Colitis is a broad term used to describe inflammation of the colon. Etiologies include inflammatory bowel disease, infectious colitis, microscopic colitis, ischemia, medication-associated colitis, radiation colitis, diversion colitis, graft-versus-host disease, and diverticulitis. In terms of special populations, neonates are at risk for necrotizing enterocolitis and immunocompromised patients are at risk for neutropenic enterocolitis.

Symptoms of colitis vary depending on etiology but can include diarrhea, abdominal pain, and hematochezia. Systemic symptoms such as fevers and chills may be present. Risk factors for colitis vary depending on the specific etiology. It is sometimes associated with somatic mutations in the NFKBIZ, TRAF3IP2, PIGR, or ARID1A genes.

For discussion of specific colitis diagnoses, see the following.

Infectious colitis caused by, eg:

• Shigella
• Campylobacter
• Diarrheal Escherichia coli
• Yersinia
• Clostridioides difficile colitis
• Amebic colitis
• Cytomegalovirus (CMV)
• Mycobacterium tuberculosis
• Salmonella

Drug-induced colitis caused by, eg:

• NSAIDs
• Checkpoint inhibitors, eg, ipilimumab, nivolumab
• See Drug Reaction Data below for further information

In addition:

• Ischemic colitis
• Ulcerative colitis
• Diverticulitis
• Crohn colitis
• Microscopic colitis
• Radiation-induced colitis
• Diversion colitis
• Neutropenic enterocolitis
• Necrotizing enterocolitis
• Food protein-induced enterocolitis syndrome