Bacterial Overgrowth Test

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Mount Sinai Hospital, New York

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What Is the Bacterial Overgrowth Test?

If your doctor suspects you have a gastrointestinal known as small intestinal bacterial overgrowth (SIBO), they may order one of several tests to look for bacterial overgrowth. A common and non-invasive one available at doctors’s offices or commercial laboratories is a breath test. Another one is a small intestinal aspirate and fluid culture.

What Is Small Intestinal Bacterial Overgrowth?

SIBO is an abnormal rise of bacteria in the small intestine. SIBO can be problematic because the bacterial overgrowth can consist of bacteria either not usually found in the gastrointestinal tract or in higher amounts than usual. SIBO typically has an obvious catalyst and can develop after certain types of stomach or intestinal surgery where a part of the small intestine is “bypassed”. Thus, the usual flow of digestive matter does not pass through the “bypassed” part of small intestine. This becomes a breeding ground for bacteria since it is not being expelled quickly enough and may cause noticeable symptoms. 

Symptoms of SIBO and When to See a Doctor

Because SIBO slows the digestive process, patients often have noticeable symptoms. Symptoms of SIBO can include:

  • Unintentional weight loss
  • Loss of appetite
  • Diarrhea
  • Nausea
  • Bloating 
  • Abdominal Pain
  • Malnutrition

The heightened levels of bacteria can adversely impact the digestive process and lead to chronic diarrhea, which rids your body of the vitamins and minerals it needs. This can cause malnutrition and unintentional weight loss. Be sure to see your gastroenterologist as soon as possible if your presenting symptoms are persistent diarrhea (lasts for more than a week), your weight loss is excessively rapid, or you have unusual abdominal pain that lasts more than several days. 

Am I At Risk for SIBO?

SIBO typically has an obvious catalyst. In many cases, it is caused by complications after having stomach surgery. Small intestine structural problems can also cause the condition, and some medical problems can cause bacterial overgrowth. Disorders include Crohn’s disease, scleroderma, celiac disease, diabetes, and radiation enteritis. It can also be caused by diverticulosis.

How Is SIBO Diagnosed?

After you schedule a visit with your gastroenterologist, they will ask you questions about your symptoms and medical history. After a physical exam, if your doctor suspects you may have SIBO, they will order one of two tests: a breath test or a small intestine aspirate and fluid culture. These are the two types of bacterial overgrowth tests. 

What Is a Small Intestine Aspirate and Fluid Culture?

The gold standard of bacterial overgrowth testing is the small intestine aspirate and fluid culture, because it is the most specific and definitive test. In order to obtain a sample of your small intestine’s fluid, your doctor will need to perform a procedure known as esophagogastroduodenoscopy (EGD). The procedure uses an endoscope and is very similar to an endoscopy. 

What Happens During an EGD Procedure?

First, you will receive intravenous anesthesia. This is an outpatient procedure, but it is an invasive test, so you shouldn’t remember or feel pain during the test. EGD uses an endoscope, which is a thin tube with a small camera inserted through the throat to examine the esophagus, stomach, and top of the small intestine. Because sometimes patients can have a gag reflex because of the scope, a mouth guard is used, and sometimes local anesthetic may be used in the mouth. 

The endoscope is inserted until it reaches the duodenum, the top of the small intestine. The biopsy can be taken through the scope. The entire procedure only takes about 10 to 20 minutes, with recovery time afterward because of the anesthesia. After being discharged home, you can return to regular activities, sometimes as soon as the next day. The sample is then sent to the lab for review. If bacteria are present, then a diagnosis of SIBO is given. 

What Is Breath Testing?

Breath testing is a less invasive bacterial overgrowth test. This test is a good alternative given its ease of use when compared to an EGD, which is more invasive and requires anesthesia . During a breath test for bacterial overgrowth, you drink a solution and breathe into a special breathalyzer. If you do have bacterial overgrowth, it will show in the results and confirm a diagnosis of SIBO. 

How Do I Prepare for Breath Testing?

While breath testing is noninvasive, your doctor will have some instructions to follow. You aren’t allowed to take any laxatives a week before the test. About 24 hours before your test, your physician will give you a special diet to follow. Around 12 hours before the test, you are expected to fast. Medications can be taken up to six hours before the test but only with water. You are not allowed to smoke at least an hour before the procedure. 

What Are the Treatments for SIBO?

As SIBO is a bacterial issue, antibiotics are the most common treatment for bacterial overgrowth. Antibiotics are typically used in the short term to treat bacterial infections and other issues, but a patient with SIBO may have to take antibiotics for the long term to prevent the regrowth of bacteria. As a result, your doctor may rotate through different antibiotics in order to minimize resistance to them. However, every case is different, and some only need a short-term course of antibiotics. Your doctor may also advise that you take certain vitamins and supplements, such as B12 and may suggest a lactose-free diet.