This Paper of the Month report considers the role of the mesentery in ileocolic resection for Crohn's disease.

What is known on the subject?

A role for the mesentery in Crohn's disease (CD) has been suggested ever since the mention of ‘creeping fat’ in the original paper describing the condition by Dr Crohn and colleagues in 1932. This hypertrophic adipose tissue surrounding the affected ileum is a hallmark of CD and correlates with locations of severe inflammation. Surprisingly however, the tissue has been largely ignored for decades, and there are only few studies available regarding its biology showing conflicting results: some show secretion of pro-inflammatory mediators such as TNFa and IL-6 implicating a pathological role, whereas others have shown a strong increase in macrophages expressing CD163, suggesting an immune regulatory function.

Recent advances in anatomical knowledge and surgical techniques have rekindled clinical interest in the mesentery. Currently, the potential benefit of resecting more mesentery during ileocecal resections is evaluated in two large clinical trials (NCT03172143 and NCT0254205), with the aim to reduce clinical recurrences.

What this study adds

The manuscript by Coffey et al [1], is the first retrospective study demonstrating clinical relevance of including mesentery in ileocolic resection for Crohn's disease. The authors compared surgical recurrence rates between two cohorts: 30 consecutive patients who underwent conventional close bowel resection between 2004 and 2010, and 34 patients who underwent resection which included excision of the mesentery after 2010. The authors demonstrated a significantly reduced reoperation rate after excision of the mesentery (2.9% versus 40% in the close bowel resection group). Surgical technique and smoking were the only other independent determinants of outcome. In addition, the authors created a mesenteric disease activity index that correlated both the mucosal disease activity index, as well as the Crohn’s activity index.

Implications for colorectal practice

This paper confirms that the mesentery does have a role in Crohn's disease, and suggests that inclusion of the mesentery in ileocolic resections is associated with reduced surgical recurrences. Although the data should be viewed in perspective because of the (inherent) biases associated with any retrospective cohort series, it would be a clinical breakthrough if adjusting surgical technique could reduce surgical recurrences from 40% to 3%. Even if the difference were much smaller, the reduced recurrence rate could be clinically relevant, as current guidelines already recommend postoperative prophylactic medical therapy for a mean 2 years reduction in clinical recurrence of 13% (95% CI 2-24%). [2]

One major drawback of the study is the fact that the close bowel resection group was operated between April 2004 and April 2010, whereas the mesenteric excision group was operated upon after August 2010. The difference in length of follow-up will be an obvious confounder for recurrences. Although the authors documented that the majority of surgical recurrences were seen within 24 months, most literature shows that only clinical recurrence will be seen within 24 month, whereas surgical recurrence is generally only seen after more than 5 years (in the current manuscript mean follow-up was 49 months in the mesenteric resection group). Therefore, no firm conclusions can be drawn just yet, and the manuscript should perhaps be viewed as a hypothesis generating read for colorectal surgeons interested in IBD surgery. Hopefully this paper will be the basis of starting additional research into the role of the mesentery in Crohn's disease.

  1. Coffey JC, Kiernan MG, Sahebally SM, Jarrar A, Burke JP, Kiely PA, Shen B, Waldron D, Peirce C, Moloney M, Skelly M, Tibbitts P, Hidayat H, Faul PN, Healy V, O Leary DP, Walsh LG, Dockery P, O Connell PR, Martin S, Shanahan F, Fiocchi C, Dunne C. Inclusion of the mesentery in ileocolic resection for Crohn's disease is associated with reduced surgical recurrence. Journal of Crohn's and Colitis 2018, jjx187, [Epub ahead of print].
  2. Gionchetti P, Dignass A, Danese S, Magro Dias, Rogler G, et al. 3rd European evidence-based consensus on the diagnosis and management of Crohn's disease 2016: Part 2: Surgical management and special situations. J Crohns Colitis 2017; 11(2):135-49.
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