2026 ICD-10-CM Diagnosis Code K35.201Acute appendicitis with generalized peritonitis, with perforation, without abscess

ICD-10-CM Codes›K00–K95›K35-K38›K35

ICD-10-CM K35.201
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K35.201 is a billable ICD-10-CM diagnosis code for acute appendicitis with generalized peritonitis, with perforation, without abscess. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 371 through 373. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Appendicitis and other appendiceal conditions and Peritonitis and intra-abdominal abscess.

Code Identity

ICD-10-CM Code
K35.201
Billable Status
Yes — Valid for Submission
Code Describes
Acute appendicitis with generalized peritonitis, with perforation, without abscess
Short Description
Ac appendicitis with gen peritonitis, with perf, w/o abscs
Parent Code
K35.20
Acute appendicitis with generalized peritonitis, without abscess

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK35-K38Diseases of appendix
CategoryK35Acute appendicitis
This CodeK35.201Acute appendicitis with generalized peritonitis, with perforation, without abscess

Tabular List NotesGuidance

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

Inclusion Terms

  • Appendicitis (acute) with generalized (diffuse) peritonitis following rupture or perforation of appendix NOS

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)
      • with
        • peritonitis NEC
          • generalized
            • with
              • perforation or rupture
    • Appendicitis(pneumococcal) (retrocecal)
      • with
        • peritonitis NEC
          • generalized
            • following rupture or perforation of appendix NOS
    • Appendicitis(pneumococcal) (retrocecal)
      • acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative)
        • with
          • peritonitis NEC
            • generalized
              • with
                • perforation or rupture
    • Appendicitis(pneumococcal) (retrocecal)
      • acute (catarrhal) (fulminating) (obstructive) (retrocecal) (suppurative)
        • with
          • peritonitis NEC
            • generalized
              • following rupture or perforation of appendix NOS

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
CCSR DIG016
Peritonitis and intra-abdominal abscess
Default principal diagnosis: inpatient No · outpatient No

Code History & ChangesHistory

Replacement K35.201 replaces the following previously assigned code(s):

  • K35.20 - Acute appendicitis with gen peritonitis, without abscess
FY 2024AddedAdded to the ICD-10-CM code setEffective October 1, 2023.
FY 2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About K35.201Overview

Is K35.201 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report acute appendicitis with generalized peritonitis, with perforation, without abscess on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does K35.201 group to?

When acute appendicitis with generalized peritonitis, with perforation, without abscess is the principal diagnosis on an inpatient stay, it groups to MS-DRG 371, 372, 373, with relative weights from 0.7274 to 1.7731 depending on complications. Higher weights mean higher Medicare reimbursement.

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.