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SIBO is the acronym for a disease called small intestinal bacterial overgrowth. [1-3] It is hard to know how common SIBO is. It causes digestive symptoms that are very common like belly, pain, bloating, and bowel changes. Many cases of SIBO may be missed because the diagnosis requires special testing.  It is important to know about SIBO, so you can let your doctor know if you have the signs and symptoms. Untreated SIBO can lead to serious problems from malnutrition. [1-3]
What Causes SIBO?
SIBO is caused by an abnormal growth of bacteria in your small intestine. Your small intestine is the first 20 feet of your digestive system after your stomach. Foods that you eat normally move quickly through this part of your digestive tract as they are digested and absorbed. 
Unlike the last part of your digestive tract – your colon – there is not much bacteria in your small intestine. However, if you have a condition that slows down movement through your small intestine, bacteria can have a chance to multiply. Slow-moving food and drink can be a breeding ground for bacteria. [1-3]
Some people are at higher risk for slowed digestion in the small intestine. You could be at higher risk for SIBO if: [1-3]
- You had surgery on your stomach or small intestine, such as a bypass procedure or ulcer surgery
- You had radiation therapy to your belly for cancer
- You have a disease like irritable bowel syndrome, inflammatory bowel disease, scleroderma, celiac disease, or diabetes
- You take a medication that slows down digestion like a muscle relaxant, narcotic, or acid blocker
What Are the Symptoms?
Symptoms of SIBO can seem like a stomach flu at first but they don’t go away. They can include: [1-3]
- Belly pain or bloating
- Loss of appetite and feeling full soon after starting to eat
- Nausea or vomiting
- Diarrhea or constipation
- Weight loss
Over time SIBO can cause malnutrition because you are not absorbing enough nutrients from your small intestine. These includes fats, carbohydrates, and proteins. It can also include important vitamins like A, D, E, K, and vitamin B12. You may also develop lactose intolerance. Complications of malnutrition can include nerve damage, osteoporosis, anemia, and kidney stones. [1-3]
How Is SIBO Diagnosed?
If your doctor suspects SIBO, the best way to diagnose the condition is to put a tube down into your small intestine to take a sample of your intestinal fluid and check for bacteria. Another test is a breath test. Bacteria produce a gas called methane that can be measured by a breath test. Your doctor may also do an imaging study to look for a blocked intestine and do a blood test to look for vitamin deficiencies. [1-3]
How Is SIBO Treated?
Treatment of SIBO depends on the cause, but for most people, treatment will include taking an antibiotic. In some cases, people who have a blocked intestine due to surgery or scar tissue may need surgery to restore flow through the intestine. [1-3]
People who have recurrent SIBO, long-term SIBO due to a disease, or who have developed malnutrition, may be treated with diet therapy. [1-3] These diets are hard to do on your own, and should be managed by a diet care provider. Examples include the FODMAP diet and a predigested elemental diet. Some people may benefit from probiotics. Diet treatments are controversial and not all studies agree that they are helpful. 
When to Call Your Doctor
In most cases, once SIBO is diagnosed, the right treatment will help. Let your doctor know if you have symptoms of SIBO that are not going away, especially if you had any abdominal surgery, or have any of the other risk factors. Let your doctor know if you have loss of appetite or unwanted weight loss. Get medical attention right away if you have severe abdominal pain. 
- Mayo Clinic, Small intestinal bacterial overgrowth (SIBO), https://www.mayoclinic.org/diseases-conditions/small-intestinal-bacterial-overgrowth/diagnosis-treatment/drc-20370172
- Johns Hopkins Medicine, Small Intestinal Bacterial Overgrowth (SIBO), https://www.hopkinsmedicine.org/gastroenterology_hepatology/diseases_conditions/small_large_intestine/small-intestinal-bacterial-overgrowth.html
- Clinical and Translational Gastroenterology, Small Intestinal Bacterial Overgrowth: Clinical Features and Therapeutic Management, https://journals.lww.com/ctg/Fulltext/2019/10000/Small_Intestinal_Bacterial_Overgrowth__Clinical.2.aspx