Diagnosis and Management of Irritable Bowel Syndrome with Mixed Bowel Habits

Diagnostic Approach

The American Gastroenterological Association recommends that the Rome II criteria be met for a diagnosis of IBS, including abdominal discomfort with at least 2 of 3 features: relief with defecation, onset with change in stool frequency, and onset with change in stool form 1
The European Society of Gastroenterology suggests that IBS-M subtype classification is defined by alternating hard and soft stools more than 25% of the time each, indicating mixed-pattern IBS 2
The National Institute of Diabetes and Digestive and Kidney Diseases notes that stress reactivity is a characteristic of IBS, with worsening symptoms during stress reflecting an exaggerated colonic response to psychological stimuli 3
The British Dietetic Association recommends that FODMAP sensitivity be assessed, as symptom aggravation with high-FODMAP foods indicates fermentable carbohydrate intolerance, seen in approximately 50% of IBS patients who report meal-related symptom exacerbation 2, 3

The American College of Gastroenterology recommends patient education and reassurance, including explanation of the brain-gut axis dysregulation and stress-reactivity mechanisms, and reassurance about benign prognosis and absence of structural pathology 1, 5
The National Institute of Diabetes and Digestive and Kidney Diseases suggests that a low-FODMAP diet is the evidence-based first-line dietary intervention for moderate-to-severe symptoms, delivered by a specialized dietitian, with efficacy of 70-86% in controlled trials 4, 5
The European Society of Gastroenterology recommends lifestyle modifications, including increased physical activity, regular toileting routine, adequate time for defecation, and addressing sleep hygiene and stress management 4, 5

The American Gastroenterological Association recommends low-dose tricyclic antidepressants (TCAs) for gastrointestinal symptoms, particularly pain, with efficacy in reducing symptoms 4, 5
The British Society of Gastroenterology suggests that antispasmodics (anticholinergics like dicyclomine or hyoscyamine) may help with cramping, and loperamide or codeine may be used as needed for diarrhea-predominant episodes 5
The European Society of Gastroenterology recommends osmotic laxatives (polyethylene glycol) or stimulant laxatives (senna, bisacodyl) for constipation-predominant episodes, and increase dietary fiber cautiously 5, 6, 7

The National Institute of Diabetes and Digestive and Kidney Diseases advises against pursuing exhaustive testing in young patients without alarm features, as this delays diagnosis and increases healthcare costs 4
The American College of Gastroenterology recommends against implementing low-FODMAP diet without dietitian supervision, as stringent long-term restriction risks nutrient deficiency and adverse microbiota effects 4
The European Society of Gastroenterology suggests that low-dose TCAs should not be used to treat comorbid mood disorders, as they are insufficient for psychological symptoms; use SSRIs instead if depression/anxiety is present 4
The British Dietetic Association notes that stress-related symptoms should not be dismissed as "all in the head", as stress has documented physiological effects on colonic motility via CRF pathways 3