Intestinal Atrophy Following Ileostomy is Associated with Dysbiosis

Surgical intervention to remove colon tumours, commonly requires inserting a temporary stoma upstream to allow tissue healing, with the aim of rejoining the bowel ~12 months later. Defunctioned bowel becomes atrophied and fibrotic, making reversal surgery difficult and delaying functional recovery.  This study aimed to investigate the microbial changes that occur following enteral nutrient diversion. Intrapatient comparisons between functional and defunctioned ileal tissue, including histological assessment of morphology and epithelial cell proliferation, were performed.  Mucosal-associated microflora was quantified via 16S rRNA gene copy number analysis. Luminal-associated microflora was profiled via DGGE with Sanger sequencing and qPCR analysis to genus and phylum level, respectively. Reduced villus length 47% ± 3% (n=9, p≤ 0.001) and proliferation 23.7% ± 3.6% (n=5, p≤ 0.01) confirmed atrophy of the defunctioned ileum.  DGGE analysis revealed that the microflora within defunctioned ileum is less diverse and convergence between patient flora patterns was observed.  Notably Clostridia and Streptococcus were reduced in relative terms in defunctioned bowel. Ileostomy-associated nutrient deprivation results in dysbiosis and impaired intestinal function in the defunctioned ileum. Altered host-microbial interactions at the mucosal surface likely contribute to the deterioration in function and strategies to sustain the microflora prior to reanastomosis should be investigated.