Talking About Small Intestinal Bacterial Overgrowth: SIBO

SIBO: Often Overlooked

I have been in GI nursing for about 28 years and although it’s not a newly discovered diagnosis, I have not heard of Small Intestinal Bacterial Overgrowth. SIBO has similar characteristics as some other GI issues and may get overlooked as a possibility, which may explain why it isn’t a common diagnosis.

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  • Gastrointestinal Columnist
    Specializes in Gastrointestinal Nursing. Has 31 years experience.
SIBO: Often Overlooked

So many things can happen to our bodies when the bacteria levels are interrupted. Our bodies are protected by what we call good bacteria, but when there is an overgrowth or severe decrease, things get tricky. This is what happens in the patient diagnosed with SIBO. The small intestine's job is to absorb the nutrients from the food that we eat. The 1000+ types of gut bacteria help provide nutrients to our bodies as well as aid in the absorption of potassium, digesting cellulose, etc.2.

Small Intestinal Bacterial Overgrowth is a condition that can develop after surgery,  such as after a gastric bypass or gastrectomy for cancer or ulcers 1. There are other causes of SIBO, like intestinal adhesions, celiac disease, Crohn's disease, radiation, fistulas, diabetes, etc1. SIBO is the existence of too many bacteria in the small bowel1. This overabundance of different kinds of bacteria can lead to varying problems. For instance, bile salt is metabolized by a certain kind of bacteria. With too many of these types of bacteria, it leads to malabsorption of fat which would lead to bloating and other symptoms2. A patient that has  H pylori is also at risk for SIBO.


  • Chronic diarrhea
  • Unintentional weight loss
  • Osteoporosis
  • Nutritional deficiencies
  • Bloating
  • Abdominal distention
  • Excessive belching
  • Abdominal pain
  • Fatigue
  • Weakness
  • steatorrhea
  • Vitamin deficiency
  • Vitamin excess
  • hypoproteinemia/hypoalbuminemia
  • Complications

As previously mentioned, a patient can develop a decreased level of fat, carbohydrates, and protein absorption with SIBO. Malabsorption can also develop from harmful bacteria that attacks the mucosal lining of the small intestine1.  As a result of this, the patient can develop symptoms such as malnutrition, diarrhea, and weight loss 1

Another problem created by fat not being absorbed in the small bowel is the body's capacity to fully absorb the fat-soluble vitamins - D, E, A, & K1.  Another problem created by SIBO is the body's use of Vitamin B-12. Vitamin B-12 is manufactured in the small bowel and used for the nervous system and the production of blood cells1. When a patient has Vitamin B-12 deficiency, it causes neurological problems such as mental confusion, fatigue, and numbness in the hands and feet1. Neurological damage like this is not reversible. 

Osteoporosis can also be caused by SIBO due to the lack of calcium absorption1.  Because of the difficulty in diagnosing SIBO,  these patients can develop long-term issues. Testing isn't cut and dry, which leads to more controversy.

How SIBO is Diagnosed

There are two tests that are presently used to diagnose SIBO - the breath tests and bacterial culture1. Neither test is the gold standard, leading to disagreement among the professionals on which test is better. 

Anaerobic and aerobic colony counts 

This test requires direct collection of small bowel fluids. This makes testing difficult and expensive due to the fact that an EGD would need to be done to collect the fluids. And after the expense and risk of an EGD, the bacteria may not grow in the collection medium, plus contamination of the collected fluids can happen through contaminated scope and catheter. 

Breath Testing 

Breath testing is the more popular method for testing for SIBO. It is less expensive, safer and simpler. Gas chromatography measures "exhaled hydrogen and/or methane" 2

There is no good test for diagnosing SIBO, as was mentioned before. There are a lot of variabilities, and results may vary depending on the patient, time of test, and quality of the test. 


Treatment of SIBO includes treating the overgrowth of bacteria and the problems that have occurred because of SIBO such as nutritional issues 2. Patients are instructed to lose weight and take supplements to correct their deficits2. Diet restrictions can improve the patient's health, especially those who suffer from Celiac disease. Surgery is an option for those who have strictures and fistulas, while patients with gastroparesis or motility problems can be treated with medications. Antibiotics are the main treatment for SIBO because they decrease inflammation and bacteria in the small bowel.

Treatment for SIBO is very individualistic and patient-specific.  Testing isn't clear-cut, and symptoms are similar to other gastrointestinal diseases making it difficult to diagnose. Since the treatment with antibiotics is popular with some of the other colon diseases, SIBO may go undiagnosed. 


SIBO is very simply the overgrowth of bacteria in the small bowel. For the patient, it can mean many unfortunate symptoms such as diarrhea, gas, and bloating. Long term, SIBO can cause nutritional deficits, diet restrictions and possibly surgery. Although SIBO has been around, it is not easily identified and therefore may not be treated appropriately. Hopefully in the future, as more research is done, and testing has improved, it will improve the diagnosis and treatment for SIBO. 

Have you treated a patient with SIBO? What was the treatment, and did the patient improve?


1. (SIBO) Small Intestinal Bacterial Overgrowth

2. NIH Small Intestinal Bacteria Overgrowth

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