Irritable bowel syndrome (IBS) is a common disorder that affects the large intestine (colon). Irritable bowel syndrome commonly causes cramping, abdominal pain, bloating, gas, diarrhea and constipation. IBS is a chronic condition that you will need to manage long term.
Irritable bowel syndrome (IBS) is a functional bowel disorder in which abdominal pain is associated with defecation or a change in bowel habit.
Epidemiology
Approximately 20% of the general population fulfil diagnostic criteria for IBS but only 10% of these consult their doctors because of gastrointestinal symptoms. Nevertheless, IBS is the most common cause of gastrointestinal referral and accounts for frequent absenteeism from work and impaired quality of life. Young women are affected 2-3 times more often than men. There is wide overlap with non-ulcer dyspepsia, chronic fatigue syndrome, dysmenorrhoea and urinary frequency. A significant proportion of these patients have a history of physical or sexual abuse.
Aetiology
IBS encompasses a wide range of symptoms and a single cause is unlikely. It is generally believed that most patients develop symptoms in response to psychosocial factors, altered gastrointestinal motility, altered visceral sensation or luminal factors.
Psychosocial factors
Most patients seen in general practice do not have psychological problems but about 50% of patients referred to hospital meet criteria for a psychiatric diagnosis. A range of disturbances are identified, including anxiety, depression, somatisation and neurosis. Panic attacks are also common. Acute psychological stress and overt psychiatric disease are known to alter visceral perception and gastrointestinal motility in both irritable bowel patients and healthy people. There is an increased prevalence of abnormal illness behaviour with frequent consultations for minor symptoms and reduced coping ability (Box 22.76). This is usually colicky or 'cramping', is felt in the lower abdomen and relieved by defecation. Abdominal bloating worsens throughout the day; the cause is unknown but it is not due to excessive intestinal gas. The bowel habit is variable. Most patients alternate between episodes of diarrhoea and constipation but it is useful to classify patients as having predominantly constipation or predominantly diarrhoea. The constipated type tend to pass infrequent pellety stools, usually in association with abdominal pain or proctalgia. Those with diarrhoea have frequent defecation but produce low-volume stools and rarely have nocturnal symptoms. Passage of mucus is common but rectal bleeding does not occur.
Despite apparently severe symptoms, patients do not lose weight and are constitutionally well. Physical examination does not reveal any abnormalities, although abdominal bloating and variable tenderness to palpation are common.
Diagnosis
Features of irritable bowel syndrome
- Altered bowel habit
- Colicky abdominal pain
- Abdominal distension
- Rectal mucus
- Feeling of incomplete defecation
Investigations are normal. A positive diagnosis can confidently be made in patients under the age of 40 years without resorting to complicated tests. Full blood count, ESR and sigmoidoscopy are usually done routinely, but barium enema or colonoscopy should only be undertaken in older patients to exclude colorectal cancer. Those who present atypically require investigations to exclude organic gastrointestinal disease. Diarrhoea-predominant patients justify investigations to exclude microscopic colitis (Box 22.77). This is given in doses (10-25 mg at night) which are much lower than those used to treat depression. Side-effects include dry mouth and drowsiness but these are usually mild and the drug is generally well tolerated, although patients with features of somatisation tolerate the drug poorly and lower doses should be used. It may act by reducing visceral sensation and by altering gastrointestinal motility. Other drugs may overcome abnormalities of 5-HT signalling which have been identified in some IBS patients. These include 5-HT4 agonists. Active anxiety or affective disorders should be separately treated. Psychological interventions such as cognitive behavioural therapy, relaxation and gut-directed hypnotherapy are reserved for the most difficult cases.
Most patients have a relapsing and remitting course. Exacerbations often follow stressful life events, occupational dissatisfaction and difficulties with interpersonal relationships.
Source
Davidson's medicine
