ICD-10 Code K59.31 – Toxic megacolon (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code K59.31 – Toxic megacolon
What it is
Toxic megacolon is a severe dilation of the colon with systemic illness. Use this code when documentation confirms toxic megacolon, often as a complication of colitis or other inflammatory bowel disease.
Clinical signs
Typical findings include marked abdominal distention, pain, tenderness, fever, and signs of toxicity. Clinical features vary; refer to documentation, especially when imaging or exam notes describe colonic dilation with systemic involvement.
When to use this code
Use K59.31 when the provider documents toxic megacolon as the diagnosis, whether primary or secondary to another condition. Code it from discharge summaries, consult notes, or imaging reports that clearly identify the condition. Check documentation if the record only says colitis, ileus, or bowel dilation without toxic megacolon.
Do not use for
Do not use this code for uncomplicated megacolon, constipation, or nonspecific abdominal distention. If toxic megacolon is not explicitly documented, verify the diagnosis before assigning K59.31.
Coding tip
Confirm the provider links the colon dilation to toxicity or systemic illness, not just bowel enlargement.