2026 ICD-10-CM Diagnosis Code K36Other appendicitis

ICD-10-CM Codes›K00–K95›K35-K38›K36

ICD-10-CM K36
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K36 is a billable ICD-10-CM diagnosis code for other appendicitis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 393 through 395. Coders also document this condition as atypical appendicitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Appendicitis and other appendiceal conditions.

Code Identity

ICD-10-CM Code
K36
Billable Status
Yes — Valid for Submission
Code Describes
Other appendicitis
Chapter
K35-K38
Diseases of appendix

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK35-K38Diseases of appendix
CategoryK36Other appendicitis
This CodeK36Other appendicitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Atypical appendicitis
  • Catarrhal appendicitis
  • Chronic appendicitis
  • Chronic appendicitis with perforation of appendix
  • Healed appendicitis
  • Pelvic appendicitis
  • Perforation of appendix
  • Recurrent appendicitis
  • Subacute appendicitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Chronic appendicitis
  • Recurrent appendicitis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Appendicitis(pneumococcal) (retrocecal)
      • chronic (recurrent)
    • Appendicitis(pneumococcal) (retrocecal)
      • healed (obliterative)
    • Appendicitis(pneumococcal) (retrocecal)
      • interval
    • Appendicitis(pneumococcal) (retrocecal)
      • neurogenic
    • Appendicitis(pneumococcal) (retrocecal)
      • obstructive
    • Appendicitis(pneumococcal) (retrocecal)
      • recurrent
    • Appendicitis(pneumococcal) (retrocecal)
      • relapsing
    • Appendicitis(pneumococcal) (retrocecal)
      • subacute (adhesive)
    • Appendicitis(pneumococcal) (retrocecal)
      • subsiding
    • Subsiding appendicitis

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR DIG009
Appendicitis and other appendiceal conditions
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Appendicitis

    acute inflammation of the appendix. acute appendicitis is classified as simple, gangrenous, or perforated.

  • Appendix

    a worm-like blind tube extension from the cecum.

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.

Convert K36 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
542 Other appendicitis
Exact Match The mapping is direct, with no qualifiers.

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 K36Overview

Is K36 (Other appendicitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other appendicitis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K36 group to?

When other appendicitis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 393, 394, 395, with relative weights from 0.6490 to 1.5993 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of K36?

Under the General Equivalence Mappings, other appendicitis converts to ICD-9-CM 542 (other appendicitis). The mapping is a direct match.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.