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K51.9 ICD-10-CM Code: Ulcerative colitis, unspecified

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 · 6 use-additional codes

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for K51.9 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 K51.9 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.

  • noninfective inflammatory bowel disease

Source: inherited from K50-K52

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).

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code to identify any associated fistulas, if applicable:
  • anal fistula (K60.3-)
  • anorectal fistula (K60.5-)
  • rectal fistula (K60.4-)
  • Use additional code to identify manifestations, such as:
  • pyoderma gangrenosum (L88)

Source: inherited from K51

Coder workflow for K51.9

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

Before you code K51.9

  1. K51.9 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).

    ReviewK51.90, K51.91

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

  2. Unspecified does not mean incorrect. When the record gives no greater specificity, K51.9 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    ReviewK51.4, K51.5, K51.8

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

  3. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with K51.9. 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 K51.9?
    Yes → Select that code and continue the checks below on its own page.
    No → K51.9 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewK51.90, K51.91

  2. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — K51.9 is appropriate when the documentation goes no further.

    ReviewK51.4, K51.5, K51.8

  3. Does the documentation support a condition named in K51.9’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.

    ReviewK58, K59.3

Consider K51.9. Then work the Use Additional Code note, and 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).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes1 — check before selecting K51.9(3 notes)

    Coding workflow: If the documentation supports a condition named in this note, do not simply proceed with K51.9: the two are not reported together. The one exception is when the record shows the two conditions are unrelated to each other.

    CompareK58, K59.3

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

  • Use Additional Code — after identifying K51.9(6 notes)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with K51.9 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    ReviewK60.3, K60.5, K60.4, L88

    See the official tabular notes · Guidelines I.A.13

Coding decision scenarios

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

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the specific siblings in this subcategory and what each requires the record to state.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

ReviewK51.4, K51.5, K51.8

Documentation: Both the condition K51.9 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).

ReviewK58, K59.3

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with K51.9?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

ReviewK60.3, K60.5, K60.4, L88

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

Ulcerative colitis, unspecified is a non-billable ICD-10-CM category code (K51.9). 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

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 K51.9 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 3 Excludes1 notes: K50 — Crohn's disease [regional enteritis] (via K51.-), K62.6 — Ulcer of anus and rectum (via K51.-), K63.3 — Ulcer of intestine (via K51.-).

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

Referenced by 4 Code First instructions across 2 chapters: F54 — Psychological and behavioral factors associated with disorders or diseases classified elsewhere (via K51.-), K60.3 — Anal fistula (via K51.-), K60.4 — Rectal fistula (via K51.-), K60.5 — Anorectal fistula (via K51.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

Referenced by 2 Code Also instructions: M07 — Enteropathic arthropathies (via K51.-), M08 — Juvenile arthritis (via K51.-).

These codes suggest coding this condition alongside when both are present.

Contextual Map

Every relationship of K51.9 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 K51.9 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes

Referenced by Code First instructions

Referenced by Code Also instructions

Nearest codes (40)

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 K51.9 be billed directly?

No. K51.9 (Ulcerative colitis, unspecified) 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. "K51.9 — Ulcerative colitis, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/k51.9-ulcerative-colitis-unspecified

Change history

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

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 K51.9 in its code family, with their registry titles.

View all codes in the K51 family