Crohn's Disease Forum » Forum Wiki » Small Intestine Bacterial Overgrowth (SIBO)

Small Intestine Bacterial Overgrowth (SIBO)


Small Intestine Bacterial Overgrowth (SIBO)

Small Intestine Bacterial Overgrowth (SIBO), sometimes called Small Bowel Intestinal Overgrowth (SBBO) is a potential cause of malabsorption and a myriad of other gastrointestinal symptoms when foods, medications, and supplements interact with and feed pathogenic bacteria resulting in their overgrowth, subsequent competition with beneficial bacteria, and damage to the intestines [1]

While it is beneficial to have some commensal (the good guys) bacteria present in the intestines, when specific bacteria are present in the intestines in a location they normally are not at a "colony count" in excess of 103 cfu/mL, then SIBO symptoms may develop though it isn't known if the quantity or specific type of bacteria is the more important variable.


  • Inflammation of the intestines
  • Blunting of villi
  • Gas
  • Bloating
  • Abdominal Cramping
  • Diarrhea due to hydroxylated fatty acids and deconjugated bile acids.
  • Steatorrhea (excess fat in the stool)
  • Deficiencies of fat soluble vitamins A, D, E due to fat malabsorption (vitamin K deficiency is rarely seen) and their associated symptoms
  • Oxalate kidney stones due to fat malabsorption
  • Vitamin B1, Vitamin B12, nicotinamide (vitamin B3/niacin), and iron deficiencies and their associated symptoms
  • Rosacea[4]


Small Intestine Bacterial Overgrowth is common in Crohn's Disease.[2] This is in part due to strictures, fistulas, and reduced intestinal motility and as such, the diarrhea present in Crohn's Disease may be in part caused by the SIBO in conjunction with the normal causes of resection, bile salt deficiency due to disease in the terminal ileum, and toxic affects of bile salts on the colon.

SIBO does not appear to commonly coincide with Ulcerative Colitis.[1].

SIBO can lead to vitamin B12 deficiency as the bacteria bind and utilize the B12 for their own use.[3]


It can often be difficult to diagnose SIBO as many of its symptoms appear as symptoms of other diseases or it manifests at the same time as other diseases. While there are tests that are conducted such as the Hydrogen Breath Test, the "gold standard" is a culture of aspirated intestinal fluid taken during endoscopy.[1]

Endoscopic Culture

While considered the gold standard, it is imperfect as well. It is expensive, invasive, possibly contaminated, cannot reach potential SIBO in the distal small intestine, and it is estimated that over 50% of intestinal microbes cannot be cultured anyway.

Other Causes


• Enteroenteric fistulae
• Small bowel diverticula
• Surgically-created blind loops
• Intestinal strictures
• Resection of the ileocecal valve (?)


• Intestinal dysmotility syndromes
• Absence or Reduction of stomach acid - Achlorhydria / Hypochlorhydria
• Inflammatory conditions
• Autonomic neuropathy
• Reduction of gut-associated lymphoid tissue


• Antisecretory and antimotility medications
• Immunodeficiency states
• Cirrhosis
• Radiation enteritis
• Diabetes mellitus
• Chronic pancreatitis
• Short bowel syndrome
• End stage renal disease
• Advanced age


Treatment with a Broad Spectrum Antibiotic is usually effective however it often has to be repeated at regular intervals. Diets such as the Specific Carbohydrate Diet and Low FODMAP Diet attempt to starve the pathogenic bacteria to their nutrients.

Types of Bacteria

There are a variety of types of pathogenic bacteria that can cause problems associated with SIBO such as facultative anaerobes and aerobes. However, anaerobic bacteria are thought to be the main culprits and in their present, normal absorption of vitamin B12 may be compromised.[1]


Popular Threads Discussing Small Intestine Bacterial Overgrowth (SIBO)

Page Tools
No one has commented on this article.

Page Tools
Search this Page

All times are GMT -5. The time now is 04:26 AM.
Copyright 2006-2017