Information on IBS, Irritable Bowel Syndrome and IBS Treatment - Dirk Budka
 
 
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SIBO/SBBO



What is small intestinal bacterial overgrowth (SIBO)?

The small bowel, also known as the small intestine, is the section of the gastrointestinal tract that connects the stomach with the colon. The main purpose of the small intestine is to digest and absorb food into the body. The small intestine is approximately 21 feet in length and begins in the duodenum (into which food from the stomach empties), followed by the jejunum, and then the ileum (which empties the food that has not been digested into the large intestine or colon).
The entire gastrointestinal tract, including the small intestine, normally contains bacteria. The number of bacteria is greatest in the colon (at least 1,000,000,000 bacteria per milliliter (ml) of fluid) and much lower in the small intestine (less than 10,000 bacteria per ml of fluid). Moreover, the types of bacteria within the small intestine are different than the types of bacteria within the colon. Small intestinal bacterial overgrowth (SIBO) refers to a condition in which abnormally large numbers of bacteria (at least 100,000 bacteria per ml of fluid) are present in the small intestine and the types of bacteria in the small intestine resemble more the bacteria of the colon than the small intestine.
Small intestinal bacterial overgrowth (SIBO) is also known as small bowel bacterial overgrowth (SBBO).

What causes small intestinal bacterial overgrowth?

The gastrointestinal tract is a continuous muscular tube through which digesting food is transported on its way to the colon. The coordinated activity of the muscles of the stomach and small intestine propels the food from the stomach, through the small intestine, and into the colon. Even when there is no food in the small intestine, muscular activity sweeps through the small intestine from the stomach to the colon.
The muscular activity that sweeps through the small intestine is important for the digestion of food, but it also is important because it sweeps bacteria out of the small intestine and thereby limits the numbers of bacteria in the small intestine. Anything that interferes with the progression of normal muscular activity through the small intestine can result in SIBO. Simply stated, any condition that interferes with muscular activity in the small intestine allows the bacteria to stay longer and multiply in the small intestine. The lack of muscular activity also may allow bacteria to spread backwards from the colon and into the small intestine.
Many conditions are associated with SIBO.
# Post Food Poisoning Syndrome (PFPS) is relatively common.
# Long-term viral infections can have an influence on the flora of the small intestines.
# Neurologic and muscular diseases can alter the normal activity of the intestinal muscles. Diabetes mellitus damages the nerves that control the intestinal muscles. Scleroderma damages the intestinal muscles directly. In both cases, abnormal muscular activity in the small intestine allows SIBO to develop.
# Partial or intermittent obstruction of the small intestine interferes with the transport of food and bacteria through the small intestine and can result in SIBO. Causes of obstruction leading to SIBO include adhesions (scarring) from previous surgery and Crohn’s disease.
# Diverticuli (out-pouchings) of the small intestine that allow bacteria to multiply inside diverticuli.

What are small intestinal bacteria overgrowth symptoms?

The symptoms of SIBO include:

# excess gas,
# abdominal bloating and distension,
# diarrhoea,
# abdominal pain.

Some patients with SIBO have chronic constipation rather than diarrhoea. When the overgrowth is severe and prolonged, the bacteria may interfere with the digestion and/or absorption of food and deficiencies of vitamins and minerals may develop. Weight loss also may occur. Patients with SIBO sometimes also report symptoms that are unrelated to the gastrointestinal tract, symptoms such as body aches or fatigue. The symptoms of SIBO tend to be chronic. A typical patient with SIBO can experience symptoms that fluctuate in intensity over months, years, or even decades before the diagnosis is made.

What is the normal relationship between bacteria and the small intestine?

At birth, there are no bacteria in the gastrointestinal tract. During birth, however, bacteria from the mother’s colon and vagina are swallowed by the infant, and, within a few weeks or months, they populate the infant’s gastrointestinal tract.
The relationship between normal intestinal bacteria and their human host is complex. The relationship is symbiotic, which means that each benefits from the other. The bacteria benefit from the warm, moist environment of the small intestine that is ideal for growing as well as the constant flow of food passing down the gastrointestinal tract. The human host benefits in several ways. For example, the normal bacteria stimulate the growth of the intestinal lining and the immune system of the intestine. They prevent the growth of disease-causing bacteria within the intestine. They produce vitamin K, which is absorbed and used by the host. In fact, the bacteria are important even for the muscular activity of the small intestine. Without bacteria, there is reduced muscular activity.
There is a delicate balance between the bacteria of the gastrointestinal tract and the human host. The gastrointestinal tract, particularly the small intestine, contains an extensive immune system. The immune system protects the intestine from disease-causing viruses, bacteria, and parasites. (The effects of the immune response have been experienced by anyone who has experienced gastroenteritis.) The interesting fact is that the intestine does not attack the normal bacteria within it, only disease-causing bacteria. Somehow, the intestine becomes tolerant of the normal bacteria and does not mount an attack against them. The intestine has other ways that may be important in protecting it from bacteria, both normal and disease-causing. As mentioned previously, muscular activity keeps the numbers of bacteria within the intestine at a low level. Mucus that is secreted into the intestine coats the intestinal lining and prevents the bacteria from touching the lining. The intestine secretes antibodies that can block, and sometimes kill, bacteria as well as substances that prevent the growth of bacteria. Finally, the lining of the intestine can produce receptors for toxic substances produced by bacteria and can prevent the substances from having their toxic effects.

What conditions cause increased production of gas?

There are three situations in which abnormally increased amounts of gas are produced in the colon.
1. Malabsorption of sugars and carbohydrates. Reduced digestion or absorption by the small intestine allows increased amounts of sugar and carbohydrate to reach the colon where greater amounts of gas are produced. The most common example of malabsorption leading to increased production of gas is lactose (milk) intolerance. Lactose intolerance is due to a genetic lack of the enzyme in the lining of the small intestine that digests lactose, the sugar in milk. Other causes of malabsorption that can lead to excessive production of gas include: (1) malabsorption of other sugars such as sucrose, sorbitol, or fructose; (2) diseases of the pancreas that cause inadequate amounts of pancreatic enzymes (that are necessary for digesting sugars and carbohydrates in the small intestine) to enter the small intestine; and (3) diseases of the lining of the small intestine (for example, celiac disease) that reduce the sugar and carbohydrate-digesting enzymes in the lining and reduce absorption of sugars and carbohydrates.
2. Rapid intestinal transit. Normal digestion and absorption of sugars and carbohydrates requires time. If food passes through the small intestine too rapidly, there is not enough time for digestion and absorption to be completed, and more sugar and carbohydrate reach the colon. The best example of rapid intestinal transit is among individuals who have had a large amount of their small intestine removed surgically. There are also a small number of individuals with intact small bowel who, for unexplained reasons, have abnormally rapid transit through the small intestine.
3. Small intestinal bacterial overgrowth (SIBO). In patients with SIBO, large numbers of gas-producing bacteria are present in the small intestine. The abundant bacteria in the small intestine compete with the small intestine for sugars and carbohydrates and produce large amounts of gas.

How does small intestinal bacterial overgrowth cause symptoms?
When bacteria digest food in the intestine, they produce gas. The gas can accumulate in the abdomen giving rise to abdominal bloating or distension. Distension can cause abdominal pain. The increased amounts of gas are passed as flatus (flatulence or farts). The bacteria also probably convert food into substances that are irritating or toxic to the cells of the inner lining of the small intestine and colon. These irritating substances produce diarrhea (by causing secretion of water into the intestine). There is some evidence that the production of one gas by the bacteria—methane—causes constipation.
Bacteria in the small intestine, when present in large numbers, can compete with the human host for the food that is eaten. This can lead to malnutrition with vitamin and mineral deficiencies. In advanced cases of SIBO, the bacteria use up enough food that there are insufficient calories for the host, thereby leading to weight loss.

How is small intestinal bacterial overgrowth diagnosed?
Hydrogen breath test procedure
For the hydrogen breath test, individuals fast for at least 12hours. At the start of the test, the individual ingests a small amount of the test sugar (usually lactulose or glucose). All samples of breath are analyzed for hydrogen and methane every 10 - 20 minutes. For more details and information about the msml-laboratories CLICK HERE.


There is a striking similarity between the symptoms of irritable bowel syndrome and SIBO. It has been theorized that SIBO may be responsible for the symptoms of at least some patients with irritable bowel syndrome. The estimates run as high as 50% of patients with irritable bowel syndrome. Support for the SIBO theory of IBS comes from the observation that many patients with irritable bowel syndrome are found to have an abnormal hydrogen breath test, and some patients with irritable bowel syndrome have improvement of their symptoms after treatment with antibiotics, the primary treatment for SIBO. Furthermore, it has been reported that successful treatment of symptoms with antibiotics causes the hydrogen breath test to revert to normal, suggesting that bacteria indeed are causing the symptoms. Although this theory is tantalizing and there is much anecdotal information that supports it, the rigorous scientific studies that are necessary to prove the theory have just begun. Nevertheless, many physicians have already begun to treat patients with irritable bowel syndrome for SIBO. The intriguing issue yet to be elucidated is the reason why individuals who appear normal develop SIBO and IBS. The most popular theory is that patients with irritable bowel syndrome have a subtle abnormality in the function of their intestinal muscles that allows SIBO to occur.