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SIBO: Diagnosis and Treatment

By December 27, 2018 December 28th, 2018 No Comments

Do you suffer from these symptoms on a regular basis: bloating, gas, abdominal pain, fatigue?  Have you tried everything to make it better?  Cut out cruciferous vegetables, implemented exercise, used medication?  If you feel like you’ve tried every intervention possible to reduce your uncomfortableness, but nothing seems to be helping, you may want to investigate a newer medical diagnosis called Small Intestinal Bacterial Overgrowth or SIBO. 

SIBO is defined as bacterial overgrowth in the small intestine.  The human intestinal microbiome is extremely complex with a high population and diversity of bacteria.  The duodenum and jejunum (parts of the small intestine) normally contain very small amounts of bacteria.  The last part of the small intestine, the ileum, is considered the transition zone between sparse populations of gut bacteria and the very large populations of gut bacteria found in the large intestine.   Any imbalance of these intestinal micro-organisms, both in quality and quantity, may result in serious health consequences, including SIBO. 

Some researchers suggest that SIBO is significantly underdiagnosed; however, the number of people with SIBO overall remains unknown.  This may be due to the disease still being poorly understood, but also because of the different diagnostic tests used.  Some studies suggest that between 6 to 15% of healthy, asymptomatic people have SIBO, while up to 80% of people with irritable bowel syndrome (IBS) suffer from SIBO.  Many individuals do not seek medical advice for their SIBO symptoms and consider their symptoms normal.  Another problem with diagnosis is that the most commonly used tests, breath tests that measure levels of hydrogen and methane gas, still have fairly high rates of false negative results. 

The most common symptoms of SIBO include:

  • Bloating and abdominal distention
  • Abdominal pain/discomfort
  • Gas and belching
  • Diarrhea
  • Weakness/fatigue

SIBO is also largely associated with other medical diagnoses, like IBS, Crohn’s, and celiac disease, because of the imbalance in gut bacteria these conditions may cause.  SIBO develops when the mechanisms that control intestinal bacteria populations are disrupted.  The two processes that most commonly influence bacterial overgrowth include decreased gastric acid secretion and small intestine dysmotility (when the muscles of the digestive tract do not work as they should).  In addition, disturbances in gut immune function and structural abnormalities of the GI tract (i.e. gastric bypass surgery) also increase the likelihood of developing SIBO.  Once present, bacterial overgrowth may cause an inflammatory response in the intestinal barrier, further exacerbating the typical symptoms of SIBO.

The diagnosis of SIBO is controversial and there is substantial disagreement in the literature regarding which diagnostic test is the most appropriate and accurate.  Two tests most commonly used include bacterial culture and breath tests.   The most direct method of assessing gut bacteria population is to perform colony counts in the small bowel.  However, there are several hurdles associated with this method, including invasiveness, cost, and risk of contamination of equipment.  The challenges of directly measuring small bowel bacteria led to the development of indirect tests, including breath testing; which is now considered the predominant method to evaluate patients for overgrowth.  These methods all rely on the modification of a substrate, like lactulose, glucose, or sucrose (all easily metabolized carbohydrates) by bacteria.  For example, Johns Hopkins uses a lactulose breath test and may diagnose SIBO if hydrogen or methane is present in your breath shortly after ingesting the lactulose solution. 

If you are diagnosed with SIBO, the immediate goals are to correct the underlying cause of the overgrowth, treat the overgrowth, and provide nutrition support as needed.   Treatment aimed at correcting the underlying cause of SIBO can include many interventions.  Treatment will be dietary if celiac disease is the cause or treatment may be surgical if there is a structural problem with the GI tract.  Medical treatment, like those that help to manage gastric reflux, may be helpful as well if the underlying issue is a mobility issue like gastroparesis.

Treating the overgrowth usually means using antibiotic therapy.  Antibiotics can reduce or eliminate the bacterial overload and reverse the mucosal inflammation associated with overgrowth and malabsorption.  However, some studies show that despite treatment with antibiotics, recurrence develops in almost half of patients in one year; which is likely due to a discrepancy in the duration and regimen needed. 

Nutrition support, particularly in those patients with weight loss or vitamin and mineral deficiencies, is an important part of SIBO treatment.  Supplementation and maintenance of vitamin B12 and fat-soluble vitamins (A, D, E, and K), with correction of calcium and magnesium deficiencies, are key components of treatment.  Attempts at treating SIBO with probiotics have shown mixed results.  A placebo-controlled trial of Lactobacillus showed an improvement in diarrhea and a reduction in hydrogen breath levels that was sustained for 21 days after completing treatment.  However, other trials have not shown such encouraging results; therefore, further studies are needed to define the role of probiotic therapy in SIBO. 

If you are experiencing SIBO symptoms on a regular basis, I encourage you to reach out to your physician and ask about diagnostic testing.  In addition, make sure to work with a trusted registered dietitian to correct any nutritional deficiencies! References:
Bures, J., Cyrany, J., Kohoutova, D., Förstl, M., Rejchrt, S., Kvetina, J., … & Kopacova, M. (2010). Small intestinal bacterial overgrowth syndrome. World journal of gastroenterology: WJG, 16(24), 2978.

Corazza, G. R., Menozzi, M. G., Strocchi, A., Rasciti, L., Vaira, D., Lecchini, R., … & Gasbarrini, G. (1990). The diagnosis of small bowel bacterial overgrowth: reliability of jejunal culture and inadequacy of breath hydrogen testing. Gastroenterology, 98(2), 302-309.

Dukowicz, A. C., Lacy, B. E., & Levine, G. M. (2007). Small intestinal bacterial overgrowth: a comprehensive review. Gastroenterology & hepatology, 3(2), 112-22.

Gaon, D. A. V. I. D., Garmendia, C. A. R. M. E. N., Murrielo, N. O., De Cucco Games, A., Cerchio, A. N. G. E. L., Quintas, R. I. C. A. R. D. O., … & Oliver, G. U. I. L. L. E. R. M. O. (2002). Effect of Lactobacillus strains (L. casei, L. acidophillus strains CERELA) on bacterial overgrowth-related chronic diarrhea. MEDICINA-BUENOS AIRES-, 62(2), 159-163.

Haboubi, N. Y., Lee, G. S., & Montgomery, R. D. (1991). Duodenal mucosal morphometry of elderly patients with small intestinal bacterial overgrowth: response to antibiotic treatment. Age and ageing, 20(1), 29-32.

Lauritano, E. C., Gabrielli, M., Scarpellini, E., Lupascu, A., Novi, M., Sottili, S., … & Gasbarrini, G. (2008). Small intestinal bacterial overgrowth recurrence after antibiotic therapy. The American journal of gastroenterology, 103(8), 2031.

Romagnuolo, J., Schiller, D., & Bailey, R. J. (2002). Using breath tests wisely in a gastroenterology practice: an evidence-based review of indications and pitfalls in interpretation. The American journal of gastroenterology, 97(5), 1113-1126.

Stotzer, P. O., Blomberg, L., Conway, P. L., Henriksson, A., & Abrahamsson, H. (1996). Probiotic treatment of small intestinal bacterial overgrowth by Lactobacillus fermentum KLD. Scandinavian journal of infectious diseases, 28(6), 615-619.

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