Small Intestinal Bacterial Overgrowth (SIBO)

The normal steady movement of intestinal contents (peristalsis) is important to help maintain a proper balance of bacteria in the small intestine. Conditions in which intestinal contents slow or pool in one place allow excess bacteria to grow. Such conditions include certain types of surgery on the stomach, intestines, or both. Disorders such as diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more , systemic sclerosis Systemic Sclerosis Systemic sclerosis is a rare, chronic autoimmune connective tissue disorder characterized by degenerative changes and scarring in the skin, joints, and internal organs and by blood vessel abnormalities... read more , and amyloidosis Amyloidosis Amyloidosis is a rare disease in which abnormally folded proteins form into collections called amyloid fibrils that accumulate in various tissues and organs, sometimes leading to organ dysfunction... read more also can slow peristalsis, causing bacterial overgrowth.

The excess bacteria consume nutrients, including carbohydrates and vitamin B12, leading to lower calorie intake and vitamin B12 deficiency Vitamin B12 Deficiency Vitamin B12 deficiency can occur in vegans who do not take supplements or as a result of an absorption disorder. Anemia develops, causing paleness, weakness, fatigue, and, if severe, shortness... read more . The bacteria also split bile salts, which are secreted by the liver to aid digestion (see Gallbladder and Biliary Tract Gallbladder and Biliary Tract The gallbladder is a small, pear-shaped, muscular storage sac that holds bile and is interconnected to the liver by ducts known as the biliary tract. (See also Overview of the Liver and Gallbladder... read more ). The loss of bile salts causes difficulty absorbing fats, leading to diarrhea and poor nutrition.

The most common symptom of small intestinal bacterial overgrowth is bloating.

Other symptoms are abdominal discomfort, diarrhea Diarrhea in Adults Diarrhea is an increase in the volume, wateriness, or frequency of bowel movements. (See also Diarrhea in Children.) The frequency of bowel movements alone is not the defining feature of diarrhea... read more , excess flatulence, weight loss, or symptoms of nutritional deficiencies. Some people have severe diarrhea or steatorrhea (light-colored, soft, bulky, greasy, and unusually foul-smelling stool).

Doctors base the diagnosis of small intestinal bacterial overgrowth on typical symptoms, particularly in people who have had certain types of surgery or have certain disorders.

Doctors may take a fluid sample from a flexible tube inserted into the small intestine in a procedure called endoscopy Endoscopy Endoscopy is an examination of internal structures using a flexible viewing tube (endoscope). In addition to examinations, doctors can use endoscopy to do biopsies and give treatment. Endoscopes... read more . Doctors culture the fluid to determine the type and amount of bacteria present.

Or doctors may do a breath test. When bacteria in the intestines break down certain sugars, hydrogen and methane are produced. Doctors do a breath test to help them determine how much hydrogen or methane a person exhales through breathing. After drinking a liquid containing a certain sugar (glucose or lactulose) mixed with water, a person exhales into a collection bag at 1-hour intervals over a period of 4 hours. The bags are then analyzed. If the amount of hydrogen or methane in the breath rises significantly after consuming either of the liquids, the person has small intestinal bacterial overgrowth.

Sometimes people have abnormalities of their internal structures that make them susceptible to bacterial overgrowth. To identify these abnormalities, doctors take x-rays of the stomach and small intestines after a person drinks a liquid that shows up on x-rays (called an upper gastrointestinal [GI] series).

Most people get better with antibiotics given by mouth for 10 to 14 days.

Because the excess bacteria grow faster with carbohydrates, people should eat a diet higher in fat and lower in carbohydrates and fiber.

Doctors prescribe supplements to correct any nutritional deficiencies.