Bacterial overgrowth

Classification

Bacterial overgrowth, also known as small intestinal bacterial overgrowth (SIBO), is a condition characterized by an abnormal increase in the number of bacteria in the small intestine. This can lead to various gastrointestinal symptoms and malabsorption of nutrients.

Pathophysiology

The small intestine normally contains fewer bacteria compared to the large intestine. In bacterial overgrowth, the balance is disrupted, leading to excessive bacterial colonization. This can result from several factors, including:

• Impaired motility of the small intestine, which can occur in conditions such as diabetes mellitus and scleroderma.
• Anatomical abnormalities, such as strictures or diverticula.
• Reduced gastric acid secretion, which can occur with the use of proton pump inhibitors.

The overgrowth of bacteria can interfere with digestion and absorption by:

• Deconjugating bile acids, leading to fat malabsorption.
• Consuming nutrients, leading to deficiencies.
• Producing gases and other byproducts that cause symptoms.

Symptoms

Common symptoms of bacterial overgrowth include:

• Bloating and abdominal distension
• Diarrhea or steatorrhea (fatty stools)
• Abdominal pain or discomfort
• Malnutrition and weight loss
• Fatigue

Diagnosis

Diagnosis of bacterial overgrowth can be challenging. Common diagnostic methods include:

• Hydrogen breath test: Measures hydrogen and methane in the breath after ingestion of a sugar solution.
• Small bowel aspirate and culture: Considered the gold standard but is invasive.
• Clinical response to treatment: Sometimes used as a diagnostic tool.

Treatment

Treatment of bacterial overgrowth typically involves:

• Antibiotics: Such as rifaximin or metronidazole to reduce bacterial load.
• Dietary modifications: Low FODMAP diet or specific carbohydrate diet to reduce symptoms.
• Addressing underlying conditions: Such as improving motility or correcting anatomical issues.

Prognosis

With appropriate treatment, symptoms of bacterial overgrowth can be managed effectively. However, recurrence is common, especially if underlying conditions are not addressed.

Also see

• Irritable bowel syndrome
• Lactose intolerance
• Celiac disease
• Gastroesophageal reflux disease