergic defecation (DD)—is important, but colonic transit time (CTT) assessment remains underused, particularly in diverse and resource-limited settings. Methods: We performed a systematic narrative review of CTT measurement methodologies, clinical relevance, ethnic variability, and regional adaptations, with emphasis on Indian and Asian populations compared to Western cohorts. Results: CTT protocols vary widely across different populations and research contexts, with marker quantities ranging from 20 to 50 per day to balance marker visibility and patient compliance. X-ray acquisition timing ranges from 27 hours to 11 days post-marker ingestion, reflecting local practices and patient characteristics. Supine positioning for abdominal radiographs is most common to improve image quality and reduce radiation exposure. Asian populations (e.g., India, Korea) consistently report faster colonic transit times (mean ∼15.4 hours) compared to Western populations (30–40 hours), highlighting the critical need for population-specific normative data to ensure accurate interpretation. Diagnostic protocols have been adapted for subgroups such as pediatric patients and individuals with neurogenic disorders, further underscoring the necessity for tailored CTT approaches. Despite its clinical value in differentiating constipation subtypes and informing management—particularly in refractory cases—CTT remains a “forgotten modality”, underutilized due to limited clinician awareness, lack of standardized protocols, and resource constraints. Conclusion: CTT measurement, while often overlooked, is a powerful diagnostic tool for precise constipation subtyping and management optimization. Standardized, regionally validated protocols and broader adoption are urgently needed. To mitigate these limitations, supine position is preferred for abdominal radiograph in a ROM study because it results in significantly lower radiation dose and better image quality compared to erect position. Educational initiatives and technological innovations, including artificial intelligence-based radiograph interpretation, can revitalize CTT as a cornerstone of constipation care, especially in Asian and resource-limited settings.