Diagnosis:
Rome IV criteria
- Recurrent abdominal pain for least 1 day a week for 3 months associated with 2 of following
- Pain related to defecation
- Associated with change in stool frequency
- Associated with change in stool form
IBS subtypes:
- IBS predominant constipation
- IBS predominant diarrhoea
- IBS with mixed bowel habits
- IBS unclassified
The older Manning criteria emphasised pain relieved with defecation, visible abdominal distention, passage of mucus pr and sensation of incomplete evacuation. The pain is classically described as a cramping sensation with variable intensity and severity; it may occur at any site in the abdomen though it is classically in the LIF. The pain may occasionally deteriorate with defecation in some patients.
History:
An accurate medication history is required as many drugs may cause GI upset.
- Drugs associated with constipation
- Analgesics
- Anticholinergics
- Antihistamines
- Antidepressants
- Antispasmodics
- Antipsychotics
- Iron and aluminium supplements
- Antihypertensive including calcium channel blockers
- Drugs associated with diarrhoea
- Antibiotics
- Antihypertensives
- Oral hypoglycaemics – metformin
- NSAIDs
- Magnesium supplements
- Alcohol
- Multiple others
A good dietary history is valuable, eg. are symptoms aggravated by consumption of lactose, a high gluten load or high fibre consumption (eg. recent adoption of vegan diet)
Alarm features:
- Age of onset over age 50
- Rectal bleeding or melaena
- Nocturnal diarrhoea
- Progressive abdominal pain
- Unexplained weight loss
Physical Examination:
- A physical exam is usually normal but it is always worth documenting the patients weight.A rectal examination is of limited value in most cases.
Investigations:
- FBP & Fe studies
- Coeliac serology – coeliac occurs in 1.4% of general population and in up to 4% of patients presenting with IBS type symptoms
- In patients with diarrhoea
- Stool for MC&S and giardia antigen
- CRP
- Faecal calprotectin
- FOBT testing – a negative result in patients without alarm symptoms is reassuring
Patients without alarm features
- If patients meet diagnostic criteria and tests are negative then additional investigations may not be required. Food allergy testing is of little or no value.
Patients with alarm features or abnormal test results
- Additional investigations including upper and lower GI scopes and trans abdominal imaging (USS/CT) may be required depending on the symptom profile and investigation results
Differential diagnosis
- Coeliac disease
- IBD including microscopic / collagenous colitis
- NCGS – non coeliac gluten sensitivity
- Small intestinal bacterial overgrowth
- Colonic neoplasia
- Functional abdominal pain (centrally mediated pain syndrome)
- Narcotic bowel syndrome
- Other functional GI disorders
Indications for referral
- Presence of alarm features
- Abnormal investigations
Management of IBS
- Thorough explanation of symptoms and firm reassurance.
- Explain the chronic and benign nature of the problem and detail that the symptoms may vary in severity and frequency. Patients frequently change their symptom profile from one subtype of IBS to another. Up to 30% of patients will improve without any intervention
- Diet and lifestyle modification
- Both a low FODMAP diet and strict traditional IBS diet improve IBS symptoms. Simple lactose and or gluten avoidance may help some patients but if unhelpful then a formal trial of a low FODMAP diet should be considered. Information regarding the low FODMAP diet can be accessed via a diet sheet available from the GESA website and the patient can download the Monash University low FODMAP app on their smart phones. It is advisable for patients to educate themselves, at least partially, before consulting a dietitian.
- Exclusion of gas-producing foods eg beans, onion, celery, carrots, raisins, bananas, brussels sprouts & chickpeas, alcohol and caffeine may help to reduce flatulence. This can be an uncomfortable symptom for those with underlying visceral hypersensitivity.
- Physical activity (20to 60 minutes of moderate to vigorous activity 3-5 days a week) should be advised as this has been shown to improve symptoms.
- Psyllium supplements may help in some patients with constipation.
- Medication
- Osmotic laxatives for constipation. Movicol probably has less complications (eg flatulence) than lactulose. Stimulant laxatives may cause cramping pain but some patients find these are the only effective laxatives for them. Epsom salts (magnesium sulphate) can be used, beginning with a teaspoon dissolved in water and working up to a tablespoon daily if required.
- Antidiarrhoeal agents eg loperamide can be used safely in the long term when diarrhoea is disabling and pathological causes have been excluded.
- Anti spasmodic agents eg buscopan, mebeverine and concentrated peppermint are known to provide short term relief of symptoms of abdominal pain but the long term efficacy has not been established
- Antidepressants. Tricyclics such as amitriptyline and nortriptyline have analgesic properties independent of their mood improving effects. Also, via their anticholinergic properties they slow intestinal transit. This class of drug can beof use in those with diarrhoea where there is associated sleep disturbance. They should be avoided in patients when constipation is prominent and in this subgroup an SSRI may be superior. Always commence on a low dose making adjustments at 3-4 weekly intervals depending on response.
- Anxiolytics should be limited to short term use (less than 2 weeks) to help reduce acute situational anxiety. Longer term use may be associated with lower pain thresholds as they can decrease brain serotonin.
- Hypnotherapy
- A controlled trial demonstrating efficacy of hypnotherapy was first published in 1984 and its use in this condition has increased in the last decade. It is important to consult a psychologist with specific training in this modality.
- Faecal microbiota transplant.
- There is no evidence of a sustained response to FMT in any trial. A single trial did demonstrate a partial response at 3 months which was not sustained and multiple other random controlled trials have not demonstrated any efficacy. This form of therapy is not available currently in WA.
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