ICD-10-CM Code K65.9

Peritonitis, unspecified

Version 2020 Billable Code

Valid for Submission

K65.9 is a billable code used to specify a medical diagnosis of peritonitis, unspecified. The code is valid for the year 2020 for the submission of HIPAA-covered transactions. The ICD-10-CM code K65.9 might also be used to specify conditions or terms like aseptic peritonitis, bacterial peritonitis, fat necrosis of peritoneum, fibrinous peritonitis, infectious peritonitis, mesenteric fat necrosis, etc

Short Description:Peritonitis, unspecified
Long Description:Peritonitis, unspecified

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with guidance for inclusions, exclusions, descriptions and more. The following references are applicable to the code K65.9:

Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Bacterial peritonitis NOS

Index to Diseases and Injuries

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for the code K65.9 are found in the index:


The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Aseptic peritonitis
  • Bacterial peritonitis
  • Fat necrosis of peritoneum
  • Fibrinous peritonitis
  • Infectious peritonitis
  • Mesenteric fat necrosis
  • Mesenteric peritonitis with mesenteric fat necrosis
  • Peritonitis
  • Pneumococcal peritonitis
  • Postoperative peritonitis
  • Primary peritonitis
  • Ventriculoperitoneal shunt-associated peritonitis

Clinical Information

  • CHYLOUS ASCITES-. presence of milky lymph chyle in the peritoneal cavity with or without infection.
  • 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 result in autosomal recessive transmission; simple heterozygous autosomal dominant form of the disease.
  • 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.
  • 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.
  • 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.

Diagnostic Related Groups

The ICD-10 code K65.9 is grouped in the following groups for version MS-DRG V37.0 What are Diagnostic Related Groups?
The Diagnostic Related Groups (DRGs) are a patient classification scheme which provides a means of relating the type of patients a hospital treats. The DRGs divides all possible principal diagnoses into mutually exclusive principal diagnosis areas referred to as Major Diagnostic Categories (MDC).
applicable from 10/01/2019 through 09/30/2020.


Convert K65.9 to ICD-9

Code Classification

  • Diseases of the digestive system (K00–K93)
    • Diseases of peritoneum and retroperitoneum (K65-K68)
      • Peritonitis (K65)

Code History

  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016
    (First year ICD-10-CM implemented into the HIPAA code set)
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020

Information for Patients

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.

Disorders of the peritoneum are not common. They include

  • Peritonitis - an inflammation of the peritoneum
  • Cancer
  • Complications from peritoneal dialysis

Your doctor may use imaging tests or lab tests to analyze the peritoneal fluid to diagnose the problem. Treatment of peritoneal disorders depends on the cause.

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