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Dyssynergic Defecation Is Associated With Small Intestinal Bacterial Overgrowth
John A Damianos1, Ayah Matar1, Houssam Halawi1
1Division of Gastroenterology and Hepatology, Clinical Enteric Neuroscience Translational and Epidemiological Research (C.E.N.T.E.R.), Mayo Clinic, Rochester, Minnesota, USA.
Neurogastroenterology and Motility
|November 8, 2025
Summary
Dyssynergic defecation (DD) is linked to microbial overgrowth (MO), including small intestinal bacterial overgrowth (SIBO) and intestinal methanogen overgrowth (IMO). Patients with DD showed higher rates of SIBO and IMO, suggesting DD may be a risk factor for MO.
Area of Science:
- Gastroenterology
- Microbiology
- Physiology
Background:
- Microbial overgrowth (MO) in the small intestine, encompassing small intestinal bacterial overgrowth (SIBO) and intestinal methanogen overgrowth (IMO), is associated with gastrointestinal symptoms and can result from stasis.
- Dyssynergic defecation (DD) is a condition linked to constipation and slow colonic transit (STC).
Purpose of the Study:
- To investigate the relationship between dyssynergic defecation (DD) and microbial overgrowth (MO).
Main Methods:
- Retrospective analysis of patients undergoing anorectal manometry (ARM) and balloon expulsion testing (BET) for DD, alongside MO testing (small intestinal aspirate culture or breath testing).
- SIBO was assessed using two culture thresholds (≥10^5 CFU/mL and ≥10^3 CFU/mL).
- Chi-square tests were employed to compare positive and negative results.
Main Results:
- At the ≥10^3 CFU/mL threshold, SIBO was more prevalent in DD patients compared to STC (85.5% vs. 64.7%).
- Intestinal methanogen overgrowth (IMO) was also more common in DD patients than in STC (p=0.021).
- Patients with DD exhibited significantly longer BET times and lower anal relaxation, irrespective of SIBO or IMO diagnosis.
Conclusions:
- Dyssynergic defecation (DD) may serve as a risk factor for developing microbial overgrowth (MO).
- A significant proportion of DD patients present with evidence of methanogenesis, indicating a link between defecation disorders and MO.
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