Differential Diagnosis for Colitis with a Rash of the Anus
- Single most likely diagnosis
- Ulcerative colitis with perianal disease: This condition is a type of inflammatory bowel disease (IBD) that can cause inflammation and ulcers in the colon, leading to symptoms such as diarrhea, abdominal pain, and weight loss. Perianal disease, including perianal fistulas and abscesses, can cause a rash around the anus.
- Other Likely diagnoses
- Crohn's disease with perianal involvement: Similar to ulcerative colitis, Crohn's disease is a type of IBD that can cause inflammation in any part of the gastrointestinal tract, including the anus. Perianal disease is more common in Crohn's disease and can cause a rash, fistulas, and abscesses.
- Infectious colitis (e.g., Clostridioides difficile, Salmonella, Shigella): Certain infections can cause colitis and lead to symptoms such as diarrhea, abdominal pain, and fever. A rash around the anus can occur due to the infection or as a result of perianal irritation.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Neutropenic colitis: This is a life-threatening condition that occurs in people with neutropenia (low white blood cell count), often due to chemotherapy or immunosuppression. It can cause severe abdominal pain, diarrhea, and a rash around the anus.
- Ischemic colitis: This condition occurs when there is a reduction in blood flow to the colon, which can cause abdominal pain, diarrhea, and a rash around the anus. It can be life-threatening if not promptly treated.
- Rare diagnoses
- Behçet's disease: This is a rare autoimmune disorder that can cause inflammation in various parts of the body, including the colon and anus. It can lead to symptoms such as diarrhea, abdominal pain, and a rash around the anus.
- Eosinophilic colitis: This is a rare condition characterized by an accumulation of eosinophils (a type of white blood cell) in the colon, which can cause inflammation and symptoms such as diarrhea, abdominal pain, and a rash around the anus.