Overgrowth of the Small Intestine Overview

small intestine overgrowth

With a small intestinal bacterial overgrowth an overgrowth of the small intestine with microbes of more is called a hundred thousand organisms per milliliter. The microbial overgrowth manifests itself in many unspecific symptoms such as abdominal pain, flatulence, chronic diarrhea and leads to damage to the intestinal villi. In the further course there is malassimilation and the associated weight loss as well as deficiency symptoms.

What is small intestine overgrowth?

According to phonejust, small intestine overgrowth (DDFB) is a microbial overcrowding of the small intestine. One hundred thousand germs per milliliter are considered the lower limit for a DDFB. The Anglo-Saxon expression small intestinal bowel (bacterial) overgrowth (SIBO) is even more precise.

The small intestine connects directly to the stomach and is separated from the large intestine by the ileocecal valve, also known as the Bauhin valve. Put simply, the enzymatic breakdown of the main nutrients takes place in the small intestine, and the intestinal villi absorbs the broken down substances as well as the vitamins and some of the minerals. Compared to the large intestine, the healthy small intestine is only sparsely populated by intestinal microbes.

Normally there are around one thousand to ten thousand germs per milliliter of intestinal mucus in the small intestine. In contrast, the large intestine is populated with one hundred billion to one trillion germs per gram of intestinal mucus. Incorrect colonization of the small intestine therefore corresponds to microbial overgrowth and overgrowth at the same time.


The healthy small intestine has several protective mechanisms with which it protects itself against over-colonization and over-settlement. Passive protection against colonization by colon bacteria is provided by the Bauhin valve (ileocecal valve), which is located at the transition from the small intestine to the large intestine. Like a check valve, it also prevents reflux of the food pulp from the large intestine into the small intestine.

Active protection consists in the antibiotic substances that the Paneth cells produce in the small intestine and prevent incorrect colonization from occurring. If the mentioned and other protective mechanisms fail, a DDFB can occur. The main causes for the occurrence of the small intestine colonization are a defective ileocecal valve and the so-called short bowel syndrome.

Short bowel syndrome can result from an artificial, acquired or, in rare cases, congenital shortening of the small intestine. The starting point of the DDFB is usually a disused or inactive intestinal loop in which the passage of the intestinal contents is greatly slowed down. A slowed passage can also be the result of a disruption of the natural peristalsis. Other causative factors can be insufficient acid production in the stomach or a reduced supply of digestive enzymes from the pancreas and bile.

Symptoms, ailments & signs

The main symptoms that occur can usually be traced back to an increased formation of digestive gases and a reduced absorption capacity of the small intestine, so that malassimilation can lead to typical deficiency symptoms that trigger health symptoms and complaints.

Increased gas formation leads to a bloated stomach and causes abdominal pain in different places because the gas cannot be discharged naturally, but mainly diffuses into the blood and is “exhaled” in the lungs. The main symptoms are often accompanied by chronic diarrhea and intestinal inflammation, which lead to weight loss.

In many cases, the symptoms are similar to those of irritable bowel syndrome. In less frequent cases – especially as a result of short bowel syndrome – bacterial breakdown of bile salts can occur, so that fat digestion is disturbed and so-called fatty stools are formed. The bacterial malocclusion in the shut-down or inactive section of the intestine leads, among other things, to a vitamin B12 deficiency, which is considered to be the main trigger factor for anemia.

Diagnosis & course

In principle, a sample of small intestinal mucus can provide information about bacterial colonization. However, the procedure requires an elaborate small intestine specimen, especially if samples are to be taken from sections of the intestine further down. A relatively elegant method is a breathing air test, with which the detection of hydrogen in the breathing air is carried out.

Lactulose (not to be confused with lactose) as a test substance has proven to be effective and informative. Lactulose is a disaccharide made up of the two monosaccharides galactose and fructose. Lactulose is not normally metabolized in the small intestine.

If there is hydrogen formation in the small intestine, which can be proven by the breath test, this is considered an indication of DDFB. If left untreated, the course of the disease depends on the causal factors. If the causes are not recognized and not treated, it can lead to serious courses with a poor prognosis. However, DDFB is generally easy to treat.


The over-colonization of the small intestine leads to severe discomfort and complications in the area of ​​the intestine and stomach. In most cases, the symptoms are similar to those of gastrointestinal disorders. The patient suffers from severe abdominal pain and diarrhea. Flatulence, dizziness and vomiting can also occur.

Often the affected person also loses their appetite, which can be reflected in an underweight. The constant diarrhea leads to dehydration. In the worst case, the bowel becomes inflamed. Due to the gastrointestinal complaints, it is often no longer possible for those affected to carry out physical activities, which restricts their everyday life.

Food intake is also only possible to a limited extent. Treatment is usually medication or surgery. Usually there are no further complaints or complications. In some cases, the affected person has to forego certain foods or ingredients due to the overgrowth in the small intestine.

The treatment does not prevent a renewed colonization of the small intestine, so that the patient can develop it again. This disease does not limit or reduce life expectancy.

When should you go to the doctor?

Intestinal dysbiosis is on the rise, but is rarely correctly diagnosed. Incorrect colonization in the small intestine can be detected using a hydrogen breath test.

Self-tests can be found on the Internet with which people can determine if there is an overgrowth in the small intestine with persistent digestive disorders. The hydrogen breath test is usually described as the gold standard in diagnostics. A visit to the gastroenterologist is recommended if the intestinal problems persist. The reason: The breath test can give a negative result in non-responders, even if there is an overgrowth in the small intestine.

In the case of persistent fermentation complaints as a result of bacterial overgrowth in the small intestine, the self-diagnosis “irritable bowel” is written down in the memory, although this is often incorrect. Food intolerance is also not always present.

Improper self-treatment can worsen the underlying problem. If those affected react by avoiding supposedly intolerable foods, an unbalanced diet is the result. Instead of risking nutritional deficiency symptoms, a visit to the gastroenterologist would be more sensible.

Incorrect colonization of the small intestine can occur due to age. But it can also be the result of Crohn’s disease or short bowel syndrome. If the bacterial colonization in the intestine gets mixed up, it should be put back in order quickly. After all, the functionality of the human immune system is related to the correctly functioning microbiome.

Treatment & Therapy

Treatment is primarily aimed at eliminating the cause of DDFB. A causal therapy can, for example, consist of a surgical procedure that restores the functionality of the Bauhin valve or removes blind loops of the small intestine or bottlenecks (stenoses). If the supply of bile to the small intestine is impaired, therapy aims to restore the functions of the pancreas and gallbladder.

At the same time, nutritional supplements and vitamin replacement therapies are necessary in many cases. The actual DDFB usually responds well to certain antibiotics, so that a treatment can then follow that supports the development of a microbiome typical of the small intestine. Overall, the prognosis at DDFB can be classified as favorable if the causes and the DDFB itself are treated in a targeted manner.

Outlook & forecast

Small intestine overgrowth can be treated well in most cases. An early diagnosis always has a positive effect on the further course of the disease.

In some cases, patients need surgery. Furthermore, the disease can also be defeated well by taking medication, whereby there are usually no particular complications. If the small intestine colonization occurs due to an allergy or an intolerance, the person concerned must forego the triggering substance.

This is the only way to permanently alleviate the symptoms. Furthermore, stress can also increase the colonization of the small intestine, so that in many cases relaxation exercises can alleviate the disease.

If left untreated, the condition can lead to serious bowel complications. In the worst case, this leads to a tear in the intestine, which can lead to the death of the person concerned. An immediate surgical intervention is necessary. Likewise, the complaints of an over-colonization of the small intestine often lead to psychological upset or to depression. With timely treatment, the life expectancy of the patient will not be reduced by the disease.


Preventive measures to avoid over-colonization of the small intestine consist mainly of avoiding substances that promote the development of DDFB. This is especially true for foods to which an individual sensitivity or intolerance has been proven.

In principle, a healthy lifestyle, in which natural foods and exercise play a role, as well as phases of stress that alternate with phases of relaxation, can be recognized as having a preventive effect.


The small intestine overgrowth can occur in the context of food intolerance or irritable bowel syndrome. However, both can also be the cause of the same. Pancreatic insufficiency can also be related to it. The overgrowth in the small intestine is often based on a relaxation of the ileocecal valve.

The overgrowth of harmful bacteria in the small intestine is often underestimated. Misdiagnoses are the order of the day. Appropriate examinations are only carried out if there are persistent intestinal problems. Various methods can be used as therapy. These can be surgical procedures. These require postoperative follow-up care and long-term observation of the patient.

In other cases, antibiotics are usually prescribed in the case of an overgrowth in the small intestine. If these do not work, the treating physicians speak of antibiotic-responsive enteritis. The aftercare measures depend on the underlying disease. They also endeavor to compensate for the incorrect colonization in the small intestine by taking suitable measures. Pro- and prebiotics and foods with a high content of resistant starch come into question. Flora killers should be avoided.

Unfortunately, general practitioners rarely focus on the microbion in the small intestine. It is not the cause of a disorder that is treated, but the symptom. This is why there are many unsuccessful attempts at self-treatment, especially in the case of malocclusion in the small intestine. Follow-up care by a gastroenterologist can also be inadequate in this regard. In the case of incorrect colonization, the diagnosis is often not followed by therapy.

You can do that yourself

An adaptation of the behavior in everyday life and self-help measures can support a drug or surgical treatment of the small intestine overgrowth (DDFB) well. It is important that the causes of the DDFB are correctly identified and specifically treated.

If the colonization of the small intestine occurs in an ascending manner via the defective Bauhin valve (ileocecal valve), it is urgently necessary to surgically replace the valve or to make it functional again so that no new colonization can develop.

In other cases, the causes of the development of DDFB lie in a slow passage of the food pulp through the small intestine due to short bowel syndrome due to a disused intestinal loop or due to decreased intestinal peristalsis. Insufficient acid production in the stomach or a reduced flow of bile juices and digestive enzymes from the pancreas into the small intestine have a similar effect.

Self-help measures to accompany antibiotic therapy consist of a balanced diet that is rich in minerals, vitamins and enzymes. Fermented foods such as sauerkraut or yoghurt are particularly beneficial.

The Paneth cells in the intestinal mucosa are supported in the synthesis of their own antibiotic substances to regulate the bacterial colonization of the small intestine. If the DDFB is caused by insufficient intestinal peristalsis, there is the possibility of self-help through self-massage. In a relaxed supine position with legs slightly bent, the stomach is gently massaged in a clockwise direction without applying pressure.

small intestine overgrowth