Upper Gastrointestinal Crohn’s Disease: Shedding Light on the Obscure L4 Classification Meaning

<b>Background/Objectives</b>: Upper gastrointestinal Crohn's disease (UGI-CD) is inconsistently defined and often underrecognized, obscuring epidemiology, complicating diagnosis, and delaying tailored care. The absence of a unified, operational definition with segment-specific criteria hinders reproducibility and comparability across studies. <b>Methods</b>: We performed a narrative synthesis of adult and pediatric studies and major guidelines, examining definitions, prevalence, diagnosis, and management. Where possible, findings were mapped to upper GI segments (esophagus, stomach, duodenum, proximal small bowel). <b>Results</b>: Definitions of UGI-CD are heterogeneous. Prevalence varies widely and rises with systematic foregut assessment; isolated upper GI disease without ileocolonic involvement is rare. Diagnosis relies on esophagogastroduodenoscopy with biopsies, complemented by cross-sectional imaging and enteroscopy. Management should extend beyond standard ileocolonoscopy, with segment-tailored monitoring. Anti-TNF agents show the most consistent efficacy in esophagogastroduodenal disease, whereas benefits are attenuated in proximal small bowel involvement. For stricturing disease, endoscopic balloon dilation is suitable for short, non-penetrating strictures but often requires repetition; surgery is preferred for complex anatomy or failed dilation. A short summary of the article's main findings is provided. <b>Conclusions</b>: UGI-CD remains poorly standardized across definition, epidemiology, and management. We propose a pragmatic diagnostic and monitoring pathway and highlight priorities for research: segment-based reporting, inclusion of upper GI-only cohorts, and validation of treatment targets aligned with treat-to-target care-steps essential to improve early recognition and patient outcomes.