ICD-10 Code K51.913 – Ulcerative colitis, unspecified with fistula (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K51.913 – Ulcerative colitis, unspecified with fistula
What it is
This code identifies ulcerative colitis when the provider documents a fistula, but does not specify the colitis type beyond “unspecified.” Use it when the record supports both ulcerative colitis and a fistula complication.
Clinical signs
Findings may include chronic bloody diarrhea, abdominal pain, urgency, and rectal bleeding. A fistula may be documented on exam, imaging, or specialist assessment; clinical features vary, so refer to documentation.
When to use this code
Use K51.913 when the chart states ulcerative colitis and also documents a fistula, without further subtype detail. It is appropriate for encounters focused on evaluation, monitoring, or management of this inflammatory bowel disease complication.
If the provider later specifies a more exact ulcerative colitis category, code the documented subtype instead. Check documentation when fistula location or relationship to the colitis is unclear.
Do not use for
Do not use this code for Crohn disease, perianal fistula without ulcerative colitis, or ulcerative colitis without fistula. If the record does not support a fistula, choose the more specific non-fistula ulcerative colitis code.
Coding tip
Confirm that both diagnoses are documented together; do not infer a fistula from symptoms alone.