Small Intestine Bacterial Overgrowth (SIBO) vs. Irritable Bowel Syndrome (IBS)

Author: Alexander Salerno, MD
December 23, 2019

There is usually a low quantity of bacteria present in our guts that helps the body with digestion. However, when this amount of bacteria becomes excessive within the small intestine, it is called small intestine bacterial overgrowth or SIBO. This is often caused by a digestive illness or anatomical abnormality, which further leads to malnutrition as the bacteria uses up the nutrients of the body.

Irritable bowel syndrome, often referred to as IBS or spastic colon, is a condition in which trouble with bowel habits is experienced, where either the kind of stool is different or the patient goes either more often or less than normal. And this is accompanied by abdominal pain or discomfort in the belly.

Recently, it has been suggested that SIBO can lead to IBS. Before examining the connection, it is best to understand the symptoms, diagnosis, and treatment for each of the diseases.

The symptoms of SIBO include abdominal pain, especially after consuming food, bloating, diarrhea, indigestion, constipation, cramps, gas, and a feeling of fullness. The cause of SIBO could be anatomic abnormalities in the small bowel, pH changes, small intestine muscular action malfunction, or malfunction of the immune system. Those suffering from chronic conditions, such as Crohn’s disease, hypothyroidism, Parkinson’s, diabetes, HIV, etc., or those who have undergone GI tract surgery, are also prone to SIBO. The diagnosis of SIBO is done via a physical examination of the abdomen and by a breath test since the excess bacteria release hydrogen and methane gases. A sample study of the small intestine is also done for further testing. Treatment of SIBO includes antibiotics, such as rifaximin, metronidazole, and ciprofloxacin, along with diet changes which include a balanced diet, smaller portions at frequent intervals, avoiding gluten if suffering from celiac disease, an elemental diet, or even including probiotics.

IBS is a chronic condition that needs to be managed over a longer period of time that affects the large intestine. The symptoms include excessive gas, abdominal bloating, cramps and pain (which is relieved after passing stool), constipation or diarrhea, and mucus in stools. It is a cause for concern when there is weight loss, rectal bleeding, unexplained vomiting, and diarrhea at night, difficulty in swallowing, anemia, and persistent pain. IBS can be caused by muscle contractions of the intestines being too strong or weak, inflammation in the intestine, abnormalities of the nervous system sending poorly coordinated signals to the intestine and muscles, infection or inflammation of the intestines, or also possibly changes in the gut bacteria. Stress, food, and hormones often act as triggers for IBS; women under 50 who have a family history of IBS or a mental health problem are at greater risk. To diagnose the disease, after the first basic checkup is done to rule out other diseases, tests such as colonoscopy, flexible sigmoidoscopy, CT scan or X-ray, upper endoscopy, breath test, and lactose intolerance test or stool test are carried out. As part of treatment, gluten-high, FODMAPS, and high gas food must be avoided.

Because the symptoms of both the diseases are similar, researchers have found that SIBO could be an underlying cause of IBS. Also, antibiotic treatment for SIBO worked for IBS as well, thus suggesting a connection between the two.

Dr. Alexander G. Salerno

About Alexander Salerno, MD

Salerno Medical Associates medical practice & founder of Urban Healthcare Initiative Program (UHIP) and Community Healthcare Outreach Program (CHOP)