Diagnosing and Treating Irritable Bowel Syndrome - Latest Expert Advice

One in six people will suffer from Irritable Bowel Syndrome at some point in their lives; this article describes the causes, symptoms, diagnostic tests and treatments for the condition and will be of help to anyone who suffers from the symptoms of IBS.

Irritable Bowel Syndrome (IBS) - Contents

Who to see about IBS: the Gastroenterologist, the GP, the Pharmacist and the Dietician

Many people experience Irritable Bowel Syndrome (IBS) symptoms.  Often the symptoms are mild but for many the condition is a long term burden. Many patients worry that a more serious underlying problem might be the cause.  This concern can often by reduced by a simple professional assessment without the need for invasive tests.  Tests to exclude serious disease are important when appropriate and, in older patients, may help to reduce the risk of future colonic malignancy.  Management of IBS should start with carefully listening to the patient’s clinical history, performing appropriate examination and investigation and then starting treatment, preferably based on diet and non-pharmaceutical therapy.  Many patients can be managed by their family doctor and pharmacist.  For those with more significant symptoms a gastroenterologist and dietician are often the best team to help the patient manage the condition.

Latest thinking and treatments for Irritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS) is very common, affecting one out of 6 adults.  Although the symptoms of IBS vary there are typical features which can help doctors make an accurate diagnosis without using invasive investigations.  A diagnosis of IBS also relies on checking for worrying symptoms, which doctors call ‘warning’ or ‘red flag’ signs.  If these are present then more thorough investigation is needed.  The first step therefore, is to exclude serious disease; often with as little intervention as possible.  The second is to treat the condition as effectively as possible.  Finally, it is important to provide explanation and support to minimise the impact of remaining symptoms on their lives and lifestyle and to allow the patient to manage the condition in the long term, themselves.

Why does IBS happen?

The true answer is that nobody knows for sure.  It is also true that IBS is likely to be caused by more than one problem and there are probably many different processes which, when defective, lead to IBS symptoms.  There is a difference between people with mainly constipation-predominant IBS (C-IBS) and those with mainly diarrhoea-predominant (D-IBS).  Very often the condition does not neatly fall into one of these categories with many patients experiencing alternating constipation and diarrhoea.

Enteric Nervous System - There is no doubt that a major cause of IBS is there being a problem with the way the nerves inside the gastrointestinal tract work.  The intestines have a complex neuronal network, called the ‘enteric nervous system’, which picks up signals from the contents of the intestines and organises the way our guts move and digest.  We can think of the enteric nervous system as our ‘little brain’.  If the ‘little’ brain sends messages to our ‘big brain’ that there is a problem in the intestine (whether true or not) then the big brain will respond by giving instructions to the little brain to increase intestinal movement and this causes spasms, bloating and increased or decreased bowel movements.  When we are asleep these signals do not ‘get through’ unless there really is a problem.  This may explain why patients with IBS are rarely woken from sleep by intestinal problems whereas those with more serious diseases can be woken by symptoms.  The influence of the ‘big brain’ may also explain why anxiety and stress is more common with patients with IBS and also why so many treatments seem to work in the condition.  Perhaps if the big brain is convinced by a treatment sufficient to ignore the complaints of the little brain complaint, the symptoms will diminish.  We should not ignore this powerful phenomenon, nor disregard it as ‘placebo’.  Mind over matter is a very useful tool in reducing symptoms in many conditions, particularly IBS.  

Mast cells – These are inflammatory cells found in the lining of the gut which are important in allergies. In some patients, mostly with D-IBS, research has shown increased mast cell activity.  Treatments aimed at controlling this activity have not yet been proven to help, however.  

Serotonin - In both types of IBS there is often a problem with a nerve messenger called serotonin; in D-IBS there is too little, in C-IBS too much.  Drugs which increase serotonin in C-IBS improve symptoms.  Serotonin is also an important nerve messenger in the ‘big brain’.  This might explain why some patients improve with small doses of drugs normally used to treat depression.  

Genetics – IBS is more common in people with a family history of the same problem.  Exactly which genes are responsible is the subject of continuing scientific interest.

Bacteria – Some patients have abnormal levels of gut bacteria, particularly in the small intestine which should be fairly bacteria-free.  Antibiotic therapy can improve symptoms in some patients, and in some others probiotic treatments are effective.  There is a difficulty in finding microbial treatments becaus each of us has different sorts of natural gut bacteria and it is hard to know which ones are excessive and which are deficient in individuals with IBS. 

Food allergy/intolerance – This is an area of great interest and also misunderstanding in IBS.  Diet is important in treatment and certainly many patients tolerate certain foods poorly.  However, true food allergy usually causes symptoms that effect many parts of the body, including shortness of breath, wheeze, facial swelling, rash, and a drop in blood pressure.  These effects occur much less often than in IBS and when they do are often severe.  Sadly, many of the common ‘food allergy’ tests are not based on clear scientific evidence.  As a result they may identify foods that can actually be eaten without a problem and not pick up foods which cause symptoms.  A fully trained dietician is likely to be more helpful in managing food related symptoms than using these ‘food allergy’ tests.

What are the Typical Features of IBS?

Abdominal pain - The patient experiences abdominal pain or discomfort which is often felt in the lower part of the abdomen, but quite commonly moves about and can be felt in the back, pelvis and occasionally, even down the legs.  The pain typically gets better after a bowel action.  

Change in the stool pattern – With IBS there is almost always a change in the pattern of stool frequency and/or consistency.  Some patients tend more towards constipation, others are more generally loose (often with fragmented, pellet-like or stringy stools) and some vary between constipation and loose stools.  Many patients have a sensation that they have not finished a bowel action and need to return to the toilet within a short space of time after evacuation, particularly first thing in the morning.  This is called ‘incomplete evacuation’.  

Passage of mucous - Patients also often pass mucous or slime in the stool.  Mucous is the natural lubricant of the bowel.  In IBS more lubricant than normal is produced.  

Bloating and wind - Bloating is particularly common in women, especially after a meal (post-prandial bloating).  At times this can be so severe the person looks pregnant.  Excessive wind is a frequent and embarrassing feature of the condition.  Expelling wind often reduces the discomfort or pain and should be encouraged as it may reduce discomfort (we were made to live in the open air, after all!). 

Exacerbated by food and stress - Symptoms are often worse at times of stress and sometimes with particular foods (see below).  

The Rome III Criteria for IBS – Doctors can use these to help make the diagnosis.  These state that the following symptoms must be present for six months and be present for at least three days a month for the last three months.  Abdominal pain must be present with addition of two of the following:

  1. The pain gets better with bowel opening
  2. When the pain happens there is a change in the number of stools passed
  3. When pain happens there is a change in the way the stool looks

Most doctors recognise that these should not be used to make a diagnosis of IBS unless there are also no ‘alarm’ or ‘warning’ features suggesting a different condition.  

When should we be worried that bowel symptoms are not due to IBS?

Many serious bowel disorders can mimic IBS but almost always have other features that should raise concern and lead to investigation.  

Duration of the symptoms – IBS is a long-term condition.  It can start with a bowel infection, an operation or trauma to the intestine but the starting point in most patients is not obvious.  Anyone with recent symptoms that are not getting better may well have a different problem.  

Rectal bleeding - The passage of blood is NOT a feature of IBS and should always be fully assessed. However, particularly in patients who have piles, straining at stool because of IBS can lead to the passage of bright red blood. This is usually seen at the end of the motion and is not mixed in with the stool.  If there is pain in the anus at the time the bowels are open there may be an anal fissure, which is a tiny cut in the back passage lining which can be exquisitely painful.  Onset in patients over 40 or with a recent change in the bowel habit should always prompt investigation of this symptom.  

A lump in the abdomen or rectum – Any one feeling a lump in the abdomen that does not pass on opening their bowels or any in the anus or rectum should see a doctor for a full examination

Age – The main concern here is bowel cancer.  Although this can occur at almost any age, it is incredibly rare under 20, very rare under 30 and rare under 50.  Cases in young people do however happen and may be becoming more common.  Younger people with severe symptoms should be taken just as seriously as others as they may also have conditions such as inflammatory bowel disease.  It is important to know your family history as if bowel cancer has happened to young relatives you might be at risk.  However, if an older family member is affected this is more likely to be because of bad luck than bad genes.  

The ‘Red Flag’ or ‘Warning’ features – Those features listed below should be always investigated, as should lesser symptoms, or those in younger people, that are started fairly recently and are worsening over days, weeks or months.  The ages are not given as a single figure as there is no absolute cut off above which we should become concerned.  The red flag features are:

  • The passage of dark blood, or blood mixed in with the stool, particularly if the stool has become looser or more frequent
  • New onset of any blood in the stool in a patient over 40–45
  • Recent onset of stools looser than normal for more than 3 weeks, in those over 40–50 and 6 weeks if less than 40-50
  • Unexplained significant weight loss with altered bowel habit at any age
  • Iron deficiency anaemia in any male and any female who does not have significant menstrual blood loss
  • Anyone with a mass in the abdomen, anus or rectum
  • Any person with very severe bowel symptoms, at any age

What tests should be done to diagnose IBS?

Most patients, and in particular those with mild long-standing symptoms typical of IBS, need no or few tests.  It may well be sensible to do blood tests, which should include a full blood count, blood markers for inflammation, kidney, liver and thyroid function and a blood antibody test for coeliac disease.  A rectal examination is sensible if there are anal or rectal symptoms.  Patients with consistent diarrhoea, any severe symptoms or ‘alarm’ features, as listed above, should be referred for consideration of further tests, usually involving either a flexible sigmoidoscopy or colonoscopy.  A gastroenterologist with an interest in the condition, and working with a qualified dietician, is probably the best clinician to investigate and treat IBS.  

How should IBS be treated?

There are a great many treatments that are claimed to be effective to treat IBS.  Many of those thought to work seem do so through the powerful and important ‘placebo effect’.  Studies in IBS comparing a new treatment to placebo often find that well over a third of patients get better on placebo alone.  The same is true of other conditions and diseases, which explains why doctors prefer to use treatments that have been proven to be better than placebo in properly conducted trials.  

However, the placebo effect can still help patients to get better.  If the patient has a proper assessment and a good explanation of the symptoms, and can be reassured that there is no serious disease, this will help the ‘big brain’ to be less upset by the ‘little brain’ referred to above.  Relaxation therapy, and other treatments to combat stress and anxiety, may improve symptoms by the same mechanism.  

Diet - Diet is important, with some foods commonly tolerated poorly in IBS.  These are not usually true food allergies as in this situation there will usually be signs of ill-health such as rash, wheeze, a fever or other symptoms when the food is eaten.  In food intolerance the food causes symptoms confined to the intestine.  It is my practice to start with a simple avoidance program.  Patients are asked to avoid food substances in sequence for one or two weeks and are then reintroduced.  This should start with wheat-containing foods, followed by dairy products, then fatty and sugary foods, fruit and vegetables, and others if needed.  A professional dietician can be very helpful in assisting with dietary approach to treatment.

Bulking agents, laxatives and antidiarrhoeals – All are useful in different forms of the condition, mostly in reducing or increasing stool frequency, with little effect on pain or bloating.  Patients with alternating constipation and diarrhoea can find it hard to balance the use of these agents.

Antispasmodics - Crampy pains are often improved by antispasmodic agents such as mebeverine, alverine citrate, peppermint capsules and hyoscine.  Diarrhoeal symptoms can be improved with small doses of Imodium or loperamide.  Many patients with constipation are helped by fibre supplements; others find that bloating worsens with this therapy.  

Antibiotics – The small intestine is normally free of bacteria.  Small intestinal overgrowth may be responsible for symptoms in some patients with IBS, though the scientific evidence varies.  There is no doubt that some patients improve with antibiotic therapy and a few with probiotic therapy. One antibiotic, rifaximin, has shown promise in clinical trials.

Serotonin Agonists – The first of these agents caused serious side effects and were withdrawn from the US market but a newer one, prucalopide, has proven safe and effective in constipation-predominant IBS.  

Antidepressants – Low doses of both the tricyclic and SSRI antidepressants are effective in some patients with IBS, mostly those with the diarrhoea predominant type.  Side-effects can limit their usefulness, however.  

There are many other therapies, including many complementary and alternative therapies which claim to be effective in IBS, and many patients will swear by one or other of these.  Simple measures are best and if possible all drugs, conventional or otherwise should be avoided.  Where they are needed this should be with professional advice and guidance.  Your family doctor and pharmacist will often be able to help sufficiently – where more advice and treatment it is recommended that the next step is referral to an experienced gastroenterologist.

For further information on the author of this article, Consultant Gastroenterologist and Hepatologist, Dr Andrew Millar, please click here.
The part of the body that contains the stomach, intestines, liver, gallbladder and other organs. Full medical glossary
Relating to the abdomen, which is the region of the body between the chest and the pelvis. Full medical glossary
Various conditions caused by exaggerated reactions of the immune system (hypersensitivity reactions) to a variety of substances. Full medical glossary
A reduced level of haemoglobin, which carries oxygen in the blood. Anaemia causes tiredness, breathlessness and abnormally pale skin. Full medical glossary
A small (but intensely painful) tear in the skin of the anus, usually due to passing a hard stool. Full medical glossary
One of a group of special proteins in the blood that are produced in response to a specific antigen and play a key role in immunity and allergy. Full medical glossary
The external opening of the back passage, the rectum. Full medical glossary
A group of organisms too small to be seen with the naked eye, which are usually made up of just a single cell. Full medical glossary
A fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. Full medical glossary
A common name for the large and/or small intestines. Full medical glossary
Abnormal, uncontrolled cell division resulting in a malignant tumour that may invade surrounding tissues or spread to distant parts of the body. Full medical glossary
The basic unit of all living organisms. Full medical glossary
A condition in which the lining of the small intestine becomes damaged by oversensitivity to gluten, a protein found in wheat, rye and other cereals. Full medical glossary
The large intestine. Full medical glossary
Examination of the colon and rectum with a colonoscope, an imaging instrument that is inserted through the anus. Full medical glossary
a common condition where stools are not passed as frequently as normal Full medical glossary
Feelings of sadness, hopelessness and a loss of interest in life, combined with a sense of reduced emotional well-being Full medical glossary
The process of determining which condition a patient may have. Full medical glossary
When bowel evacuation happens more often than usual, or where the faeces are abnormally liquid. Full medical glossary
One of the three main food constituents (with carbohydrate and protein), and the main form in which energy is stored in the body. Full medical glossary
The raising of the body temperature above norma, which may be accompanied by symptoms such as shivering, headache and sweating. Full medical glossary
A viral infection affecting the respiratory system. Full medical glossary
A doctor who specialises in the digestive system and its disorders. Full medical glossary
The gut, which begins at the mouth and ends at the anus. Full medical glossary
The basic unit of genetic material carried on chromosomes. Full medical glossary
An anticholinergic drug. Full medical glossary
irritable bowel syndrome, a combination of abdominal pain and constipation, diarrhoea, or bouts of each that occur in the absence of any other diagnosed disease Full medical glossary
Invasion by organisms that may be harmful, for example bacteria or parasites. Full medical glossary
The body’s response to injury. Full medical glossary
A group of inflammatory conditions of the intestine. The two major forms are Crohn’s disease and ulcerative colitis. Full medical glossary
relating to the intestines, the digestive tract between the stomach and the anus Full medical glossary
The section of gut, or gastrointestinal tract, from the stomach to the anus. Full medical glossary
The major part of the digestive tract. Full medical glossary
One of two bean-shaped organs that are located on either side of the body, below the ribcage. The main role of the kidneys is to filter out waste products from the blood. Full medical glossary
A large abdominal organ that has many important roles including the production of bile and clotting factors, detoxification, and the metabolism of proteins, carbohydrates and fats. Full medical glossary
Bundle of fibres that carries information in the form of electrical impulses. Full medical glossary
Bundles of fibres that carry information in the form of electrical impulses. Full medical glossary
The system that gathers and stores information and is in overall control of the body. The brain and spinal cord form the central nervous system. Full medical glossary
Nerve cell. Full medical glossary
The bony basin formed by the hip bones and the lower vertebrae of the spine; also refers to the lower part of the abdomen. Full medical glossary
A craving to eat non-food substances such as earth or coal. Full medical glossary
Relating to the rectum, the lowest part of the bowel leading to the anus. Full medical glossary
The last part of the large intestine, where faeces are stored before being passed. Full medical glossary
Examination of the lower part of the intestine with a sigmoidoscope, an instrument with an attached light source and camera or optical system. Full medical glossary
An abbreviation for selective seratonin re-uptake inhibitors, a relatively new class of drug used to treat depression Full medical glossary
A tube placed inside a tubular structure in the body, to keep it patent, that is, open. Full medical glossary
Relating to injury or concern. Full medical glossary
A gland in the neck that produces hormones with a role in controlling metabolism. Full medical glossary
A physical injury or emotionally painful event. Full medical glossary