How should I approach the management of IBS in a patient with predominant diarrhea versus one with predominant constipation?

Management of IBS with predominant diarrhoea: Advise the patient to reduce intake of insoluble fibre such as wholemeal or high-fibre flour, bran cereals, and whole grains like brown rice, as these may exacerbate symptoms. Recommend avoiding foods and drinks that can worsen diarrhoea, including caffeine, alcohol, carbonated drinks, and gas-producing foods. Patients should avoid sorbitol-containing products (e.g., sugar-free sweets and some diabetic or slimming products). Loperamide is the first-line pharmacological treatment for diarrhoea and should be titrated to achieve a soft, well-formed stool (Bristol Stool Form Scale type 4). Probiotics may be tried for at least 4 to 12 weeks, discontinuing if no benefit is seen. Encourage adequate fluid intake and regular physical activity to improve overall symptoms and wellbeing ¹,².

Management of IBS with predominant constipation: Advise increasing soluble fibre intake gradually using supplements like ispaghula or foods high in soluble fibre such as oats and linseed, to minimize bloating and flatulence. Lactulose should be discouraged as a laxative. If constipation persists despite laxatives, consider linaclotide after at least 12 months of symptoms and failure of other laxatives. Regular physical activity is recommended to improve constipation symptoms. Pharmacological options include laxatives tailored to the patient’s response, and if symptoms persist, low-dose tricyclic antidepressants (TCAs) may be considered. Psychological interventions may be offered if symptoms remain refractory after 12 months ¹,².

Common management principles: Provide clear explanation of IBS as a chronic condition with fluctuating symptoms related to the gut-brain axis, reassure about the benign nature of IBS, and offer dietary and lifestyle advice tailored to symptoms. Encourage regular meals, adequate hydration, stress management, and physical activity. Refer to a dietitian for specialist dietary advice, including low-FODMAP diets, if initial advice is insufficient. Follow-up within 2 months is recommended to assess symptom control and consider further management ¹,².