What are the symptoms of Small Intestinal Bacterial Overgrowth (SIBO)?

Symptoms of Small Intestinal Bacterial Overgrowth (SIBO)

Small Intestinal Bacterial Overgrowth (SIBO) primarily presents with malabsorption, abdominal discomfort, diarrhea, constipation, flatulence, and bloating. 1

Core Gastrointestinal Symptoms

SIBO manifests through a constellation of digestive symptoms that significantly impact quality of life:

• Abdominal discomfort/pain - Often occurring shortly after eating due to non-propulsive contractions in the small bowel 1
• Bloating - A hallmark symptom resulting from excessive fermentation and gas production 1
• Diarrhea - Common due to malabsorption and altered gut motility 1
• Constipation - May be the first symptom in some patients, especially those with underlying motility disorders 1
• Flatulence/excessive gas - Due to bacterial fermentation of unabsorbed nutrients 1
• Malabsorption - Leading to nutritional deficiencies and weight loss in severe cases 1

Additional Gastrointestinal Manifestations

• Steatorrhea (fatty stools) - Results from fat malabsorption due to bacterial deconjugation of bile salts 1
• Feeling of incomplete bowel emptying - Common in SIBO patients 1
• Abdominal distension - Physical swelling of the abdomen due to gas accumulation 1
• Rushing to have bowels open - Urgency can be a prominent symptom 1
• Nausea and vomiting - May occur in severe cases, especially with underlying motility disorders 1

Systemic Manifestations

In more advanced or severe cases, SIBO can lead to systemic symptoms due to malabsorption and metabolic disturbances:

• Weight loss - Due to chronic malabsorption of nutrients 1
• Fatigue - Often related to nutritional deficiencies 2
• Vitamin deficiencies - Particularly fat-soluble vitamins (A, D, E) and B12 1
• Symptoms of specific nutrient deficiencies - Such as night blindness, poor color vision, dry flaky skin (vitamin A deficiency) or ataxia (vitamin E deficiency) 1
• D-lactic acidosis - In rare cases, bacteria can produce D-lactic acid leading to neurological symptoms 1

Clinical Patterns in Different Populations

SIBO symptoms may vary based on underlying conditions:

• In chronic pancreatitis patients - SIBO occurs in up to 92% of those with pancreatic exocrine insufficiency, often confusing the clinical picture 1
• In inflammatory bowel disease - SIBO is common (up to 30% in Crohn's disease) and may exacerbate underlying symptoms 1
• In patients with motility disorders - Symptoms of gut stasis like abdominal distension and large volume vomiting may predominate 1

Important Clinical Considerations

• Symptoms of SIBO often overlap with other functional gastrointestinal disorders, particularly irritable bowel syndrome, making diagnosis challenging 2, 3
• The severity of symptoms generally correlates with the degree of bacterial overgrowth and the specific bacterial composition 4
• Symptoms may worsen after meals, particularly those high in fermentable carbohydrates 4, 3
• SIBO should be considered in patients with unexplained persistent gastrointestinal symptoms, especially those with risk factors such as prior surgery, diabetes, or PEI 1

Understanding this symptom profile is crucial for early recognition and appropriate management of SIBO, as prompt treatment can significantly improve quality of life and prevent complications related to chronic malabsorption.