RECTAL cancer surgery triggers perioperative microbiome shifts, with lower diversity plus increased Enterococcus and Streptococcus.
Perioperative Microbiome Shifts After Rectal Cancer Surgery
The gut microbiome is increasingly studied for its potential role in postoperative complications, including anastomotic leakage, yet human data capturing perioperative change over time remain limited. In this descriptive pilot study, investigators examined the perioperative microbiome of patients undergoing rectal resection for malignancy with primary anastomosis, with or without a diverting ileostomy.
Seventeen patients were included from two Amsterdam-based studies conducted between April 2020 and April 2022. The team collected multiple sample types to map perioperative microbiome dynamics, including preoperative stool, intraoperative anastomotic colonic tissue and swabs, and postoperative stool. Bacterial DNA was analyzed using 16S rRNA gene sequencing to compare composition across time points and sampling locations.
Antibiotics, Diversity, and Postoperative Clustering
Across the perioperative microbiome timeline, postoperative stool showed a clear shift compared with preoperative and intraoperative samples. The authors observed increased relative abundance of Enterococcus and Streptococcus postoperatively. At the same time, postoperative samples demonstrated a significant decrease in alpha diversity, suggesting a less diverse microbial community after surgery.
Beta diversity analyses further supported that postoperative stool formed distinct clusters, including separation of ileostomy samples from other perioperative specimens. Notably, preoperative oral antibiotics were associated with altered intraoperative microbiome composition and reduced postoperative alpha diversity, highlighting how common perioperative practices may shape observed microbial patterns.
Why These Early Findings Matter
The authors emphasized that perioperative microbiome dynamics should be considered when designing and interpreting studies that link the microbiome to clinical outcomes after rectal cancer surgery. As a hypothesis-generating pilot, the findings are preliminary and require confirmation in larger cohorts, including work that tests whether observed shifts have a causal relationship with postoperative outcomes.
Reference: Wienholts K et al. The perioperative microbiome of patients undergoing rectal cancer surgery: A pilot study. Colorectal Dis. 2026;28(2):e70397.
