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ICD-10-CM 2027 diagnosis code

K51.91Ulcerative colitis, unspecified, with complications

Not billable — use a more specific code

K51.91 is a header code, so it can't be reported by itself. Choose one of the 6 more specific codes beneath it.

Code unchanged since ICD-10-CM took effect on October 1, 2015. Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About K51.91

K51.91 is the ICD-10-CM diagnosis code for ulcerative colitis, unspecified, with complications. It belongs to category K51 (ulcerative colitis), block K50-K52 (noninfective enteritis and colitis) and chapter 11 (diseases of the digestive system). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

Within K51.9 (ulcerative colitis, unspecified), K51.91 is specifically for ulcerative colitis, unspecified, with complications. Related codes cover without complications (K51.90).

To report this condition, pick the subcode that matches the documentation: K51.911 (bleeding), K51.912 (obstruction), K51.913 (fistula), K51.914 (abscess), K51.918 (complication) and K51.919 (complications).

Use an additional code to identify any associated fistulas, if applicable: anal fistula (K60.3-), anorectal fistula (K60.5-) and rectal fistula (K60.4-). Use an additional code to identify manifestations, such as: pyoderma gangrenosum (L88).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Specific codes under K51.91

Notes that apply from higher levels

Instructions written at a parent level also apply to K51.91.

› From K51 Ulcerative colitis
Excludes1
  • Crohn's disease [regional enteritis] (K50.-)
Use additional code
  • code to identify any associated fistulas, if applicable:
  • anal fistula (K60.3-)
  • anorectal fistula (K60.5-)
  • rectal fistula (K60.4-)
  • code to identify manifestations, such as:
  • pyoderma gangrenosum (L88)

Broader instructions also apply from K50-K52 Noninfective enteritis and colitis and Chapter 11: Diseases of the digestive system.

Code history

  1. 2016
  2. 2017
  3. 2018
  4. 2019
  5. 2020
  6. 2021
  7. 2022
  8. 2023
  9. 2024
  10. 2025
  11. 2026
  12. 2027
  • FY2016 (effective 10/1/2015): Added (first year of ICD-10-CM)
  • No changes since FY2016.

Common questions about K51.91

Is K51.91 billable?

No. K51.91 is a header code. Report one of its more specific subcodes instead.