Ms. Emma Williams, a 32-year-old marketing executive, presents to her GP with a 12-month history of recurrent abdominal pain and altered bowel habits. She describes crampy lower abdominal pain that occurs at least 3 days per week, often relieved after opening her bowels. Her bowel habits alternate between constipation (hard, pellet-like stools) and loose stools, sometimes multiple times per day. She experiences significant bloating, particularly in the evenings, and excessive flatulence. Symptoms are worse during stressful periods at work and around her menstrual period. She denies rectal bleeding, nocturnal symptoms, or unintentional weight loss. She has tried over-the-counter peppermint oil with some benefit. She reports the symptoms significantly affect her quality of life, causing anxiety about being away from toilet facilities. Examination reveals a soft, non-tender abdomen with no masses or organomegaly.
Definition:
Irritable Bowel Syndrome (IBS) is a functional gastrointestinal disorder characterized by chronic or recurrent abdominal pain associated with altered bowel habits (diarrhoea, constipation, or both) in the absence of organic disease.
Epidemiology:
Rome IV Diagnostic Criteria for IBS:
Recurrent abdominal pain, on average, at least 1 day per week in the last 3 months, associated with 2 or more of the following:
Additional requirements:
Important note: IBS is a positive diagnosis based on symptoms, NOT a diagnosis of exclusion (though red flag features must be excluded)
IBS Subtypes (based on predominant stool pattern using Bristol Stool Form Scale):
Note: Subtypes can change over time - patients should be reclassified if bowel habit pattern changes
Other Common Symptoms (not part of diagnostic criteria but frequently present):
Red Flag Features (Alarm Symptoms) - MUST Investigate:
The presence of any of these features suggests organic disease rather than IBS:
Additional Features Warranting Further Investigation:
Initial Investigations:
For patients WITHOUT red flags (typical IBS presentation):
Additional tests in IBS-D (diarrhoea-predominant):
If above tests normal → diagnosis of IBS can be made based on positive Rome IV criteria
For patients WITH red flags:
Further Specialist Investigations (if diagnosis unclear or refractory symptoms):
Important Principles:
The pathophysiology of IBS is multifactorial and not completely understood. It is now recognized as a disorder of gut-brain interaction involving multiple mechanisms:
1. Visceral Hypersensitivity:
2. Altered Gut Motility:
3. Gut-Brain Axis Dysfunction:
4. Post-Infectious IBS:
5. Gut Microbiome Alterations:
6. Low-Grade Inflammation and Immune Activation:
7. Altered Serotonin Metabolism:
8. Increased Intestinal Permeability:
9. Food Sensitivities:
Contributing/Trigger Factors:
Integrated Model:
Current understanding is that IBS results from complex interactions between:
This biopsychosocial model explains the heterogeneous nature of IBS and why multifaceted treatment approach is often needed.
Management of IBS requires an individualized, multimodal approach addressing physical and psychological aspects.
1. Explanation, Reassurance, and Therapeutic Relationship:
2. Lifestyle Modifications:
3. Dietary Interventions:
General dietary advice (first-line):
Food and symptom diary:
Low FODMAP diet (if first-line dietary advice unsuccessful):
Specific dietary exclusions (if indicated):
Probiotics:
4. Pharmacological Treatment (Targeted by Predominant Symptom):
For abdominal pain/spasm:
For diarrhoea (IBS-D):
For constipation (IBS-C):
For bloating:
5. Psychological Therapies:
6. Follow-up and Review:
Important Principles:
IBS vs IBD - Key Differences:
| Feature | IBS | IBD (Crohn's, UC) |
|---|---|---|
| Pathology | Functional disorder - no structural/biochemical abnormality | Chronic inflammatory disease with visible inflammation |
| Symptoms | Abdominal pain, bloating, altered bowel habit. Worse with stress | Diarrhoea (often bloody), abdominal pain, weight loss, fever |
| Nocturnal symptoms | Rare - symptoms don't wake patient | Common - night-time diarrhoea typical |
| Rectal bleeding | Not typical (only from haemorrhoids/fissures) | Common, blood mixed with stool |
| Weight loss | Not a feature | Common |
| Blood tests | Normal (FBC, CRP, ESR all normal) | Anaemia, raised CRP/ESR, thrombocytosis, hypoalbuminaemia |
| Faecal calprotectin | Normal (\<50 μg/g) | Elevated (often >250 μg/g) |
| Endoscopy | Normal macroscopic appearance | Visible inflammation, ulceration, strictures |
| Histology | Normal or minimal changes | Chronic inflammation, crypt distortion, ulceration |
| Prognosis | Benign, fluctuating, does not progress to serious disease | Chronic, may have complications (strictures, fistulas, cancer risk) |
| Extra-intestinal manifestations | None | Common (arthritis, skin, eye, liver involvement) |
| Treatment | Lifestyle, diet, symptom-based medication, psychological therapy | Anti-inflammatory drugs, immunosuppressants, biologics, surgery |
Important Clinical Points:
Psychological Factors and IBS:
The relationship between psychological factors and IBS is complex, bidirectional, and integral to the condition:
Prevalence of Psychological Comorbidity:
Mechanisms Linking Psychology and IBS:
Psychological Factors as Risk Factors:
Impact of Psychological Factors:
Clinical Implications:
Biopsychosocial Model of IBS:
Modern understanding integrates biological, psychological, and social factors:
All interact to produce and perpetuate IBS symptoms. Effective management addresses all three domains.