Adult Constipation: MCCQE1 Preparation Guide

Introduction

Constipation is a prevalent gastrointestinal complaint in Canada, affecting approximately 15% to 30% of the adult population. For MCCQE1 preparation, it is crucial to differentiate between functional constipation and constipation secondary to organic pathology or pharmacotherapy.

The Medical Council of Canada (MCC) expects candidates to demonstrate a rational approach to the diagnosis and management of constipation, applying the CanMEDS framework—particularly the Medical Expert and Health Advocate roles—to address lifestyle factors and screening requirements.

Etiology and Pathophysiology

Understanding the underlying cause is the first step in the clinical reasoning process for the MCCQE1. Causes are broadly categorized into primary (functional) and secondary.

Clinical Evaluation

The goal of the evaluation is to rule out organic causes (especially malignancy) and identify functional disorders.

1. History Taking (CanMEDS Communicator)

Focus on the nature of symptoms, duration, and associated features.

• Character: Frequency, consistency (use Bristol Stool Scale), straining, need for digital disimpaction.
• Diet/Lifestyle: Fiber intake, fluid intake, physical activity level.
• Medication Review: Review all Rx and OTC drugs (especially recent changes).

2. Physical Examination

• Abdominal Exam: Distention, masses, bowel sounds, tenderness.
• Digital Rectal Exam (DRE): Mandatory in the workup of constipation. Evaluate for:
  • Anal tone (resting and squeeze)
  • Masses, hemorrhoids, fissures
  • Stool in the rectal vault (impaction)
  • Gross blood

Diagnostic Approach

For the MCCQE1, adhere to Choosing Wisely Canada recommendations: do not over-investigate young patients without alarm features.

Management Strategies

Management should be stepwise. Emphasize non-pharmacological interventions first, aligning with the Health Advocate role.

Non-Pharmacological Management

• Patient Education: Reassurance regarding normal bowel habits.
• Dietary Fiber: Increase gradually to 25–30 g/day (e.g., bran, psyllium).
• Hydration: Ensure adequate fluid intake.
• Physical Activity: Encouraged, though evidence is variable.
• Toilet Training: Post-prandial toileting (utilizing the gastrocolic reflex).

Pharmacological Management

If lifestyle modifications fail, introduce laxatives.

Canadian Guidelines

Canadian Association of Gastroenterology (CAG) & Choosing Wisely

1. Do not perform a colonoscopy for constipation in patients <50 years without alarm features or family history.
2. Opioid-Induced Constipation (OIC): Prophylactic laxatives (usually a stimulant +/- osmotic) should be initiated when starting chronic opioids.
3. Colorectal Cancer Screening:
   • Average risk: Start at age 50 with FIT (Fecal Immunochemical Test) every 2 years OR flexible sigmoidoscopy every 10 years.
   • Note: Colonoscopy is the diagnostic test for positive screens or symptomatic patients (like those with constipation + alarm features).

Key Points to Remember for MCCQE1

• DRE is essential: Never skip the Digital Rectal Exam in a constipation workup scenario.
• New onset in elderly: New onset constipation in a patient >50 is cancer until proven otherwise (requires colonoscopy).
• Medication Review: Always check for Calcium Channel Blockers (Verapamil) and Opioids.
• Hypothyroidism: A classic “hidden” cause in exam questions; check TSH.
• Overflow Diarrhea: In elderly, institutionalized patients, “diarrhea” may actually be fecal impaction with overflow. Treat the impaction, not the diarrhea (avoid anti-diarrheals).
• Dyssynergia: Consider pelvic floor physiotherapy (biofeedback) for defecatory disorders.

Sample Question

Scenario A 68-year-old male presents to his family physician complaining of a 3-month history of worsening constipation. He reports having a bowel movement only once every 4-5 days, and the stool is hard and difficult to pass. He has noted a 4 kg unintentional weight loss over the same period. He has no family history of colorectal cancer. His past medical history is significant for hypertension and osteoarthritis. Medications include Amlodipine and Acetaminophen. Physical examination reveals a soft, non-tender abdomen. Digital rectal examination shows no masses, but the rectal vault is empty. There is trace blood on the examining glove.

Which one of the following is the most appropriate next step in management?

• A. Reassure the patient and prescribe a bulk-forming laxative
• B. Switch Amlodipine to an ACE inhibitor
• C. Refer for a colonoscopy
• D. Order an abdominal CT scan
• E. Order a serum TSH level

Explanation

The correct answer is:

• C. Refer for a colonoscopy

Explanation: This patient presents with new-onset constipation at age 68, associated with alarm features (unintentional weight loss and positive blood on DRE). According to Canadian guidelines, these findings raise the suspicion of colorectal cancer or other structural pathology. Therefore, structural visualization of the colon via colonoscopy is the mandatory next step.

• Option A is incorrect because while bulk-forming laxatives are first-line for functional constipation, this patient has alarm features requiring investigation before symptomatic treatment alone.
• Option B is incorrect. While calcium channel blockers like Amlodipine can cause constipation, the presence of weight loss and rectal bleeding points to an organic cause rather than a medication side effect alone. Modifying the medication does not address the need to rule out malignancy.
• Option D is incorrect. While a CT scan can visualize the abdomen, it is not the gold standard for mucosal visualization or biopsy of colonic lesions. Colonoscopy is the preferred initial diagnostic test.
• Option E is incorrect. Hypothyroidism can cause constipation, but it does not typically cause rectal bleeding, and ruling it out does not negate the need to investigate the alarm symptoms.

References

1. Canadian Association of Gastroenterology. Clinical Practice Guidelines.
2. Toronto Notes 2024. Gastroenterology Chapter: Constipation.
3. Choosing Wisely Canada. Gastroenterology Recommendations.
4. Longstreth GF, et al. Functional Bowel Disorders. Gastroenterology. 2016 (Rome IV Criteria).
5. Medical Council of Canada. Objectives for the Qualifying Examination Part I.