What is the definition and management guidelines for constipation?

Definition and Management of Constipation

Constipation is defined as the slow movement of feces through the large intestine, resulting in infrequent bowel movements and the passage of dry, hard stools, which can significantly impact quality of life. 1

Definition and Diagnostic Criteria

According to the Rome III criteria, chronic constipation requires the presence of at least two of the following symptoms for at least 12 weeks in the previous 12 months (not necessarily consecutively):

• Straining during bowel movements
• Lumpy or hard stool
• Sensation of incomplete evacuation
• Sensation of anorectal blockage or obstruction
• Manual evacuation procedures to remove stool
• Fewer than 3 bowel movements per week 1

The Rome IV criteria has added opioid-induced constipation (OIC) to the section on Bowel Disorders, defined as "constipation triggered or worsened by opioid analgesics." 1

Pathophysiology

Normal colonic function involves:

• Fluid absorption through the colon
• Waste transport via peristalsis (primarily mediated by serotonin)
• Rectal distension leading to urge to defecate
• Average colonic transit time of 20-72 hours 1

Constipation occurs when these mechanisms are disrupted due to:

1. Primary causes (colonic or anorectal dysfunction)
2. Secondary causes (disease or medication-related)

Classification of Constipation

Constipation can be classified as:

1. Functional (Primary) Constipation:

   • Normal transit constipation
   • Slow transit constipation
   • Outlet constipation/dyssynergic defecation

2. Secondary Constipation:

   • Medication-induced (especially opioids)
   • Metabolic disorders (e.g., hypothyroidism)
   • Neurological conditions
   • Structural abnormalities
   • Irritable bowel syndrome with constipation (IBS-C)

Management Guidelines

First-Line Treatment

The American College of Oncology and American Gastroenterological Association recommend osmotic laxatives (preferably polyethylene glycol) and stimulant laxatives as first-line agents for treating constipation due to their effectiveness and safety profile. 2

Recommended first-line agents:

1. Osmotic Laxatives:

   • Polyethylene Glycol (PEG): 17-34g daily; response time 1-3 days 2
   • Lactulose: 15-30ml twice daily; latency 2-3 days 2
   • Magnesium salts: Use with caution in renal impairment 2

2. Stimulant Laxatives:

   • Senna: Stimulates motor and secretory effects on the colon 2
   • Bisacodyl: 10-15mg daily for short-term use in refractory constipation 2

Second-Line Treatment

For inadequate response to first-line agents:

• Combine osmotic and stimulant laxatives
• Consider adding magnesium hydroxide, lactulose, or sorbitol 2

For Refractory Constipation

• Enemas: Normal saline, soap solution, or osmotic micro-enema 2
• For opioid-induced constipation: Consider peripherally acting μ-opioid receptor antagonists (PAMORAs) like methylnaltrexone (0.15mg/kg subcutaneously every other day) 2
• Linaclotide: FDA-approved for chronic idiopathic constipation (CIC) in adults (145 mcg orally once daily; 72 mcg once daily may be used based on individual presentation or tolerability) 3

For Fecal Impaction

• Digital fragmentation and extraction of stool
• Followed by enemas (water or oil retention) or suppositories 2

Non-Pharmacological Interventions

• Increase fluid intake
• Increase dietary fiber
• Increase physical activity
• Establish proper toileting routine and positioning
• Discontinue non-essential constipating medications 2

Common Pitfalls to Avoid

1. Relying solely on bulk laxatives like psyllium for opioid-induced constipation (ineffective) 2
2. Undertreating with inadequate dosing or failing to escalate therapy when needed 2
3. Using docusate alone (limited efficacy as standalone agent) 2
4. Not increasing laxative dose when increasing opioid dose 2
5. Missing proximal impaction during assessment 2

Maintenance Therapy

• Implement maintenance bowel regimen immediately after disimpaction to prevent recurrence
• Goal: One non-forced bowel movement every 1-2 days
• Regular monitoring of stool frequency, consistency, and abdominal comfort 2

Special Considerations

Opioid-Induced Constipation

• Prophylactic stimulant laxative (senna) plus stool softener recommended
• Consider PAMORAs for refractory cases 2

Elderly Patients

• May present with nonspecific symptoms like delirium, anorexia, and functional decline
• At higher risk for constipation; requires careful monitoring

Pediatric Patients

• Linaclotide is contraindicated in patients less than 2 years of age due to risk of serious dehydration 3
• For children 6-17 years with functional constipation, linaclotide 72 mcg orally once daily is FDA-approved 3

By following these evidence-based guidelines for the definition and management of constipation, clinicians can effectively address this common and distressing condition while improving patients' quality of life.