Bacterial Overgrowth Syndrome


Bacterial overgrowth syndrome which is also abbreviated as BOS, is a term that is used in describing clinical materializations that occur when the usually small amount of bacteria living in the proximal ileum, duodenum, jejunum, and stomach crucially increase or surpassed by other pathogens. (Compare with Afferent Loop Syndrome)

bacterial overgrowth syndrome

There was once a time that the upper intestinal tract was thought to be an environment free from bacteria, but low levels of numerous bacteria are now believed to be present within its surface. These microorganisms are presumed to exist from time of birth to adulthood, with a close relationship with the human host.

The formed relationship is thought to be important for immunity preservation, digestive processes, and intestinal development. Bacterial varieties that may be present are oral streptococci, enterococci, lactobacilli and other anaerobes that are gram-positive.

Symptoms of Bacterial Overgrowth Syndrome

The most common symptoms that occur in Bacterial Overgrowth Syndrome are:

Symptoms of advanced BOS can possibly develop into malabsorption findings and these are:

  • Inflammation of the skin
  • Night blindness
  • Atrophy or the wasting away of cells
  • Excess fat in feces
  • Rosacea which is a skin condition that can cause redness in the face will red bumps
  • Involuntary contraction of muscles


Structural disorders or defects interrupt the mechanisms that protect and shield against bacteria which may result to bacterial overgrowth syndrome. Widespread presence of BOS increases with age.

Unusual movements of the small intestine caused by the following conditions could lead to BOS and these are:

  • Hypothyroidism
  • Scleroderma
  • Inflammatory bowel disease
  • Amyloidosis disorder
  • Diabetic autonomic neuropathy
  • Intestinal pseudo-obstruction


The physician will first evaluate the symptoms of bacterial overgrowth syndrome. Other possible diagnostic methods that may be performed by the physician are:

  • Endoscopy – The physician uses an endoscope and inserts it into the small intestine in order to get some fluid sample.
  • Stool culture – The fluid is cultured by the physician to determine the amount of bacteria present.
  • 14C-xylose breath test – A person gulps down a liquid that contains a special radioactive marker which is carbon-14 which is attached to a sugar called xylose. If the xylose is broken down by the bacteria, carbon-14 could be noticed in the person’s breath.
  • Upper Gastrointestinal (GI) series – The purpose of this examination is to identify abnormalities in the internal structures by taking X-rays of the small intestines and stomach after the patient drinks a liquid dye.


Treatments in bacterial overgrowth syndrome should involve the correction of the underlying disease that is present if there is any.

Treatment options include:

Antibiotic Therapy – Almost all individuals get better with antibiotics taken orally for 10 to 14 days. Antibiotics are powerful medications that can fight bacterial infections in the body.

Nutritional Support – This is a type of therapy for those who cannot sustain enough nourishment by drinking or eating. The support is received through a catheter or needed that is placed in the vein or with a feeding tube directed to the stomach. Since the excess bacteria grow much faster than carbohydrates, individuals with BOS must eat a diet high in fat and lower in fiber and carbohydrates. Physicians prescribe certain supplements to correct the patient’s nutritional deficiencies.

ICD 9 Code of BOS

The 2012 ICD-9-CM diagnosis code 579.8 is applicable for Bacterial Overgrowth Syndrome. This is a billable medical code that is used for the purpose of indicating a diagnosis on reimbursement claims with service date issued on or before September 30, 2015. The ICD-10-CM Code that has to be used for claims dated on or after October 1, 2015 is 2015/16 ICD-10-CM K90.89.


  4. Bures J, Cyrany J, Kohoutova D, et al (2010 Jun 28). Small intestinal bacterial overgrowth syndrome. World J Gastroenterol. 16(24):2978-90.
  5. Quigley EM, Abu-Shanab A (2010 Dec. 24). Small intestinal bacterial overgrowth. Infect Dis Clin North Am. (4):943-59, viii-ix.
  6. Rubio-Tapia A, Barton SH, Rosenblatt JE, Murray JA (2009 Feb). Prevalence of small intestine bacterial overgrowth diagnosed by quantitative culture of intestinal aspirate in celiac disease. J Clin Gastroenterol. 43(2):157-61.

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