From the Guidelines
Small intestinal bacterial overgrowth (SIBO) typically manifests with a range of gastrointestinal symptoms including bloating, abdominal distension, abdominal pain, diarrhea, and flatulence, as well as systemic symptoms such as fatigue, malabsorption, and vitamin deficiencies 1.
Clinical Manifestations
The clinical manifestations of SIBO can vary depending on the extent of bacterial overgrowth, the specific bacterial species involved, and any underlying conditions that may have predisposed to SIBO.
- Gastrointestinal symptoms: bloating, abdominal distension, abdominal pain, diarrhea, and flatulence
- Systemic symptoms: fatigue, malabsorption, weight loss, and vitamin deficiencies (particularly B12, fat-soluble vitamins A, D, E, and K)
- Steatorrhea (fatty stools) can occur when fat absorption is impaired
- Food intolerances, especially to carbohydrates, as bacteria ferment these substances causing increased gas production and discomfort
Diagnosis and Treatment
Diagnosis is typically confirmed through breath testing (hydrogen or methane) or jejunal aspirate cultures, though clinical presentation plays a crucial role in suspecting this condition 1.
- Antibiotic therapy, such as metronidazole, amoxicillin-clavulanate, doxycycline, and norfloxacin, is often used to treat SIBO
- Non-absorbable antibiotics, such as rifaximin, may also be used
- Probiotics may be considered as an adjunctive therapy, although more research is needed to confirm their effectiveness
Management
The management of SIBO should prioritize the treatment of underlying conditions, such as intestinal motility disorders, anatomical abnormalities, or immunodeficiency states, in addition to antibiotic therapy 1.
- Antidiarrheal drugs, such as loperamide, may be used for symptomatic relief
- Bile salt sequestrants, such as cholestyramine, may be used to treat bile salt malabsorption
- Octreotide may be used to reduce secretions and slow gastrointestinal motility in refractory cases of SIBO.
From the Research
Clinical Manifestations of Small Intestinal Bacterial Overgrowth
- The clinical manifestations of small intestinal bacterial overgrowth (SIBO) can vary, but common symptoms include bloating, flatulence, abdominal distention, abdominal pain, and diarrhea 2, 3, 4.
- Severe cases of SIBO may present with nutritional deficiencies due to malabsorption of micro- and macronutrients 3.
- Abdominal bloating, gas, distension, and diarrhea are common symptoms, but they do not predict a positive diagnosis of SIBO 4.
- Predisposing factors for SIBO include proton-pump inhibitors, opioids, gastric bypass, colectomy, and dysmotility 4.
Diagnostic Criteria and Methods
- The current accepted criteria for the diagnosis of SIBO is the presence of coliform bacteria isolated from the proximal jejunum with >10^5 colony-forming units/mL 3.
- Diagnostic methods include small bowel aspirate/culture, glucose or lactulose breath testing, and rapid molecular sequencing 3, 4.
- Glucose or lactulose breath testing is noninvasive but an indirect method that requires further standardization and validation for SIBO 4.
Treatment Options
- Treatment of SIBO usually involves antibiotics, aiming to provide symptom relief through eradication of bacteria in the small intestine 4.
- Systemic antibiotics such as norfloxacin and metronidazole have been shown to be efficacious in limited numbers of controlled studies 4.
- Rifaximin, a nonsystemic antibiotic, has been shown to be effective against SIBO and well tolerated in 15 studies 4.
- High doses of rifaximin (1600 mg/day) have been shown to be more effective than lower doses (1200 mg/day) in treating SIBO, with a decontamination rate of 80% and low side-effects incidence 5.
- Rifaximin may be a highly effective therapy in providing symptom relief from the effects of SIBO, particularly for patients with hydrogen-positive SIBO 6.