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ICD-10-CM 2027 diagnosis code

K35.21Acute appendicitis with generalized peritonitis, with abscess

Not billable — use a more specific code

K35.21 is a header code, so it can't be reported by itself. Choose one of the 3 more specific codes beneath it.Short description: Acute appendicitis with gen peritonitis, with abscess

Code last changed in FY2024 (effective October 1, 2023). Source: official FY2027 ICD-10-CM release from CDC/NCHS and CMS. Page updated September 29, 2026. About our data

About K35.21

K35.21 is the ICD-10-CM diagnosis code for acute appendicitis with generalized peritonitis, with abscess. It belongs to category K35 (acute appendicitis), block K35-K38 (diseases of appendix) and chapter 11 (diseases of the digestive system). It is a header code, so it can't be reported by itself; one of its 3 subcodes must be used instead.

Within K35.2 (acute appendicitis with generalized peritonitis), K35.21 is specifically for acute appendicitis with generalized peritonitis, with abscess. Related codes cover without abscess (K35.20).

To report this condition, pick the subcode that matches the documentation: K35.210 (abscess), K35.211 (abscess) and K35.219 (unspecified as to perforation).

It was added in FY2019, effective October 1, 2018, and changed in FY2024.

Specific codes under K35.21

Notes that apply from higher levels

Instructions written at a parent level also apply to K35.21.

Broader instructions also apply from 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
  • FY2019 (effective 10/1/2018): Added
  • FY2024 (effective 10/1/2023): Expanded — no longer billable

Common questions about K35.21

Is K35.21 billable?

No. K35.21 is a header code. Report one of its more specific subcodes instead.