Many
patients with bloating, abdominal pain, constipation, or diarrhea are diagnosed
with irritable bowel syndrome and never get adequate responses to treatment.
Others are given no diagnosis at all for their suffering, which leads to even
less chance of recovery. Our experience is that many of these perplexing
patients have commensal microbial overgrowth. This article details the complex
issue of small intestine bacterial overgrowth (SIBO)
SIBO is a condition in which abnormally large numbers of
commensal bacteria (or other microorganisms) are present in the small
intestine. SIBO is a common cause of IBS – in fact it is involved in over half
the cases of IBS and as high as 84% in one study using breath testing as the
diagnostic marker.2 It accounts for 37% of cases when endoscopic cultures of
aerobic bacteria are used for diagnosis.3 Eradication of this overgrowth leads
to a 75% reduction in IBS symptoms.4Either bacterial overgrowth or the
overgrowth of methanogenic archaea leads to impairment of digestion and
absorption and produces excess quantities of hydrogen, hydrogen sulfide, or
methane gas. Hydrogen and methane are not produced by human cells but are the
metabolic products of fermentation of carbohydrates by intestinal organisms.
When commensals (oral, small intestine, or large intestine flora) multiply in
the small intestine to excessive numbers, IBS is likely. Hydrogen/methane
breath testing is the most widely used diagnostic method for this condition.
Stool analysis has no value in diagnosing SIBO.
Symptoms of SIBO include:
- bloating/abdominal gas
- flatulence, belching
- abdominal pain, discomfort, or cramps
- constipation, diarrhea, or a mixture of the two
- heartburn
- nausea
- malabsorption: steatorrhea; iron, vitamin D, vitamin K, or B12 deficiency with or without anemia; and osteoporosis5
- systemic symptoms: headache, fatigue, joint/muscle pain, and certain dermatology conditions
Other diseases associated with SIBO include hypothyroidism,
lactose intolerance, gallstones, Crohn's disease, systemic sclerosis, celiac
disease, chronic pancreatitis, diverticulitis, diabetes with autonomic
neuropathy, fibromyalgia and chronic regional pain syndrome, hepatic
encephalopathy, non-alcoholic steatohepatitis, interstitial cystitis, restless
leg syndrome, acne rosacea, and erosive esophagitis.6–21 Based on clinical
experience, we suspect that biliary dyskinesia and lymphocytic colitis may also
be associated with SIBO.
In our practices we have found that the following indicators
increase the chances that a patient's IBS is caused by SIBO:
- when a patient develops IBS following a bout of acute gastroenteritis (postinfectious IBS);
- when a patient reports dramatic transient improvement in IBS symptoms after antibiotic treatment;
- when a patient reports worsening of IBS symptoms from ingesting probiotic supplements that also contain prebiotics;
- when a patient reports that eating more fiber increases constipation and other IBS symptoms;
- when a celiac patient reports insufficient improvement in digestive symptoms even when carefully following a gluten-free diet;
- when a patient develops constipation type IBS (IBS-C) after taking opiates;
- when a patient has a chronic low ferritin level with no other apparent cause;
- when abdominal imaging reveals a large gas accumulation obscuring the pancreas
- when small bowel follow-through imaging reveals areas of "flocculation."22