Diagnosis and Management of Colitis

Initial Assessment and Laboratory Workup

The National Comprehensive Cancer Network recommends beginning with stool evaluation to rule out infectious causes, specifically Clostridioides difficile, ova and parasites, and viral pathogens, before initiating any immunosuppressive therapy 1, 2
Documenting the patient's baseline bowel habits and quantifying the increase in stool frequency above baseline is essential for establishing the severity of colitis 1
The severity of colitis can be graded, with Grade 1 being less than 4 additional bowel movements/day without colitis symptoms, Grade 2 being 4-6 additional bowel movements/day with mild/moderate colitis symptoms, Grade 3 being more than 6 additional bowel movements/day with severe symptoms, and Grade 4 being life-threatening complications 1, 3
Blood or mucus in stool suggests infectious colitis, inflammatory bowel disease, or ischemic colitis and mandates immediate workup 3, 2, 4
Hemodynamic instability indicates severe disease requiring urgent intervention 4

A CT abdomen/pelvis with IV contrast is indicated for Grade ≥2 colitis to assess for complications and rule out alternative diagnoses 3, 2
Colonoscopy or flexible sigmoidoscopy with biopsy is strongly considered for all Grade ≥2 colitis to establish etiology and guide treatment 3, 2, 5
Early endoscopy (≤7 days from symptom onset) reduces symptom duration and steroid treatment duration 3
Biopsy findings showing ulceration predict steroid-refractory disease requiring early biologic therapy (infliximab or vedolizumab) 3, 5

Patients with blood in stool require evaluation for peptic ulcer disease, malignant bleeding, diverticulosis, angiodysplasia, hemorrhoids, and ischemia 3, 2
Age >60 years, low-flow states, shock, and vasoconstrictor medications increase the risk of ischemic colitis 4
Test for CMV in addition to standard infectious workup in patients at risk for ischemic colitis 4
If a patient is on immune checkpoint inhibitors, recognize that symptoms typically develop 6-8 weeks after starting treatment 1
Higher rates of colitis occur with CTLA-4 blockade and combination PD-1/PD-L1 plus CTLA-4 therapy 1