2026 ICD-10-CM Diagnosis Code K35Acute appendicitis

ICD-10-CM Codes›K00–K95›K35-K38›K35

ICD-10-CM K35
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K35 is a non-billable ICD-10-CM category code for acute appendicitis, so it cannot be submitted on claims. Use a more specific code from this category instead, such as K35.200, K35.201, K35.209, and K35.210.

Code Identity

ICD-10-CM Code
K35
Billable Status
No — Non-Billable Category
Code Describes
Acute appendicitis
Chapter
K35-K38
Diseases of appendix

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK35-K38Diseases of appendix
CategoryK35Acute appendicitis
This CodeK35Acute appendicitis

Specific Coding for Acute appendicitisOverview

Non-specific codes like K35 require more characters. Use one of these billable codes instead:

  • K35.2 for Acute appendicitis with generalized peritonitis

  • K35.20 for Acute appendicitis with generalized peritonitis, without abscess

  • K35.21 for Acute appendicitis with generalized peritonitis, with abscess

  • K35.3 for Acute appendicitis with localized peritonitis

  • Use K35.30 for Acute appendicitis with localized peritonitis, without perforation or gangrene

  • Use K35.31 for Acute appendicitis with localized peritonitis and gangrene, without perforation

  • Use K35.32 for Acute appendicitis with perforation, localized peritonitis, and gangrene, without abscess

  • Use K35.33 for Acute appendicitis with perforation, localized peritonitis, and gangrene, with abscess

  • K35.8 for Other and unspecified acute appendicitis

  • Use K35.80 for Unspecified acute appendicitis

  • K35.89 for Other acute appendicitis

Patient EducationClinical

Appendicitis

The appendix is a small, tube-like organ attached to the first part of the large intestine. It is located in the lower right part of the abdomen. It has no known function. A blockage inside of the appendix causes appendicitis. The blockage leads to increased pressure, problems with blood flow, and inflammation.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K35Overview

Is K35 (Acute appendicitis) a billable code?

No. This is a category header that groups the codes for acute appendicitis, and headers cannot be submitted on claims. Claims for acute appendicitis need a more specific code from this category, such as K35.200, K35.201, and K35.209.