From the Research
Approximately 60-80% of patients with Small Intestine Bacterial Overgrowth (SIBO) have bacterial overgrowth primarily in the distal small bowel. This distribution pattern is significant because the distal small intestine, particularly the ileum, normally contains higher bacterial concentrations than the proximal regions but still far fewer than the colon. In SIBO, failure of normal protective mechanisms allows colonic-type bacteria to colonize the distal small bowel first before potentially spreading proximally. This pattern explains why breath tests measuring hydrogen and methane, which detect fermentation occurring in the small intestine, often show delayed peaks in SIBO patients. The predominance of distal involvement also influences treatment approaches, as some antibiotics like rifaximin achieve higher concentrations in the distal small bowel 1. Understanding this distribution helps explain why some patients may experience symptoms like bloating and distension that worsen throughout the day as food reaches the more heavily colonized distal segments.
Some key points to consider in the management of SIBO include:
- The use of rifaximin, a nonsystemic antibiotic, which has been shown to be effective against SIBO and well tolerated 2.
- The potential for herbal therapies to be as effective as rifaximin for resolution of SIBO by lactulose breath testing 3.
- The importance of considering the distribution of bacterial overgrowth in the small intestine when selecting treatment options, as this can impact the effectiveness of different therapies.
It's worth noting that the evidence on the exact percentage of patients with SIBO who have bacterial overgrowth primarily in the distal small bowel is limited, and more research is needed to fully understand this condition. However, based on the available evidence, it appears that the distal small bowel is a common site of bacterial overgrowth in SIBO patients, and this should be taken into account when developing treatment plans 4, 5.