Small intestine bacterial overgrowth (SIBO) has been gaining recognition over the last few years. It is being diagnosed and treated by providers outside of GI due to its seemingly increased prevalence.
SIBO is defined as an increased amount of bacterial organism within the small intestines, bypassing the usual protective mechanisms. The small bowel usually has a low microorganism count compared to the large intestines. If small bowel motility and clearance is impaired, bacteria can migrate upward from the large bowel, possibly resulting in tissue injury.
SIBO symptoms can overlap with other GI conditions, which may contribute to a delay in diagnosis. Overgrowth from the colon into the small bowel can result in bloating, gas, diarrhea, and abdominal discomfort. In extreme cases there can be malabsorption and weight loss due to inflammation and increased intestinal permeability. Similar symptoms can also be seen in IBS, IBD (Crohn’s and Ulcerative colitis), pancreatic insufficiency, or after various GI surgeries.
Several conditions can predispose an individual to an abnormal movement and clearance of the small bowel. IBS, chronic pancreatitis, and immune disorders can lead to the development of SIBO. Medications, including narcotics and other gut slowing agents, antacids, and prior antibiotic use can result in SIBO development. Anatomical abnormalities such as small bowel strictures, diverticulosis in the small intestines, and small bowel surgeries can also be contributing factors.
In my experience, one of the leading causes of slow small bowel motility is slow large bowel motility. I find that most patients will not respond as well to SIBO treatment if there is underlying constipation.
A diagnosis of SIBO is often done by breath test to evaluate for hydrogen and methane production by bacteria, after the consumption of a carbohydrate substrate, such as lactulose or glucose. An elevation of hydrogen and methane may indicate an overabundance of bacteria in the small bowel. This noninvasive approach is simple, but reliability can fluctuate due to a variety of factors including preparation, testing methods, and other patient conditions.
Lab findings are often nonspecific but can help to identify deficiencies due to malabsorption. Imaging and endoscopic studies can help to identify a cause, but generally are not used to provide an actual diagnosis.
SIBO can also be diagnosed and treated empirically, based on a patient’s complaints and presentation. This means that if your symptoms are consistent with SIBO and other possible causes have been ruled out, then you should consider treating for SIBO, which is what I generally do.
Small intestine bacterial overgrowth treatment is geared toward reducing the burden of bacteria in the small bowel. A variety of antibiotics can be used but rifaximin is the drug of choice due to its low side effect profile and higher response rates. It is effective, but expensive. There are other antibiotic options to choose from which are typically more affordable, but may be less effective. Different bacterial strains are targeted during treatment to improve outcomes, but repeat treatment is required sometimes.
Other treatment recommendations may include probiotics to help reestablish healthy gut flora. However, the data supporting probiotic use is limited. Low FODMAP diet, also recommended for IBS, can help to eliminate a lot of gas forming foods that can worsen SIBO symptoms. Reducing the use of medications that may have contributed to SIBO occurrence can help prevent future episodes. Addressing nutritional deficiencies should be prioritized long-term, as malabsorption improves with bacterial clearance.
If you think SIBO is affecting you, VNPS GI clinic may be able to help. An experienced GI NP can provide you with recommendations and treatment for SIBO.