Irritable bowel syndrome

What IBS is

IBS belongs to the disorders of gut–brain interaction: the bowel is structurally healthy, but it works and “feels” differently. It does not cause ulcers or inflammation of the bowel and does not increase the risk of colorectal cancer. Even so, the complaints are real, often recurring for years, and can affect work, eating, sleep and relationships.

It affects mainly young and middle-aged people and is more common in women. Many people have years of symptoms before getting the diagnosis, often after numerous tests that came back normal. A diagnosis of IBS does not mean “there is nothing wrong”: it means the bowel is not damaged, but its function is altered and can be treated.

Symptoms and subtypes

The main feature is recurrent abdominal pain, related to passing stool or to a change in the frequency or form of stools. It is accompanied by:

• constipation, diarrhea or alternation of the two;
• bloating and gas;
• a feeling of incomplete emptying;
• sometimes mucus in the stool.

By the predominant pattern, the subtypes are IBS-C (with constipation), IBS-D (with diarrhea) and IBS-M (mixed). The distinction matters because treatment is tailored to the subtype. Symptoms often worsen after certain meals, during stress or at certain times, and ease after a bowel movement.

Causes

There is no single cause. Several mechanisms work together: increased sensitivity of the bowel to stretching (visceral hypersensitivity), changes in bowel motility, in the gut microbiota, in the permeability of the lining and in gut–brain communication. IBS can start after an infectious gastroenteritis (an acute digestive infection), after antibiotics or during long periods of stress.

Stress and anxiety can worsen symptoms, but this does not mean the complaints are “imaginary”: the gut and the brain communicate constantly, and stress genuinely affects bowel motility and sensitivity.

How the diagnosis is made

The doctor makes the diagnosis positively, based on the typical pattern of symptoms (recurrent pain related to bowel movements, over a long period) and the clinical examination. It is not necessary to exclude every disease with every test, but the tests that are needed are done as appropriate:

• When diarrhea predominates, tests for celiac disease and markers of inflammation, such as fecal calprotectin, are usually requested to exclude inflammatory bowel disease.
• Blood count, CRP and, as appropriate, TSH.
• Colonoscopy is not routine for IBS; it is recommended when there are alarm features or when you are due for colorectal cancer screening.

Features that call for further investigation. These complaints should not be called IBS without assessment:

• blood in the stool or anemia;
• fever or unexplained weight loss;
• diarrhea that wakes you at night;
• symptoms starting for the first time after age 50;
• a family history of colorectal cancer, celiac disease or inflammatory bowel disease.

How it is treated

Treatment is tailored to the subtype and the main complaint. The aim is to control symptoms and improve daily life; several steps and some patience are often needed.

• Lifestyle: regular meals, physical activity, enough sleep, limiting caffeine and alcohol.
• Soluble fiber (for example psyllium) helps many patients, especially with constipation; bran (insoluble fiber) often worsens bloating.
• A low-FODMAP diet (carbohydrates that ferment quickly in the bowel) is a time-limited trial, best with the help of a dietitian, followed by gradual reintroduction of foods. It is not a diet for life.
• Do not remove gluten before being tested for celiac disease, because removing it makes the test inaccurate.
• Medicines according to the main complaint: antispasmodics for pain, laxatives for constipation, antidiarrheals for diarrhea, and for some people low-dose antidepressants that act on the bowel’s sensitivity and not against depression.
• Psychological therapies (cognitive behavioral therapy, gut-directed hypnotherapy) have good evidence of effectiveness, especially when stress or anxiety worsens the complaints.

What to expect

IBS is a chronic condition with periods of improvement and worsening, but it does not progress to serious disease and does not shorten life. Most patients learn to control their symptoms with the right combination of measures. Contact your doctor if complaints change character, if any alarm feature appears or if treatment gives no result after a few weeks.