Dyssynergic Defecation Is Associated With Small Intestinal Bacterial Overgrowth

ABSTRACT Background Microbial overgrowth (MO) in the small intestine can cause gastrointestinal symptoms and may arise from stasis, such as dysmotility. Microtypes of MO include small intestinal bacterial overgrowth (SIBO) and intestinal methanogen overgrowth (IMO). Dyssynergic defecation (DD) is associated with constipation and slow colonic transit (STC). Our aim was to assess the relationship between DD and MO. Methods We retrospectively identified patients who underwent both anorectal manometry (ARM) and balloon expulsion testing (BET) for DD, and MO testing using either small intestinal aspirate culture or breath testing. SIBO was analyzed using two culture thresholds: ≥ 10 5 CFU/mL and ≥ 10 3 CFU/mL. Chi‐square tests compared positive vs. negative results. Key Results 436 patients underwent culture of SB aspirates. At the ≥ 10 5 CFU/mL threshold, 41.7% were diagnosed with SIBO, and 87.4% at ≥ 10 3 CFU/mL. At ≥ 10 5 CFU/mL, percent anal relaxation was significantly lower in SIBO‐positive patients. SIBO patients were more likely to have reduced anal relaxation ( p = 0.032), but no other ARM parameters or BET > 60 s. At ≥ 10 3 CFU/mL, a more negative recto‐anal pressure differential (RAPD) was observed, along with a combination of RAPD < −45 mmHg and resting anal pressure > 90 mmHg. 637 patients underwent breath testing for MO, with 174 positive results, predominantly showing IMO (73%). In this group, BET was significantly longer, and anal relaxation was significantly lower. SIBO at ≥ 10 3 CFU/mL was more prevalent in DD than STC (85.5% vs. 64.7%, p = 0.002). IMO was more common in DD than STC ( p = 0.021). Conclusion/Inferences DD may be a risk factor for MO, often with evidence of methanogenesis.