Small intestine bacterial overgrowth (SIBO syndrome) - causes, symptoms, treatment

• SIBO team - causes
• SIBO - symptoms
• SIBO team - diagnostics
• SIBO team - treatment

VERIFIED CONTENTAuthor: Krzysztof Bialazite

Small intestinal bacterial overgrowth (SIBO) is a group of clinical symptoms caused by excessive growth of the bacterial flora in the small intestine. What are the causes and symptoms of bacterial overgrowth? How is SIBO treated?

Bacterial overgrowth( SIBO- small intestinal bacterial overgrowth) is an excessive growth of the bacterial flora in the small intestine. Depending on the cause and degree of colonization of these areas by bacteria, it can take various forms - from moderate digestive discomfort, through diarrhea, to severe absorption disorders and nutrient deficiencies.

The essence of treating theSIBOsyndrome is to find the reason for the multiplication of bacteria, their elimination and an appropriate diet with supplementation of deficient substances. Until recently,SIBOsyndrome was one of the rarely recognized disease entities, mainly among patients with anatomical defects of the gastrointestinal tract or after operations in the small intestine. Today, many more risk factors are known that could lead to an overgrowth of the bacterial flora of the small intestine, and the syndromeSIBOturns out to be more common than suspected.

The human digestive tract is a continuous structure, however, it consists of fragments of a completely different anatomical and microscopic structure. Consequently, each section of the digestive tract has a characteristic population of microorganisms that inhabit it. The smallest amount of bacteria is found in the stomach. Under normal conditions, the small intestine also has few of them, and the flora there mainly consists of the so-called Gram positive (G +) bacteria.

The large intestine is completely different in terms of microbiology, as it is colonized by huge amounts of bacteria of high differentiation and activity. We find here not only Gram positive, but also Gram negative and anaerobic bacteria. In the teamSIBOwe deal with two types of pathology:

• first, there is a quantitative increase in the bacterial population in the small intestine,>105microorganisms / ml
• secondly, the small intestine is inhabited by flora unusual for this section of the gastrointestinal tract, living in physiological conditions only in the large intestine

Now that we have defined bacterial overgrowth, another question arises: where does this amount of wrong bacteria come from in the small intestine?

SIBO team - causes

The answer is not unequivocal, and finding a specific cause can be the bane of doctors. In each case of hyperplasia, the homeostasis processes of the small intestine, which normally control the local flora, are disturbed. There are several types of disturbances that may underlie such imbalance. These include:

• gastrointestinal motility disorders
• anatomical changes
• gastric secretion disorder
• immune disorders.

Disorders of gastrointestinal motility

The slower intestinal passage causes a prolonged retention of the food content in individual sections. Thus, bacteria are not effectively moved towards the large intestine and can multiply freely. Disturbances in intestinal peristalsis are often associated with various systemic diseases, such as polymyositis, sclerodermia or amyloidosis.

Another cause may be neuropathies, i.e. disturbances in the transmission of nerve stimuli within the intestines. They occur both in patients with diseases of the nervous system (e.g. Parkinson's disease) and in other entities, e.g. diabetes. Slower intestinal transit may also affect elderly patients and patients suffering from celiac disease.

Anatomical changes

There are many anatomical differences that could predispose to the teamSIBO . One of them are gastrointestinal diverticula, relatively common in the he althy population. In the vast majority of cases they are small and asymptomatic, however, large diverticula located in the duodenum and jejunum become an excellent place for bacteria to accumulate and multiply.

Patients who have undergone surgery on the small intestine may also have different anatomy. Stagnation of the digestive content occurs frequently after operations on the excision of parts of the digestive tract with subsequent anastomosis. Another type of surgery that may complicate SIBO syndrome is the removal of the ileocecal valve.

Under normal circumstances, it forms the border between the small and large intestines. The need to remove it (e.g. in patients with Crohn's disease) poses a risk of reflux of the microbiota of the large intestine towards the intestine.thin.

Disorders of gastric secretion

Gastric juice contains hydrochloric acid, which limits the growth of bacteria in the he althy digestive tract. Patients who take drugs that inhibit gastric secretion (e.g. proton pump inhibitors) for various reasons have elevated - i.e. less acidic - gastric pH and are at risk of pathological bacterial overgrowth.

Immune disorders

All diseases that lead to immune deficiencies also lead to a decrease in immunity within the intestines. Patients with decreased levels of IgA, which is the main antibody of the mucous membranes, are particularly at risk. Immunodeficiency also occurs in patients undergoing immunosuppressive treatment, e.g. after organ transplants.

Other conditions where SIBO syndrome is more common are irritable bowel syndrome (IBS), pancreatitis, kidney failure, and Crohn's disease.

SIBO - symptoms

SIBO syndrome can cause many ailments of varying severity.Symptoms depend both on the number of bacteria in the small intestine and their type. Many of them are non-specific and also occur in other diseases of the gastrointestinal tract. Thesymptoms of SIBOinclude:

• stomach pains
• flatulence
• feeling of fullness
• diarrhea (fatty stools)
• vitamin deficiencies
• anemia.

Most patients complain of abdominal pain of varying severity, gas bloating, a feeling of fullness in the abdomen and diarrhea. A special type of diarrhea occurring in SIBO syndrome are the so-called fatty stools. A substance that helps a he althy body to digest fats is bile.

Some bacteria have the ability to metabolize bile components - bile acids - leading to its breakdown. If this type of bacteria is dominant in the multiplication of flora, greasy, putrid-smelling stools appear due to the impaired digestion of fats. A further consequence of these disorders may be a deficiency of fat-soluble vitamins such as vitamin A, vitamin D, vitamin E and vitamin K.

In severe cases, these deficiencies lead to twilight blindness (vitamin A), osteoporosis (vitamin D), bleeding tendencies (vitamin K) and neuropathy (vitamin E) - however, it should be emphasized that SIBO syndrome rarely develops to such serious complications. In addition to bacteria that break down bile, there are populations that break down carbohydrates more readily, which are more likely to cause gas and gas than diarrhea.

Regardless of the type of dominant flora,bacterial growth is always associated with microscopic damage to the intestinal mucosa and impaired nutrient absorption. One of the more common symptoms that may indicate malabsorption is anemia caused by vitamin B12 deficiency. In the case of protein absorption disorders, the so-called intestinal protein loss syndrome, the first symptom of which is swelling.

SIBO team - diagnostics

Diagnosticsof SIBO syndromeis a big challenge for doctors, because the clinical symptoms appearing in it may mimic many other diseases of the digestive system - for example food intolerance, celiac disease or irritable bowel syndrome. If a bacterial overgrowth syndrome is suspected, the following tests can be performed:

• peripheral blood count revealing vitamin deficiency anemia. B12 (this is a special type of anemia, the so-called macrocytic anemia - in a deficiency of this vitamin, the blood cells are too large)
• if anatomical defects or diverticula are suspected, imaging tests are performed, for example, an abdominal X-ray with contrast
• blood albumin test to assess intestinal protein loss
• microscopic examination of feces may reveal the presence of fats, indicating malabsorption disorders

The results of the above studies may indirectly indicate bacterial proliferation, but are not specific to theSIBO team .

There are two test methods to determine the number of bacteria growing in the intestine. These include:

• direct determination (counting under the microscope) of bacteria in the intestinal contents - the limit value for the SIBO team was the number of 105 microorganisms / ml. However, this examination has many limitations - it requires inserting a special probe or endoscope into the intestine, and often gives low results.
• indirect designation using the so-called breathing tests. These tests rely on the oral administration of a substance (e.g. glucose) readily metabolized by bacteria. Then the level of gaseous products (carbon dioxide or hydrogen) of decomposition of this substance in the patient's exhaled air is measured. The amount of gas in the exhaled air makes it possible to indirectly determine the number of bacteria inhabiting the small intestine. The undoubted advantage of breathing tests is their simplicity, non-invasiveness and safety. On the other hand, their sensitivity and specificity are limited, therefore they are always interpreted in the context of clinical symptoms and the results of other tests.

SIBO team - treatment

The basis for effective treatmentSIBO syndrome is to find the cause of the bacterial overgrowth. Surgical treatment may be beneficial for patients whose bacterial growth is caused by anatomical changes (diverticula, fistulas). Gastrointestinal motility disorders are treated pharmacologically with serotonin agonists (e.g. cisapride) or erythromycin.

A key role in controlling bacterial growth is played by properly selected antibiotics acting on gram-negative microorganisms. The most commonly used preparations include metronidazole, rifaximin and ciprofloxacin. Antibiotic therapy usually lasts from 7 to 10 days. If there is such a need, you should also remember to provide adequate supplementation. In case of deficiencies, supplements with vitamins A, D, E and B12.

Reducing the severity of unpleasant symptoms reduces the consumption of lactose. In the case of fat absorption disorders, supplementation with medium-chain triglycerides is also recommended. The role of probiotic therapy inSIBO syndromeremains unclear - some studies on the supply of strainsLactobacillusgave promising results (reduction of diarrhea, improvement of breath test results), others and did not show a positive effect of probiotics. In order to clearly establish the legitimacy of their supply, further research is necessary.

• The microbiome - what is it and what are its functions?
• Good bacteria in the body: microbes that protect against disease

About the authorKrzysztof BialaziteA medical student at Collegium Medicum in Krakow, slowly entering the world of constant challenges of the doctor's work. She is particularly interested in gynecology and obstetrics, paediatrics and lifestyle medicine. A lover of foreign languages, travel and mountain hiking.

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