Interactive Guide to SIBO in Pediatrics

Small Intestine Bacterial Overgrowth (SIBO) is a clinical condition characterized by the presence of an excessive number and/or an abnormal type of bacteria in the small intestine. Normally, the small intestine contains a relatively low bacterial population compared to the colon.

In the pediatric population, manifestations are often nonspecific and may overlap with other functional and organic gastrointestinal pathologies. Key symptoms include:

• Chronic abdominal pain: Often colicky and diffuse.
• Abdominal distension and gas: Feeling of swelling that worsens throughout the day.
• Alterations in intestinal habit: Chronic diarrhea (watery or steatorrheic), constipation, or a mixed pattern.
• Excessive flatulence and borborygmi.
• Malabsorption: It can lead to nutritional deficiencies (iron, vitamin B12, fat-soluble vitamins) and failure to thrive in severe cases.
• Nausea and loss of appetite.

SIBO is generally secondary to a disruption of defense mechanisms that prevent bacterial colonization of the small intestine. These mechanisms include gastric acid secretion, intestinal motility (migratory motor complex), ileocecal valve integrity, and mucosal immunity.

The main causes and risk factors in pediatrics are:

• Motility disorders: Chronic intestinal pseudo-obstruction, gastroparesis, opioid use.
• Anatomical anomalies: Post-surgical adhesions, diverticula, short bowel syndrome, ileocecal valve resections, fistulas.
• Reduction of gastric acidity: Chronic use of proton pump inhibitors (PPIs).
• Immunodeficiencies: IgA deficiency, common variable immunodeficiency.
• Systemic and metabolic conditions: Cystic fibrosis, celiac disease, Crohn's disease, diabetes mellitus.

The diagnosis of SIBO requires high clinical suspicion followed by confirmatory testing.

1. Clinical Suspicion and History: Identify compatible symptoms and predisposing risk factors. Perform a complete physical examination.
2. Initial Laboratory Tests: Blood count (look for macrocytic or microcytic anemia), levels of vitamin B12, folate, iron, albumin and fat-soluble vitamins (A, D, E, K) to evaluate malabsorption.
3. Breath Tests (Expired Hydrogen and Methane Test):
   • They are the most used non-invasive tests.
   • Substrates: Glucose or Lactulose.
   • Interpretation (North American Consensus):
     • Hydrogen (H2): Increase ≥20 ppm over baseline in the first 90 minutes.
     • Methane (CH4): Level ≥10 ppm at any time.
     • Combined (H2+CH4): Increase ≥15 ppm over baseline in the first 90 minutes (for low methane).
4. Jejunal Aspirate Culture:
   • Considered the "gold standards" diagnosis.
   • It is an invasive procedure that requires endoscopy.
   • Positive diagnosis: >10³ - 10⁵ colony forming units (CFU)/mL.
   • Reserved for complex cases or when breath tests are inconclusive.

SIBO treatment is multifactorial and should focus on three main areas:

1. Treat the Underlying Cause: Whenever possible, the predisposing factor should be corrected (e.g. surgical correction of an anomaly, management of the underlying disease, review of PPI use).
2. Nutritional Therapy:
   • Correction of deficits: Supplement with iron, vitamin B12, and fat-soluble vitamins as needed.
   • Dietary management: Although evidence in children is limited, diets low in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) may be useful to control symptoms. Its implementation is recommended under the supervision of a dietitian-nutritionist. The elemental diet may be an option in refractory cases.
3. Antibiotic Therapy:
   • It is the mainstay of treatment to reduce the bacterial load.
   • Broad-spectrum antibiotics with little systemic absorption are chosen.
   • Treatment usually lasts between 7 and 14 days.
   • The choice of antibiotic may depend on the gas profile on the breath test (e.g. Rifaximin + Neomycin for methane-predominant SIBO).
   • Recurrences are common, and may require repeated or prokinetic cycles.