Initial Management of Rectosigmoid Colitis
For mild to moderately active rectosigmoid colitis, start with combination therapy of oral mesalamine 2-4g daily plus topical mesalamine 1g daily (as enemas for sigmoid involvement), which is more effective than either agent alone. 1
First-Line Treatment Strategy
Topical Therapy Selection
- Use mesalamine enemas rather than suppositories for rectosigmoid involvement, as suppositories primarily target the rectum while enemas deliver medication more proximally to reach the sigmoid colon 2, 1
- Topical mesalamine is superior to topical corticosteroids and should be used as first-line topical therapy 2, 1
- Administer topical mesalamine 1g daily; once-daily dosing is as effective as divided doses and improves adherence 2, 1
Oral Therapy
- Prescribe oral mesalamine 2-4g daily or balsalazide 6.75g daily 1
- Once-daily dosing is as effective as divided doses 1
- The combination of oral plus topical therapy achieves superior remission rates compared to either modality alone 2, 1
Pre-Treatment Considerations
- Confirm active disease by sigmoidoscopy and exclude infection with stool cultures before initiating treatment 1
- Evaluate for proximal constipation with plain abdominal radiograph if present, as fecal loading can impair drug delivery to the inflamed mucosa 2, 1
- Treat constipation with stool bulking agents or laxatives if identified 1
- Avoid antidiarrheal medications as they mask worsening symptoms while allowing underlying inflammation to progress 1
Second-Line Treatment for Inadequate Response
When to Escalate
If no improvement occurs after adequate trial of combination oral and topical mesalamine therapy (typically 2-4 weeks), escalate treatment 1
Corticosteroid Therapy
- Initiate oral prednisolone 40mg daily 1
- Continue topical mesalamine as adjunctive therapy with systemic corticosteroids 1
- Taper prednisolone gradually over 8 weeks; more rapid reduction increases early relapse risk 1
- Avoid long-term steroid treatment due to significant adverse effects 1
Management of Steroid-Dependent or Refractory Disease
Steroid-Sparing Agents
For patients who become steroid-dependent (unable to taper below a certain dose without symptom recurrence) or have chronic active disease despite steroids 2, 1:
- Azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day 1
- Anti-TNF therapy (preferably combined with thiopurines for infliximab) 2
- Vedolizumab 2
- Methotrexate 2
Alternative Salvage Therapies
For endoscopically documented refractory disease despite optimized conventional therapy 2:
- Intravenous corticosteroid therapy (which induces remission in a high proportion of patients) 2
- Oral or rectal cyclosporine 2, 1
- Oral or rectal tacrolimus 2
Common Pitfalls to Avoid
Dosing Errors
- Ensure adequate mesalamine dosing of at least 2g daily for active disease; underdosing is a common cause of apparent treatment failure 1
- Verify patient adherence to prescribed therapy before concluding treatment failure 2
Diagnostic Errors
- Reassess diagnosis if treatment fails: consider irritable bowel syndrome, Crohn's disease, mucosal prolapse, microscopic colitis, or malignancy 2, 3
- Unrecognized complications such as proximal constipation or superimposed infection (particularly C. difficile) can mimic refractory disease 2
Treatment Delays
- Do not delay corticosteroid treatment if no response to optimized 5-ASA therapy occurs 1
- Transition to steroid-sparing agents promptly rather than continuing long-term steroids 1
Maintenance Therapy
Once remission is achieved, aminosalicylates are effective and safe for long-term maintenance therapy 1, 4