Family doctor

What is it?

The irritable bowel syndrome is the most common gastrointestinal disease in clinical practice. It is a condition characterised by abdominal pain or discomfort, change in stool frequency or consistency, abdominal distention, the sensation of incomplete evacuation and the passage of mucus. It can vary in severity from being a minor infrequent disorder in some to being a disabling disorder in others. While it is by no means a life-threatening condition it can cause a great deal of distress in some individuals and also poses a significant challenge to doctors involved in the management of these individuals.

IBS is a worldwide disorder with a prevalence in the community of around 20%. There is a remarkable consistency in the prevalence of this disorder in the United States of America, United Kingdom, Europe and New Zealand. However, most patients with the symptoms of IBS (60 to 75%) do not consult a doctor. Individuals with the irritable bowel syndrome constitutes up to 50% of the referrals to gastroenterologists. IBS is more common in females with the female to male predominance being 2:1. IBS is most common in the 20 to 40 year age group. Symptoms begin before the age of 35 in 50% of patients and 40% of patients are aged between 35 and 50. IBS is recognised in children and many patients can trace the onset of the symptoms back to their childhood. Onset in old age is rare and it is important in this age group to exclude more serious conditions.

What is the cause?

The cause of IBS is not known. No structural, biochemical or infectious etiology has been found. Possibilities include genetic, hormonal, dietary, infective and psychosocial factors have been considered but none have been proven to be the underlying cause. However, some of these factors can influence symptoms in individuals with IBS. It is known that certain foods such as legumes are not tolerated well by patients with IBS. It has been shown that gastrointestinal symptoms including abdominal pain, nausea and diarrhoea are more likely to be reported during menses in women with IBS. Psychosocial factors play an important role in IBS.

As mentioned previously, the greater majority of patients with IBS do not present to a doctor. It has been shown that patients not seeking medical attention are not psychologically different from healthy subjects. Therefore, while psychosocial factors do not cause the IBS symptoms, they can influence how symptomatic patients respond. It is not clear whether those who do seek medical attention actually have more severe symptoms because their psychological disturbances effect pain sensation or whether they experience similar symptoms but report them as more severe. It is not uncommon for the ongoing symptoms of IBS to start after a gastrointestinal infection, for example, after contracting travellers' diarrhoea. Although the infection resolves either spontaneously or with treatment, the individual is left with the chronic symptoms of IBS. It is possible that these individuals have the potential for IBS which is triggered by infection.

The fundamental disturbance thought to be responsible for IBS symptoms are two fold. Firstly, the IBS is thought to be the result of abnormal contractions (motility) of the large intestine (colon). Contractions lead to spasms in the colon, causing abdominal pain, diarrhoea or constipation. Secondly, it is felt that the intestines of individuals with IBS have increased sensitivity to normal events that occur in the bowel such as spasm and distension. These individuals experience abdominal pain and bloating sensations when the level of colon contractions may not be excessive. It is well know that air insufflation or balloon distention of the rectum, sigmoid colon or small intestine causes abdominal pain in IBS patients at volumes usually not painful in normal subjects. It is not know whether this is as a result of fundamental defects in the nerve cells of the bowel wall or whether the underlying problem is an altered perception of pain by the brain.

It was previously thought that the motility disturbance and hypersensitivity to pain was limited to the large intestine (colon), hence IBS was previously referred to as spastic colon. It is now known as IBS is a more generalised disorder of the gastrointestinal tract. For example, involvement of the oesophagus is not uncommon and can result in non-cardiac chest pain, heart burn, difficulty in swallowing (dysphagia) and a feeling of a lump in the throat (globus sensation). Abnormal contractions have also been demonstrated in the stomach, small intestine and gallbladder; the latter giving rise to symptoms similar to the pain of gallstones. There is also a higher incidence of gynaecological and urological symptoms in patients with the IBS. These include increased urinary frequency, dysuria (pain on passing urine), dyspareunia (pain during intercourse) and inhibited sexual desire. These individuals also have more generalised symptoms such as fatigue and lethargy.

What are the symptoms?

A diagnosis of IBS is based on a careful and detailed history to identify characteristic positive symptoms which on the one hand identify IBS and on the other, exclude conditions that mimic it, selected laboratory investigations and sigmoidoscopy (an instrument for looking up the lower bowel). In some individuals further testing (e.g. colonoscopy) will be required to exclude other disorders.

The history should include a detailed history of the abdominal pain and its association with food and bowel motion. Careful description of bowel frequency, consistency and volume should be elicited. Associated symptoms such as flatulence, bloating and gastro-oesophageal reflux should be looked for if the patient has not already volunteered this history. A careful dietary history is essential, including use of caffeine beverages, or foods and beverages sweetened with fructose or sorbitol which may cause diarrhoea, bloating or cramps. It is important that psychosocial factors be specifically looked for, including the reason for the consultation (e.g. fear of cancer). The typical symptoms of IBS which can often enable a positive diagnosis to be made are very well outlined in what is referred to as the Rome Criteria:

At least three months of continuous or recurrent symptoms of:

1) Abdominal pain or discomfort that is -

• Relieved with defaecation; and/or
• Associated with a change in frequency of stool; and -

2) Two or more of the following, at least on 1/4 of occasions or days:

• Altered stool frequency (more than 3 a day or less than 3 per week)
• Altered stool form (lumpy, hard or loose/watery stool)
• Altered stool passage (straining, urgency, or a feeling of incomplete evacuation.
• Passage of mucus; and/or
• Bloating or feeling of abdominal distension.

Patients with constipation-predominant IBS may have many days or weeks of constipation interrupted with brief episodes of diarrhoea. Constipation, which at first is episodic, eventually may become continuous and increasingly intractable to laxatives and later to enemas. Stools are usually hard and variably described as pellets, marble-like, or small hard balls. On the other hand, stool calibre may be narrow (pencil-thin or ribbon-like).

Pain may become more severe with increasing duration and severity of constipation. In half of patients evacuation leads to relief of pain but frequently there is a sensation of incomplete evacuation leading to repeated attempts at defaecation with minimal or no success. Several hours may be devoted to this process before some relief is obtained.

Diarrhoea attributable to IBS usually consists of small volumes of loose stool. Evacuation is often preceded by extreme urgency, occurring typically in the morning or after meals. The initial movement may be normal in consistency then rapidly followed by a softer, unformed stool and then by increasingly loose stools. Abdominal pain preceding the movement is commonly relieved by defaecation, albeit sometimes only briefly. Diarrhoea following a meal is another feature of IBS. This usually correlates with the quantity rather than the type of food. This diarrhoea is sometimes explosive because it consists of a mixture of gas and fluid; and it is usually associated with extreme urgency or pain. The stools in individuals with diarrhoea may be described as loose, mushy or watery.

Pain is variously described as vague, bloating, crampy, burning, dull, aching, knife-like, sharp or steady. Acute episodes of severe, sharp, knife-like pain may be superimposed on a constant or intermittent background of dull aching pain. The pain is more often localised in the left lower abdomen than at any other site and more often in the lower abdomen than in the upper abdomen. It is experienced more often in several sites than in one site. Rectal pain may be present and ranges from mildly annoying to extremely disturbing. Pain is often precipitated by meals and relieved by defaecation. Rarely does the pain awaken the patient from sleep.

Bloating or perceived abdominal distension is a common complaint in IBS, belching and excessive flatus is also commonly reported. Increased stool mucus is often seen in IBS, it can be clear or whitish.

The physical examination in IBS patients is generally unremarkable. Abdominal tenderness, often in the left lower abdomen may be elicited. The doctor should look out for possible psychological disorders. Furthermore, "alarm" symptoms which point to more serious underlying conditions should be looked for. These include onset in old age, steady progressive course, frequent awakening by symptoms, fever, weight loss and rectal bleeding.

All patients with IBS should have a few basic tests done. These include a full blood count, ESR, stool examination for occult blood and a sigmoidoscopy. In addition, specific tests may be required to exclude disorders such as parasitic infection, inflammatory bowel disease and lactose intolerance (stool examination for ova and parasites and pus cells, colonoscopy or small bowel enema and lactose tolerance test). In individuals with associated upper-abdominal symptoms, gastroscopy may be indicated.

Conditions which mimic IBS include lactose intolerance, laxative abuse, gallbladder disease, inflammatory bowel disease (ulcerative colitis and Crohn's disease), parasitic infections (such as Giardia or amebiasis), diverticular disease and more importantly colonic malignancy, especially in the older patients. Side effects of drugs may always be kept in mind as the possible cause of symptoms resembling IBS. An enquiry should also be made about the use of "over the counter" drugs which some patients may not think is necessary to mention. Others may intentionally avoid disclosing drugs they may have become dependant on.

What is the treatment?

The diagnosis of IBS heralds a long-term relationship between doctor and patient. It is very important that a positive doctor/patient relationship is established at the onset. A positive outcome is most likely when the doctor is non-judgmental, establishes realistic expectations and consistent limits, encourages the patient's understanding of the illness and involves the patient in treatment decisions. The patient needs to be reassured of the benign nature of the illness and the excellent long-term prognosis. It should be emphasised that although there is no cure for IBS, there are steps that both the doctor and patient can take to improve the symptoms.

Initial recommendations generally focus on dietary modifications. These include avoidance of dairy products, food beverages or medications containing fructose or sorbitol, excessive caffeine, or gas-forming food such as legumes. Many IBS patients believe that their symptoms are caused by specific foods and may often unnecessarily restrict what they eat.

Fibre supplements can often be recommended regardless of the presenting complaint but are particularly useful if constipation is the predominant symptom. Natural fibre such as wheat bran, wholemeal and mixed grain bread, porridge, weetbix, muesli and other bran cereals, wholemeal flour, vegetables and raw fruit are inexpensive but a significant number of patients complain that a high-fibre diet aggravates symptoms, particularly bloating and distension. Certain agents such as psylium compounds (e.g. Metamucil, Granocol, Isogel, Konsyl Orange, Metamucil Orange, Mucilax and Normacol) tend to produce less gas and are preferred in the treatment of IBS. Because these agents absorb water, they prevent excessive dehydration of stool as well as excessive liquidity. Therefore, they may be effective for both constipation and diarrhoea. These agents should be taken with meals so that they become part of the stool as it is formed. Patients are advised to eat slowly, not to chew gum or drink carbonated beverages and to avoid artificial sweeteners such a sorbitol and fructose.

While some patients will improve with the simple measures as outlined above, others will require additional medication for their symptoms. There is no single medication that will benefit all patients with this disorder. Therefore, management will be very individual.

As pain is often a major symptom in IBS, antispasmodic agents such as Colofac, Buscopan and Merbentyl are commonly used. These reduce the abdominal cramps and to a lesser degree the bloating. Anti-diarrhoeal agents (Lomotil, Imodium and related drugs) are used where diarrhoea is a prominent symptom.

Antidepressants are also very useful in the treatment of IBS. Beside their obvious benefit in those with underlying anxiety and depression, they also reduce intestinal spasm and are also known to raise the pain threshold.

A high-fibre diet and agents such as Metamucil are beneficial in patients with constipation-dominant IBS. Intermittent use of agents such as Lactulose, Senekot, Coloxyl with Senna etc. may be required. Care needs to be taken that the patient does not become dependent on laxatives. As IBS is a chronic disorder, habit forming drugs such as codeine-containing compounds should be avoided for fear of the patient developing drug dependence.

Psychotherapy is indicated as a treatment for patients with concomitant psychiatric illness and for patients who have not responded to the measures outlined above. In one trial where patients were given psychotherapy, it was shown that those who received this treatment did significantly better than those given conventional medical treatment only. Furthermore, those patients treated with psychotherapy showed a significant decrease in their need for medical consultation and investigation.

Presently, trials are being undertaken on drugs which relieve abdominal bloating, increase tolerance to colonic distension and reduce rectal sensitivity. Initial results look promising.

While IBS can be a disabling condition, long-term prognosis is very good. This condition does not lead to more serious conditions of the bowel such as inflammatory bowel disease or bowel cancer.

Conclusion:

The IBS is a rather paradoxical disorder. While on the one hand it can be an ongoing chronic disabling condition, on the other hand it has an excellent prognosis. A successful outcome will depend on an understanding of the condition and a doctor who can empathise about this often distressing but fortunately benign disorder.