The Role of Gut Microbiota in Chronic Constipation and the Therapeutic Potential of Fecal Microbiota Transplantation

OBJECTIVE: This study investigates the relationship between gut microbiota dysbiosis and chronic constipation (CC) and evaluates the therapeutic efficacy of fecal microbiota transplantation (FMT) in restoring microbial homeostasis and metabolic function. METHODS: We retrospectively analyzed existing before-after clinical data from 206 patients with CC who received FMT. No placebo or case-control group was included. Gut microbiota profiles were analyzed before and after FMT using 16S rRNA sequencing. Alpha and beta diversity indices were calculated to assess microbial community evolution. Gas chromatography-mass spectrometry (GC-MS) was employed to quantify short-chain fatty acids (SCFAs). Patients were stratified into butyrate-high and butyrate-low metabolic subtypes using a partitioning around medoids (PAM) algorithm based on pre-transplant butyrate levels. Clinical severity was independently defined using Rome IV criteria, CSBM, BSFS, and PAC-SYM. RESULTS: FMT significantly increased microbial α-diversity and shifted the community structure toward that of healthy donors. Post-transplant, the Bacteroidetes/Firmicutes ratio decreased from 46.8% to 38.9%, with a marked enrichment of beneficial taxa such as Faecalibacterium, Akkermansia, and Bifidobacterium. These shifts correlated with a significant rise in SCFA concentrations, particularly acetic and butyric acids. Butyrate deficiency was characterized by broader SCFA deficiencies and fragmented microbial networks. Multivariable binary logistic regression identified Faecalibacterium, ACE index, and acetic acid as independent predictors of clinically defined constipation severity. CONCLUSION: FMT was associated with increased microbial diversity, restoration of SCFA-producing taxa, and increased SCFA concentrations in patients with CC. These changes accompanied improvements in CSBM, BSFS, PAC-SYM, and PAC-QOL.