2026 ICD-10-CM Diagnosis Code K65.8Other peritonitis

ICD-10-CM Codes›K00–K95›K65-K68›K65

ICD-10-CM K65.8
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

K65.8 is a billable ICD-10-CM diagnosis code for other 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
K65.8
Billable Status
Yes — Valid for Submission
Code Describes
Other peritonitis
Short Description
Other 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 CodeK65.8Other peritonitis

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Acute cecitis
  • Acute cecitis with perforation AND peritonitis
  • Acute polyserositis
  • Acute serositis
  • Chronic peritonitis
  • Chronic polyserositis
  • Chronic proliferative peritonitis
  • Continuous ambulatory peritoneal dialysis associated peritonitis
  • Eosinophilia of peritoneal fluid
  • Eosinophilic peritonitis
  • Fat necrosis of peritoneum
  • Fecal peritonitis
  • Fungal peritonitis
  • Granulomatous peritonitis
  • Infection associated with peritoneal dialysis catheter
  • Infection of peritoneal dialysis catheter
  • Injury of cecum
  • Long-term disorder of dialysis
  • Mesenteric fat necrosis
  • Mesenteric fat saponification
  • Mesenteric saponification
  • Parasitic peritonitis
  • Perforation of cecum
  • Perihepatitis
  • Peritoneal dialysis-associated peritonitis
  • Peritoneal fluid abnormal
  • Peritonitis due to infected peritoneal dialysis catheter
  • Polyserositis
  • Polyserositis syndrome of dialysis
  • Sclerosing peritonitis
  • Sclerosing peritonitis as complication of peritoneal dialysis
  • Serositis
  • Typhlitis
  • Urine peritonitis

Tabular List NotesGuidance

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

Inclusion Terms

  • Chronic proliferative peritonitis
  • Peritonitis due to urine

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.

    • Capsulitis(joint)
      • hepatic
    • Cecitis
      • with perforation, peritonitis, or rupture
    • Perihepatitis
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • chronic proliferative
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • due to
        • urine
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • eosinophilic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • proliferative, chronic
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • specified NEC
    • Peritonitis(adhesive) (bacterial) (fibrinous) (hemorrhagic) (idiopathic) (localized) (perforative) (primary) (with adhesions) (with effusion)
      • urine
    • Saponification, mesenteric
    • Serositis, multiple
    • Serositis, multiple
      • peritoneal

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

  • Chylous Ascites

    presence of milky lymph (chyle) in the peritoneal cavity, with or without infection.

  • Coronavirus, Feline

    a species of coronavirus infecting cats of all ages and commonly found in catteries and zoos. cats are often found carrying the virus but only a small proportion develop disease. feline coronavirus and feline infectious peritonitis virus (fipv) are virtually the same virus in genetic and antigenetic terms, and are morphologically indistinguishable. since they only differ in their disease potential (with fipv causing a more serious illness), they are considered biotypes of each other.

  • Familial Mediterranean Fever

    a group of hereditary autoinflammation diseases, characterized by recurrent fever, abdominal pain, headache, rash, pleurisy; and arthritis. orchitis; benign meningitis; and amyloidosis may also occur. homozygous or compound heterozygous mutations in marenostrin gene encoding pyrin result in autosomal recessive transmission; simple heterozygous, autosomal dominant form of the disease also exists with mutations in the same gene.

  • Feline Infectious Peritonitis

    common coronavirus infection of cats caused by the feline infectious peritonitis virus (coronavirus, feline). the disease is characterized by a long incubation period, fever, depression, loss of appetite, wasting, and progressive abdominal enlargement. infection of cells of the monocyte-macrophage lineage appears to be essential in fip pathogenesis.

  • Peritonitis

    inflammation of the peritoneum lining the abdominal cavity as the result of infectious, autoimmune, or chemical processes. primary peritonitis is due to infection of the peritoneal cavity via hematogenous or lymphatic spread and without intra-abdominal source. secondary peritonitis arises from the abdominal cavity itself through rupture or abscess of intra-abdominal organs.

  • Peritonitis, Tuberculous

    a form of peritonitis seen in patients with tuberculosis, characterized by lesion either as a miliary form or as a pelvic mass on the peritoneal surfaces. most patients have ascites, abdominal swelling, abdominal pain, and other systemic symptoms such as fever; weight loss; and anemia.

  • Serositis

    inflammation of a serous membrane.

  • Typhlitis

    necrotizing inflammation of the cecum (typhlon in greek), sometimes spreading to the appendix and/or the ileum. symptoms include abdominal pain and diarrhea. its pathogenesis is multifactorial. typhlitis is often associated with neutropenia and chemotherapy in immunocompromised individuals (immunocompromised host).

  • Ovarian Luteinized Thecoma Associated with Sclerosing Peritonitis

    a rare usually bilateral luteinized thecoma that arises from the ovary and is associated with sclerosing peritonitis. it occurs mostly in premenopausal women. the ovarian tumor is benign but patients may develop intestinal obstruction due to the sclerosing peritonitis.

  • Sclerosing Peritonitis

    a rare peritoneal cavity disorder that is characterized by the development of dense fibrous tissue in the peritoneum and the creation of severe adhesions in the abdomen that result in partial or complete small bowel obstruction. it may be idiopathic or develop in patients who receive peritoneal dialysis treatment. patients present with abdominal distention and pain.

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 K65.8 to ICD-9-CMHistory

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

ICD-9-CM
567.89 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 K65.8Overview

Is K65.8 (Peritonitis) a billable code?

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

What MS-DRG does K65.8 group to?

When other 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 K65.8?

Under the General Equivalence Mappings, other peritonitis converts to ICD-9-CM 567.89 (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.