Small intestinal bacterial overgrowth (SIBO) is a little known gastrointestinal (GI) disorder with links to irritable bowel syndrome (IBS). Today, it takes an average of about six years for patients to receive a proper IBS diagnosis and begin a course of treatment, all the while experiencing debilitating symptoms from this disease.

Despite SIBO’s long documented medical history, it is poorly understood in comparison to similar chronic GI conditions. While there have been significant strides achieved with diagnosing and managing SIBO, there is still progress that needs to be made to advance the treatment of the condition and help patients achieve relief.

The progress that’s been made with SIBO

First discovered in 1939, SIBO occurs when excess bacteria accumulate in the small intestine, which implicates motility and causes symptoms such as severe bloating and abdominal cramps, chronic diarrhea, and frequent flatulence to name a few. These are all symptoms that can easily be misinterpreted as signs of other, more well-known conditions, such as Celiac or Crohn’s diseases, but most frequently lead to an IBS diagnosis of exclusion.

In 2000, I was part of a study that first identified SIBO was present in 78 percent of patients with IBS, and that treating it with antibiotics generally improved symptoms in patients. However, the similarities between SIBO and other GI conditions lead to challenges with monitoring known SIBO cases. Further, because patients are commonly misdiagnosed with other GI disorders, it is difficult to identify the true prevalence of SIBO.

In the 1970s, the hydrogen breath test was introduced to diagnose SIBO, and this has been instrumental in identifying SIBO. The breath test is a simple and non-invasive method for evaluating a patient’s digestion of particular sugars by measuring the amount of hydrogen exhaled. Since then, breath testing has expanded to include measuring methane as well to capture different types of SIBO or a combination of SIBO and intestinal methanogenic overgrowth (IMO) and most recently intestinal sulfide overproduction (ISO).

Promisingly, we’ve seen strong progress with managing SIBO in the last two decades. In May 2015, the U.S. Food and Drug Administration (FDA) approved rifaximin to treat IBS on the understanding that IBS was a microbiome condition, in part. Due to the growing overlap of IBS and SIBO, rifaximin became a popular antibiotic for the management of SIBO in IBS patients. This was certainly an important milestone in the history of SIBO, offering a clinical solution to patients’ symptoms.

In 2020, the first 3-breath test to measure a complete fermented gas profile of a patient’s microbiome, including levels of hydrogen, methane, and hydrogen sulfide, became available and patients could take the test from home. Previously, only hydrogen and methane breath tests had been common, but hydrogen sulfide levels have also been known to correlate with the amount of bacteria in the GI tract.

While the hydrogen test was transformative in diagnosing patients with SIBO, methane and hydrogen sulfide are important for explaining symptoms of constipation and diarrhea, respectively, among patients. Until this breath test, it hadn’t been possible for physicians to measure hydrogen sulfide, let alone all three gases in patients, but this novel breath test opened up access for more patients to receive accurate diagnoses and care.

At the beginning of 2024, the first ICD-10 codes for SIBO were introduced and have ushered in an easier way to track the prevalence of SIBO among patients and continue raising awareness of the disease. Currently there is a barrier to effective treatment because of the lack of insurance coverage, but the ICD-10 codes will play a role in collecting more data about SIBO to encourage insurance providers to extend SIBO-related coverage.

For years, antibiotics served as the primary course of treatment for chronic GI dysfunction. However, they aren’t the most effective method for SIBO, only eradicating harmful bacterial overgrowth in about 44 percent of patients. An elemental diet is the most effective method for managing SIBO and has been around since the 1940s. However, many gastroenterologists don’t recommend elemental diets to patients because they have historically been unpalatable, resulting in low patient compliance rates. Fortunately, food science innovations in the last year have addressed the taste of elemental diets to deliver palatable options for patients.

Where we go from here

The true prevalence of SIBO is still largely unknown due to a lack of awareness of the disease. It shares common symptoms with other GI dysfunctions and this complicates the patient’s ability to receive a proper diagnosis so they can take action on improving their health. There needs to be more awareness of SIBO so it can be considered alongside other common GI conditions from the start, and we can pinpoint a more accurate population size living with SIBO.

Additionally, more research is needed on SIBO and its therapeutic solutions to continue improving outcomes for patients. Management options have come a long way over the years, but there is still room to address SIBO in a more systematic manner. Uncovering new insights through further research will give providers the supporting data they need to recommend the best course of treatment for patients. In turn, more research will continue to raise awareness of SIBO and propel a cycle of conversation and advancement.

Lastly, more education among the clinical community is needed as many gastroenterologists aren’t aware of new advancements for diagnosing and managing SIBO. From breath tests that dramatically reduce the average wait for a diagnosis, to palatable elemental diets that provide patients with more effective chronic condition management solutions, there is a whole new world of care available for SIBO patients. Gastroenterologists should be armed with these new tools and research findings to improve their patients’ health outcomes and bring them much needed relief from their debilitating symptoms.

SIBO has hidden long enough in the shadows. For better patient outcomes, it’s time for this condition to come into the light.

Mark Pimentel is a gastroenterologist.