How should colitis be evaluated and treated in an adult, including differentiation between infectious and inflammatory causes and step‑wise therapy?

Colitis Treatment in Adults

Treatment should be initiated immediately based on disease severity without delaying for stool culture results, using a stepwise approach that differentiates between infectious and inflammatory causes while prioritizing corticosteroids for severe presentations. 1

Initial Evaluation and Differentiation

Immediate Diagnostic Workup

• Obtain stool cultures for bacterial pathogens, Clostridioides difficile toxin, and parasites to exclude infectious causes, but do not delay corticosteroid therapy while awaiting results if severe colitis is suspected. 2
• Perform ileocolonoscopy with biopsies from at least five sites (including ileum and rectum, two specimens per site) to confirm diagnosis, assess disease extent, and differentiate ulcerative colitis from Crohn's disease. 1
• Obtain CT abdomen/pelvis with IV and oral contrast if acute abdominal symptoms are present to assess for complications such as bowel wall thickening, pneumatosis, or perforation. 3

Severity Assessment

• Monitor vital signs four times daily, stool frequency and character (presence of blood, liquid versus solid), and abdominal examination for tenderness and rebound. 1
• Measure complete blood count, ESR or CRP, electrolytes, albumin, and liver function tests every 24-48 hours. 1
• Obtain plain abdominal radiograph if colonic dilatation is suspected (transverse colon diameter >5.5 cm indicates severe disease requiring urgent intervention). 2

Treatment Algorithm by Disease Type and Severity

Ulcerative Colitis

Mild to Moderate Disease

• Start oral mesalazine 2-4 g daily (once-daily dosing preferred for adherence) as first-line therapy. 2
• For distal disease (proctitis), add topical 5-aminosalicylates for superior efficacy. 4, 5
• If inadequate response after 2-4 weeks, add oral prednisolone 40 mg daily, tapering gradually over 8 weeks. 1, 2

Severe Disease (Hospitalization Required)

• Initiate intravenous corticosteroids immediately: hydrocortisone 400 mg/day or methylprednisolone 60 mg/day. 1, 2
• Provide IV fluid and electrolyte replacement, blood transfusion to maintain hemoglobin >10 g/dL, and subcutaneous heparin for thromboembolism prophylaxis. 1
• Administer nutritional support (enteral or parenteral) if malnourished. 1
• Establish joint management with gastroenterology and colorectal surgery from admission, informing patients of 25-30% colectomy risk. 1, 2

Rescue Therapy for Steroid-Refractory Disease

• Evaluate response by day 3 using objective criteria: >8 stools/day or 3-8 stools/day with CRP >45 mg/L predicts 85% colectomy rate and indicates need for rescue therapy. 2
• If inadequate response by day 3-5, escalate to infliximab 5 mg/kg IV at weeks 0,2, and 6, or ciclosporin 2 mg/kg/day IV. 2

Surgical Indications

• Urgent surgery is indicated for: toxic megacolon without improvement after 24-48 hours of medical treatment, colonic perforation, massive hemorrhage with hemodynamic instability, or failure of rescue therapy after 4-7 days. 2
• Peritoneal signs (rebound tenderness, guarding, rigidity) require immediate surgical consultation. 3

Crohn's Disease (Colonic Involvement)

Mild Ileocolonic Disease

• High-dose mesalazine 4 g daily may be sufficient as initial therapy. 1

Moderate to Severe Disease

• Oral prednisolone 40 mg daily is appropriate, reduced gradually over 8 weeks (more rapid reduction associated with early relapse). 1
• For isolated ileo-caecal disease with moderate activity, budesonide 9 mg daily is an option but marginally less effective than prednisolone. 1

Severe Disease

• Intravenous steroids (hydrocortisone 400 mg/day or methylprednisolone 60 mg/day) with concomitant IV metronidazole, as it may be difficult to distinguish active disease from septic complications. 1
• Consider azathioprine 1.5-2.5 mg/kg/day or mercaptopurine 0.75-1.5 mg/kg/day as adjunctive therapy and steroid-sparing agents. 1
• Infliximab 5 mg/kg is effective but should be avoided in patients with obstructive symptoms. 1

Ischemic Colitis

Nongangrenous Disease (Medical Management)

• Bowel rest with NPO status, nasogastric decompression if needed, and IV fluid resuscitation to optimize perfusion. 3
• Serial abdominal examinations every 4-6 hours to detect clinical deterioration and monitor for peritonitis development. 3

Gangrenous Disease (Surgical Management)

• Peritoneal signs, CT findings of pneumatosis intestinalis, portal venous gas, or free intraperitoneal air necessitate urgent surgical intervention. 3
• Note: Mortality for nongangrenous disease is <5%, whereas gangrenous ischemic colitis carries 50-85% mortality even with surgery. 3

Maintenance Therapy Post-Remission

Ulcerative Colitis

• Lifelong maintenance therapy is recommended with aminosalicylates (mesalazine ≥2 g daily), azathioprine 1.5-2.5 mg/kg/day, or mercaptopurine 0.75-1.5 mg/kg/day to reduce relapse risk and potentially decrease colorectal cancer risk. 1, 2
• Discontinuation may be reasonable only for distal disease in remission for 2 years in patients averse to medication. 1

Critical Pitfalls to Avoid

• Do not delay corticosteroid therapy while awaiting stool microbiology results in suspected severe inflammatory colitis, as acute onset UC is difficult to distinguish from infectious colitis. 1
• Avoid rapid prednisolone reduction (<8 weeks), as this is associated with early relapse. 1
• Do not use infliximab in Crohn's patients with obstructive symptoms. 1
• Consider alternative explanations for symptoms in Crohn's disease (bacterial overgrowth, bile salt malabsorption, fibrotic strictures) before escalating therapy. 1