Digestive Support and SIBO

What is SIBO?

Small intestinal bacterial overgrowth (SIBO) is a condition in which there is an excessive number of bacteria in the small intestine. These bacteria ferment the simple carbohydrates we consume in food and can lead to symptoms of abdominal pain, bloating, flatulence, and diarrhea and/or constipation. 

What causes SIBO?

Many correlations and associations have been drawn between certain factors and the pathogenesis of SIBO. SIBO is characterized not only with microbial overgrowth but also disruption of the migrating motor complex (MMC) of the gut, which alters the normal contractions that move food through the small intestine, allowing for microbes to multiply in the small intestine. Many things can impact the MMC function (positively and negatively), including prescription drugs, abdominal surgery, and food poisoning. Because the MMC functions through nerve transmission, other conditions seemingly not obviously related to the GI can still impact it, like neurologic disorders and even mood disorders like anxiety and depression. As such, there are a diverse number of potential causes for developing SIBO and part of an accurate diagnosis is a thorough review of the patient’s medical history.

How is SIBO diagnosed?

The gold-standard for testing SIBO for decades has been an endoscopic small bowel aspirational biopsy with culture. There are many reasons why this may not be the best method for diagnosis. For one, it is an invasive surgical procedure. In fact, many gastroenterologists do not perform endoscopic small bowel aspirates, so it is not widely available. Also, the rate of false positives can be very high with this test as samples are only taken from one or a few specific spots in the small intestine (that is 26 feet in length); we know that SIBO can form in “patches” and thus the chance of simply missing the affected area during aspiration collection using this technique is quite possible. Lastly, there is a significant expense associated with this type of procedure. Because of these obstacles, while SIBO has been an accepted medical diagnosis for many years, it has been under-reported and under-diagnosed for a long time. 

In recent years, gas analyzer technology has been better developed for medical diagnostic purposes which has led to a newer, more widely available and accessible way of diagnosing SIBO through the use of breath testing. Breath testing uses our knowledge of the bacterial fermentation of carbohydrates in SIBO to identify whether a patient has an overgrowth or not. Lactulose is not absorbed by the human GI tract and so it is generally used as the carbohydrate substrate in breath tests as it should pass through the length of the gut, allowing it to be fermented by any SIBO anywhere, if present. When the lactulose is fermented by microorganisms, they produce gases that are absorbed into the blood stream and excreted in our breath. The breath test measures the levels of these gases that the patient breathes out after consuming a lactulose sample. Elevations in the gases, as well as how long after the consumption of the lactulose the elevations occur, can not only diagnose the presence of SIBO, but can also suggest what types of organisms are predominantly involved in that case. It is a more sensitive test than aspirational biopsy, because breath testing allows us to evaluate the entire length of the GI for the presence of SIBO, not just specific areas (while neglecting others) as with an aspirational biopsy.

How is it treated?