Peritonitis (K65) ICD-10-CM
The K65 code range covers peritonitis with 8 ICD-10-CM diagnosis codes. 7 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Code Also
A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
- if applicable diverticular disease of intestine K57
Use Additional Code
The “use additional code” indicates that a secondary code could be used to further specify the patient’s condition. This note is not mandatory and is only used if enough information is available to assign an additional code.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
- acute appendicitis with generalized peritonitis K35.2
- aseptic peritonitis T81.6
- benign paroxysmal peritonitis E85.0
- chemical peritonitis T81.6
- gonococcal peritonitis A54.85
- neonatal peritonitis P78.0 P78.1
- pelvic peritonitis, female N73.3 N73.5
- periodic familial peritonitis E85.0
- peritonitis due to talc or other foreign substance T81.6
- peritonitis in chlamydia A74.81
- peritonitis in diphtheria A36.89
- peritonitis in syphilis late A52.74
- peritonitis in tuberculosis A18.31
- peritonitis with or following abortion or ectopic or molar pregnancy O00 O07 O08.0
- peritonitis with or following appendicitis K35
- puerperal peritonitis O85
- retroperitoneal infections K68
Codes in the K65 Range 8 codes · 7 billable
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the K65 range.
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.
Retractile Mesenteritis
This entity represents the fibrotic stage of MESENTERY inflammation.
Serositis
Inflammation of a serous membrane.
About the K65 Code Range
Peritonitis is inflammation of the lining of the abdominal cavity caused by infection, an autoimmune process, or a chemical process.
The subdivisions distinguish generalized (acute) peritonitis (K65.0), a peritoneal abscess (K65.1), and spontaneous bacterial peritonitis (K65.2). Separate codes identify choleperitonitis (K65.3) and sclerosing mesenteritis (K65.4). Other peritonitis has K65.8; unspecified peritonitis has K65.9.
Questions About This Page
How many billable codes are in the K65 range?
Of the 8 codes in this range, 7 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the K65 range classify?
The range classifies peritonitis. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
