What is the evidence‑based treatment algorithm for an adult with presumed inflammatory bowel disease presenting with colitis?

Treatment Algorithm for Adult Colitis in Presumed Inflammatory Bowel Disease

Begin intravenous corticosteroids immediately when severe colitis is suspected—do not delay therapy while awaiting stool culture results. 1, 2

Initial Assessment and Diagnostic Work-Up

Severity stratification drives all treatment decisions and must be performed at presentation:

• Monitor vital signs four times daily, record stool frequency with blood presence, and perform daily abdominal examination for tenderness or rebound 3, 1
• Obtain laboratory panel (CBC, ESR/CRP, electrolytes, albumin, liver function tests) every 24–48 hours to track inflammatory activity 3, 1
• Perform plain abdominal radiograph when colonic dilatation is suspected; transverse colon diameter >5.5 cm indicates severe disease requiring urgent intervention 3, 1
• Send stool cultures for bacterial pathogens, Clostridioides difficile toxin, and parasites, but never postpone corticosteroid therapy while awaiting these results 1, 2
• Perform ileocolonoscopy with biopsies from at least five sites (including ileum and rectum, two specimens per site) to confirm diagnosis and differentiate ulcerative colitis from Crohn's disease 1, 2

Treatment Algorithm by Disease Extent and Severity

Mild-to-Moderate Distal Colitis (Proctitis to Sigmoid)

First-line therapy combines topical and oral aminosalicylates:

• Initiate topical mesalazine 1 g daily (suppositories for proctitis, enemas for proctosigmoiditis) plus oral mesalazine 2–4 g daily 3, 1
• This combination is more effective than either agent alone 3, 1
• Topical corticosteroids are less effective than topical mesalazine and should be reserved for patients intolerant of topical mesalazine 3
• If proximal constipation develops, add stool bulking agents or laxatives 3, 4

Escalation for inadequate response after 2–4 weeks:

• Add oral prednisolone 40 mg daily with gradual taper over 8 weeks 3, 1
• Continue topical agents as adjunctive therapy 3
• Never taper prednisolone faster than 8 weeks—rapid tapering precipitates early relapse 1, 4

Mild-to-Moderate Extensive or Left-Sided Ulcerative Colitis

Oral aminosalicylates are first-line therapy:

• Start oral mesalazine 2–4 g daily (once-daily dosing preferred) 3, 1
• Alternative: balsalazide 6.75 g daily 3, 1
• Olsalazine 1.5–3 g daily causes higher diarrhea rates in pancolitis; reserve for left-sided disease 3, 1

Escalation for inadequate response after 2–4 weeks:

• Add oral prednisolone 40 mg daily with 8-week taper 3, 1
• For persistent rectal symptoms, add topical mesalazine or corticosteroid suppositories/enemas 1
• Patients requiring more than one corticosteroid course per year need azathioprine 1.5–2.5 mg/kg/day or mercaptopurine 0.75–1.5 mg/kg/day as steroid-sparing agents 1

Mild Ileocolonic Crohn's Disease

High-dose mesalazine may be sufficient:

• Start mesalazine 4 g daily as initial therapy 1, 4
• Sulfasalazine 4 g daily is effective for colonic Crohn's but has higher side-effect rates; reserve for patients with reactive arthropathy 3, 1

Moderate-to-Severe Crohn's Disease

Oral corticosteroids are the mainstay:

• Oral prednisolone 40 mg daily with 8-week taper 1, 4
• For isolated ileocecal moderate disease, budesonide 9 mg daily is an alternative, though marginally less effective than prednisolone 1
• In steroid-dependent disease (>1 course/year), initiate azathioprine 1.5–2.5 mg/kg/day or mercaptopurine 0.75–1.5 mg/kg/day 1
• These thiopurine agents have slow onset (8–12 weeks) and should be used adjunctively, not as sole therapy for active disease 1

Severe Colitis Requiring Hospitalization

Immediate admission and joint gastroenterology-surgery management are mandatory:

Initial Management

• Start intravenous hydrocortisone 400 mg/day or methylprednisolone 60 mg/day immediately 3, 1, 2
• Provide intravenous fluid and electrolyte replacement 3, 1
• Transfuse blood to maintain hemoglobin >10 g/dL 3
• Administer subcutaneous heparin for venous thromboembolism prophylaxis 3, 2
• Offer enteral or parenteral nutritional support if malnourished 3, 1
• For Crohn's disease, add intravenous metronidazole because active disease is difficult to distinguish from septic complications 1

Monitoring and Rescue Therapy Decision Points

• Counsel patients that colectomy risk is approximately 25–30% 1, 2
• By day 3, >8 stools/day or 3–8 stools/day with CRP >45 mg/L predicts ≈85% colectomy rate and signals need for rescue therapy 1
• Rescue options: infliximab 5 mg/kg IV at weeks 0,2,6 or ciclosporin 2 mg/kg/day IV 3, 1
• Never continue IV corticosteroids beyond 7–10 days without escalating to rescue therapy or surgery 2

Surgical Indications

Urgent surgery is indicated for:

• Toxic megacolon not improving after 24–48 hours of medical therapy 1
• Colonic perforation 1, 2
• Massive hemorrhage with hemodynamic instability 1, 2
• Failure of rescue therapy after 4–7 days 1
• Presence of peritoneal signs (rebound tenderness, guarding, rigidity) 1

Maintenance Therapy After Remission

Lifelong maintenance is generally recommended:

• Continue aminosalicylates (mesalazine ≥2 g daily) for all ulcerative colitis patients with left-sided or extensive disease 1, 2, 4
• Azathioprine 1.5–2.5 mg/kg/day or mercaptopurine 0.75–1.5 mg/kg/day for chronic active steroid-dependent disease 1, 4
• Ongoing aminosalicylate therapy reduces relapse risk and may provide protection against colorectal cancer 1, 4
• Discontinuation may be considered only for distal disease in remission ≥2 years in patients averse to medication 1, 4

Critical Pitfalls to Avoid

• Do not postpone corticosteroid therapy while awaiting stool microbiology results in suspected severe inflammatory colitis 1, 2
• Avoid rapid prednisolone tapering (<8 weeks)—it is associated with early disease relapse 1, 4
• Do not use infliximab in Crohn's disease patients with obstructive symptoms 1
• Never use anti-diarrheal medications in severe colitis 2
• Active sepsis (e.g., intra-abdominal abscess) is an absolute contraindication to anti-TNF therapy 1
• Screen for tuberculosis before initiating anti-TNF therapy 1
• Before escalating therapy in Crohn's disease, exclude bacterial overgrowth, bile-salt malabsorption, or fibrotic strictures 1