Irritable Bowel Syndrome (IBS)

A 29-year-old woman presents with a 6-month history of recurrent abdominal pain associated with bloating and altered bowel habits. She reports episodes of diarrhea alternating with constipation. Her symptoms are often worse during periods of stress and improve after defecation. She denies fever, weight loss, rectal bleeding, or nocturnal symptoms. Physical examination is unremarkable. Laboratory investigations including CBC, CRP, celiac serology, and stool studies are normal. Diagnosis?

Diagnosis is Irritable Bowel Syndrome (IBS).

1. Definition

1. Irritable bowel syndrome is a chronic functional gastrointestinal disorder.
2. It is characterized by:
1. Recurrent abdominal pain
2. Altered bowel habits
3. Absence of structural disease explaining symptoms
3. IBS is a positive clinical diagnosis based on Rome IV criteria.

2. Etiology / Associations

1. Exact cause is multifactorial and incompletely understood.
2. Contributing factors:
1. Altered gastrointestinal motility
2. Visceral hypersensitivity
3. Gut–brain axis dysfunction
4. Psychological stress and anxiety
5. Altered intestinal microbiota
6. Post-infectious changes
7. Low-grade intestinal inflammation
3. Associated conditions:
1. Anxiety disorders
2. Depression
3. Fibromyalgia
4. Chronic fatigue syndrome

 

3. Pathophysiology

1. Altered gut motility leads to diarrhea, constipation, or mixed bowel patterns
2. Visceral hypersensitivity causes exaggerated pain perception
3. Stress affects autonomic and enteric nervous system activity
4. Dysbiosis and low-grade mucosal inflammation may contribute
5. Increased intestinal permeability may trigger symptoms
6. Abnormal gut–brain interaction amplifies symptom severity

4. Clinical Features

4.1 Abdominal Symptoms

1. Recurrent abdominal pain or cramping
2. Pain related to defecation
3. Bloating and abdominal distension
4. Excessive flatulence

4.2 Bowel Habit Changes

1. Diarrhea (IBS-D)
2. Constipation (IBS-C)
3. Mixed bowel pattern (IBS-M)
4. Mucus in stool
5. Feeling of incomplete evacuation
6. Urgency

4.3 Associated Features

1. Fatigue
2. Anxiety or depression
3. Sleep disturbance
4. Urinary symptoms

4.4 Alarm Features (Red Flags)

1. Unintentional weight loss
2. Rectal bleeding
3. Iron deficiency anemia
4. Nocturnal diarrhea
5. Fever
6. Family history of colorectal cancer, celiac disease, or inflammatory bowel disease
7. Onset after age 50
8. Palpable abdominal or rectal mass

5. Diagnosis

5.1 Rome IV Criteria

1. Recurrent abdominal pain occurring at least 1 day/week in the last 3 months associated with two or more of the following:
1. Related to defecation
2. Associated with change in stool frequency
3. Associated with change in stool form
2. Symptom onset should be at least 6 months before diagnosis

5.2 IBS Subtypes

1. IBS-C: constipation predominant
2. IBS-D: diarrhea predominant
3. IBS-M: mixed diarrhea and constipation
4. IBS-U: unclassified

5.3 Investigations

1. Basic investigations are usually normal
2. Initial evaluation may include:
1. CBC
2. CRP or fecal calprotectin
3. Celiac serology
4. Stool studies if diarrhea predominant
3. Colonoscopy is indicated if:
1. Alarm features are present
2. Age-appropriate colorectal cancer screening is needed
3. Diagnosis is uncertain

6. Differential Diagnosis

1. Inflammatory bowel disease (IBD)
2. Celiac disease
3. Lactose intolerance
4. Colorectal cancer
5. Microscopic colitis
6. Chronic gastrointestinal infections
7. Hyperthyroidism or hypothyroidism
8. Malabsorption syndromes
9. Small intestinal bacterial overgrowth (SIBO)

7. Management

7.1 General Measures

1. Establish good physician–patient relationship
2. Reassurance and education
3. Stress reduction
4. Regular exercise
5. Adequate sleep

7.2 Dietary Therapy

1. Low-FODMAP diet may improve symptoms
2. Avoid trigger foods:
1. Caffeine
2. Alcohol
3. Fatty foods
4. Gas-producing foods
3. Increase soluble fiber (psyllium).
4. Avoid excessive insoluble fiber in some patients

7.3 Pharmacologic Therapy

IBS-C

1. Fiber supplements
2. Osmotic laxatives (polyethylene glycol)
3. Secretagogues:
1. Linaclotide
2. Lubiprostone

IBS-D

1. Loperamide
2. Bile acid binders
3. Rifaximin
4. Eluxadoline
1. Avoid in patients without a gallbladder or with pancreatitis risk

Pain / Bloating

1. Antispasmodics
2. Peppermint oil
3. Low-dose tricyclic antidepressants
4. SSRIs in selected patients

7.4 Psychological Therapy

1. Cognitive behavioral therapy
2. Gut-directed hypnotherapy
3. Stress management techniques

8. Monitoring

1. Monitor symptom severity and quality of life
2. Assess response to dietary and pharmacologic therapy
3. Reevaluate if alarm features develop
4. Avoid excessive unnecessary investigations

9. Complications

1. Reduced quality of life
2. Anxiety and depression
3. Work and social impairment
4. Frequent healthcare utilization
5. IBS does not increase mortality
6. IBS does not increase risk of colorectal cancer

10. Key Clinical Insight

1. Chronic recurrent abdominal pain associated with altered bowel habits and normal basic investigations strongly suggests IBS

11. Key Exam Points

1. IBS is diagnosed using Rome IV criteria
2. IBS is a positive clinical diagnosis in the absence of alarm features
3. Low-FODMAP diet is commonly beneficial
4. Psychological stress commonly worsens symptoms
5. IBS does not cause weight loss, bleeding, fever, or nocturnal diarrhea
6. Fecal calprotectin helps distinguish IBS from IBD
7. Colonoscopy is unnecessary in most young patients without red flags
8. IBS subtypes guide treatment
9. Reassurance and lifestyle modification are essential components of management