K59.31 — Toxic megacolon
K59.31 is a billable, specific ICD-10-CM code for toxic megacolon. It is valid for submission on a claim.
Excludes1 inherited from the categories above K59.31
These are not written on K59.31, but they bind it: a note on a category applies to every code beneath it. Billing K59.31 with anything listed here is a denial.
Written on K59.3 — Megacolon, not elsewhere classified
Excludes2 inherited from the categories above K59.31
Also inherited, and the opposite of Excludes1: these conditions are not part of K59.31, but a patient can have both, so you may code both.
Risk adjustment
K59.31 risk-adjusts. Under the CMS-HCC V28 model it maps to this category:
- HCC 78 Intestinal Obstruction/Perforation0.326 RAF
Coefficient shown for the Community Non-dual Aged segment. A higher HCC in the same hierarchy will suppress this one, so capturing it does not always add score.
Medicare coverage
K59.31 is named in 6 Medicare coverage policies — 6 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A55937Billing and Coding: Diagnostic Colonoscopy
- A56394Billing and Coding: Colonoscopy and Sigmoidoscopy-Diagnostic
- A56421Billing and Coding: CT of the Abdomen and Pelvis
- A56456Billing and Coding: Colonoscopy/Sigmoidoscopy/Proctosigmoidoscopy
How K59.31 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to K59.31.
- Megacolon›toxic NEC
- Dilatation›colon›toxic
Code history
K59.31 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.
Related codes at this level
Codes that share K59.3. If K59.31 is not quite right, the correct code is usually one of these.
Questions about K59.31
- Is K59.31 a billable ICD-10-CM code?
- Yes. K59.31 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does K59.31 sit in the tabular list?
- Diseases of the digestive system (K00-K95), in the block Other diseases of intestines (K55-K64).
- What cannot be coded together with K59.31?
- K59.31 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above K59.31 (K59.3, K59) and apply to it just the same.