Small intestinal bacterial overgrowth is a condition in which very large numbers of bacteria grow in the small intestine. Various conditions and abnormalities disrupt the normal low number of bacteria and species present in the intestine. Gut-related symptoms such as diarrhea and bloating often accompany the disease. Treatment consists of antibiotics in combination with causal treatment of the bacterial overgrowth in the small intestine.
- Causes of bacterial overgrowth in the small intestine
- Symptoms: Intestinal problems
- Diagnosis and examinations
- Treatment via antibiotics and/or probiotics
- Disease prognosis
- Complications large numbers of bacteria in the small intestine
Bacterial overgrowth in the colon is associated with alcohol abuse / Source: Jarmoluk, Pixabay
Causes of bacterial overgrowth in the small intestine
The small intestine is the part of the digestive system that connects the stomach to the large intestine (colon). The small intestine digests and absorbs food into the body. The small intestine consists of three parts: the duodenum, the small intestine and the ileum. The entire gastrointestinal tract, including the small intestine, contains a normal number of bacteria. The number of bacteria is greatest in the large intestine, but much lower in the small intestine. The types of bacteria in the small intestine are also different from the types of bacteria in the large intestine. Small intestinal bacterial overgrowth refers to a condition in which there are abnormally large numbers of bacteria in the small intestine, while more types of bacteria from the large intestine are present in small intestinal disease. With an overgrowth of bacteria in the small intestine, the small intestine consumes nutrients that the body needs, leading to malnutrition. The excess bacteria also damage the mucous membrane in the small intestine. This makes it even more difficult for the body to absorb nutrients.
Conditions that lead to a bacterial overgrowth in the small intestine include:
- conditions that cause movement problems in the small intestine, such as diabetes mellitus (diabetes) and scleroderma (build-up of scar tissue in the skin and organs)
- alcohol abuse
- antibiotic treatments
- surgical procedures that create a loop in the small intestine that allows excessive bacteria to grow. An example is a Billroth II type of stomach removal (gastrectomy).
- complications of diseases or surgery that create bulges or blockages in the small intestine. Crohn’s disease (condition involving abdominal pain, diarrhea and weight loss) and celiac disease are some of these conditions.
- small bowel diverticulitis, which causes small sac-like bulges to appear in the inner lining of the intestine. These bag-shaped bulges, which are more common in the large intestine, allow many bacteria to grow.
- insufficient functioning of the pancreas
- a weakened immune system, such as with AIDS or immunoglobulin deficiency
- some cases of irritable bowel syndrome (symptoms of diarrhea and constipation)
- short bowel syndrome resulting from the surgical removal of the small intestine
- cirrhosis of the liver
- kidney failure
Symptoms: Intestinal problems
The clinical features of overgrowth are mainly diarrhea and fatty diarrhea. Greasy stools, flatulence, bloating, abdominal pain, cramps and weight loss also occur. A mild B12 deficiency often occurs, but this is rarely severe enough to produce a neurological deficit. As the disease progresses, malnutrition and vitamin deficiencies develop due to the body’s inability to absorb nutrients from the intestine.
Diagnosis and examinations
Bacterial overgrowth is confirmed with the hydrogen breath test. In addition, a blood test is useful for bacterial overgrowth of the colon. The doctor also takes an X-ray in the small intestine. A biopsy or culture in the small intestine is sometimes necessary. Another test for detecting bacterial overgrowth in the small intestine is an endoscopy (internal examination of the inside of the body).
The doctor may confuse a bacterial overgrowth in the intestine with the following clinically similar conditions:
- afferent loop syndrome
- chronic pancreatitis (inflammation of the pancreas with abdominal pain and digestive problems)
- celiac disease (stomach and intestinal problems due to eating gluten)
- ulcerative colitis
- cyclospora (foodborne infection with diarrhea)
- intestinal motility disorders
- intestinal carcinoid tumor (carcinoid syndrome: secretion of serotonin in the body)
- intestinal diverticulosis
- intestinal fistulas
- lactose intolerance (symptoms when consuming milk and dairy products)
- malabsorption (problems with nutrient absorption)
- pneumatosis cystoides intestinalis
- irritable bowel syndrome
- tropical thrush
- VIPomas (neuroendocrine tumors in pancreas with diarrhea)
- Crohn’s disease
- Whipple’s disease
Treatment via antibiotics and/or probiotics
If possible, the doctor corrects the underlying condition (for example by cutting away a stricture). If this is not possible, the patient is given one or more courses of antibiotics. The type and duration of the medication does depend on the patient’s health and the symptoms present. In some cases, drugs accelerate intestinal motility. A low-carbohydrate diet is also useful for many patients. Some doctors prefer to prescribe probiotics, others opt for a combination of antibiotics and probiotics. In addition, the patient must consume sufficient fluid and nutrition. A dehydrated patient is given fluids intravenously (through a vein) in the hospital. Malnourished patients also receive nutrition through a vein (total parenteral nutrition – TPN).
The prognosis depends on the effectiveness of treatment of the underlying disease. The response to antibiotics is also unpredictable, although most patients respond well to these medications. Finally, a relapse of the disease is quite common.
Complications large numbers of bacteria in the small intestine
Patients with severe symptoms of bacterial overgrowth in the small intestine sometimes develop malnutrition. Other possible complications include:
- a liver disease
- osteomalacia (softening of the bone)
- osteoporosis (loss of bone mass with risk of bone fractures)
- excessive bleeding due to vitamin deficiency