Ascites (R18) ICD-10-CM
The R18 code range covers ascites with 3 ICD-10-CM diagnosis codes. 2 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- fluid in peritoneal cavity
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.
Codes in the R18 Range 3 codes · 2 billable
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the R18 range.
Ascites
Accumulation or retention of free fluid within the peritoneal cavity.
Malignant Ascites
Accumulation of fluid in the peritoneal cavity resulting from the growth of primary or metastatic malignant neoplasms in the peritoneum.
About the R18 Code Range
Ascites means free fluid collects or remains in the space inside the abdomen. It falls among symptoms and signs involving the digestive system and abdomen.
R18 separates malignant ascites, R18.0, from other ascites, R18.8.
Questions About This Page
How many billable codes are in the R18 range?
Of the 3 codes in this range, 2 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 R18 range classify?
The range classifies ascites. 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.
