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R18 ICD-10-CM Code: Ascites

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Coding at a Glance

Tabular directives
1 inclusion term · 3 Excludes1 · 9 Excludes2

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for R18 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on R18 itself; “inherited from” names the category or block whose note applies here.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • fluid in peritoneal cavity

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from R10-R19

Coder workflow for R18

MedCoder structured workflow — derived from this code’s own official record

Before you code R18

  1. R18 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

    ReviewR18.0, R18.8

    See the relationships section · Guide: How to choose an ICD-10-CM code →

  2. Check whether an established diagnosis that explains this sign or symptom is documented. If one is, review whether the documented diagnosis changes the coding pathway: a symptom that is integral to a confirmed diagnosis is not reported separately, while one not routinely associated with it may be. Signs and symptoms are reported when no definitive diagnosis is established (Guidelines I.B.4, I.B.5, I.B.6, I.C.18.b).

    Guide: Symptom code vs confirmed diagnosis →

  3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with R18. Excludes1 conditions are not reported together with this code unless the record shows they are unrelated (Guidelines I.A.12.a).

    See the official tabular notes

Choose the right path

  1. Does the documentation support one of the more specific codes beneath R18?
    Yes → Select that code and continue the checks below on its own page.
    No → R18 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewR18.0, R18.8

  2. Is an established diagnosis that explains this sign or symptom documented?
    Yes → Review whether the documented diagnosis changes the coding pathway: a symptom integral to it is not reported separately.
    No → Continue — the sign or symptom code stands when no definitive diagnosis is established.
  3. Does the documentation support a condition named in R18’s Excludes1 note?
    Yes → Do not simply proceed: review the excluded code. Both are reported only when the record shows the two conditions are unrelated.
    No → Continue.

    ReviewK70.31, K70.11, K71.51

Consider R18. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Official instructions as workflow

  • Excludes1 — check before selecting R18(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with R18: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareK70.31, K70.11, K71.51

    See the official tabular notes · Guidelines I.A.12.a

  • Excludes2 — not part of R18(9 notes)

    Coding workflow: The conditions named in this note are not included in R18. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareQ40.0, K56, P76, K31.3, N94

    See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The sign or symptom is documented, and the same record establishes a diagnosis that routinely includes it.

Coding question: Is R18 reported in addition to the diagnosis?

Path: Review the documented diagnosis and whether the classification treats this finding as integral to it.

Reason: Signs and symptoms integral to a confirmed diagnosis are not coded separately; those not routinely associated with it may be reported when present (Guidelines I.B.5, I.B.6, I.C.18.b).

Documentation: Both the condition R18 describes and a condition named in its Excludes1 note are documented for the same encounter.

Coding question: Can both codes be reported?

Path: Review the Excludes1 note and the excluded code, and look for a provider statement on whether the two conditions are related.

Reason: Excludes1 means the two are not coded together; the exception is when the record shows the conditions are unrelated to each other (Guidelines I.A.12.a).

ReviewK70.31, K70.11, K71.51

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Ascites is a non-billable ICD-10-CM category code (R18). A more specific billable subcode must be selected for claims submission.

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Verify Before Coding

  • Not billable as written — a more specific code is required: R18.0, R18.8.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name R18 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 2 Excludes1 notes: R19.0 — Intra-abdominal and pelvic swelling, mass and lump, R60 — Edema, not elsewhere classified.

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Excludes2 note: K66 — Other disorders of peritoneum.

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Contextual Map

Every relationship of R18 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run R18 with these 14 related codes in Claim Check

Hierarchy

Excludes1

Excludes2 (24)

Referenced by Excludes1 notes

Referenced by Excludes2 notes

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Can R18 be billed directly?

No. R18 (Ascites) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "R18 — Ascites." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/r18-ascites

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Ascites

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to R18 in its code family, with their registry titles.