Immune Checkpoint Inhibitor-Induced Colitis

• Differential Diagnoses: Infectious colitis, enteritis, hyperthyroidism, ischemic colitis, celiac disease, pancreatic insufficiency, IBS, chemotherapy-induced diarrhea.

• Diarrhea Grading (CTCAE):

  • Grade 1: <4 stools/day over baseline.

  • Grade 2: 4-6 stools/day, limiting instrumental ADLs.

  • Grade 3: ≥7 stools/day, hospitalization required, limiting self-care ADLs.

  • Grade 4: Life-threatening, urgent intervention needed.

  • Grade 5: Death.

• Management Plan:

  • If dyspepsia, GERD, nausea present: consider EGD.

  • For Grade 2-4 diarrhea:

    • Abdominal CT to evaluate for colitis/perforation/megacolon.

    • NPO after midnight for colonoscopy with rush pathology.

    • Send labs: CBC, CMP, TSH, TTG IgA, total IgA, CRP, blood cultures (if febrile).

    • Stool studies: C. diff, microsporidia, bacterial culture (Salmonella, Shigella, Campylobacter, Yersinia, E. coli), ova & parasites, fecal calprotectin/lactoferrin.

    • IV fluids for support.

  • If no colitis on colonoscopy or imaging but persistent diarrhea:

    • Consider Loperamide 2-4mg Q4H (max 16mg/day).

    • Consider cholestyramine 4g BID.

  • If hypotensive, check lactate levels.

• Steroid Therapy for Refractory Diarrhea:

  • Grade 2/3 diarrhea (without fever/hypotension, tolerating PO):

    • consider 0.5–2 mg/kg prednisone equivalent daily with a taper of 4–6 weeks

    • Taper by 10mg/week once improved (<4 stools/day over baseline), goal to discontinue in 6 weeks.

  • If no improvement in 2-3 days: Escalate to IV steroids or biologics (infliximab/vedolizumab).

  • Grade 4 symptoms or systemic symptoms (fever, hypotension, PO intolerance): Require urgent biologic therapy if no response within 3 days.

Discharge Criteria:

• Normal vital signs (no fever, hypotension).

• ≤4 stools/day over baseline.

• Resolution of severe abdominal pain.

• Tolerance of oral diet.

GUIDELINES: AGA 2021