What is Diarrhea?

Diarrhea can develop as a result of many abnormalities. Motility related causes of diarrhea include small intestinal bacterial overgrowth (SIBO) and irritable bowel syndrome (IBS).




Rapid gut transit can sometimes be seen in irritable bowel syndrome. This condition is known as irritable bowel syndrome with diarrhea predominance or IBS-D. This should be distinguished from constipation predominant and mixed type IBS where patients have alternating diarrhea and constipation.

Excessive gassiness and bloating (Small Intestinal Bacterial Overgrowth)

What is SIBO and what might it represent?

The symptoms below can represent a number of intestinal disorders but may be signs of small intestinal bacterial overgrowth. The small intestine normally contains relatively small amounts of bacteria. However, the bacteria can become abundant as a result of changes in the normal movement of the intestines and cause symptoms due to their overabundance as bacteria produce gases such as hydrogen during digestion. SIBO is more common in women than men.

What are some of the symptoms?

  • Bloating
  • Gassiness
  • Abdominal pain
  • Diarrhea

How is the diagnosis made?

The diagnosis is made by performing a breath test which requires ingestion of a sugar such as lactulose. Samples of the patient’s breath are collected at different time points. The amount of exhaled hydrogen gas is measured. A positive test is when the amount of hydrogen gas is above a certain threshold.

How is this condition treated?

Treatment usually includes a course of antibiotics and treatment of the underlying condition that caused excess small intestinal bacteria to collect. SIBO may recur and so several courses of antibiotics may be needed over time.

Irritable Bowel Syndrome (IBS)

What is it?

It is a motility disorder of the colon. There are several hypotheses about its primary cause(s) including food intolerances and disruption in the balance of colonic bacterial content. Research is underway.

What are symptoms of IBS?

  • Abdominal pain
  • Diarrhea, constipation or both
  • Excessive gas/bloating

How is it diagnosed?

It is diagnosed based on reported symptoms. However, certain tests may be ordered including celiac testing, lactose intolerance testing, upper endoscopy and colonoscopy in order to exclude other conditions.

How is it treated?

Fiber supplements or high fiber diet

Low FODMAP diet [This is a diet which includes elimination of certain complex carbohydrates (Fermentable Oligosaccharides Disaccharides Monosaccharides and Polyols) from the diet. These complex carbohydrates are sometimes difficult for patients with IBS to digest. The diet is usually done under the guidance of a health care provider]

Treatment of diarrhea/constipation using anti-diarrheals or laxatives

Pain and antispasmodic medications

Probiotics (Probiotics are manufactured forms of bacteria which promote normal gut function by restoring the balance of healthy bacteria)