What is the diagnosis and management plan for a patient with sudden severe bowel pressure, urgency, bloating, and excessive gas, with a history of diarrhea and incontinence?

Diagnosis: Irritable Bowel Syndrome with Diarrhea (IBS-D) with Possible Bile Acid Diarrhea

This 39-year-old patient meets clinical criteria for IBS-D based on recurrent abdominal pain with urgency, diarrhea, bloating, and mucus per rectum in the absence of alarm features, but requires targeted investigation to exclude bile acid diarrhea (BAD) and microscopic colitis before initiating treatment. 1

Diagnostic Approach

Immediate Laboratory Testing Required

• Full blood count, C-reactive protein (or ESR), and coeliac serology to exclude inflammatory and structural disease 1
• Faecal calprotectin (patient is <45 years with diarrhea) to exclude inflammatory bowel disease 1
• Thyroid function tests given the sudden onset and severity of symptoms 1
• Serum B12, red cell folate, ferritin, calcium, and albumin to evaluate for malabsorption 1

Consider Colonoscopy with Biopsies

Colonoscopy should be performed in this patient despite age <45 years due to atypical features suggesting microscopic colitis: nocturnal-type urgency patterns (symptoms occur randomly, not just postprandially), mucus per rectum, relatively short duration (<12 months), and the severity of symptoms with incontinence 1. The family history of multiple cancers (though not bowel cancer) adds diagnostic uncertainty that warrants visualization 1.

Bile Acid Diarrhea Testing

SeHCAT scanning or serum 7α-hydroxy-4-cholesten-3-one should be performed given the sudden severe urgency, incomplete evacuation, and diarrhea pattern 1. BAD is present in 20-30% of patients with IBS-D symptoms and responds specifically to bile acid sequestrants 2. The vegetarian diet may be relevant as this can affect bile acid metabolism 1.

Management Algorithm

First-Line Interventions (Initiate Immediately)

1. Dietary Modifications

• Stop all caffeine-containing beverages (patient has already stopped coffee/tea—reinforce this) 1
• Trial lactose and fructose restriction for 2 weeks as these are the most common food intolerances in IBS-D (60% fructose, 51% lactose intolerance) 1
• Commence soluble fiber (ispaghula) at 3-4 g/day, building gradually to avoid worsening bloating; avoid wheat bran which may exacerbate symptoms 1
• Regular exercise should be advised as first-line therapy 1

2. Symptomatic Control for Urgency/Incontinence

• Loperamide 2-4 mg as needed before situations requiring travel (e.g., driving, away from home) to prevent incontinence episodes 1, 3
• Loperamide improves stool frequency and urgency but has mixed results for abdominal pain 3
• Avoid chronic daily use to prevent constipation and potential complications 4

3. Abdominal Pain and Bloating

• Antispasmodics with anticholinergic effects (e.g., hyoscine butylbromide, dicyclomine) for episodic pain 1
• Consider low-dose tricyclic antidepressant (e.g., amitriptyline 10-25 mg at bedtime) if pain persists despite initial measures, as tricyclics have proven efficacy for IBS pain 1

Second-Line Dietary Therapy

Low FODMAP diet supervised by a trained dietitian if symptoms persist after 4 weeks of first-line measures 1. This should be implemented for 2-4 weeks with systematic reintroduction according to tolerance 5. The patient's vegetarian diet requires careful planning to maintain adequate nutrition during FODMAP restriction 1.

Specific Treatment Based on Test Results

If SeHCAT <15% or elevated 7α-hydroxy-4-cholesten-3-one (indicating BAD):

• Bile acid sequestrant (cholestyramine 4 g once or twice daily, or colesevelam 625 mg 1-3 tablets twice daily) 1
• Response rates are higher with SeHCAT retention <10% or <5% 1

If microscopic colitis confirmed on biopsy:

• Budesonide 9 mg daily is first-line treatment
• Consider stopping any NSAIDs, PPIs, or SSRIs if being used 1

If small intestinal bacterial overgrowth (SIBO) suspected (excessive gas with foul odor, bloating):

• Rifaximin 550 mg three times daily for 14 days 5, 6
• Rifaximin is FDA-approved for IBS-D and has demonstrated efficacy in reducing bloating and improving stool consistency 6

Prescription Medications for Refractory IBS-D

If symptoms remain severe after above measures:

Option 1: Rifaximin 550 mg three times daily for 14 days 6

• FDA-approved for IBS-D with demonstrated efficacy for adequate relief of symptoms (41% vs 31% placebo) 6
• Can be repeated for symptom recurrence 6
• Addresses potential SIBO component contributing to bloating and gas 5

Option 2: Eluxadoline 100 mg twice daily with food 4, 3

• FDA-approved for IBS-D
• Contraindicated if patient has had cholecystectomy, sphincter of Oddi dysfunction, pancreatitis, severe liver impairment, or alcohol abuse 4
• Reduce to 75 mg twice daily if taking OATP1B1 inhibitors 4
• Effective for both diarrhea and abdominal pain 3

Critical Considerations Before Travel to India

Address urgency and incontinence risk before the 5-week trip:

• Ensure loperamide is available for acute use during travel 3
• If BAD confirmed, initiate bile acid sequestrant at least 2 weeks before departure 1
• Provide written management plan for acute symptom flares
• Consider short course of rifaximin before travel if SIBO suspected 5
• Advise on food and water precautions to prevent infectious diarrhea superimposed on IBS-D

Common Pitfalls to Avoid

Do not attribute nocturnal symptoms or mucus PR to IBS alone—these are atypical features requiring investigation for microscopic colitis 1. Do not perform hydrogen breath testing for lactose or SIBO—these have no role in routine IBS assessment and dietary restriction trials are more practical 7. Do not use IgG food antibody testing—this is not recommended and lacks evidence 1. Do not delay positive diagnosis—making a confident diagnosis of IBS-D (after appropriate testing) prevents unnecessary repeated investigations and improves patient outcomes 1.

Reassurance and Education

Communicate clearly that IBS-D is a chronic disorder of gut-brain interaction with visceral hypersensitivity as the main pathophysiology 1. Emphasize that IBS is not associated with increased cancer risk or mortality, though it significantly affects quality of life 1. Explain that symptoms fluctuate with stress, illness, and diet, and that the goal is symptom control rather than cure 1. The patient's stress response when away from toilets likely worsens symptoms through the gut-brain axis 1.