Anastomotic leak occurs independently from microbiota shifts associated with surgical bowel preparation

Abstract

Following bowel surgery, infectious complications, including anastomotic leak (AL), remain major sources of morbidity and mortality. Bowel preparation is often administered with the assumption that gut decontamination reduces post-surgical complications. In this study, we tested this hypothesis using a murine model of colon surgery. The mice were fed either regular chow or a high-fat, high-sugar Western diet. The day before surgery, the mice received one of four interventions: water (control), mechanical bowel preparation (MBP), oral antibiotics (OA), or both MBP and OA. We found no differences in the rates of AL among the experimental groups, and diet did not appear to affect the outcomes. Exploratory analyses showed changes in the gut microbiome consistent with the different treatments, but investigations of fecal short-chain fatty acids and RNA sequencing of colonic tissue did not reveal specific effects of the treatments or the presence of AL. However, we did identify bacterial genera that may be causally associated with AL and developed a predictive index from stool samples as a marker for the presence of AL. Future research is needed to identify and validate a microbial predictive tool and to uncover the microbial-driven mechanisms that lead to AL.

Keywords: Anastomotic leak; Colorectal surgery; Microbiome; Mouse model; Western diet.

Fig. 1

Experimental design. N = 144 mice were placed on SD or WD for 10–12 weeks. They received either MBP, OA, SBP, or water ab lib for 24 h prior to colon anastomosis. Necropsy was performed on POD7 to assess anastomotic healing. Fecal pellets were collects 24 h preoperatively (preop), on the morning of surgery (DOS), on POD4, and POD7. This image was created using Biorender.com.

Fig. 2

Principal coordinate analysis of Bray–Curtis dissimilarities (r² = 0.57) at POD4. SD-fed mice are shown in blue and WD-fed mice are shown in orange. Treatment groups are indicated by symbols which are conserved across both diets. Samples overlayed with × indicated mice that had AL across all time points.

Fig. 3

Distribution of predominant genera among fecal samples for WD-fed mice. For clarity, the top 10 predominant genera are shown and the less abundant genera were consolidated. Each genus consolidated had a mean relative abundance < 2.8% of normalized sequence reads. (f) Indicates the taxon could not be classified to greater resolution than family.

Fig. 4

Distribution of predominant genera among matched fecal, serum, and tissue samples collected at POD7. Numbers in parentheses reflect sample sizes used for data analysis. For clarity, the top 10 predominant genera are shown and the less abundant genera were consolidated. Each genus consolidated had a mean relative abundance < 2.3% of normalized sequence reads. (f) Indicates the taxon could not be classified to greater resolution than family. SourceTracker indicates the percent of the community in tissue and serum samples that could be attributed to the fecal communities.

Fig. 5

Dot plots showing pathways that were significantly activated or suppressed in mice with AL. The y-axis shows pathways with differential transcript abundances. Adjusted p-values in the legend and gene ratios (axis title in x-axis) for each significantly enriched pathway are represented as a function of color and size of dots, respectively. GeneRatio represents count/setSize wherein 'count' is the number of genes that belong to a given gene-set (here, KEGG), while 'setSize' is the total number of genes in the gene-set (here, KEGG).

Fig. 6

Anastomotic healing classification: (A) no AL, (B) contained AL (abscess), (C) gross peritonitis. (D–F) Superficial wound healing classification: (D) healed, (E, F) incisional breakdown present.