Prevalence of jejunal involvement in CD

What is known

• In a meta-analysis of 26 studies (>10,000 patients), among UGI-CD patients jejunal involvement was 36% and proximal ileal 32%, behind stomach (56%) and duodenum (55%). ¹
• Pooled UGI-CD prevalence was 13% overall and 23% when limited to systematic endoscopic screening, indicating much detected disease is subclinical. ¹
• In an Asian cohort of 483 CD patients, 38.3% carried an L4 phenotype at presentation, though this figure aggregates EGD, jejunal, and proximal ileal subtypes rather than isolating jejunal disease. ²

What is unknown / caveats

• Reported UGI-CD prevalence varies widely (12–80%) across retrospective series depending on screening intensity and diagnostic method
• No retrieved chunk reports isolated jejunal prevalence as a fraction of the entire CD population. The 36% is a proportion within UGI/L4-CD
• L4 is a heterogeneous single Montreal category grouping EGD, jejunal, and proximal ileal disease, so definitions vary between studies
• Prevalence is method-dependent. Capsule endoscopy/MRE reclassified up to 64% of patients in one study
• The population-wide prevalence of jejunal CD is not directly reported in the retrieved evidence and is confounded by variable screening and phenotyping.

References

1. Lusetti F, Bezzio C, De Bernardi A, Puricelli M, Manes G, Saibeni S. Upper Gastrointestinal Crohn's Disease: Shedding Light on the Obscure L4 Classification Meaning. J Clin Med. 2025. PMID: 41303293.

2. Mao R, Tang RH, Qiu Y, Chen BL, Guo J, Zhang SH, Li XH, Feng R, He Y, Li ZP, Zeng ZR, Eliakim R, Ben-Horin S, Chen MH. Different clinical outcomes in Crohn's disease patients with esophagogastroduodenal, jejunal, and proximal ileal disease involvement: is L4 truly a single phenotype?. Ther Adv Gastroenterol. 2018. PMID: 29899757.

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Draft, generated by the IBDology RAG and not yet clinician-reviewed. Answers are grounded in the retrieved literature listed above; a high faithfulness score means the answer matches its sources, not that the sources are correct.