possible causes of SIBO

Impairment of Motility

Content
1. Impaired Motility
1.1 Post-infectious irritable bowel syndrome
1.2 Hypothyroidism
1.3 Diabetes
1.4 Dysautonomias
1.5 Scleroderma

1. Impaired Motility

The term “intestinal motility” describes the movement ability of the intestine. During the digestive phase, the intestinal movement is involved not only in transporting food but also in mixing it with digestive juices and mechanically breaking it down. Apart from the digestive phase, there is also the interdigestive phase.

The so-called MMC (migrating motor complex) occurs in the fasting state (about 90 minutes after the last meal). This specific contraction pattern serves to clean the stomach and small intestine. Among other things, indigestible fibers, as well as the food chyme and the bacteria within it, are moved into the colon. When the motility of the small intestine is reduced, this cleansing complex is also negatively affected, which can lead to easier colonization of bacteria (1). There are several reasons why intestinal motility can be impaired. These include post-infectious irritable bowel syndrome, hypothyroidism, diabetes, dysautonomia, or scleroderma. Less commonly, chronic vagus nerve irritation or previous head trauma may also lead to restricted intestinal motility.

1.1 Post-infectious irritable bowel syndrome

Motility may be impaired due to gastrointestinal infections. After an infectious gastrointestinal illness, such as caused by Salmonella or Campylobacter (2), irritable bowel syndrome (IBS) can develop, which is referred to as post-infectious IBS. In many cases, this can be traced back to small intestinal bacterial overgrowth (SIBO) (3). A failure in antibody production against the bacteria can also lead to an autoimmune reaction targeting the pacemaker cells of the intestine (interstitial cells of Cajal), thereby reducing intestinal motility (2). Additionally, a slowed MMC is observed in IBS patients with SIBO (4).

1.2 Hypothyroidism

Hypothyroidism is the medical term for an underactive thyroid. Thyroid hormones are involved in regulating metabolic processes. When there is a deficiency in thyroid hormones, intestinal motility often decreases (5). Therefore, hypothyroidism is considered a risk factor for the development of SIBO (6).

1.3 Diabetes

Diabetes is also considered a risk factor for the development of SIBO (7). A possible explanation is that diabetes, due to elevated blood sugar levels, can damage the nerves in the digestive tract, which impairs intestinal motility.

1.4 Dysautonomias

Dysautonomia is the umbrella term for conditions that affect the function of the autonomic nervous system. The autonomic nervous system includes both the sympathetic and parasympathetic nervous systems. While the sympathetic system generally prepares the body for increased activity, the parasympathetic system counters this and is responsible for proper digestion. If the autonomic nervous system is damaged, it affects intestinal motility, which in turn facilitates the development of SIBO. Examples of dysautonomia include Ehlers-Danlos syndrome and postural tachycardia syndrome (POTS). Thus, SIBO treatment may improve some symptoms of POTS (8).

1.5 Scleroderma

Scleroderma leads to fibrous and sclerotic changes in the connective tissue of the skin. A form of scleroderma, progressive systemic scleroderma, can also affect internal organs. Scleroses are hardenings caused by an increase in connective tissue. These can impede the flow of food through the small intestine, making scleroses a risk factor for the development of SIBO (9,10).

References

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