Is it really IBS — or something more?
Bloating, excess gas, stomach pains after eating, chronic constipation, or frequent diarrhea — these are symptoms many people live with daily, often self-diagnosing or being told they have Irritable Bowel Syndrome (IBS). But what if the real cause has been missed?
Research shows that more than 50% of patients diagnosed with IBS may actually be experiencing abnormal intestinal bacterial or microbial overgrowth — a distinct condition that requires a different diagnostic and treatment approach.
What is IBS?
Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder causing abdominal pain, bloating, and changes in bowel habits — including both constipation and diarrhea. While IBS is a legitimate diagnosis, it is also frequently used as a catch-all label when the true underlying cause has not yet been identified.
Two conditions often mistaken for IBS
SIBO — Small Intestinal Bacterial Overgrowth
Under normal circumstances, most gut bacteria reside in the large intestine. When the digestive tract moves too slowly or has structural abnormalities, bacteria can migrate and overgrow in the small intestine. When carbohydrates and sugars are consumed, these bacteria rapidly ferment them, producing excessive hydrogen gas — leading to:
- Bloating and abdominal distension
- Diarrhea
- Bad breath
- Depletion of nutrients, particularly Vitamin B12
- In more severe cases, bile acid disruption causing fat malabsorption and oily, floating stools
IMO — Intestinal Methanogen Overgrowth
Methanogens are single-celled microorganisms that take up the hydrogen produced by gut bacteria and convert it into methane gas. Methane has a specific effect on the intestinal wall — it slows gut motility, leading to chronic constipation that can be difficult to resolve without identifying this underlying cause.
How are SIBO and IMO diagnosed?
Both SIBO and IMO can be diagnosed through several methods. The most widely used current gold standard is the Hydrogen and Methane Breath Test — a non-invasive diagnostic test that analyses the gases exhaled in the breath to detect abnormal bacterial or methanogen activity in the gut. It is painless, straightforward, and provides actionable results that allow treatment to be precisely targeted.
Bangkok Hospital Pattaya’s Gastrointestinal and Liver Center is the first private hospital in the Eastern Region of Thailand to offer this innovation, helping patients find accurate answers to their gastrointestinal symptoms without the need for invasive procedures.
Frequently Asked Questions About SIBO, IMO, and IBS
What is the difference between IBS, SIBO, and IMO?
IBS is a functional gastrointestinal disorder diagnosed based on symptoms. SIBO (Small Intestinal Bacterial Overgrowth) and IMO (Intestinal Methanogen Overgrowth) are specific conditions involving abnormal microbial growth in the gut that can cause symptoms identical to IBS. More than 50% of IBS patients may actually have SIBO or IMO — making accurate diagnosis essential for effective treatment.
What are the symptoms of SIBO?
Common SIBO symptoms include bloating, abdominal distension, diarrhea, bad breath, and nutrient deficiencies — particularly Vitamin B12. In more severe cases, fat malabsorption can occur, causing oily or floating stools.
What are the symptoms of IMO?
IMO typically causes chronic constipation rather than diarrhea. The methane gas produced by methanogens slows intestinal movement, making constipation persistent and difficult to manage without treating the underlying cause.
How is SIBO or IMO diagnosed?
The standard diagnostic method is the Hydrogen and Methane Breath Test — a non-invasive, painless test that measures the levels of hydrogen and methane in exhaled breath following ingestion of a test solution. Results indicate whether abnormal bacterial or methanogen overgrowth is present in the small intestine.
Is the breath test painful or invasive?
No. The Hydrogen and Methane Breath Test is completely non-invasive and painless. It involves drinking a test solution and breathing into a collection device at timed intervals — no needles, no scopes, and no discomfort.
Can SIBO or IMO be treated?
Yes. Once accurately diagnosed, both SIBO and IMO can be treated with targeted therapy — typically involving specific antibiotics or other medications to reduce abnormal microbial overgrowth, alongside dietary guidance to support recovery and reduce recurrence.
Why is it important to distinguish between IBS, SIBO, and IMO?
Because the treatments are different. Managing IBS with lifestyle changes and fiber supplementation will not resolve SIBO or IMO, and may even worsen symptoms in some patients. Accurate diagnosis ensures that treatment is targeted at the actual cause rather than the symptoms alone.
Where can I get tested for SIBO and IMO in Pattaya?
The Hydrogen and Methane Breath Test is available at Bangkok Hospital Pattaya’s Gastrointestinal and Liver Center — the first private hospital in the Eastern Region of Thailand to offer this diagnostic innovation.
For more information or to book an appointment, contact the Gastrointestinal and Liver Center, Bangkok Hospital Pattaya. Tel. 0 3825 9999
References:
1.Rezaie A, Buresi M, Lembo A, Lin H, McCallum R, Rao S, Schmulson M, Valdovinos M, Zakko S, Pimentel M. Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus. Am J Gastroenterol. 2017;112:775-784.
2.Ghoshal UC, Shukla R, Ghoshal U. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut Liver.2017;11:196-208.
3.Yang L, Gong JJ, Mo XJ, Qian XX. Extraoral halitosis in functional dyspepsia and its association with small intestinal bacterial overgrowth. J Breath Res. 2025;19.
