Polyethylene glycol-based bowel preparation and gut dysbiosis: Clinical implications beyond colon cleansing

Table 1 Major microbiota and mucosal alterations associated with polyethylene glycol bowel preparation

Alteration	Main findings	Proposed biological consequence	Evidence level
Reduced microbial diversity[8,9]	Transient decrease in alpha-diversity after lavage	Ecological instability and reduced resilience	Human observational
Depletion of butyrate-producing Firmicutes[9,13]	Reduction in SCFA-producing taxa	Impaired epithelial energy supply and barrier maintenance	Human + mechanistic
Expansion of Proteobacteria[10,11]	Relative increase in opportunistic taxa	Potential loss of colonization resistance	Human observational
Altered bile acid metabolism[4,12]	Shifts in microbial metabolic pathways	Immune and metabolic dysregulation	Metabolomic
Mucus layer thinning[5,15,16]	Reduced MUC2 expression and goblet cell alterations	Increased epithelial permeability	Experimental
Altered immune signaling[39,41]	Increased IL-6/IL-8 and reduced Treg activity	Transient pro-inflammatory state	Experimental
Delayed microbiota recovery in vulnerable hosts[52,53]	Prolonged dysbiosis in elderly/IBD/metabolic disease	Reduced mucosal resilience	Clinical observational

SCF: Short-chain fatty acid; IL: Interleukin; Treg: Regulatory T cells; IBD: Inflammatory bowel disease.

Table 2 Strategies to mitigate polyethylene glycol-associated dysbiosis while preserving bowel cleansing efficacy

Strategy	Proposed mechanism	Potential benefit	Current evidence
Split-dose PEG[58]	Reduced continuous osmotic stress	Faster microbiota recovery	Clinical
Low-volume PEG formulations[58]	Lower luminal osmotic burden	Reduced ecological disruption	Emerging clinical
Probiotics[54-57]	Restoration of microbial balance	Reduced GI symptoms and faster recovery	Clinical + meta-analysis
Prebiotic/fiber-enriched diets[53]	Support of SCFA-producing bacteria	Enhanced microbial resilience	Clinical observational
Butyrate/glutamine supplementation[59,60]	Barrier protection and epithelial repair	Reduced permeability and inflammation	Experimental

PEG: Polyethylene glycol; GI: Gastrointestinal; SCFA: Short-chain fatty acid.