Irritable bowel syndrome (IBS) is a group of symptoms—including abdominal pain and changes in the pattern of bowel movements without any evidence of underlying damage. These symptoms occur over a long time, often years. It has been classified into four main types depending on whether diarrhea is common, constipation is common, both are common, or neither occurs very often (IBS-D, IBS-C, IBS-M, or IBS-U respectively). IBS negatively affects quality of life and may result in missed school or work. Disorders such as anxiety, major depression, and chronic fatigue syndrome are common among people with IBS.
The causes of IBS are not clear. Theories include combinations of gut–brain axis problems, gut motility disorders, pain sensitivity, infections including small intestinal bacterial overgrowth, neurotransmitters, genetic factors, and food sensitivity. Onset may be triggered by an intestinal infection, or stressful life event. IBS is a functional gastrointestinal disorder. Diagnosis is based on signs and symptoms in the absence of worrisome features. Worrisome features include onset at greater than 50 years of age, weight loss, blood in the stool, or a family history of inflammatory bowel disease. Other conditions that may present similarly include celiac disease, microscopic colitis, inflammatory bowel disease, bile acid malabsorption, and colon cancer.
There is no cure for IBS. Treatment is carried out to improve symptoms. This may include dietary changes, medication, probiotics, and counseling. Dietary measures include increasing soluble fiber intake, a gluten free diet, or a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP). The medication loperamide may be used to help with diarrhea while laxatives may be used to help with constipation. Antidepressants may improve overall symptoms and pain. Patient education and a good doctor–patient relationship are an important part of care.
The primary symptoms of IBS are abdominal pain or discomfort in association with frequent diarrhea or constipation and a change in bowel habits. Symptoms usually are experienced as acute attacks that subside within one day, but recurrent attacks are likely. There may also be urgency for bowel movements, a feeling of incomplete evacuation (tenesmus), bloating, or abdominal distension. In some cases, the symptoms are relieved by bowel movements. People with IBS, more commonly than others, have gastroesophageal reflux, symptoms relating to the genitourinary system, chronic fatigue syndrome, fibromyalgia, headache, backache, and psychiatric symptoms such as depression and anxiety. About a third of men and women who have IBS also report sexual dysfunction typically in the form of a reduction in libido.
The exact cause of irritable bowel syndrome (IBS) isn’t known. But health experts believe that faulty communication between the brain and the intestinal tract is one cause of symptoms. In some people, this miscommunication causes abnormal muscle contractions or spasms, which often cause cramping pain. The spasms may speed the passage of stool, causing diarrhea. Or they may slow it down, causing constipation or bloating.
IBS affects between 25 and 45 million Americans. Most of them are women. People are most likely to get the condition in their late teens to early 40s.
IBS is a mix of belly discomfort or pain and trouble with bowel habits: either going more or less often than normal (diarrhea or constipation) or having a different kind of stool (thin, hard, or soft and liquid).
What Are the Symptoms of IBS?
People with IBS have symptoms that can include:
Diarrhea (often described as violent episodes of diarrhea)
Constipation alternating with diarrhea
Belly pains or cramps, usually in the lower half of the belly, that get worse after meals and feel better after a bowel movement
A lot of gas or bloating
Harder or looser stools than normal (pellets or flat ribbon stools)
A belly that sticks out
Stress can make symptoms worse.
Some people also have urinary symptoms or sexual problems.
There are four types of the condition. There is IBS with constipation (IBS-C) and IBS with diarrhea (IBS-D). Some people have an alternating pattern of constipation and diarrhea. This is called mixed IBS (IBS-M). Other people don’t fit into these categories easily, called unsubtyped IBS, or IBS-U.