ICD-10 Code K51.513 – Left sided colitis with fistula (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K51.513 – Left sided colitis with fistula
What it is
This code identifies left-sided ulcerative colitis affecting the descending colon and sigmoid colon, with an abnormal fistulous connection. Use it when the record clearly documents both the colitis location and the fistula.
Clinical signs
Typical findings include chronic inflammatory bowel disease symptoms such as abdominal pain, diarrhea, rectal bleeding, and urgency. A fistula may be documented by imaging, endoscopy, surgery, or specialist assessment; clinical features vary, refer to documentation.
When to use this code
Use K51.513 when the provider specifically documents left-sided colitis and a fistula related to the disease. It fits encounters for confirmed disease coding, problem lists, and follow-up visits when the condition remains active. If the fistula site or colitis extent is unclear, check documentation before assigning the code.
Do not use for
Do not use this code for ulcerative colitis without a fistula, or for fistulas from surgery, trauma, or Crohn’s disease. If the chart does not confirm left-sided involvement, check documentation.
Coding tip
Assign the code only when both the left-sided distribution and fistula are explicitly documented.