Preoperative enteral nutrition in adults with complicated Crohn's disease: effect on disease outcomes and gut microbiota

Objectives: The use of exclusive enteral nutrition (EEN) in patients with Crohn's disease (CD) before surgical resection can reduce disease activity and improve nutritional status. The mechanism of EEN action is unclear, but it might involve modulation of the intestinal microbiota. The aim of this study was to evaluate the effects (namely changes in gut microbiota) of preoperative EEN in adults with complicated CD referred to surgery. Methods: This was a prospective study of adult patients with CD referred to surgery. Patients with body mass index <18.5 kg/m2, weight loss >10 %, serum albumin <3 g/dL, or a combination of some or all three, received EEN for ≥2 wk. The effects of EEN on clinical (Harvey–Bradshaw Index [HBI]) and laboratory markers (C-reactive protein [CRP], serum albumin, and fecal calprotectin) and fecal microbiota were analyzed after EEN (before surgery) and 6 mo later. We used 16 S rRNA gene sequencing to determine changes in the fecal microbiota. Results: Fifteen patients were included, of whom 60% were men with a mean age of 45.4 ± 19.1 y. Of those, 10 received EEN. The median duration of preoperative EEN was 41.5 d (15–70 d). During EEN, there was a significant reduction in mean HBI (8.7 ± 1.9 versus 4.1 ± 2.4; P = 0.001) and CRP (11.7 ± 10.3 versus 0.8 ± 0.8 mg/dL; P = 0.008) and an increase in serum albumin (3.1 ± 0.6 versus 4 ± 0.6 g/dL; P = 0.022). Two patients did not require surgery after EEN. The overall microbial composition changed after EEN (Permutational analysis of variance test, P = 0.046) and there was a significant reduction in α diversity (8 ± 2.3 versus 5.2 ± 1.5; P = 0.023). EEN significantly changed the relative abundance of 11 taxonomic operational units (OTUs). At the family level, we found this was mainly due to the decrease in the Enterobacteriaceae family (7 OTUs). Six months after surgery, α diversity was not different from that before or after EEN; at this time point 6 OTUs were significantly different, mainly due to the decrease of Clostridiales order (3 OTUs). The incidence of postoperative complications and hospital length of stay were similar in EEN and immediate surgery groups, as well as clinical and endoscopic recurrence rates 6 mo after surgery. Conclusions: Preoperative EEN improved disease activity and nutritional status in patients with CD referred to surgery. Despite being malnourished, patients given EEN did not have increased postoperative complications compared with well-nourished patients. During EEN, overall microbiota composition changed and α diversity decreased. EEN did not influence postoperative recurrence and gut microbiota 6 mo after surgery.