ICD-10 Code K51.318 – Ulcerative (chronic) rectosigmoiditis with other complication (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K51.318 – Ulcerative (chronic) rectosigmoiditis with other complication
What it is
This code identifies chronic ulcerative inflammation limited to the rectum and sigmoid colon, with an additional complication documented. Use it when the record clearly states rectosigmoiditis and another specified complication.
Clinical signs
Typical findings include persistent lower gastrointestinal inflammation, often with rectal bleeding, urgency, or diarrhea. Clinical features vary; refer to documentation for the exact complication and disease extent.
When to use this code
Use K51.318 when the provider documents ulcerative rectosigmoiditis and also names a complication that is not captured by a more specific code. It fits chronic disease involving the rectum and sigmoid only. Check documentation if the complication is unclear or if the diagnosis is described differently.
Do not use for
Do not assign this code for ulcerative colitis without rectosigmoid involvement, or when no complication is documented. If the record says proctitis, pancolitis, or another ulcerative colitis subtype, code that specific diagnosis instead.
Coding tip
Verify both the anatomic site and the documented complication before coding, because the complication drives the “other complication” option.