ICD-10-CM 2027 diagnosis code
K59.31Toxic megacolon
K59.31 is a valid, billable ICD-10-CM code for toxic megacolon. It can be reported on claims for dates of service from October 1, 2026 – September 30, 2027.
Code last changed in FY2017 (effective October 1, 2016). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data
About K59.31
K59.31 is the ICD-10-CM diagnosis code for toxic megacolon. It belongs to category K59 (other functional intestinal disorders), block K55-K64 (other diseases of intestines) and chapter 11 (diseases of the digestive system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.
Within K59.3 (megacolon, not elsewhere classified), K59.31 is specifically for toxic megacolon. Related codes cover other megacolon (K59.39).
As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.
In MS-DRG v44.0, it is part of the grouping logic for DRG 393 (Other Digestive System Diagnoses with MCC, relative weight 1.5881), DRG 394 (Other Digestive System Diagnoses with CC, relative weight 0.9228) and DRG 395 (Other Digestive System Diagnoses without CC/MCC, relative weight 0.6382), in MDC 06 (Diseases and Disorders of the Digestive System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
It was added in FY2017, effective October 1, 2016.
Before ICD-10, this condition was coded in ICD-9-CM as 556.9 (ulcerative colitis, unspecified).
Notes that apply from higher levels
Instructions written at a parent level also apply to K59.31.
Broader instructions also apply from Chapter 11: Diseases of the digestive system.
Alphabetic index entries
2 entriesTerms in the official ICD-10-CM index that lead to K59.31.
MS-DRG v44.0 grouping
All DRGs →Inpatient MS-DRGs this diagnosis can group to, as the principal or a secondary diagnosis, depending on the rest of the claim.
MDC 06 · Diseases and Disorders of the Digestive System
ICD-9-CM equivalent
Converter →- 556.9Ulcerative colitis, unspecifiedapproximate
From the CMS 2018 General Equivalence Mappings (GEMs), the final GEMs release.
Code history
- 2016
- 2017
- 2018
- 2019
- 2020
- 2021
- 2022
- 2023
- 2024
- 2025
- 2026
- 2027
- FY2017 (effective 10/1/2016): Added
- No changes since FY2017.
Common questions about K59.31
Is K59.31 billable?
- Yes. K59.31 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can K59.31 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict K59.31 as a principal diagnosis.
Is K59.31 a CC or MCC?
- K59.31 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.
What DRG does K59.31 group to?
- K59.31 is used in the MS-DRG v44.0 logic for MS-DRG 393 (Other Digestive System Diagnoses with MCC), MS-DRG 394 (Other Digestive System Diagnoses with CC) and MS-DRG 395 (Other Digestive System Diagnoses without CC/MCC). Which one applies depends on whether it is the principal diagnosis and on the rest of the claim.
What is the ICD-9 code for K59.31?
- The CMS General Equivalence Mappings map K59.31 to ICD-9-CM 556.9.