Irritable bowel syndrome: diagnosis and management

Short abstract

Irritable bowel syndrome is often dismissed as just being a nuisance rather than anything more serious, but its symptoms can seriously diminish a patient's quality of life. When the disease is better understood and treatment is tailored to the individual patient, it can often be rewarding to manage

What is it, and who gets it?

Irritable bowel syndrome (IBS) is a chronic condition characterised by abdominal pain, bowel dysfunction, and abdominal bloating in the absence of any structural abnormality. A number of pathophysiological abnormalities, however, can often be identified.¹ About 10-15% of the adult population in the United Kingdom is affected by irritable bowel syndrome.²

Aetiology

IBS is now clearly understood to be a multifactorial condition, with a variety of factors contributing to expression of the disease rather than its just being due to psychopathology.. These include motility, visceral sensation, central processing, genetics, dietary factors, inflammation, and neurotransmitters.¹

Exacerbating factors

Stress exacerbates IBS rather than being causative in any way. If stress is severe and chronic—for example, stress caused by continuous domestic strife—it can result in the disorder being virtually untreatable.³

Antibiotics need to be used with care in patients with IBS. Some antibiotics, particularly erythromycin, can make the condition worse.⁴

Non-steroidal anti-inflammatory drugs are often prescribed for the pain associated with IBS, but they may exacerbate symptoms. Paracetamol does not upset IBS.⁵

How do I diagnose it?

In the absence of a specific diagnostic test, the diagnosis remains largely clinical.

History

Patients typically report

• Abdominal pain or discomfort

• Disordered bowel habit, with either diarrhoea, constipation, or alternating diarrhoea and constipation

• Abdominal bloating or distension.

Many patients experience extracolonic features that can be useful for making the diagnosis:

• Low backache

• Constant lethargy

• Nausea

• Thigh pain

• Urinary symptoms:

  Frequency

  Urgency

  Urge incontinence

• Gynaecological symptoms:

  Dysmenorrhoea

  Dysparaeunia.⁶

The diagnosis of IBS is usually made intuitively with remarkable safety and reliability. Attempts to refine this clinical approach into guidelines have resulted in several diagnostic criteria being created: the Manning criteria, Rome I criteria, Rome II criteria, and Rome III criteria (in preparation).

Such criteria have proved useful for research purposes by ensuring homogeneity of patient populations, but their applicability in clinical practice is extremely limited and they are seldom used. Unless much more reliable guidelines are developed, doctors are likely to continue with the pragmatic approach they are using now.

Diagnostic uncertainty is more likely with diarrhoea predominant rather than constipation predominant IBS. Inflammatory bowel disease has to be considered when diarrhoea is present, especially if it is accompanied by perianal soreness (unusual in patients with IBS) or features such as arthralgia, mouth ulcers, or eye signs.

Examination

The abdomen should be normal on examination, although some tenderness is often found, particularly in the left or right iliac fossa. A palpable caecum should not cause concern but obviously needs to be distinguished from a mass associated with Crohn's disease.

Investigations

The concept that IBS is a diagnosis by exclusion is outdated. Investigation can often be kept to a minimum and should be used to exclude realistic alternatives. A full blood count and erythrocyte sedimentation rate are often sufficient, but a normal erythrocyte sedimentation rate does not definitively rule out inflammatory bowel disease. Examination of the colon is advisable in patients older than 50 years, and this is particularly important if the symptoms are recent in onset.⁷

Currently, some uncertainty exists about the need to screen for coeliac disease with endomysial antibody or tissue transglutaminase, although some authors say that screening should be undertaken routinely.⁸ Testing certainly is indicated in the presence of a family history or malabsorption. The threshold for investigation should be lower in the presence of “red flag” features:

• Rectal bleeding

• Anaemia

• Weight loss

• Late age of onset

• Acute onset

• Family history of cancer

• Family history of inflammatory bowel disease

• Signs of infection.⁷

How should I treat it?

The treatment of IBS is notoriously unsatisfactory, and no new drug has become available in the United Kingdom in the past 20 years. Consequently, none of the currently available options has been subjected to controlled trials conducted to modern standards. The following approaches are usually applied in the order in which they are discussed.

Dietary manipulation

An increase in fibre is often advised in the first instance. This is surprising, as there is little evidence to show that it is effective—in fact, insoluble fibre (for example, bran) often makes the condition worse by exacerbating bloating and pain.⁹ Fibre may help constipation; the commercially available soluble fibre preparations are the least likely to cause problems. Other food items that can exacerbate symptoms are coffee, chocolate, and sugar substitutes such as sorbitol or fructose. Any food suspected of causing problems must be excluded from the diet for at least one month. It is best to omit one food at a time; otherwise, confusion arises about which item is a problem if improvement occurs. More strict exclusion diets have also been shown to be helpful but are time consuming and best done under the supervision of a dietitian.¹⁰ True IgE mediated dietary allergy is probably relatively unimportant in IBS, but there is some preliminary evidence that eliminating foods on the basis of the presence of IgG antibodies to food may have a role.¹¹

Antispasmodics

Antispasmodics are available in two varieties:

• Anticholinergics—hyoscine and dicyclomine

• Smooth muscle relaxants—alverine, mebeverine, and peppermint oil.

It is impossible to predict who will respond to a particular preparation and therefore it is worth trying them all. Combinations of a smooth muscle relaxant and anticholinergic are sometimes effective, and taking them “as necessary” helps to minimise tachyphylaxis, which can occur after prolonged use.

Antidiarrhoeals

Antidiarrhoeal agents include loperamide, diphenoxylate, and codeine phosphate. Loperamide especially is useful as it also tends to increase the tone of the anal sphincter. Codeine can lead to dependency. Patients should be encouraged to titrate the dose of an antidiarrhoeal according to their needs, and they need to be reassured that regular use is not a problem and will not damage their bowel.

Laxatives

Laxatives include senna, bisacodyl, polyethylene glycol, and sodium picosulphate. In a similar way to antidiarrhoeals, laxatives are often best used in the form of a regular small dose rather than precipitating a catharsis now and again. Patients should be reassured that there is no evidence to suggest that laxatives “damage” the bowel, and that long term use is acceptable. Lactulose is best avoided, as it causes a lot of flatus and can exacerbate bloating.

Antidepressants

The tricyclic antidepressants and selective serotonin reuptake inhibitors are used, but there is more evidence to support the use of tricyclics. The tricyclics tend to cause constipation and consequently are particularly suited to diarrhoea predominant IBS. If such antidepressants are used in patients with constipation, a laxative may also have to be given. The selective serotonin reuptake inhibitors do not cause constipation.¹²

Behavioural treatments

Behavioural treatments include psychotherapy, cognitive behavioural therapy, and hypnotherapy. Evidence supports all of these treatments, but they are time consuming, costly to provide, and vary widely in their availability. They probably are best reserved for treatment in secondary and tertiary care.¹³,¹⁴

New treatments

Probiotics

Probiotics are “friendly bacteria” such as lactobacilli and bifidobacteria. Different strains can elaborate different mediators, which confer different properties on different organisms. This means that the therapeutic activity of one strain can be completely different from that of another strain. Combinations may not be a good idea, as they could inhibit one another. One probiotic strain (Bifidobacterium infantis 35624) has shown potential in patients with IBS, but further work is needed.¹⁵,¹⁶

Type 3 serotonin receptor antagonists

Alosetron, cilansetron, and ramosetron have been developed for the treatment of diarrhoea predominant IBS and show a positive effect in clinical trials. Ischaemic colitis has been reported with alosetron and cilansetron, although this seems to be self limiting if the drug is stopped. In addition, any type 3 serotonin receptor antagonist needs to be discontinued promptly if constipation develops.¹⁷ Alosetron is available in the United States but not in the United Kingdom.

Type 4 serotonin receptor agonists

Tegaserod is used for constipation predominant IBS and has proved effective in clinical trials. It is now on the market in several countries, including the United States, but not in the United Kingdom. No major safety issues seem to be associated with this drug.¹⁸

When should I refer my patient?

Many patients with IBS respond to a combination of education about the condition and simple measures to deal with symptoms. Referral for further assessment should be considered if there is doubt about the diagnosis or the patient becomes refractory to treatment.

What is the outlook?

IBS should probably be regarded as a lifelong condition, just as patients with a history of migraine will nearly always continue to have a tendency towards migraines. Patients should thus expect to have symptoms intermittently, especially if they are exposed to any exacerbating factors.

IBS in secondary care

Most cases of IBS are relatively mild, and the patient can cope with the condition reasonably well. Symptoms in patients who attend hospital clinics are much more severe; because IBS is so common, these patients are numerous. The factors below are more characteristic of patients seen in secondary and tertiary care than of those seen in general practice.

Pain

The pain of IBS can be exceptionally severe. Many women equate it with the pain of childbirth.

Bowel dysfunction

In some cases of constipation, bowel movements can be separated by many days or sometimes weeks. Patients with the diarrhoea predominant form of the condition can experience extreme urgency. Faecal incontinence is not uncommon and is devastating when it occurs.

Distension

Distension might be regarded as an unimportant feature, but, in some instances, the abdominal girth can increase by 10-12 cm by the end of the day.

Flatus

Flatus is a universal occurrence, but patients with IBS seem to experience more flatus problems, perhaps because so many patients are on high fibre diets, which are known to generate more gas. Dietary modification sometimes helps.

Sexual function

Eighty per cent of patients who attend hospital clinics say that their IBS significantly impairs sexual function. This compares with a figure of 30% in patients with Crohn's disease or ulcerative colitis. Dyspareunia is the main complaint; this usually follows intercourse and may persist for many hours or days.¹⁹

Sample questions

Here is a small sample of the questions that you can find at the end of this module. To see all the questions and to get the answers, go to www.bmjlearning.com/ and search for “irritable bowel syndrome”.

1. Which of the following statements about bloating in patients with irritable bowel syndrome is correct?

   1. Bloating when present is diagnostic of irritable bowel syndrome
   2. Bloating is more common in women with irritable bowel syndrome than in men with irritable bowel syndrome
   3. Bloating is usually at its worst in the morning
   4. Bloating is ranked as the least bothersome of all symptoms of irritable bowel syndrome

2. Which one of the following statements about post-infectious irritable bowel syndrome is correct?

   1. About half of all patients with irritable bowel syndrome date their problem to a preceding infection
   2. Steroids are the treatment of choice
   3. Patients generally present with diarrhoea predominant irritable bowel syndrome
   4. The most common infective organism is Yersinia

3. Which one of the following statements about probiotics is correct?

   1. Probiotics are inactivated bacteria that are beneficial to health
   2. Almost any strain of probiotic is helpful in patients with irritable bowel syndrome
   3. Probiotics may help prevent acute infectious diarrhoea

4. A 55 year old man has a diagnosis of longstanding irritable bowel syndrome and benign prostatic hyperplasia. Which of the following medications would you avoid giving this man?

   1. Peppermint oil
   2. Mebeverine
   3. Dicyclomine

Summary points

Irritable bowel syndrome is often regarded as a trivial, largely psychological disorder that is impossible to treat

Patients with severe disease have a range of symptoms that can seriously erode quality of life

Abdominal pain can sometimes be devastating, and the bowel dysfunction is not infrequently accompanied by incontinence

Better understanding of the pathophysiology, and tailoring treatment to the individual, can make irritable bowel syndrome a surprisingly rewarding condition to manage

Suicide

In a recent report, 38% of patients who attended a tertiary care clinic seriously considered ending their lives solely because of their bowel problem.²⁰ The patients were not especially depressed, and the suicidal ideation was considered to be centred around hopelessness related to the prospect of little relief from their problem in the future.

Extracolonic symptoms

The extracolonic symptoms listed earlier are important for several reasons:

• Diagnostic utility—the more of these symptoms that are present, the more likely the patient is to have IBS

• Reassurance—patients are often alarmed by the presence of all these disparate symptoms, suspecting that a major disease might be overlooked. An understanding that they all form part of the syndrome provides some reassurance

• Inappropriate referral and treatment.

Many patients with IBS are referred to gynaecological clinics, where they can undergo a variety of unnecessary investigations and sometimes even removal of the uterus or ovaries. Abdominal surgery unfortunately tends to make the symptoms of IBS even worse and should be avoided where possible.

Patients with IBS are also over-represented in urological clinics. They tend to be offered antibiotics for presumed recurrent urinary infections, but such drugs can exacerbate the bowel problem.

The low backache associated with IBS can lead to orthopaedic referral, and patients with IBS have been shown to have an excessive history of back surgery compared with controls.²¹

Absenteeism

IBS is a major cause of absenteeism from work which is a reflection of symptom severity as opposed to work avoidance.²²

Stigmatisation

Patients with IBS often are reluctant to admit to others that they have this condition because of fear that they will be labelled as psychologically disturbed. Potential employers often are reluctant to employ patients with IBS because of their reputation for absenteeism.

Quality of life

Given the severity and range of symptoms in some patients with IBS, that quality of life is eroded is not surprising. Quality of life can be measured with a questionnaire such as the 36 item short form; such an approach has shown that patients with IBS who attend hospital clinics have worse quality of life than those with chronic renal disease or diabetes.

Conclusion

IBS is an extremely challenging condition to manage. Effective treatment involves understanding the whole situation and tailoring the treatment to the individual. It is difficult, but not impossible, to offer at least some help to most patients with the condition.