How would you manage a 58-year-old male with alternating bowel habits, experiencing non-bloody diarrhea (Diarrhea) 3-4 times a day and constipation with bowel movements every 3 days, without abdominal pain, vomiting, or signs of dehydration?

Management of 58-Year-Old Male with Alternating Bowel Habits

This patient requires colonoscopy given his age over 50 years, followed by baseline laboratory investigations to exclude organic disease before considering a diagnosis of irritable bowel syndrome (IBS). 1

Immediate Diagnostic Approach

Age-Mandated Investigation

• Colonoscopy is mandatory for this patient because he is 58 years old, regardless of symptom characteristics, due to higher pretest probability of colon cancer in patients over age 50. 1
• This is non-negotiable even in the absence of alarm features (no blood, weight loss, or anemia). 1

Baseline Laboratory Testing

Obtain the following screening tests before or concurrent with colonoscopy:

• Complete blood count (CBC) to exclude anemia 1
• C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) to screen for inflammatory conditions 1
• Celiac serology (tissue transglutaminase antibodies) 1
• Stool for occult blood (Hemoccult) 1
• Serum chemistries and albumin 1
• Stool for ova and parasites given the diarrheal component 1
• Faecal calprotectin is recommended for patients with diarrhea, particularly if under age 45, but can be considered here to exclude inflammatory bowel disease 1

Differential Diagnoses (In Order of Priority)

Must-Exclude Diagnoses

1. Colorectal cancer - Age over 50 mandates exclusion via colonoscopy 1
2. Inflammatory bowel disease (IBD) - Can present with alternating symptoms; excluded by colonoscopy with biopsy and calprotectin 1
3. Microscopic colitis - Requires colonic biopsies during colonoscopy 1
4. Celiac disease - Excluded by serology 1
5. Parasitic infection (especially Giardia) - Excluded by stool ova and parasites 1

Likely Functional Diagnoses (After Exclusion of Organic Disease)

1. Irritable bowel syndrome, mixed type (IBS-M) - Most likely given alternating diarrhea and constipation pattern 1
2. Bile acid malabsorption - Consider if patient has history of gallbladder disease or cholecystectomy 2

Clinical Features Supporting IBS Diagnosis

This patient's presentation is highly consistent with IBS based on:

• Abnormal stool frequency: 3-4 bowel movements per day during diarrheal episodes (>3/day is abnormal) and every 3 days during constipation (<3/week is abnormal) 1
• Abnormal stool form: Alternating loose/watery and hard stools 1
• Duration of 4 weeks meets the temporal criterion (symptoms for at least 12 weeks in preceding 12 months, though this patient has only 4 weeks documented) 1

Critical caveat: The absence of abdominal pain essentially excludes classic IBS by Rome criteria, which require abdominal pain or discomfort as a cardinal feature. 1, 3 This patient has NO abdominal pain, making the diagnosis atypical.

Management Algorithm

Step 1: Complete Investigations (Weeks 1-2)

• Perform colonoscopy with biopsies 1
• Obtain all baseline laboratory tests 1

Step 2: If Investigations Are Normal (Week 3)

Initial Conservative Management

• Patient education and reassurance about the benign nature of functional bowel disorders 1
• Dietary modifications: 1, 4
  • Regular meal patterns (avoid skipping meals)
  • Adequate fluid intake (≥1.5 L/day)
  • Avoid gas-producing foods (cauliflower, legumes)
  • Consider food diary to identify triggers 4

Pharmacological Management for Alternating Pattern

For diarrheal episodes:

• Loperamide 2-4 mg before meals and at bedtime, titrated to effect (maximum 16 mg/day) 4, 5, 6
• Loperamide is preferred because it is non-addictive and non-sedating 2, 4

For constipation episodes:

• Soluble fiber (psyllium/ispaghula) 3-4 g/day, gradually increased to avoid bloating 4, 7
• Start low and titrate slowly; avoid insoluble fiber (wheat bran) which may worsen symptoms 4

Important pitfall: Avoid using loperamide during constipation phases and fiber during diarrhea phases - treat symptomatically based on current bowel pattern. 1

Step 3: If Inadequate Response After 3-6 Weeks

Consider Bile Acid Malabsorption

• Trial of cholestyramine if patient has history of gallbladder disease or if diarrhea predominates 2, 4

Consider Antispasmodics (If Pain Develops)

• Antispasmodics (e.g., hyoscyamine, dicyclomine) for meal-related symptoms 4, 6
• Peppermint oil as alternative for global symptom relief 4, 6

Second-Line Options

• Low FODMAP diet supervised by trained dietitian 4, 8, 9
• Tricyclic antidepressants (amitriptyline 10 mg at bedtime, titrated to 30-50 mg) for global symptom improvement, even without pain 4, 6

Step 4: Refractory Symptoms

• Psychological therapies (cognitive-behavioral therapy, hypnotherapy) if quality of life significantly impaired 4, 3
• Probiotics as adjunctive therapy 6, 9

Critical Pitfalls to Avoid

1. Never skip colonoscopy in patients over 50 - this is the single most important intervention to avoid missing colorectal cancer 1

2. Do not diagnose IBS without excluding organic disease - functional diagnosis requires absence of structural/biochemical abnormalities 1

3. Recognize this patient lacks abdominal pain - classic IBS requires pain as cardinal feature; consider alternative functional bowel disorders (functional diarrhea, functional constipation) 1, 3

4. Avoid treating alternating IBS with single-modality therapy - loperamide alone may worsen constipation; fiber alone may worsen diarrhea 1

5. Do not use high-fiber diet during diarrheal phases - this can exacerbate symptoms 1

6. Manage expectations realistically - complete symptom resolution is often not achievable; focus on improving quality of life 4

Follow-Up Plan

• Reassess in 3-6 weeks after initiating treatment 1
• Red flags requiring urgent re-evaluation: new onset of blood in stool, unintentional weight loss, fever, severe pain, or progressive worsening 1
• If symptoms change character or new symptoms develop, reconsider organic causes 1