2026 ICD-10-CM Diagnosis Code K38.3Fistula of appendix

ICD-10-CM Codes›K00–K95›K35-K38›K38

ICD-10-CM K38.3
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K38.3 is a billable ICD-10-CM diagnosis code for fistula of appendix. 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. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Appendicitis and other appendiceal conditions.

Code Identity

ICD-10-CM Code
K38.3
Billable Status
Yes — Valid for Submission
Code Describes
Fistula of appendix
Short Description
Fistula of appendix
Same as the full description in the CMS dataset.
Parent Code
K38
Other diseases of appendix

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK35-K38Diseases of appendix
CategoryK38Other diseases of appendix
This CodeK38.3Fistula of appendix

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fistula of appendix

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.

    • Fistula(cutaneous)
      • appendix, appendicular

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

Patient EducationClinical

Colonic Diseases

Your colon, also known as the large intestine, is part of your digestive system. It's a long, hollow tube at the end of your digestive tract where your body makes and stores stool. Many disorders affect the colon's ability to work properly. Some of these include:

Read the full article at MedlinePlus

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

Convert K38.3 to ICD-9-CMHistory

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

ICD-9-CM
543.9 Diseases of appendix NEC
Approximate The match is approximate rather than exact.

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 K38.3Overview

Is K38.3 (Other diseases of appendix) a billable code?

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

What MS-DRG does K38.3 group to?

When fistula of appendix 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 K38.3?

Under the General Equivalence Mappings, fistula of appendix converts to ICD-9-CM 543.9 (diseases of appendix NEC). The mapping is approximate, so confirm the match fits the documentation.

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.