Irritable bowel syndrome

Irritable bowel syndrome is a disorder affecting the interaction between the gut and the brain, which can cause recurrent abdominal pain, bloating and changes in bowel habits. Its symptoms can vary over time and mainly present as diarrhoea, constipation or a combination of both.

What is irritable bowel syndrome?

Irritable bowel syndrome, also known by the acronym IBS and sometimes referred to as irritable colon, affects the functioning and sensitivity of the digestive system, particularly the large bowel. The term ‘irritable colon’ is still commonly used, although ‘irritable bowel syndrome’ better describes a condition involving various digestive and neurological mechanisms.

In people with this condition, the bowel may respond more intensely to normal stimuli, such as digestion, gas or the passage of stools. The speed of bowel transit may also be altered, leading to diarrhoea, constipation or a combination of both.

It is currently considered one of the so-called gut-brain interaction disorders. This means that the symptoms may be related to changes in digestive sensitivity, bowel movement and the way in which the gut and the nervous system exchange and process information.

Causes and associated mechanisms

Irritable bowel syndrome does not have a single cause. In each individual, mechanisms relating to intestinal sensitivity, bowel motility and communication between the digestive tract and the nervous system may be involved to varying degrees.

One such mechanism is visceral hypersensitivity, which causes certain bowel movements or distensions that would normally be barely noticeable to be experienced as more intense pain or discomfort. Changes in motility may also occur: accelerated bowel transit promotes diarrhoea and urgency, whilst slower transit may contribute to constipation, straining or a feeling of incomplete evacuation.

In some people, symptoms begin following a bout of gastroenteritis. Individual predisposition, certain dietary factors, sleep patterns, hormonal changes and emotional or social factors may also play a role. Stress can increase digestive sensitivity and alter the perception of symptoms, but it does not, on its own, explain the onset of the syndrome.

The gut microbiota is also being investigated as one of the possible factors involved. However, there is currently no specific microbiota pattern that would allow irritable bowel syndrome to be diagnosed using a commercially available test.

Symptoms

The most characteristic symptom is recurrent abdominal pain associated with changes in bowel movements. It may be related to defecation and accompanied by changes in the frequency or consistency of stools. The pain may improve, worsen or change after going to the toilet and does not always disappear after a bowel movement.

Bloating, abdominal distension, an urge to have a bowel movement and a feeling of incomplete evacuation are also common. Some people notice mucus in their stools.

Symptoms tend to fluctuate, with periods of improvement and phases when they worsen. They may change after certain meals, during periods of increased stress, following an infection, due to sleep disturbances, or at certain times of the menstrual cycle. In some people, fatigue, headaches, pelvic pain, anxiety or mood swings may also occur alongside these symptoms.

Types of irritable bowel syndrome

Classification is based primarily on the pattern of bowel movements. There may be IBS with a predominance of constipation, IBS with a predominance of diarrhoea, a mixed form in which both patterns alternate, or a form that does not clearly fit into the above groups.

The pattern may change over time. Identifying which pattern predominates at each stage is of practical importance because certain treatments are specifically targeted at constipation, diarrhoea or pain and are not equally effective for all forms of the syndrome.

Symptoms requiring specific assessment

The presence of blood in the stools, anaemia of unknown cause, fever, persistent vomiting, an abdominal mass or unintentional weight loss requires investigation into other possible explanations for the symptoms.

Symptoms that have started recently or are progressive, cause repeated waking during the night, or occur in people with a relevant family history of colorectal cancer, inflammatory bowel disease or coeliac disease also warrant particular attention. These circumstances help the doctor decide whether further tests are necessary.

Diagnosis

Irritable bowel syndrome can be diagnosed on the basis of a consistent pattern of symptoms, a thorough clinical assessment and a limited number of tests selected on a case-by-case basis. The aim is not to carry out every available gastrointestinal investigation, but to verify that the symptoms are consistent with the syndrome and to assess whether there are any factors that would suggest the need to investigate other conditions.

The so-called Rome criteria help to identify this pattern. They take into account the presence of recurrent abdominal pain related to bowel movements or accompanied by changes in the frequency or consistency of stools. The doctor also assesses the patient’s age, how long the symptoms have been present, family history, medication and any signs that might warrant further investigation.

In people with characteristic symptoms, basic tests may be requested. When diarrhoea is the predominant symptom, it may be advisable to investigate coeliac disease and check for signs of intestinal inflammation through blood tests or by measuring faecal calprotectin, a protein that can be detected in the stools.

Colonoscopy and other gastrointestinal tests

When the pattern of symptoms is consistent with irritable bowel syndrome, the investigation is initially guided by the medical history, physical examination and specific laboratory tests. Based on these results, the specialist decides whether further investigation with additional tests is necessary.

A colonoscopy allows the inside of the colon to be examined directly and biopsies to be taken where necessary. It may be recommended if certain symptoms are present, if test results are abnormal, if there is a relevant family history, if there are lingering doubts about the diagnosis, or if colorectal cancer screening is indicated based on age or individual risk.

Breath tests are used in specific situations to investigate, for example, certain problems relating to the digestion or absorption of certain sugars, or when there is a specific clinical suspicion.

The study of the gut microbiota remains an area of research, and although it is gaining increasing acceptance in selected cases, the diagnosis of irritable bowel syndrome is currently based on the pattern of symptoms, clinical assessment and any targeted tests that may be necessary.

The choice of each test therefore addresses a specific question. The aim is to carry out the investigation progressively and to select the tests that can genuinely help to explain the symptoms or rule out other conditions.

Treatment

Treatment is tailored to the bowel pattern, the predominant symptom and the impact that the symptoms have on daily life. The aim may differ for each person: to reduce pain, improve constipation, control diarrhoea or urgency, reduce bloating, or achieve a combination of these aims.

Management may combine changes to diet and lifestyle, physical activity, medication and, in selected individuals, treatments specifically targeting the communication between the gut and the brain. The strategy may be adjusted as symptoms change.

Diet and lifestyle

There is no one-size-fits-all diet for irritable bowel syndrome. Recommendations should be tailored to each person’s tolerance and avoid broad restrictions that serve no clear purpose. Maintaining relatively regular mealtimes, eating slowly, avoiding excessively large meals and identifying foods that repeatedly trigger symptoms can be helpful.

Soluble fibre, such as psyllium, may help to alleviate constipation and certain general symptoms. It is advisable to introduce it gradually, as a sudden increase in fibre intake can lead to flatulence and bloating.

The low-FODMAP diet temporarily reduces certain short-chain carbohydrates that are poorly absorbed in the small intestine and may ferment once they reach the colon. The term ‘FODMAP’ encompasses several types of these carbohydrates, found in foods such as certain dairy products, fruit, vegetables, pulses and cereals.

In some people with irritable bowel syndrome, reducing these for a limited period can help to alleviate pain, bloating or changes in bowel movements. This is followed by a gradual reintroduction to identify which foods and quantities trigger symptoms and which are well tolerated.

The aim is not to maintain a restrictive diet permanently, but to achieve a diet that is as varied, balanced and personalised as possible. Where appropriate, specialist nutritional support helps ensure the diet is followed correctly.

Medicines

Medicines are selected according to the predominant symptoms. There are specific treatments for constipation and diarrhoea, as well as options targeting abdominal pain, spasms or urgency.

Antispasmodics and certain peppermint oil preparations may help some people with pain. Probiotics constitute a highly diverse group: their effects depend on the strain, combination and formulation, so the results of one product cannot automatically be extrapolated to all others.

Treatments targeting the gut-brain axis

When pain or other symptoms persist, neuromodulators may be used at tailored doses. Some belong to families of medicines that are also used in psychiatry, but in irritable bowel syndrome they are used for their ability to modify pain processing and digestive sensitivity.

Certain psychological interventions specifically designed for these disorders, such as cognitive-behavioural therapy or gut-focused hypnotherapy, may also form part of the treatment for selected individuals. They act on the regulatory mechanisms of the gut-brain axis and do not imply that digestive symptoms are imaginary or exclusively psychological in origin.

Progression and monitoring

Irritable bowel syndrome usually follows a chronic or recurrent course, with periods of varying intensity. Bowel patterns may also change, so a management strategy that is appropriate at one stage may need to be adjusted later on.

The impact of the syndrome depends on both the severity and the unpredictability of the symptoms. Pain, urgency or changes in bowel movements can interfere with work, rest, travel or social activities. A clearly explained diagnosis and a tailored treatment plan help to set specific goals and avoid unnecessary interventions.

Follow-up also allows for a review of dietary restrictions, an assessment of whether medication remains appropriate, and a reassessment of the diagnosis if symptoms different from the usual ones appear.

Specialists involved

The care pathway for irritable bowel syndrome depends on the nature of the symptoms and the complexity of each individual case. Some people may receive initial guidance and treatment without the need for complex investigations; others require a more specialised gastrointestinal assessment, specific tests or a combined approach addressing diet and the gut-brain axis.

At the Publio Cordón Memorial Hospital, the Digestive System Department is involved in the diagnosis and monitoring of these digestive symptoms. When the clinical picture is consistent with irritable bowel syndrome or other functional digestive disorders, the hospital also has a Gut-Brain Axis Disorders Unit, which forms part of the Gastroenterology Department and is specifically dedicated to the diagnosis and management of irritable bowel syndrome, functional dyspepsia and other disorders related to the interaction between the digestive and nervous systems.

This specialist assessment enables us to determine whether the pattern of symptoms is consistent with IBS, to identify situations where further investigation is advisable, and to select only those tests that can provide relevant information. When an endoscopic examination is indicated — for example, a colonoscopy due to certain symptoms or risk factors — the Gastrointestinal Endoscopy Unit may be involved. This unit carries out diagnostic and therapeutic endoscopic procedures within the Gastroenterology Department.

Diet can be particularly important when symptoms are related to specific foods, or in cases of constipation, diarrhoea, or when a low-FODMAP diet is being considered. The Gut-Brain Axis Disorders Unit itself provides specialised care in clinical digestive nutrition, with specific expertise in irritable bowel syndrome. This enables dietary changes to be addressed within the digestive system itself and avoids restrictions that are more extensive than necessary.

For some people, treatment may incorporate interventions targeting the gut-brain axis. Depending on the predominant problem and individual needs, it may be useful to involve professionals with experience in specific psychological therapies or mental health. The hospital has specialists in psychiatry for situations where there is also a specific indication for this speciality; their involvement is not automatically part of IBS treatment and is decided on a case-by-case basis.

Therefore, the treatment pathway is not the same for everyone. In some cases, the focus may be on confirming the diagnosis and adjusting the diet or medication; in others, it may be necessary to carry out a colonoscopy, investigate certain symptoms in greater depth, or incorporate specific strategies targeting the gut-brain axis. The composition of the team is adapted to the needs that arise during diagnosis, treatment and follow-up.

Living with irritable bowel syndrome

The unpredictability of pain, diarrhoea, constipation or the urgent need to find a toilet can affect everyday activities and cause anxiety. Understanding the pattern of symptoms and having a strategy to manage them often makes it easier to resume activities that had previously been restricted.

Identifying specific personal triggers can be helpful, but the aim is not to constantly monitor every meal or gradually eliminate entire food groups. A sufficiently varied diet, tailored to individual tolerance, forms part of long-term management.

Management does not have to mean the complete elimination of any discomfort either. For many people, a more useful aim is to make symptoms less frequent, more predictable and less disruptive to work, travel, rest or social life.

Treatment may need to be adjusted as bowel patterns change. An ongoing relationship with the healthcare team allows you to review which measures are working, discontinue those that are no longer necessary, and adapt the strategy to each stage.

Medical information for general guidance

The purpose of this content is to facilitate understanding of irritable bowel syndrome, the mechanisms that may be involved in its onset, its various forms of presentation, and the options available for its diagnosis and treatment. It also aims to help explain why the assessment and management may differ depending on whether pain, diarrhoea, constipation, bloating or other symptoms are predominant.

At the Publio Cordón Memorial Hospital, we believe it is important for medical information to be accurate, understandable and useful in guiding each individual through their care journey. Our specialists devote part of their work to explaining conditions, tests and treatment options in an accessible way, helping patients and their families to better understand each stage and participate with greater confidence in decisions about their health. This commitment to knowledge and public outreach is also part of our dedication to research and the advancement of medicine.

The information provided in this factsheet is general in nature and cannot be used to establish a diagnosis or select an individual treatment. A medical assessment must take into account the pattern and progression of symptoms, personal and family medical history, a physical examination and, where necessary, additional tests specific to each individual.

In the event of severe symptoms, those that appear suddenly, or those consistent with a possible medical emergency, a proper medical assessment is required.