Chronic Constipation: Evaluation and Treatment
Start with lifestyle modifications and dietary therapy, then escalate to polyethylene glycol (PEG) as first-line pharmacological therapy; if inadequate response, advance to prescription secretagogues (linaclotide, plecanatide) or prucalopride, all of which have strong recommendations with moderate evidence. 1
Initial Evaluation
Exclude Secondary Causes First
- Organic diseases: Perform colonoscopy if alarm features present (blood in stool, weight loss, new onset after age 50, family history of colorectal cancer)
- Medication-induced: Review opioids, anticholinergics, calcium channel blockers, iron supplements
- Systemic diseases: Check thyroid function, calcium levels, glucose (diabetes), neurological conditions 2, 3
Characterize the Constipation Pattern
Determine if patient has:
- Decreased frequency type: Fewer than 3 bowel movements per week
- Difficult defecation type: Straining, hard stools, incomplete evacuation, anorectal blockage sensation, need for digital maneuvers 2, 3
Physical Examination Essentials
- Digital rectal examination: Assess for fecal impaction, anal fissures, hemorrhoids, rectal masses, pelvic floor dyssynergia (paradoxical contraction during simulated defecation) 4
- Bristol Stool Form Scale: Document stool consistency objectively 4
Treatment Algorithm
Step 1: Lifestyle and Dietary Interventions (First-Line for All)
Fiber supplementation: Start with 14 g per 1,000 kcal daily intake, ensuring adequate hydration to prevent bloating 1. Note that evidence quality is limited, but this remains standard initial therapy 5.
Specific foods with evidence:
- Prunes: 2 servings daily (moderate evidence) 5
- Kiwifruit: 2-3 fruits daily (moderate evidence) 5
- Rye bread: As dietary staple (low evidence) 5
Hydration: Increase fluid intake, particularly high mineral-containing water (5 recommendations with low-moderate evidence) 5
Step 2: Over-the-Counter (OTC) Osmotic Laxatives
Polyethylene glycol (PEG) 17 g daily is the preferred first-line pharmacological agent:
- Durable response demonstrated over 6 months
- No clear maximum dose; titrate based on response
- Common side effects: bloating, abdominal discomfort, cramping
- Cost: $10-45/month 1
Alternative osmotic agents:
- Lactulose 15 g daily: Only osmotic studied in pregnancy; may cause limiting flatulence 1
- Magnesium oxide 400-500 mg daily: Use caution in renal insufficiency and pregnancy 1
Step 3: Stimulant Laxatives (Short-Term or Rescue Only)
Use for occasional rescue therapy, NOT chronic daily use:
- Bisacodyl 5-10 mg daily or Senna 8.6-17.2 mg daily (conditional recommendation, low evidence) 1
- Limit to 4 weeks of continuous use or less
- Long-term safety and efficacy unknown
- Side effects: cramping, abdominal discomfort, potential electrolyte imbalance with excessive use 1
Step 4: Prescription Agents for OTC Failures
When OTC agents fail, escalate to prescription therapies with STRONG recommendations 1:
Guanylate Cyclase-C Agonists (Secretagogues)
Linaclotide (Strong recommendation, moderate evidence):
- Take 30 minutes before first meal on empty stomach
- Studied for 12 weeks in trials; no label limit
- Main side effect: diarrhea (may lead to discontinuation) 1
Plecanatide (Strong recommendation, moderate evidence):
- Similar profile to linaclotide
- Studied for 12 weeks; no label limit
- Diarrhea risk 1
Prokinetic Agent
Prucalopride (Strong recommendation, moderate evidence):
- 5-HT4 receptor agonist
- Studied 4-24 weeks; no label limit
- Side effects: headache, abdominal pain, nausea, diarrhea 1, 6
Chloride Channel Activator
Lubiprostone 24 μg twice daily (Conditional recommendation, low evidence):
- Take with food and water to minimize nausea (dose-dependent side effect)
- Studied for 4 weeks; no label limit
- Can be used as replacement or adjunct to OTC agents 1
All three prescription agents (linaclotide, plecanatide, prucalopride) have strong recommendations with moderate evidence, making them preferred over lubiprostone which has only conditional recommendation with low evidence 1.
When to Perform Specialized Testing
Reserve physiological testing for patients who:
- Fail multiple pharmacological therapies
- Strongly suspected defecatory disorder (excessive straining, digital maneuvers needed, sensation of blockage)
Available Tests
- Anorectal manometry: High-resolution preferred; comprehensive anorectal function assessment (high level of evidence) 6
- Balloon expulsion test: Simple screening for defecatory disorders 6, 7
- Colonic transit study: Radiopaque markers to differentiate slow transit vs. normal transit 7
- Defecography (MRI or conventional): Evaluate structural abnormalities, pelvic floor dyssynergia 7
Biofeedback Therapy
Recommended for patients with confirmed disordered defecation/pelvic floor dyssynergia on testing 6, 8. Usefulness still being determined in broader populations 2.
Critical Pitfalls to Avoid
Do not use stimulant laxatives chronically: Reserve for rescue therapy only; long-term safety unproven 1
Do not proceed to surgery without exhausting all medical options: Surgery is last resort only 8
Do not forget to take lubiprostone with food: Significantly reduces nausea risk 1
Do not increase fiber without adequate hydration: Worsens bloating and discomfort 1
Do not order expensive physiological tests before trying adequate pharmacological therapy: Reserve testing for treatment failures or suspected defecatory disorders 6, 7
Magnesium-containing laxatives in renal disease: Avoid or use extreme caution 1