Irritable Bowel Syndrome, and how it differs from IBD and infective bowel disease
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| Irritable Bowel Syndrome, and how it differs from IBD and infective bowel disease |
Quick summary
- IBS is a functional gut disorder. Symptoms include pain, bloating, and change in bowel habit. Evidence shows global prevalence varies with diagnostic criteria, roughly 4 to 14 percent.
- IBD is inflammatory disease of the gut wall. It includes Crohn's disease and ulcerative colitis. Diagnosis needs endoscopy or imaging. NICE recommends specialist assessment and objective tests.
- Infective bowel disease means acute infection of the gut. Common causes include viruses, bacteria, and parasites such as Salmonella, Campylobacter, and enterotoxigenic E. coli. Presentation is often acute diarrhea, fever, or bloody stools.
What is IBS
IBS is a disorder of gut function. You get recurrent abdominal pain linked to bowel habit change. There is no visible inflammation on endoscopy in typical IBS.
Key symptoms
- Recurrent abdominal pain related to bowel movements
- Altered stool frequency or form, with subtypes: IBS-D, IBS-C, mixed
- Bloating and urgency
- Symptoms often fluctuate over months to years
Practical points
- Use Rome IV criteria for clinical diagnosis.
- Red flags require urgent workup: weight loss, fever, persistent bleeding, progressive anemia.
- Management targets symptoms: diet, fibre guidance, gut-directed therapies, low FODMAP when appropriate.
Global prevalence estimates differ by criteria. Population studies report 4 to 11 percent with Rome IV or III, and some meta-analyses report about 14 percent depending on methods. Use local data if available.
What is IBD
IBD is chronic inflammation of the bowel. It causes tissue damage. It includes Crohn's disease and ulcerative colitis.
Key symptoms
- Persistent diarrhea, often with blood
- Abdominal pain and weight loss
- Systemic signs: fever, anemia
Diagnosis and course
- Diagnose with blood tests, stool tests, endoscopy, histology, and imaging.
- Management uses anti-inflammatory drugs, immunomodulators, biologics, and surgery when needed.
- Incidence is rising in many middle income countries. Rates remain higher in Western nations. In India, prevalence is increasing though lower than in the West.
What is infective bowel disease
Term describes acute infectious gastroenteritis or infectious colitis. Onset is sudden. Symptoms often include vomiting, watery or bloody diarrhea, and fever.
Common pathogens
- Viruses: norovirus, rotavirus
- Bacteria: Salmonella, Shigella, Campylobacter, enterotoxigenic E. coli, Clostridioides difficile
- Parasites: Giardia, Entamoeba histolytica
Workup and treatment
- Stool culture and microscopy if presentation suggests bacterial or parasitic cause.
- Supportive care is mainstay: fluids and electrolytes.
- Use targeted antibiotics only when indicated by severity or specific pathogens.
How to tell them apart, fast
| Feature | IBS | IBD | Infective bowel disease |
|---|---|---|---|
| Onset | Chronic, months to years | Chronic, progressive | Acute, hours to days |
| Pain type | Crampy, related to bowel habit | Severe, persistent, may localize | Severe, often with systemic features |
| Stool changes | Constipation, diarrhea, or both, without blood | Diarrhea often with blood or mucus | Watery or bloody diarrhea common |
| Systemic signs | Usually absent | Often present: fever, weight loss, anemia | Often present: fever, dehydration |
| Investigations | Normal blood tests, normal endoscopy typically | Raised inflammatory markers, endoscopic inflammation, histology positive | Stool culture, PCR, sometimes endoscopy if severe |
| Treatment focus | Symptom control, diet, psychological therapies | Suppress inflammation, immune therapy, surgery | Eradicate pathogen, supportive care |
Use red flags to decide urgency. Red flags include fever, persistent bleeding, unintentional weight loss, and severe anemia. These point away from simple IBS and require urgent investigation.
Clinical approach checklist
- Take a focused history. Note onset, stool pattern, blood, recent travel, antibiotic use.
- Look for red flags. If present, arrange urgent tests and specialist referral.
- Order baseline tests: full blood count, CRP, stool tests when needed.
- Use endoscopy and imaging when inflammation or infection is suspected.
- Manage empirically for dehydration and severe symptoms while workup runs.
Takeaway for your practice
- Do not label chronic abdominal pain as IBS without excluding red flags.
- Use symptom criteria for IBS but confirm when signs of inflammation appear.
- Reserve antibiotics for proven or strongly suspected bacterial disease.
- Refer promptly if tests suggest IBD or if symptoms are severe.
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