2026 ICD-10-CM Diagnosis Code K65.0Generalized (acute) peritonitis

ICD-10-CM Codes›K00–K95›K65-K68›K65

ICD-10-CM K65.0
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K65.0 is a billable ICD-10-CM diagnosis code for generalized (acute) peritonitis. 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 Peritonitis and intra-abdominal abscess.

Code Identity

ICD-10-CM Code
K65.0
Billable Status
Yes — Valid for Submission
Code Describes
Generalized (acute) peritonitis
Short Description
Generalized (acute) peritonitis
Same as the full description in the CMS dataset.
Parent Code
K65
Peritonitis

Code Classification

ChapterK00–K95Diseases of the digestive system
SectionK65-K68Diseases of peritoneum and retroperitoneum
CategoryK65Peritonitis
This CodeK65.0Generalized (acute) peritonitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute bacterial peritonitis
  • Acute generalized peritonitis
  • Acute infectious generalized peritonitis
  • Acute infectious peritonitis
  • Acute pelvic peritonitis
  • Acute peritonitis
  • Acute suppurative peritonitis
  • Chronic inflammation of pelvic peritoneum
  • Chronic peritonitis
  • Pelvic peritonitis
  • Purulent peritonitis
  • Subphrenic peritonitis

Tabular List NotesGuidance

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

Inclusion Terms

  • Pelvic peritonitis (acute), male
  • Subphrenic peritonitis (acute)
  • Suppurative peritonitis (acute)

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.

    • Cellulitis(diffuse) (phlegmonous) (septic) (suppurative)
      • pelvis, pelvic (chronic)
        • male
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • acute (generalized)
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • diaphragmatic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • diffuse
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • disseminated
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • eosinophilic
        • acute
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • fibropurulent
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • general (ized)
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • pancreatic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • pelvic
        • male
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • purulent
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • septic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • subdiaphragmatic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • subphrenic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • suppurative
    • Rupture, ruptured
      • cecum (with peritonitis)
    • Suppuration, suppurative
      • pelvis, pelvic
        • male

Clinical ClassificationClinical

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

CCSR DIG016
Peritonitis and intra-abdominal abscess
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Pelvic Peritonitis

    inflammation of the peritoneum surrounding the pelvic organs.

Patient EducationClinical

Peritoneal Disorders

Your peritoneum is the tissue that lines your abdominal wall and covers most of the organs in your abdomen. A liquid, peritoneal fluid, lubricates the surface of this tissue.

Read the full article at MedlinePlus

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

Convert K65.0 to ICD-9-CMHistory

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

ICD-9-CM
567.21 Peritonitis (acute) gen
Approximate The match is approximate rather than exact.
ICD-9-CM
567.29 Suppurat peritonitis 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 K65.0Overview

Is K65.0 (Peritonitis) a billable code?

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

What MS-DRG does K65.0 group to?

When generalized (acute) peritonitis 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.

What is the ICD-9 equivalent of K65.0?

Under the General Equivalence Mappings, generalized (acute) peritonitis converts to ICD-9-CM 567.21 (peritonitis (acute) gen) and 567.29 (suppurat peritonitis 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.