What are the symptoms and treatment options for irritable bowel syndrome (IBS)?

Irritable Bowel Syndrome: Symptoms and Treatment

Core Symptoms of IBS

IBS is defined by recurrent abdominal pain or discomfort occurring at least 3 days per month for the past 3 months, associated with altered bowel habits. 1, 2

The key diagnostic symptoms include:

• Abdominal pain or discomfort that is relieved with defecation, or associated with a change in stool frequency or consistency—the absence of abdominal pain essentially excludes IBS 1, 2, 3
• Altered stool frequency: more than 3 bowel movements per day or fewer than 3 per week 1
• Altered stool form: hard/lumpy stools or loose/watery stools 1
• Straining during bowel movements 1
• Urgency (having to rush to have a bowel movement) 1
• Feeling of incomplete bowel evacuation 1
• Passage of mucus (white material) during bowel movements 1
• Abdominal fullness, bloating, or distension 1, 2

IBS Subtypes Based on Predominant Bowel Pattern

IBS is categorized into three subtypes that guide treatment selection 1, 4:

• Diarrhea-predominant (IBS-D): one or more of loose/watery stools, increased frequency, or urgency with none of the constipation features 1
• Constipation-predominant (IBS-C): one or more of hard/lumpy stools, decreased frequency, or straining with none of the diarrhea features 1
• Mixed/Alternating (IBS-M): alternating presence of both diarrhea and constipation patterns 1, 4

Non-Gastrointestinal Symptoms

Patients with IBS commonly report extraintestinal symptoms that support the diagnosis 1:

• Lethargy and poor sleep 1
• Fibromyalgia and chronic musculoskeletal pain 1
• Urinary frequency and dyspareunia 1
• Anxiety, depression, and multiple somatic complaints 1

Treatment Approach: Algorithmic Framework

Step 1: Foundation for All IBS Patients

An effective physician-patient relationship, patient education, reassurance, and dietary counseling are prerequisites for any IBS treatment. 1

• Regular physical exercise should be recommended to all IBS patients as foundational therapy, as it improves global symptoms 5, 6
• Soluble fiber supplementation (ispaghula/psyllium) starting at 3-4 g/day and gradually increasing to 25 g/day improves global symptoms and abdominal pain 5, 6
• Avoid insoluble fiber (wheat bran) as it consistently worsens symptoms in IBS patients 1, 5
• Probiotics may be tried for 12 weeks for global symptoms and abdominal pain; discontinue if no improvement 5, 2

Step 2: Symptom-Specific Pharmacological Treatment

For IBS-D (Diarrhea-Predominant):

• Loperamide (2-4 mg up to four times daily) reduces stool frequency, urgency, and fecal soiling 5, 6
• Rifaximin (550 mg three times daily for 14 days) is effective as a second-line agent, though its effect on abdominal pain is limited 5, 7
• 5-HT3 receptor antagonists (such as alosetron) are effective second-line options for severe IBS-D 5, 2

For IBS-C (Constipation-Predominant):

• Polyethylene glycol (osmotic laxative) should be started first, titrating the dose according to symptoms 5
• Linaclotide (290 mcg once daily on an empty stomach) is the most effective second-line agent when first-line therapies fail, addressing both abdominal pain and constipation 5, 8
• Lubiprostone (8 mcg twice daily) is an alternative if linaclotide is not tolerated, though nausea is a common side effect 5, 2, 9
• Bisacodyl (10-15 mg daily) can be added as a stimulant laxative for severe constipation 5

Critical pitfall: Do not prescribe anticholinergic antispasmodics like dicyclomine for IBS-C, as they reduce intestinal motility and worsen constipation 5, 6

For Abdominal Pain and Cramping:

• Antispasmodics (particularly those with anticholinergic properties like dicyclomine 40 mg four times daily) are effective for meal-exacerbated pain, though they cause dry mouth, visual disturbance, and dizziness 1, 5, 6
• Peppermint oil is an effective antispasmodic with fewer systemic side effects 5, 6, 2, 9

Step 3: Second-Line Neuromodulators for Refractory Symptoms

Tricyclic antidepressants (TCAs) are the most effective second-line treatment for global symptoms and abdominal pain when first-line therapies fail. 5, 8, 6

• Amitriptyline should be started at 10 mg once daily at bedtime and titrated slowly (by 10 mg/week) to 30-50 mg daily 5, 8, 6
• Continue for at least 6 months if symptomatic response occurs 5, 6
• Caution in IBS-C: TCAs may worsen constipation through anticholinergic effects; ensure adequate laxative therapy is in place 5, 8

Selective serotonin reuptake inhibitors (SSRIs) are effective alternatives when TCAs are not tolerated or worsen constipation 5, 9

Step 4: Psychological Therapies for Persistent Symptoms

When symptoms persist despite 12 months of pharmacological treatment, consider 5, 8:

• Cognitive-behavioral therapy (CBT) specific for IBS 5, 2, 3
• Gut-directed hypnotherapy 5, 3
• Dynamic (interpersonal) psychotherapy for patients who relate symptom exacerbations to stressors or have associated anxiety/depression 5

These therapies are particularly effective in patients with overt psychiatric disorders and stress-exacerbated symptoms 1

Critical Pitfalls to Avoid

• Do not pursue extensive investigations once IBS is diagnosed in patients under 45 without alarm features (weight loss, rectal bleeding, nocturnal symptoms, anemia, family history of inflammatory bowel disease or celiac disease) 1, 8, 6
• Do not recommend IgG antibody-based food elimination diets as they lack evidence 5
• Do not recommend gluten-free diets unless celiac disease has been confirmed 5
• Avoid opioids for chronic abdominal pain management due to risks of dependence, narcotic bowel syndrome, and worsening of IBS symptoms 8, 6
• Review treatment efficacy after 3 months and discontinue if no response 5, 6
• Recognize that high-fiber diets do not apply to IBS-D and are poorly tolerated by most IBS patients, potentially worsening abdominal discomfort 1

Treatment Efficacy Expectations

The efficacy of current therapeutic options is limited: benefit is often restricted to specific symptoms (diarrhea, constipation, or pain) and occurs in only 10-20% of patients beyond placebo effect 1. Managing patient expectations is crucial, as complete symptom resolution is often not achievable; the goal is symptom relief and improved quality of life 5.