Small bowel bacterial overgrowth syndrome (SBBOS) is a disorder characterised by excessive amounts of bacteria in the small bowel resulting in gastrointestinal symptoms.

Normal gut microbiome:

• The upper part of the small intestine is almost sterile, containing only a few organisms derived from the mouth.
• Gastric acid kills some ingested organisms and intestinal motility keeps bacterial counts in the jejunum low.
• The normal terminal ileum contains faecal-type organisms, mainly Escherichia coli and anaerobes, and the colon has abundant bacteria.

Aetiology

• bacterial overgrowth is normally found in association with a structural abnormality of the small intestine, such as a sticture or diverticulum

Risk factors for SBBOS:

• neonates with congenital gastrointestinal abnormalities
• scleroderma
• diabetes mellitus

PC

It should be noted that many of the features overlap with irritable bowel syndrome:

• chronic diarrhoea
• steatorrhoea - occurs because of conjugated bile salt deficiency
• bloating, flatulence
• abdominal pain