Small Intestinal Bacterial Overgrowth

Small Intestinal Bacterial Overgrowth (SIBO) is a condition where excessive bacteria build up in the small intestine. These bacteria disrupt normal digestion and absorption, often causing chronic bloating, gas, pain, or loose stools.

At The Royal Buckinghamshire Hospital, we support the investigation and management of persistent gastrointestinal symptoms in adults. While breath testing is the most common method for diagnosing SIBO, some patients may be referred for endoscopy or further investigations to rule out other digestive conditions.

Please note: All endoscopic procedures require a referral from a Consultant or Private GP. You can access a referral by booking an appointment with one of our Consultant Endoscopists or Private GP.

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What Causes SIBO?

SIBO develops when there is an abnormal increase in bacteria — or a change in the type of bacteria — in the small bowel. This can interfere with the absorption of nutrients and cause chronic gastrointestinal symptoms.

Common causes and contributing factors:

• Reduced gut motility (e.g. due to diabetes, ageing, or IBS)
• Previous abdominal surgery (e.g. bowel resections, gastric bypass)
• Low stomach acid or use of acid-suppressing medication
• Structural abnormalities of the bowel
• Chronic conditions such as coeliac disease or Crohn’s disease

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Symptoms of SIBO

Symptoms may be persistent or intermittent, and include:

• Bloating and abdominal distension
• Excessive wind or flatulence
• Cramping or discomfort after eating
• Diarrhoea or loose stools
• Fatigue
• Unintentional weight loss in severe cases

SIBO symptoms often mimic other conditions such as irritable bowel syndrome (IBS) or food intolerances.

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Diagnosis

SIBO is usually diagnosed using a hydrogen or methane breath test, which measures gas levels produced by bacteria after drinking a sugary solution. This is a non-invasive outpatient test that some private services offer.

In some cases, patients may be referred for further investigation, including upper GI endoscopy to assess for anatomical abnormalities, or stool tests to rule out other causes of symptoms.

Explore Our Endoscopy Services

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Treatment and Management

Treatment for SIBO often includes:

• Antibiotics (e.g. rifaximin) to reduce bacterial overgrowth
• Dietary changes, such as a low-FODMAP or elemental diet
• Probiotics and gut motility support in selected cases
• Managing underlying conditions that contribute to gut dysmotility or poor digestion

Our consultants can assess your symptoms and offer onward referral for appropriate testing and treatment where indicated.