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.