What is the diagnosis and management approach for Irritable Bowel Syndrome with Constipation (IBS-C)?

Diagnosis of IBS-C

IBS-C is diagnosed clinically using symptom-based criteria in patients under 45 without alarm features, requiring only limited investigations (celiac serology) rather than exhaustive testing. 1, 2

Diagnostic Approach

Making the Positive Diagnosis

• Diagnose IBS-C based on symptoms alone when the patient meets Rome IV criteria: recurrent abdominal pain at least 1 day per week in the last 3 months, associated with altered bowel habits (constipation), in the absence of alarm features. 1, 3

• Patients meeting Rome IV criteria are 21 times more likely to have IBS-C than not have IBS-C after limited workup, making this a highly secure diagnosis. 1

• Communicate the diagnosis confidently using patient-friendly language to explain gut-brain axis dysregulation, emphasizing that symptoms are real, taken seriously, and not associated with increased cancer risk or mortality. 1

Limited Investigations Required

• Perform celiac serology in all suspected IBS patients as the only routine investigation needed. 1, 2

• Avoid colonoscopy unless alarm symptoms are present (unintentional weight loss ≥5%, blood in stool, fever, anemia, family history of colon cancer or inflammatory bowel disease). 1, 2

• The yield of colonoscopy in IBS is extremely low, and normal examination does not provide reassurance to patients. 1

Exclude Red Flags Specific to IBS-C

• In suspected IBS-C with atypical features (obstructive defecation symptoms, severe straining), consider evaluation for dyssynergic defecation and other defecatory disorders before finalizing IBS-C diagnosis. 1

• Look for features suggesting alternative diagnoses: nocturnal symptoms, progressive worsening, age >50 with new-onset symptoms, or unintended weight loss. 1, 2

Patient Education at Diagnosis

• Explain IBS-C as a chronic disorder of gut-brain interaction with recurrent fluctuating symptoms triggered by stress, illness, drugs, and eating. 1

• Emphasize that the main pathophysiology is visceral hypersensitivity, which is the target of most treatments. 1

• Set realistic expectations: cure is unlikely, but substantial improvement in symptoms, social functioning, and quality of life is achievable. 1

• Stress that IBS affects quality of life to the same degree as organic diseases like inflammatory bowel disease, validating the patient's experience. 1

Management Framework After Diagnosis

First-Line: Lifestyle and Dietary Modifications

• Recommend regular physical activity to all IBS-C patients, as exercise provides significant symptom management benefits. 2, 4

• Start soluble fiber supplementation (ispaghula/psyllium) at 3-4 g/day, gradually increasing to avoid bloating, as this is effective for constipation and global symptoms. 2, 4

• Avoid insoluble fiber (wheat bran) as it may worsen symptoms, particularly bloating. 2

• Ensure adequate hydration, regular time for defecation, and proper sleep hygiene. 2

Second-Line: Pharmacotherapy for Persistent Symptoms

• For abdominal pain and cramping: Use antispasmodics (dicyclomine) as first-line therapy, particularly when symptoms are meal-related. 2, 4

• For constipation: Linaclotide 290 mcg once daily is the most efficacious secretagogue for IBS-C when fiber supplementation is insufficient. 3

• For global symptoms and pain refractory to above: Low-dose tricyclic antidepressants (amitriptyline 10 mg once daily, titrating to 30-50 mg) are the most effective pharmacological treatment, though they may worsen constipation. 1, 3, 4

Third-Line: Specialized Interventions

• Consider low FODMAP diet delivered by a trained dietitian in three phases (restriction, reintroduction, personalization) for moderate-to-severe symptoms, but avoid in patients with eating pathology or severe mental illness. 1, 2

• Refer for IBS-specific cognitive behavioral therapy or gut-directed hypnotherapy when symptoms persist despite pharmacological treatment for 12 months. 2, 3

Referral Thresholds

• Gastroenterologist: If diagnosis is in doubt or symptoms are refractory to primary care treatment. 1, 3

• Specialist gastroenterology dietitian: If patient has dietary deficits, nutritional deficiency, unintended weight loss, or requests dietary modification. 1, 3

• Gastropsychologist: If moderate-to-severe anxiety/depression, suicidal ideation, low social support, impaired quality of life, or motivational deficiencies affecting self-management. 1

Critical Pitfalls to Avoid

• Do not pursue extensive testing once IBS-C diagnosis is established in patients under 45 without alarm features. 2, 4

• Do not order IgG-based food allergy testing, as true food allergy is rare in IBS. 2

• Adjust visit frequency to accommodate mental health needs, as under-managed anxiety and depression negatively affect IBS treatment responses. 1

• Review treatment efficacy after 3 months and discontinue ineffective medications rather than continuing indefinitely. 3, 4