What are the treatment options for slow transit constipation?

Treatment of Slow Transit Constipation

Start with polyethylene glycol (PEG) as first-line osmotic therapy, escalate to stimulant laxatives (bisacodyl or senna) for regular use every 1-2 days, and consider prucalopride as a prokinetic agent if standard laxatives fail—but only after definitively excluding defecatory disorders through anorectal testing. 1, 2, 3

Critical Pre-Treatment Diagnostic Step

Before treating presumed slow transit constipation, you must rule out defecatory disorders first, as this is the most common diagnostic pitfall:

• Defecatory disorders can cause secondary slow transit that improves once the primary pelvic floor dysfunction is treated, making transit testing misleading if performed prematurely 3, 1
• Assess colonic transit only after excluding defecatory disorders OR if pelvic floor retraining fails to resolve symptoms 3, 1
• Look for these specific historical clues suggesting defecatory disorder: prolonged straining before elimination, difficulty passing soft stools or enema fluid, need for perineal/vaginal pressure to evacuate, or digital disimpaction 3
• Perform digital rectal examination looking for paradoxical contraction or incomplete relaxation of pelvic floor during simulated defecation 3

Exclude Secondary Causes

Before diagnosing idiopathic slow transit constipation, rule out:

• Structural colon disease (stricture, cancer, anal fissure, proctitis) via colonoscopy or barium enema 3
• Metabolic disturbances: Check thyroid function (hypothyroidism), serum calcium (hypercalcemia), and glucose (diabetes mellitus) 3
• Neurologic disorders: Parkinson's disease, spinal cord lesions, multiple sclerosis 3
• Medication-induced constipation: Review all current medications 1

Stepwise Pharmacologic Management Algorithm

Step 1: Lifestyle and Dietary Modifications

• Increase dietary fiber to 20-25g daily, prioritizing soluble fiber such as psyllium 1
• Add oats and flaxseed to the diet 1
• Ensure at least 8 cups of fluid daily, preferably water or non-caffeinated beverages 1
• Increase physical activity within patient capabilities 1

Step 2: First-Line Osmotic Laxatives

• Polyethylene glycol (PEG) with or without electrolytes is the preferred first-line osmotic agent 1, 4
• Note that fiber supplements are generally ineffective in true slow transit constipation since the diagnosis requires high-fiber diet during transit testing 4
• Unabsorbed sugar-based osmotic laxatives (lactulose, sorbitol) are also generally ineffective in slow transit constipation 4

Step 3: Stimulant Laxatives

• Bisacodyl or senna should be used regularly (2-3 times per week) to achieve non-straining bowel movements every 1-2 days 1, 4
• There is no evidence that chronic use of stimulant laxatives causes harm when used at this frequency 4
• Studies show diminished colonic motor response to stimulants in slow transit constipation, but they remain first-line therapy 4

Step 4: Prokinetic Agents

When standard laxatives fail, consider prokinetic therapy:

• Prucalopride 2 mg once daily (1 mg in elderly, escalate to 2 mg if needed after 2-4 weeks) is a selective 5-HT4 receptor agonist that stimulates high-amplitude propagating contractions 2
• Prucalopride reduces mean colonic transit time by 12 hours compared to placebo (from baseline of 65 hours) 2
• In clinical trials, 19-38% of patients achieved ≥3 complete spontaneous bowel movements per week versus 10-20% with placebo 2
• Median time to first complete spontaneous bowel movement ranges from 1.4-4.7 days versus 9.1-20.6 days with placebo 2
• Alternative: Misoprostol 200 mcg every other morning, escalating to tolerance or efficacy (avoid in women of childbearing potential due to abortifacient effects) 4
• Alternative: Colchicine 0.6 mg three times daily, though long-term efficacy is not well-studied 4

Non-Pharmacologic Interventions

Biofeedback Therapy

• Biofeedback is effective in approximately 60% of patients with slow transit constipation even without outlet dysfunction, making it a risk-free option worth attempting 4
• Particularly valuable in patients with coexisting pelvic floor dyssynergia 4

Surgical Options (Last Resort)

Surgery should only be considered after:

• Documented slow transit on objective testing
• Normal anorectal function confirmed
• No evidence of generalized intestinal dysmotility
• Failed comprehensive medical management
• Significant disability affecting quality of life

Subtotal colectomy with ileorectal anastomosis is the standard surgical approach, but carries significant early and late morbidity that must be balanced against current disability 4, 5

• One study reported 15% perioperative mortality and 50% requiring additional operations, with poor functional outcomes (median Wexner constipation score 11.5,50% still meeting Rome II criteria for constipation) 6
• Ileostomy is preferred if anorectal dysfunction or impaired continence mechanisms are present 4
• Avoid partial colonic resections, as marker studies do not define pathophysiology adequately 4

Common Pitfalls to Avoid

• Do not assume reduced stool frequency equals slow transit—frequency correlates poorly with delayed colonic transit 3, 1
• Do not perform colonic transit testing before excluding defecatory disorders, as secondary slow transit from pelvic floor dysfunction will lead to inappropriate treatment 3, 1
• Do not use stimulant laxatives on a daily or multiple-times-daily basis unnecessarily, as this increases cramping without added benefit; every-other-day or 2-3 times weekly is sufficient 4
• Do not proceed to surgery without confirming normal anorectal function and excluding generalized dysmotility, as outcomes are poor in these populations 4, 5