Small Bowel Bacterial Overgrowth

What is small bowel bacterial overgrowth?

Small bowel bacterial overgrowth is also commonly referred to as small intestinal bacterial overgrowth (SIBO). The small intestine and large intestine both contain bacteria that help with normal function of the intestine including digestion and immunity. Normally, the large intestine has a much larger number of bacteria than the small intestine. In SIBO, the small intestine develops a much higher number of bacteria than the large intestine. One of the primary roles of the small intestine is to absorb nutrients that the body needs. Over time, the change seen in the small intestine due to the increased amount of bacteria can lead to poor absorption of nutrients in the small bowel and malnutrition.

Causes of SIBO

There can be many causes that can contribute to increased number of bacteria developing in the small intestine. Factors that decrease acid production or decrease the movement (motility) of the GI tract or lead to damage to the lining of the intestine can contribute to the development of SIBO. Some of the causes leading to SIBO can be either congenital (present at birth) disorders or surgical interventions that can result in abnormal motility (movement of the digestive system and contents within it) in the small intestine. Decreased motility leads to poor movement of the food and bacteria through the small intestine. Bacteria is not swept through effectively and remains in the small intestine for a longer time, allowing bacteria to multiply. 

Some of the conditions linked to increased risk for developing bacterial overgrowth include: 

  • Celiac disease
  • Gastroparesis
  • Small bowel dysmotility
  • Chronic pancreatitis
  • Connective tissue disorders
  • Inflammatory bowel disease (IBD)
  • Irritable bowel syndrome
  • Chronic intestinal pseudo-obstruction
  • Medications
  • Prior GI surgery

Symptoms of small bowel bacterial overgrowth

The symptoms of SIBO include:

  • Abdominal bloating
  • Flatulence, excessive gassiness
  • Abdominal pain or discomfort
  • Abdominal distention
  • Diarrhea
  • Unintentional weight loss
  • Nausea

These symptoms are not specific to SIBO and can be seen with several other GI conditions in the absence of SIBO.

Diagnosing SIBO

Diagnosing SIBO includes obtaining a comprehensive medical, surgical and symptom history to identify risk factors and symptoms that may be suggestive of bacterial overgrowth. The physical exam will help your child's physician evaluate for malabsorption and underlying disorders that have been linked to an increased risk for SIBO.

Diagnostic screening testing may include imaging (CT, MRI, X-ray) of the abdomen and bowel to evaluate for dilated loops of bowel and screen for any areas of narrowing of the bowel causing decreased motility through the intestines.

Diagnostic testing for SIBO includes:

  • Bacterial culture of the bowel
  • Hydrogen breath test

Bacterial culture of the bowel

The bacterial culture of bowel is a direct method of testing using endoscopy to obtain aspirate and culture samples from the small intestine. This test is not commonly used due to the procedure being invasive and requiring endoscopy to obtain specimen. The results obtained are only indicative of the location where the specimen was obtained and can underestimate the total number of actual bacteria present in other areas of the small bowel.

Hydrogen breath test

The most common test used to diagnose bacterial overgrowth is the hydrogen breath test.

This test is a simple and non-invasive way to indirectly test for bacterial overgrowth. During this test, your child will drink a substrate (glucose or lactulose) that will interact with the bacteria in the small bowel to produce byproducts that can be measured in the exhaled breath. Timed interval measures of the exhaled breaths are used to detect changes in hydrogen production and methane production which are indicative of bacterial overgrowth

Treatment for SIBO

The goals of treatment for SIBO are to correct the predisposing or underlying cause of bacterial overgrowth, provide nutritional support, and treat the bacterial overgrowth.

Treatment is aimed to identify and correct the underlying causes of bacterial overgrowth and may include diet management and medication management. In some instances, surgical management may be indicated to correct identified defects in the intestinal anatomy that can contribute to bacterial overgrowth.

Dietary management is aimed at providing education to families about foods that do not contribute to producing excess gas and providing dietary guidance to maintain vitamin and nutritional needs.

Medication management for SIBO

Antibiotics are prescribed for management of SIBO to reduce the bacterial overgrowth and treat the inflammation to the bowel lining caused by SIBO.

Some of the antibiotics commonly used include:

  • Metronidazole (Flagyl®)
  • Ciprofloxacin (Cipro®)
  • Neomycin
  • Amoxicillin-Clavulanic Acid (Augmentin)
  • Rifaximin (Xifaxan®)

The specific antibiotic used is based on each individual patient's history. 

Duration of treatment with antibiotics may be short term (seven to 14 days) or a longer course may be prescribed. Antibiotics may also be cycled for use during a specified amount of time for each month as ordered.

Probiotics for SIBO

Probiotics can also be used in management of bacterial overgrowth due to their effects on reducing bacteria in the bowel from colonizing.

Prokinetics can be used jointly with the antibiotic therapy in the management of bacterial overgrowth in patients that have dysmotility of the small bowel associated with diagnoses such as gastroparesis or chronic intestinal pseudo obstructions. 

Some of the prokinetics commonly used include:

  • Erythromycin
  • Azithromycin
  • Metoclopramide (Reglan®)
  • Cisapride
  • Domperidone

Long-term outlook for children with SIBO

  • Improvement of symptoms and quality of life with treatment
  • Positive outlook if underlying and predisposing conditions identified and managed

Follow-up care

Follow-up care for small intestinal bacterial overgrowth requires ongoing management based on symptoms and the continued management of underlying causes leading to bacterial overgrowth.

Why choose CHOP for SIBO care

We have extensive experience in the diagnosis and management of bacterial overgrowth secondary to a variety of underlying factors and conditions. CHOP excels in providing comprehensive care for every patient, including the medical, pharmaceutical and nutritional management of bacterial overgrowth and the underlying condition.

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