Irritable bowel syndrome (IBS) is a ‘functional’ gastrointestinal disorder. This means that the cause of it is not a specific and identifiable disease entity, but a plausible consequence of disordered functioning of the bowels. Other names for IBS that occur in literature include “spastic colon”, “irritable colon” and “nervous colon”.
IBS is characterized by abdominal pain or discomfort which is often relieved by defecation and is related to a change in bowel frequency and stool form. There may also be difficulty in passing stools, needing straining, passage of mucus and also a subjective sensation of bloatedness and abdominal distention. There are various sub-types of IBS, depending on whether the symptoms are related more to constipation, to diarrhoea or to alternating constipation and diarrhoea.
The cause of IBS is uncertain. Theories include altered gastrointestinal motility which results in abnormally quick or slow movement of the bowels; abnormal sensitivity to the sensation of movement of the contents of the intestines; an association with depression, stress or anxiety in the patient, or microscopic inflammation of the bowels perhaps caused by bacteria which have not been identified.
IBS is a substantial problem in most countries, with a prevalence of about 4% in Singapore and up to 20% in UK and USA. Some of the variation may be due to cultural differences in health seeking behaviour. Americans and Europeans suffer more from IBS than Asians and Africans. It is also more common amongst Caucasian women and Indian men. Half of these patients have symptoms before the age of 35, and IBS may even occur in childhood. In patients above 40 years, more serious conditions must be excluded before IBS is diagnosed. IBS is an important condition in the community because up to 20% of all IBS sufferers seek medical care, and up to 50% of all gastroenterological referrals are for investigation of suspected IBS. Work absenteeism, lost wages and economic losses due to IBS are significant.
When a patient appears with symptoms suggestive of IBS, a careful history must be taken with particular emphasis on the relationship between symptoms and food intake, the stool form and pattern of bowel movements, whether passing motion relieves pain and bloatedness and any other features that may raise suspicion of more serious diseases such as gastrointestinal cancers, inflammatory bowel disease, malabsorption, hormonal problems, gallbladder or pancreatic disease. Atypical symptoms which raise suspicion of more serious diseases include- acute symptoms, progressive symptoms, night symptoms, loss of appetite or weight, fever, rectal bleeding, painless diarrhoea or constipation and oil in the stools.
In clinical examination, there are few abnormal findings. The patient appears healthy; there may be a tender or palpable sigmoid colon and the patient may be excessively tense, nervous or anxious. Special attention is paid to older patients (over the age of 40) because the probability of serious illnesses especially cancer rises rapidly after this age.
A doctor may order investigations as guided by the clinical presentation. Common tests include blood, urine and stool tests. Endoscopic examination by gastroscopy and/or colonoscopy is often performed as these are reliable methods of excluding diseases in the digestive tract. Imaging tests such as ultrasound or computerized tomographic (CT) scans may also be done. In IBS, all tests will be negative, or there will only be minor findings that do not explain the symptoms.
Treatment for IBS depends on the symptoms bothering the patient. Sometimes the sheer knowledge, that there is no serious disease is sufficient to make a patient feel better, and he or she may not want medicines for otherwise tolerable symptoms. When needed, treatment could include high-fibre stool bulking agents, anti-spasmodic, pro-kinetic or anti-diarrhoea drugs. Recent studies suggest that some patients may benefit from the antibiotic, Rifaximin.
It is essential to counsel and reassure patients that there is no serious illness, although the problem may come and go over a long period of time. Notably, IBS does not lead to cancer nor shorten a patient’s life. If there are psychological factors such as anxiety or depression, these need to be dealt with. The occasional patient may need to be referred to a psychologist or psychiatrist for help.
The key to successful management of IBS is a strong patient-doctor relationship. Expectations must be managed, because symptoms may be difficult or take time to control. Most importantly, a patient must not lose confidence and end up seeing multiple doctors, resulting in unnecessary or repeated investigations. If there are identifiable stressors, a patient needs to be led to acknowledge them and learn coping techniques.