Irritable bowel syndrome: a new twist to an old tale
Professor Nick Read on a poorly understood problem that affects one in five
Fourteen million Britons, a fifth of the population, are said to suffer from irritable bowel syndrome (IBS). This single condition costs the NHS more than £200 million in direct health costs and far more in terms of time off work and general disability. So it comes as a shock to realise a disease that makes life such misery for so many people does not actually exist.
Gastroenterologists invented IBS in the 1970s to provide a diagnosis for people suffering from abdominal and bowel symptoms with no obvious pathological basis. So, if they did not have Crohn's disease, diverticulitis, ulcerative colitis, gastroenteritis or colonic cancer, they suffered from IBS.
Unhappy with the notion of a diagnosis by exclusion, successions of medical opinion leaders have sought to refine the diagnostic criteria so the syndrome can be diagnosed confidently without time-consuming and expensive tests to rule out other diseases.
The most recent diagnostic criteria are 'at least 12 weeks in the preceding 12 months of abdominal discomfort that is either relieved by defecation or associated with changes in the frequency or form of stool in the absence of structural or metabolic abnormalities to explain the symptoms'. I fail to see how this takes us any further forward. As the philosopher Karl Popper once said: 'When men do not understand mechanisms, they invent terms'.
Having ring-fenced a collection of common bowel symptoms with no definitive pathology or aetiology, clinical scientists set about investigating features of the disease they had created. We now know sufferers are predominantly women, mainly young, live in Westernised cities and tend to suffer to a greater extent from psychological disturbance and traumatic life events.
The same applies to a whole raft of new diseases: chronic fatigue syndrome; fibromyalgia syndrome; functional dyspepsia; temporomandibular joint syndrome; hypoglycaemic syndrome; candidiasis hypersensitivity and so many others. Each medical specialty has its collection of medically unexplained symptoms and new illnesses.
Not surprisingly, there is extensive overlap. Sixty per cent of patients with IBS have features of functional dyspepsia, 20 per cent have chronic fatigue syndrome and 20 per cent have fibromyalgia.
This overlap leads to an inevitable conclusion that these are not so much separate diseases but all part of a much larger illness paradigm. Years ago, before medical science created the myth of discovering a treatable cause for all known ailments, such functional illnesses were grouped together under headings of melancholia, neurasthenia, hysteria and hypochondriasis.
Implicit in these descriptions was an understanding of the relationship between the illness, emotion and what had happened to the patient. So the invention of IBS and other new illnesses may be seen as but the latest twist to an age-old tale.
The feeling of what happens
We all know when something happens to us, we feel it in the body. The gut is a particularly eloquent organ of emotional expression. Gut feelings and gut reactions have permeated the language I can't stomach it; you make me sick; a lump in the throat; disgusted; gutted; shit scared all have their basis in physiology.
If we can put those reactions into context we can resolve what caused them and they will go away. But if we can't acknowledge our fears or deal with what has happened then the visceral feelings and reactions are consolidated into an illness an illness with no pathological basis.
Under normal circumstances the parasympathetic nervous system induces a relaxed regulated state of gut activity that facilitates digestion, but if something is troubling us the sympathetic nervous system the body's alarm system is activated.
This increases visceral sensitivity and disturbs gut motility, causing painful spasms, bloating and bowel disturbance. So the neuromuscular disorder often reported in IBS is not so much a definite disease of the nerves or the muscles in the gut wall, it is the disturbance in gut motility and sensitivity brought about by an imbalance of the autonomic nervous system and the hypothalamo-pituitary adrenal axis.
Neurohumoral dysregulation, however, will affect all the organs of the body. So why do some people present predominantly with bowel symptoms while others have headaches, backache or breathlessness? Is there some other factor that focuses attention on the bowel?
IBS can be triggered by an attack of gastroenteritis, but not in everybody. Fewer than 20 per cent of people with gastroenteritis go on to develop IBS.
So what causes some people to continue to have bowel symptoms while others just get better? Research we reported in The Lancet a few years ago suggested it might be stress. Those who continued to have symptoms had more anxiety and depression at the time of their acute illness and had experienced more difficult life situations in the six months before than those who got better.
This suggested to us the ongoing emotional tension acted through the sympathetic nervous system to maintain increased sensitivity and bowel disturbance. The symptoms and signs of the original illness had been recruited to express unresolved emotional issues. The same kind of scenario was evoked to explain the chronic fatigue that can follow viral infections, persistent headaches after injury, chronic backache after back injury and pelvic pain after hysterectomy.
A similar situation may also explain food intolerance. Most patients with IBS complain of food intolerance, but when patients undergo standard immunological testing, fewer than 3 per cent have any objective evidence of an allergy. It is often more a case of a sensitive gut that reacts to anything that goes into it than a specific food intolerance.
When unexplained intolerances to specific foods occur, it can often be conditioned by some specific gut-wrenching experience or fear. One of my patients developed a long-standing intolerance to fish because she was eating it when her boyfriend dumped her.
There is more to gut reactions than memory and conditioning. The gut is intimately connected to an emotional brain that functions through meaning and metaphor.
In the same way as embarrassment causes flushing of the face and neck, distress lacrimation and desire penile tumescence, so disgust induces gastric stasis, and anger colonic peristalsis and secretion. Gut reactions can persist as long as the situation causing them remains unresolved.
Soothing the turbulent bowel
I believe IBS (and indeed many other unexplained illnesses) are not just all in the body, nor all in the mind. They are disorders of the whole person. Management is not just a matter of giving a pill or going on a diet unless the patient has faith in the specific treatment and can use that faith to generate confidence to get better. Best treatments are those that tap into the patient's belief.
Probiotics, seeding the gut with beneficial bacteria to protect against pathogenic species, tap into powerful contemporary fears of pollution and contamination, not to mention eco-terrorism, and have some scientific credibility.
But evidence that bacterial populations are decimated in IBS and probiotics can replenish them is unconvincing.
New drugs alosetron and tegasarod, that act on serotonin receptors to rectify bowel sensitivity and reactivity, would appear to strike at a fundamental neurochemical mechanism, but they only augment the effect of the placebo control by 10-20 per cent and it is difficult to believe they may not in time be overridden by the effects of emotional tension. Henri Rousseau said: 'You'd better use the new drugs quickly before they lose their effect.'
Medical management of illnesses like IBS should be a partnership based on understanding of the illness narrative and a trusting engagement between doctor and patient.
Treatment must be compatible with the patient's beliefs. The doctor should help the patient find his or her way to get better and not seek to consolidate the illness with algorithms and pills.
Greater collaboration with patient charities and self-help organisations can help reduce the
burden on the medical profession and lead to better public understanding of this illness and a quicker return to health.
· IBS describes abdominal and bowel symptoms without obvious pathology or aetiology
· Patients are mainly women living in the Westernised cities who suffer to a greater extent from psychological disturbance and traumatic life events
· 60 per cent of patients with IBS have features of functional dyspepsia, 20 per cent have chronic fatigue syndrome and 20 per cent have fibromyalgia
· Neuromuscular disorder often reported in IBS is disturbance in gut motility and sensitivity brought about by an imbalance in the autonomic nervous system and the hypothalamo-pituitary adrenal axis
· Patients who suffer IBS symptoms after gastroenteritis tend to have had more anxiety and depression during their acute illness