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Irritable Bowel Syndrome (IBS)
Irritable Bowel Syndrome or IBS is one of the commonest diagnoses made on
people with abdominal symptoms. It seems to be very common in most
countries across the globe and there are claims that 10% of the population
may at some point suffer from the condition. Although such numbers are
difficult to verify there is no doubt that Irritable Bowel Syndrome is a very
common condition. Its severity varies tremendously. The majority of affected
individuals have mild symptoms which occur periodically. Most people with IBS
can control their symptoms with dietary manipulations or stress management,
or with the help of their family doctors with various antispasmodic and anti-
diarrhoea medications. For most of those people the knowledge of an
established IBS diagnosis is reassuring and as it happens with a lot of chronic
conditions, the patients manage to deal with it for long periods without always
resorting to the doctor. Therefore the true extent of symptoms in the affected
population is difficult to estimate.
However there are a smaller number of individuals who get much more severe
symptoms and a number of studies have shown that IBS can affect the quality
of life of those people as well as causing absence from work and chronic
consumption of medication. Those patients are frequent attenders of the
general practitioners and gastroenterologists.
The bowel has a limited “repertory” of symptoms. A number of very different
conditions such as bowel cancer, inflammatory bowel disease, diverticular
disease, IBS etc. present with very similar symptoms which are in themselves
insufficient to provide the diagnosis.
IBS has a wide range of symptoms but the commoner are abdominal pain,
distention/ bloating, diarrhoea, constipation. An association with more general
symptoms such as headaches, backache, dyspepsia, fatigue, urinary
symptoms, dyspareunia (painful vaginal intercourse) and psychological
symptoms has often been reported but has not adequately been explained. A
form of abnormal “smooth muscle hyperactivity or hypersensitivity” has been
hypothesized to explain the symptoms form various organs.
The abdominal pain in IBS is usually colicky (cramps) and is relieved by going
to the toilet.
The periodic change of bowel movements can take the form of diarrhoea/
increased frequency/presence of non formed stools, constipation or alternation
of constipation – diarrhoea.
Presence of mucous in the stools is common. On the contrary IBS is never a
cause for bleeding per rectum, therefore whenever the patient reports
bleeding an alternative or additional diagnosis should be sought.
Some factors which help establishing the diagnosis are: female patients, age
below 45, long standing and periodically occurring symptoms.
Attempts have been made to create diagnostic criteria which would establish
the IBS diagnosis more firmly. The “Manning” criteria and the “Rome” criteria
have been introduced and evaluated in number of studies however they have
not been successful in achieving generalised status and they leave a lot to be
desired.
Essentially the diagnosis of Irritable Bowel Syndrome:
a. Should be made always by a physician and, preferably not a general
practitioner but someone who specializes in bowel problems such as a
gastroenterologist or a colorectal surgeon.
b. Should be made only after all organic causes of bowel disease have
been excluded – and this is not always easy, several investigations may be
required.
c. Should be made only after the physician has followed the patient for an
appropriate length of time to establish the chronicity and pattern of symptoms.
Unfortunately some patients are given a diagnosis of IBS on the basis of a
single visit and quick history on the grounds of their age or absence of family
history of cancer. IBS is so common that it is inevitable that will overlap with
some other conditions which require different management. Common
diagnoses which may be missed because of co-existence and overlapping
symptoms are bowel cancer, mild inflammatory bowel disease, celiac disease,
diverticular disease, small bowel adhesions, food intolerance etc.
A few facts about IBS
Many studies have identified a relationship between psychological factors and
attacks of symptoms on IBS patients. A similar link can be found in some other
bowel conditions. The link may be disorder of neurotransmitters such as
serotonin, a molecule which is involved in the pathogenesis of depression as
well as IBS.
20% of IBS sufferers report IBS symptoms on a first degree relative.
Studies on twins suggest that there is a genetic component in IBS which has
not so far been identified.
Abnormal motility in IBS has been linked to abnormal response to gas by the
bowel wall. This is called visceral hypersensitivity and is associated with
hyperalgesia, which means a low threshhold for pain. Hyperalgesia makes
colonoscopy particularly uncomfortable for IBS patients and it has been
suggested that this symptom may be specific for IBS. It is not certain where the
origin of hyperalgesia lies. It could be originating from abnormal or
hypersensitive sensors from the gut wall or alternatively, IBS patients could
have a Central Nervous System which is hypersensitive to stimuli from the
bowel and reacts with abnormal motility contractions and pain.
There are quite a few cases of IBS which develop after infectious gastroenteritis
. Microscopic changes in lymphocytes and neuroendocrine cells have been
identified. Post-infectious IBS could be a form of auto-immunity.
Inflammation may be not always obvious but is definitely present on some IBS
patients who have microscopic inflammation presenting with rather subtle
lymphocyte and mast cell abnormalities.
Probiotics, bacteria which exist in yogourt, may have a partial beneficial effect
on IBS, something which supports the theory of inflammation.
Serotonin, is a neurotransmitter which exists in the brain, the platelets and in
the gut. Its secretion is stimulated by multiple factors, including hormonal
mechanisms and infectious agents. Abnormalities of serotonin activity have
been confirmed in IBS and pharmaceutical agents based on serotonin are now
available in the USA but not yet in the UK. The mains ones are:
Tegaserod a 5HT4 agonist for females with constipation.
Alosetron, a 5HT3 agonist in females with diarrhoea – ischaemic colitis.
Cilansetron, a 5HT3 agonist for both males and females with diarrhoea.
Apart form the serotonin - acting medications, the rest of the medication used
on IBS is largely aiming at symptomatic treatment.
Depending on the form of IBS, loperamide can used to control diarrhoea,
laxatives to improve constipation and antispasmodic agents such as
mebeverine, buscopan, colpermin etc. to reduce pain and bloating.
Antidepressants such as amitryptiline are used in low doses not for their anti-
depressant effect but because they improve pain and motility of the bowel.
There is no consistently effective diet for improving IBS. Although high fibre is
generally recommended there are IBS patients who cannot tolerate
vegetables. Generally, studies to exclude food intolerance syndromes should
be made on every IBS patient under investigations.