ICD-10-CM 2027
ICD-10 code for acute appendicitis
From the official ICD-10-CM alphabetic index entry “Appendicitis (pneumococcal) (retrocecal) › acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative)”. Page updated September 29, 2026.
About coding acute appendicitis
The ICD-10-CM code for acute appendicitis is K35.80 (Unspecified acute appendicitis). The official index lists 18 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on K35.80.
Within K35.8, choose K35.80 (Unspecified acute appendicitis) only when documentation doesn't support a more specific option: other acute appendicitis (K35.89).
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.
More specific acute appendicitis codes (official index)
- with
- gangrene K35.891 — Other acute appendicitis without perforation, with gangrene
- peritoneal abscess K35.33 — Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess
- peritonitis NEC K35.33 — Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess
- generalized K35.209 — Acute appendicitis with generalized peritonitis, without abscess, unspecified as to perforation
- with
- abscess K35.219 — Acute appendicitis with generalized peritonitis, with abscess, unspecified as to perforation
- with perforation or rupture K35.211 — Acute appendicitis with generalized peritonitis, with perforation and abscess
- following rupture or perforation of appendix NOS K35.211 — Acute appendicitis with generalized peritonitis, with perforation and abscess
- without perforation or rupture K35.210 — Acute appendicitis with generalized peritonitis, without perforation, with abscess
- perforation or rupture K35.201 — Acute appendicitis with generalized peritonitis, with perforation, without abscess
- following rupture or perforation of appendix NOS K35.201 — Acute appendicitis with generalized peritonitis, with perforation, without abscess
- without rupture or perforation of appendix K35.200 — Acute appendicitis with generalized peritonitis, without perforation or abscess
- localized K35.30 — Acute appendicitis with localized peritonitis, without perforation or gangrene
- with
- gangrene K35.31 — Acute appendicitis with localized peritonitis and gangrene, without perforation
- perforation K35.32 — Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess
- and abscess K35.33 — Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess
- specified NEC K35.890 — Other acute appendicitis without perforation or gangrene
- with gangrene K35.891 — Other acute appendicitis without perforation, with gangrene
- with localized peritonitis K35.31 — Acute appendicitis with localized peritonitis and gangrene, without perforation
Common questions about acute appendicitis ICD-10 codes
What is the ICD-10 code for acute appendicitis?
- K35.80 — Unspecified acute appendicitis. More specific codes apply when the documentation supports them: K35.891, K35.33, K35.33, K35.209 and others below.
Is K35.80 billable?
- Yes. K35.80 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can K35.80 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict K35.80 as a principal diagnosis.
Is K35.80 a CC or MCC?
- K35.80 is a CC (complication or comorbidity) under MS-DRG v44.0, unless excluded by the principal diagnosis.