ICD-10 Code K51.31 – Ulcerative (chronic) rectosigmoiditis with complications (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K51.31 – Ulcerative (chronic) rectosigmoiditis with complications
What it is
K51.31 identifies chronic ulcerative inflammation limited to the rectosigmoid region, with documented complications. Use it when the record clearly states rectosigmoid involvement and a complication is present.
Clinical signs
Clinical features vary; refer to documentation. Commonly recorded findings include rectal bleeding, diarrhea, urgency, abdominal cramping, and endoscopic evidence of chronic inflammatory disease in the rectosigmoid area.
When to use this code
Use this code when the provider documents ulcerative rectosigmoiditis and also notes a complication linked to the condition. The complication must be supported in the chart, not assumed from severity alone. If the record does not specify complications, check documentation before coding.
Do not use for
Do not use K51.31 for ulcerative colitis without a documented complication, or when disease location is elsewhere in the colon. If the note is nonspecific, check documentation.
Coding tip
Verify both the anatomic site and the complication in the provider note before assigning K51.31.