Small intestinal bacterial overgrowth


Small intestinal bacterial overgrowth (SIBO) is a disorder where there’s an excessive growth of bacteria in the small intestine, particularly types that are not usually found in that section of the digestive system. This imbalance can be triggered by factors such as surgery or disease that slow down the transit of food and waste, providing an ideal environment for bacterial proliferation. Commonly, the condition leads to symptoms like diarrhea, and in severe cases, can cause weight loss and malnutrition.

SIBO is frequently associated with complications arising from abdominal surgeries but can also occur due to structural issues within the digestive tract or certain diseases. The presence of too many bacteria disrupts the normal balance of gut flora, which can impair digestion. The overgrowth of inappropriate bacteria can outcompete beneficial bacteria, leading to further digestive distress.

Treatment for SIBO often involves antibiotics to reduce the bacterial overload. In some instances, surgery may be necessary to address underlying structural problems that contribute to the condition. Managing SIBO effectively requires restoring the delicate balance of the intestinal flora and ensuring proper digestive function.


SIBO symptoms can mimic many other gastrointestinal disorders, and frequently, has been worsened by another illness. Common symptoms include:

  • A sensation of bloating or discomfort after meals.
  • Appetite loss
  • Bloating
  • Constipation
  • Diarrhea
  • Fatigue
  • Gas
  • Indigestion
  • Malnutrition
  • Nausea
  • Stomachache
  • Unexplained weight loss

If any of the signs and symptoms persist, consult a healthcare provider for proper diagnosis and treatment. In case of severe abdominal pain, immediate medical attention is necessary.

It is also advised to look out for persistent diarrhea, rapid and unintended weight loss, or abdominal pain lasting beyond a few days, as these could signal underlying problems.


The small intestine, spanning approximately 20 feet in length, plays a pivotal role in nutrient absorption. Here, food combines with digestive fluids, promoting the absorption of nutrients into the bloodstream. This process is facilitated by a complex interplay of chemical and mechanical processes that help maintain the equilibrium of gut bacteria.

For small intestinal bacterial overgrowth (SIBO) to occur, a disruption in these processes is typically necessary. Factors regulating bacteria in the small intestine include gastric acid, bile, enzymes, and immunoglobulins. Unlike the large intestine, which generally harbors fewer bacteria due to rapid movement of contents and bile presence, the small intestine can become a breeding ground for bacteria if food stagnates.

SIBO can be precipitated by various conditions that affect the small intestine, including:

  • Structural problems: Issues like small bowel diverticulosis, obstructions, and abdominal adhesions often arise from digestive diseases or surgical complications. These structural problems can impede movement and the normal clearing of bacteria, providing more niches for bacteria to accumulate.
  • Hypochlorhydria (low stomach acid): Reduced levels of stomach acid can be caused by H. pylori infection, prolonged use of medications such as antacids and proton pump inhibitors, or gastric bypass surgery.
  • Medical conditions: Diseases that slow the movement of food and waste through the small intestine, such as Crohn’s disease, radiation enteritis, scleroderma, celiac disease, and diabetes, can contribute to SIBO.
  • Excessive use of certain medications: Antibiotics, narcotics, and gastric acid suppressants can disrupt the normal balance of gut bacteria, potentially leading to SIBO.

Risk factors

Several factors can contribute to one’s risk of developing SIBO, such as:

  • Old age
  • Taking more medications
  • Small bowel diverticulosis
  • Undergone medical procedures, such as gastric surgery and abdominal surgery
  • Damage to the small intestine
  • A minor intestinal structural flaw
  • Fistula, or an irregular gap connecting two bowel segments
  • Various gastrointestinal conditions such as diabetes, lupus, celiac disease, inflammatory bowel diseases, irritable bowel syndrome, pancreatitis, and colon cancer
  • Exposure to radiation
  • Disorders that weaken the immune system, such as Crohn’s disease, scleroderma affecting the small intestine, or intestinal lymphoma