Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a functional disorder defined clinically by the combination of abdominal discomfort and changes in bowel habits, with no organic cause. The prevalence in Spain varies between 3.3 and 13.6%.

Irritable bowel syndrome is slightly more frequent in women than in men. The most frequent subtypes are Constipation Predominant, Alternating Type (diarrhoea and constipation alternate). The Diarrhoea Predominant subtype is distributed equally between the genders.

Irritable bowel syndrome can be associated with other conditions, such as fibromyalgia and chronic fatigue syndrome.

Although some studies disagree whether IBS increases or decreases with age, the majority of studies suggest that the prevalence is less frequent in the elderly.

Frequent symptoms

Pain or abdominal discomfort that is relieved through defecation and/or passing wind

Pain or abdominal discomfort associated with a change in bowel movements (diarrhoea, constipation or the alternation of both) or in the consistency of stools (hard, liquid or semi-liquid)

Sensation of bloating or abdominal distension

The urgent need to defecate

Faecal tenesmus (non-satisfaction after defecation)

Faecal incontinence

Presence of mucus in stools

Excessive effort during defecation

Sensation of incomplete evacuation

Other related systems: heartburn, slow digestion, early satiety, anal pain

Irritable bowel syndrome subtypes

Constipation Predominant IBS

Diarrhoea Predominant IBS

Alternating Type IBS (alternating times of diarrhoea and constipation)

Intestinal symptoms that may be present

Period pain

Muscular pain

Pain in bones



Psychological disorders such as anxiety, distress, depression.

The clinical progress of IBS is characterised by the presence of symptoms alternating with periods in which there are no symptoms.

Several studies have demonstrated that patients with IBS have a lower quality of life than the general population.

Irritable bowel syndrome causes

Although the exact cause of IBS is unknown, certain pathophysiological mechanisms involved are:

Genetic and environmental factors

Alterations in gastrointestinal motility (bowel movements)

Intestinal hypersensitivity

Bacterial overgrowth

After gastroenteritis (after an episode of infectious diarrhoea)

Psychological alterations (anxiety, depression, somatisation, cancer phobia, etc.)

History of physical or sexual abuse

Acute psychological stress could affect bowel movements and bowel sensitivity, which would explain that reason why more than half of patients with IBS associate episodes of exacerbated symptoms with stressful situations.

The menstrual cycle influences the perception of symptoms and the psychological state of women with IBS.

Irritable bowel syndrome symptoms and warning signs

Symptoms from 50 years of age

Presence of nocturnal symptoms



Unintentional weight loss

Presence of blood in faeces

Family history of bowel cancer

Family history of Crohn’s disease or ulcerative colitis

Family history of coeliac disease

In these cases, it is essential to differentiate the diagnosis from other organic conditions

Complementary tests used

Full blood test with inflammation reactants, iron metabolism and other vitamins, thyroid hormones, coeliac test, etc.

Stool cultures with parasites

Ileocolonoscopy with biopsies

Gastroscopy with biopsies

Lactose H2 Breath Test

Study of the small intestine (endoscopic capsule, Full MRI scan, full CAT scan, etc.)

Irritable bowel syndrome treatment

The doctor’s support and the patient’s trust in the doctor are fundamental. The doctor should calm the patient and explain the completely benign nature of the disorder in an easy-to-understand way, and the reasons for the symptoms, and helping detect and control the triggering factors.

Physical exercise, a balanced diet and taking sufficient time for defecation are factors that improve the symptoms and evolution of this disorder.

Physical exercise can improve abdominal pain and constipation significantly.

Certain dietary changes can help abdominal pain: avoiding copious meals, eating food that is low in fat and rich in protein can help reduce abdominal pain, avoiding flatulent foods improves abdominal distension, consuming abundant dietary fibre (fruit, vegetables, wheat bran, etc.) and water (1-2 litres per day) helps reduce constipation.

Selected medication can be used, depending on the patient’s symptoms. Pain and abdominal distension are improved with intestinal motility inhibitors (spasmolytic) and low doses of anti-depressives. Diarrhoea and constipation can be managed with antidiarrhoeals and laxatives, respectively.

Some patients also benefit from psychological treatment.