Microscopic clean margin is associated with reduced endoscopic recurrence after bowel resection for ileocolic Crohn's disease (CD). We aimed to investigate whether the extent of creeping fat could help indicate microscopic inflammation beyond naked eye assessment of the bowel wall and reduce endoscopic recurrence after ileocolic resection.

Despite proactive prophylactic treatment administered after surgery for Crohn's disease (CD) patients, early postoperative endoscopic recurrence (EPER) still occurs in 50-80% of patients within six months, increasing the risk of long-term clinical and surgical recurrence. Risk factors for EPER have already been identified, including active smoking, disease behavior, younger age, concomitant perianal disease, prior intestinal resections, and microscopic resection margin positivity. Recently, the influence of microscopic inflammation at the resection margin on EPER has been highlighted by various studies and meta-analysis.

From a surgical perspective, it has become common practice to conservatively resect 2cm width from the gross lesion to lower re-operation risks, while the optimal strategy to attain the microscopic clean margin and minimize EPER remain unclear, considering the limited accuracy of frozen-section examinations. More importantly, the diseased mucosa proximal to the ileal lesion can be healed by preoperative optimization, potentially concealing deeper lesions at the muscularis propria and serosal levels from visual assessment during surgery. Therefore, identifying a macroscopic marker that highly correlates with microscopic inflammation is essential to help locate the clean division.

As a hallmark of CD, the hyperplasia of mesenteric adipose tissue (MAT) or "Creeping fat," was found directly triggered by transmural inflammation and bacterial translocation from CD affected lumen11. Correspondingly, creeping fat has been found to correlate with macroscopic mucosal abnormalities observed after opening the bowel12. However, its relationship with microscopic inflammation, as well as its potential role in determining the division position to achieve better EPER outcomes, remains to be clarified.

Inclusion Criteria:

• Localized ileocolic CD

Exclusion Criteria:

• Patients with a stoma,residuallesion ,history of bowel resection,or post-operative abdominalinfection were excluded

For the pathological study, we prospectively enrolled consecutive CD patients who underwent ileocolic resections between January 2021 and August 2021 at the 6th Hospital of Sun Yat-Sen University (SYSU6H) For the surgical study, we retrospectively enrolled consecutive CD patients that underwent ileocolic resection from January 2013 to July 2020