ICD-10-CM Tabular Index · Chapter 11 · FY 2026 K65–K68
Diseases of peritoneum and retroperitoneum (K65-K68) ICD-10-CM
The K65–K68 section covers diseases of peritoneum and retroperitoneum with 22 ICD-10-CM diagnosis codes, of which 18 are billable in fiscal year 2026. The section is organized into the 4 code ranges listed below.
✓ Built from the official CMS FY 2026 datasetEffective Oct 1, 2025 – Sep 30, 2026
The info icon previews the code ranges inside each row and its instructional notations from the official Tabular List.
About the K65–K68 Code Range
ICD-10 codes K65-K68 cover diseases affecting the peritoneum and retroperitoneum, including various types of peritonitis, abscesses, adhesions, and disorders within the abdominal and retroperitoneal spaces. This range specifically addresses inflammatory, infectious, fibrotic, and hemorrhagic conditions impacting these body areas.
Codes in the K65 series identify different forms of peritonitis, such as generalized acute peritonitis (K65.0), spontaneous bacterial peritonitis (K65.2), peritoneal abscess (K65.1), and bile-related inflammation known as choleperitonitis (K65.3). Synonyms like "acute infectious generalized peritonitis" and "primary bacterial peritonitis" help clarify coding accuracy. The K66 subgroup relates to other peritoneal disorders like postinfection or postprocedural adhesions (K66.0) and hemoperitoneum (K66.1), which describes bleeding within the peritoneal cavity. Finally, the K68 codes address conditions involving the retroperitoneum, including abscesses such as psoas muscle abscess (K68.12), retroperitoneal fibrosis (K68.2), and hematomas (K68.3). These codes assist coders in accurately recording complex abdominal and retroperitoneal infections, inflammations, and fluid collections.
Questions About This Page
How many codes are in the K65-K68 range?
The K65-K68 range contains 22 ICD-10-CM diagnosis codes in FY 2026. 18 of them are billable, and the rest are category headers that organize the section.
What conditions does K65-K68 cover?
The range covers diseases of peritoneum and retroperitoneum. The code ranges listed above break it into groups of related conditions, and each one links to its own page with the full code list.
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.
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
A type 2 excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
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.
