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Distinguishing Between Irritable Bowel Syndrome or Small Intestinal Bacteria Overgrowth

stomach pain

When it comes to matters of the gut, it can be tough to pinpoint your symptoms and understand what they might be telling you. Two conditions of the intestines that are similar in nature are Irritable Bowel Syndrome (IBS), and Small Intestinal Bacteria Overgrowth (SIBO). In this post we’ll highlight the differences between them so you can start to determine which one ails you, or, if it’s actually both.

Identifying Irritable Bowel Syndrome

IBS is a commonly known syndrome with the following typical symptoms:

  • Abdominal bloating (swelling of the belly)
  • Abdominal pain
  • Diarrhea, constipation, or both

It is often a diagnosis of exclusion when conventional gastro-intestinal testing does not find an underlying cause. IBS can be particularly painful. Gas trapped in the large intestine can create significant bloating and pain. Patients with these symptoms may also suffer with bowel urgency, straining or a sense of incomplete evacuation, and the passage of mucus in stools. Symptoms are often made worse by eating. Some patients also report lethargy, nausea, backache, and bladder symptoms.

IBS Treatment

IBS was first described in 1820 and was given the name Irritable Bowel Syndrome in 1944. Estimates are that 15-45% of the global population may be affected by it. There is no known cause, although correlations have been found with stress, intestinal motility disorders, pain sensitivity, infections including SIBO, genetic factors, neurotransmitters, and food sensitivity. Although there is no cure, treatments such as dietary changes, medication, probiotics, and counseling have been found to be helpful in alleviating symptoms.

IBS Research and Testing

More recent research has been finding that low-grade inflammation and immune activation is present in the intestinal mucosa (the cells that line the intestines) in patients with IBS. Chronic infections in the colon can include parasites, yeast overgrowth, presence of pathogenic bacteria, and dysbiosis or imbalance in our normal flora. Employing comprehensive stool tests can uncover some of these underlying causes of IBS. Testing from laboratories such as Diagnostic Solutions, Genova, or Doctors Data are very helpful in identifying infections and helping clinicians get to the underlying root of many complicated IBS cases.

Identifying Small Intestinal Bacterial Overgrowth

What if the infection cause is actually in the small intestine? Small Intestinal Bacterial Overgrowth (SIBO) is defined as an accumulation of bacteria in the small intestine. The overgrowth is bacteria that normally live in the gastrointestinal tract but have abnormally overgrown in the small intestine, which cannot function as it should with so many bacteria.


SIBO can present with the same symptoms as IBS: abdominal bloating and pain, diarrhea, constipation or both. However, it can result in additional symptoms.

Signs you may have SIBO:

  • Food reactions, especially to carbohydrates. In many cases, patients have to maintain a very restrictive diet; and deviating from it even slightly causes negative symptoms to return.
  • Gastro-esophageal reflux (GERD)
  • Nausea
  • Fatigue
  • Weight loss
  • Abdominal bloating is worse at night due to the build up of gas that accumulates after every meal
  • Chronically low ferritin levels without explanation
  • Symptoms occur after any of the following:
    • Food poisoning
    • After taking a proton pump inhibitor for GERD
    • Opiate narcotics
    • Abdominal surgery
  • The use of antibiotics gives temporary improvement in symptoms
  • Probiotics containing pre-biotics worsen symptoms
  • Eating a clean diet worsens the condition
  • Celiac patients eliminate gluten and don’t feel better
  • Fiber worsens constipation


Additionally, SIBO can be the underlying cause of other health conditions that you wouldn’t normally associate with it, such as:

  • Restless Leg Syndrome
  • Interstitial Cystitis
  • Rosacea
  • Fibromyalgia
  • Rheumatoid Arthritis
  • Psoriasis

Testing for SIBO

Testing for SIBO is done through collection of breath samples on a day after you complete a 24-hour diet and 12-hour fast. Breath samples are collected over a 2 to 3-hour period after lactulose is consumed and analyzed for the presence of hydrogen and methane gases. Testing to detect the presence of hydrogen sulfide is currently under development at the Cedars-Sinai Medically Associated Science and Technology Program.

In our next post, we’ll share how to distinguish between methane, hydrogen, and hydrogen sulfide-producing bacteria and treatment.

Interested in speaking with one of our doctors about your intestinal health? Call us: 303-884-7557.