What is the recommended stepwise management of constipation, including lifestyle modifications, osmotic and stimulant laxatives, and criteria for specialist referral?

Stepwise Management of Chronic Constipation

Start with polyethylene glycol (PEG) 17g once daily as first-line pharmacological therapy for chronic constipation, reserving fiber supplements only for mild cases in patients who can maintain adequate fluid intake. 1

Initial Assessment and Red Flags

Before initiating laxatives, obtain a plain abdominal X-ray to exclude bowel obstruction, which has a sensitivity of 74-84% for confirming obstruction. 2, 3 Look specifically for:

• Dilated bowel loops (>3cm small bowel, >6cm colon)
• Air-fluid levels
• Absence of rectal gas
• Fecal loading pattern versus obstruction pattern 3

Laxatives are absolutely contraindicated in bowel obstruction because they increase intraluminal pressure and can precipitate perforation, peritonitis, and septic shock. 3

Check thyroid function and review medications that may cause constipation. 1

Lifestyle Modifications (Concurrent with Pharmacotherapy)

• Privacy and positioning: Ensure toilet access and use a small footstool to assist gravity and facilitate easier straining 1
• Fluid intake: Focus on patients in the lowest quartile of daily fluid intake (standard fiber doses require 8-10 ounces of fluid) 1
• Activity: Increase mobility within patient limits, even bed-to-chair transfers 1
• Toileting routine: Attempt defecation twice daily, 30 minutes after meals, straining no more than 5 minutes 1

Pharmacological Management Algorithm

First-Line: Osmotic Laxatives

Polyethylene glycol (PEG) 17g once daily mixed in 8 oz liquid is the gold-standard initial therapy with a strong recommendation based on moderate-certainty evidence. 1, 2

Key advantages of PEG:

• Durable response over 6 months 1
• Safest option in chronic kidney disease due to minimal systemic absorption 2
• Safe in pregnancy due to lack of systemic absorption 2
• Excellent safety profile in elderly patients 1, 2

Titrate the PEG dose to achieve at least one spontaneous bowel movement every 1-2 days. 2

Side effects include abdominal distension, loose stool, flatulence, and nausea. 1

Alternative First-Line Options (If PEG Unavailable)

• Lactulose: Conditional recommendation, less preferred than PEG 1
• Magnesium oxide: Conditional recommendation, but absolutely avoid in any degree of renal impairment due to dangerous hypermagnesemia risk 1, 2, 3

Fiber Supplements: Limited Role

Fiber has only a conditional recommendation and should be reserved for mild constipation in specific patients. 1

When to consider fiber:

• Mild-to-moderate symptoms
• Diets deficient in fiber
• Ambulatory patients who can maintain adequate fluid intake (at least 8 oz per dose) 2

Contraindications for fiber:

• Opioid-induced constipation (absolutely contraindicated) 1, 2
• Non-ambulatory patients with low fluid intake (risk of mechanical obstruction) 2
• Patients with severe constipation 1

Best evidence exists for psyllium, though even this is low quality. 1 Chief side effect is flatulence. 1

Second-Line: Add Stimulant Laxatives

If inadequate response to PEG alone after appropriate titration, add a stimulant laxative. 2

Strong recommendations for:

• Sodium picosulfate 1
• Bisacodyl (oral tablet or rectal suppository) 2

Conditional recommendation for:

• Senna (2 tablets twice daily) 1, 3

These agents enhance intestinal motility and peristalsis. 2 They should generally be reserved for PRN use or added to osmotic therapy rather than used as monotherapy. 4

Rectal Interventions for Fecal Impaction

When digital rectal exam identifies a full rectum or fecal impaction, suppositories and enemas are preferred first-line therapy. 1

Options include:

• Glycerin or bisacodyl suppository 10mg 3
• Fleet enema or tap water enema 3

Enema contraindications:

• Neutropenia or thrombocytopenia
• Paralytic ileus or intestinal obstruction
• Recent colorectal/gynecological surgery
• Recent anal or rectal trauma
• Severe colitis, inflammation, or infection
• Toxic megacolon
• Undiagnosed abdominal pain
• Recent pelvic radiotherapy 1, 3

Sodium phosphate enemas are contraindicated in renal dysfunction and limited to maximum once daily when unavoidable. 2

Third-Line: Prescription Secretagogues and Prokinetics

If constipation persists after 3 months of optimized PEG ± stimulant therapy, reassess for mechanical obstruction, metabolic abnormalities, or medication effects before escalating. 2

Strong recommendations for:

• Linaclotide 1
• Plecanatide 1
• Prucalopride (serotonin type 4 agonist) 1

Conditional recommendation for:

• Lubiprostone 1

Special Population Considerations

Opioid-Induced Constipation

All patients receiving opioid analgesics should be prescribed prophylactic laxatives unless contraindicated by pre-existing diarrhea. 1 Constipation is nearly universal with opioids and tolerance does not develop. 2

Preferred regimen:

• Osmotic laxative (PEG or lactulose) combined with stimulant laxative (senna or bisacodyl) 1, 2
• Bulk laxatives like psyllium are absolutely contraindicated 1, 2

If first-line fails:

• Peripherally acting μ-opioid receptor antagonists (methylnaltrexone, naloxegol, naldemedine) 2
• Combined opioid/naloxone medications reduce OIC risk 1

Renal Impairment

PEG is the safest and preferred option due to minimal systemic absorption. 2

Absolutely avoid:

• Magnesium-containing laxatives (any degree of renal impairment) 1, 2, 3
• Sodium phosphate preparations 2

Monitor patients on diuretics or cardiac glycosides for dehydration and electrolyte imbalances. 1

Elderly Patients

PEG 17g/day offers excellent efficacy and safety profile. 1, 2

Key prevention measures:

• Ensure toilet access, especially with decreased mobility 1
• Dietetic support for anorexia of aging and chewing difficulties 1
• Individualize laxatives based on cardiac and renal comorbidities 1

Pregnancy

Both psyllium and PEG are safe due to lack of systemic absorption, though excessive fiber can cause maternal bloating. 2

Criteria for Specialist Referral

Refer to gastroenterology when:

• Inadequate response after 3 months of optimized PEG + stimulant therapy 2
• Severe symptoms, sudden changes in bowel habits, or blood in stool 1
• Suspected dyssynergic defecation requiring anorectal physiologic testing and biofeedback therapy 2, 4

Common Pitfalls to Avoid

• Do not prescribe docusate based on tradition—multiple trials show no clinical benefit 2, 3
• Do not use bulk-forming agents in opioid-induced constipation—they are contraindicated and may worsen symptoms 1, 2
• Do not fail to prescribe prophylactic laxatives when initiating opioids—constipation is nearly universal 2
• Do not use magnesium-containing laxatives in any degree of renal impairment—risk of dangerous hypermagnesemia 1, 2
• Do not start laxatives without excluding bowel obstruction in patients with severe symptoms 3