What is the appropriate treatment for colitis, including infectious, ischemic, microscopic, ulcerative colitis, and Crohn‑related colitis?

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Last updated: February 15, 2026 • View editorial policy

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Treatment of Colitis

Treatment of colitis must be tailored to the specific etiology—infectious, ischemic, microscopic, ulcerative colitis, or Crohn's disease—with infectious causes excluded before initiating immunosuppressive therapy for inflammatory bowel disease. 1, 2

Initial Diagnostic Approach

Before initiating treatment for any suspected inflammatory colitis, exclude infectious causes through stool testing (bacterial culture, C. difficile, ova and parasites). 1, 2 This is critical because immunosuppressive therapy given for presumed IBD in the setting of undiagnosed infection can lead to catastrophic outcomes.

  • Obtain stool inflammatory markers (fecal calprotectin >150 mg/g or lactoferrin) in patients with ≥4 bowel movements daily above baseline to stratify risk and guide need for endoscopy. 1, 2
  • Perform endoscopy with biopsies from multiple colonic segments before initiating high-dose systemic glucocorticoids to confirm diagnosis and assess severity. 1, 2
  • In sexually active patients with proctitis symptoms, screen for sexually transmitted infections (gonorrhea, chlamydia, HSV, syphilis) before attributing symptoms to IBD. 2

Treatment of Ulcerative Colitis

Mild-to-Moderate Distal UC (Proctitis and Left-Sided Colitis)

First-line therapy is combination topical mesalazine 1 g daily (suppository for proctitis, enema for left-sided) PLUS oral mesalazine 2-4 g daily, which achieves significantly higher remission rates than either agent alone. 1, 2, 3

  • Once-daily dosing of topical mesalazine is preferred over multiple daily doses for adherence. 2
  • If topical mesalazine is not tolerated, switch to topical corticosteroid (budesonide 2-4 mg suppository or hydrocortisone enema) while continuing oral mesalazine, though this is less effective. 2
  • Address proximal constipation with stool-bulking agents or laxatives, as constipation paradoxically worsens rectal symptoms in distal UC. 2, 3

If no improvement after 2-4 weeks of combination therapy, add oral prednisolone 40 mg daily, then taper gradually over 8 weeks while maintaining topical agents. 2, 3 Rapid steroid tapering leads to early relapse. 2

Mild-to-Moderate Extensive UC

First-line therapy is oral mesalazine 2-4 g daily (or balsalazide 6.75 g daily). 2, 3

  • If prompt response is required or mesalazine fails, initiate prednisolone 40 mg daily with 8-week taper. 2, 3
  • Avoid long-term steroids; patients with chronic steroid-dependent disease require azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day. 2, 3

Moderate-to-Severe UC (Mayo Endoscopy Score 2-3)

Initiate advanced therapy with infliximab, risankizumab, guselkumab, or ozanimod as first-line agents in biologic-naïve patients, as these demonstrate superior efficacy for inducing clinical remission compared to adalimumab. 2

  • Combine TNF antagonists with thiopurines or methotrexate rather than using biologic monotherapy, as combination therapy is superior for inducing remission. 2
  • In patients with prior infliximab exposure (especially primary non-responders), use ustekinumab or tofacitinib over vedolizumab or adalimumab. 2
  • JAK inhibitors (tofacitinib, upadacitinib) are recommended only after prior failure or intolerance to TNF antagonists. 2

Acute Severe UC (ASUC)

Hospitalize immediately and initiate IV methylprednisolone 40-60 mg daily (or hydrocortisone 100 mg four times daily) after fluid resuscitation. 2

  • Provide supportive care: IV fluid/electrolyte replacement with potassium supplementation ≥60 mmol/day, low-molecular-weight heparin for thromboprophylaxis (rectal bleeding is NOT a contraindication), and nutritional support if malnourished. 2
  • Monitor daily: stool frequency, vital signs, CBC, CRP, albumin, electrolytes. 2
  • Perform unprepared flexible sigmoidoscopy to assess severity and exclude CMV colitis. 2

Assess response after 3-5 days: Predictors of steroid failure include >8 stools/day OR 3-8 stools/day with CRP >45 mg/L on day 3. 2

If inadequate response by day 3-5, initiate rescue therapy with infliximab 5 mg/kg IV (weeks 0,2,6) OR ciclosporin 2 mg/kg/day IV. 2 Do NOT continue ineffective corticosteroids beyond day 5—this increases morbidity and delays necessary surgery. 2

Colectomy indications: failure of rescue therapy after 4-7 days, toxic megacolon without improvement after 24-48 hours, perforation, or massive hemorrhage. 2 Subtotal colectomy with ileostomy is the procedure of choice in emergency settings. 2

Maintenance Therapy for UC

Continue lifelong maintenance therapy with oral mesalazine ≥2 g daily to reduce relapse risk and potentially reduce colorectal cancer risk. 2, 3

  • For patients on combination biologic + immunomodulator therapy in corticosteroid-free remission ≥6 months, do not withdraw the TNF antagonist. 2
  • Biosimilars of infliximab, adalimumab, and ustekinumab are equivalent to originator drugs. 2

Treatment of Crohn's Disease-Related Colitis

For active ileal or ileocolonic Crohn's disease, treatment options include high-dose mesalazine, corticosteroids, nutritional therapy, or surgery based on disease severity. 2

  • Smoking cessation is the most important factor in maintaining remission for Crohn's disease. 2
  • Azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day are effective but reserved as second-line therapy due to potential toxicity. 2

Treatment of Microscopic Colitis

Budesonide 9 mg daily orally is first-line therapy for induction of remission in microscopic colitis (both lymphocytic and collagenous subtypes). 1, 4, 5

  • Budesonide is ineffective as prophylactic treatment but may be used for treatment of ICI-associated microscopic colitis. 1
  • Alternative therapies include bile acid sequestrants (cholestyramine, colesevelam, colestipol), biologics (infliximab, adalimumab, vedolizumab), thiopurines, or methotrexate for refractory cases. 4, 5
  • Review and discontinue potential medication triggers (NSAIDs, PPIs, SSRIs) in patients with refractory symptoms. 1, 4

Treatment of Immune Checkpoint Inhibitor (ICI) Colitis

ICI colitis typically responds to high-dose systemic glucocorticoids (0.5-2 mg/kg prednisone equivalent daily) with a 4-6 week taper. 1

  • Infliximab and vedolizumab are reasonable options for glucocorticoid-refractory ICI colitis. 1
  • Rapid progression may occur within days, particularly with ipilimumab, requiring prompt diagnosis and treatment. 1

Treatment of Infectious Colitis

Do NOT initiate immunosuppressive therapy until infectious causes are excluded. 1, 2

  • For C. difficile infection: metronidazole 500 mg three times daily orally for 10 days (non-severe) or vancomycin 125 mg four times daily orally for 10 days (severe). 2
  • Avoid antibiotics for Shiga toxin-producing E. coli (STEC) infections, as treatment may increase risk of hemolytic uremic syndrome. 2

Critical Pitfalls to Avoid

  • Never delay rescue therapy in ASUC—patients remaining on ineffective corticosteroids beyond day 5 suffer high morbidity and delayed surgery. 2
  • Do not use topical corticosteroids as first-line therapy for UC; they are less effective than topical mesalazine. 2
  • Always exclude infectious causes before attributing diarrhea to UC flare and escalating immunosuppressive therapy. 1, 2, 3
  • Do not switch between different oral 5-ASA formulations if initial therapy fails—this is ineffective. 2

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Guideline

Treatment of Colitis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

3
Guideline

Treatment of Diarrhea in Ulcerative Colitis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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