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small intestinal bacterial overgrowth
Etiology:
1) blind loop syndrome
a) gastrectomy
b) Roux-en-Y gastric bypass
c) afferent loop dysfunction post-gastrojejunostomy
2) hypochlorhydria
a) post-operative
b) atrophic gastritis, pernicious anemia
- vitamin B12 deficiency
c) antacids
1] proton pump inhibitors
2] H2-receptor antagonists
d) vagotomy
3) structural defects
a) diverticulosis of the small intestine
b) persistent small intestine dilation due to distal small intestine stricture
- Crohn's disease
- NSAIDs
- postoperative complication
c) radiation enteropathy
4) intestinal dysmotility syndromes
a) diabetes mellitus
b) scleroderma
c) intestinal pseudo-obstruction
d) autonomic neuropathy
e) amyloidosis
f) systemic myopathies
5) short bowel syndrome
6) surgical resection of ileocecal valve
7) advanced age
8) immunodeficiency
a) IgA deficiency
b) common variable immunodeficiency
9) celiac disease
10) pancreatic insufficiency
11) biliary obstruction
11) cirrhosis [1]
Clinical manifestations:
- diarrhea
- bloating
- flatulence
- weight loss
Laboratory:
- hydrogen breath test
- 14C cholylglycine breath test
- serum vitamin B12 (vitamin B12 deficiency)
- serum folate is increased
Differential diagnosis:
- celiac disease
- serum vitamin B12 & serum folate low
- lactose intolerance
- not associated with macrocytosis, a high serum folate & low serum vitamin B12
- pancreatic insufficiency
- unless severe, unlikely to diminish vitamin B12 absorption
- not comment regarding effect on serum folate [3]
Management:
- rifaximin 1st line
- trial of empiric antibiotics
- Bactrim DS, tetracycline, metronidazole
- ciprofloxacin, amoxicillin clavulanate
Related
blind loop syndrome; stagnant loop syndrome; stasis syndrome
intestinal bacteria (flora)
Specific
bacterial overgrowth syndrome
General
intestinal disease
References
- Medical Knowledge Self Assessment Program (MKSAP) 14, 16, 17, 18, 19.
American College of Physicians, Philadelphia 2006, 2012, 2015, 2018, 2021.
- Bures J, Cyrany J, Kohoutova D, Forstl M et al
Small intestinal bacterial overgrowth syndrome.
World J Gastroenterol. 2010 Jun 28;16(24):2978-90.
PMID: 20572300
- NEJM Knowledge+ Gastroenterology
- Pimentel M, Saad RJ, Long MD, Rao SSC.
ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth.
Am J Gastroenterol. 2020 Feb;115(2):165-178.
PMID: 32023228