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

Compare with another code for K51.9Check this code on a claim

Billing Status: NO. This is a non-billable ICD-10-CM code: report a more specific billable code beneath it.

Coding at a Glance

Official instructions
1 inclusion term · 3 Excludes1 · 6 use-additional instructions

What these terms mean →

Not billable · FY2027A non-billable heading in the tabular list: report a more specific code beneath it.

What you need to know

Source: CMS/NCHS Official ICD-10-CM tabular notes, quoted. From the CMS/NCHS tabular list for the release in force. A note the category or block publishes applies to this code too, and is marked with where it comes from.

Use additional codefrom K51Report with this code when documented
  • Use additional code to identify any associated fistulas, if applicable:
  • anal fistula (K60.3-)
  • anorectal fistula (K60.5-)
  • rectal fistula (K60.4-)

+2 more in Instructions

Excludes1Not reported with this code unless documented as unrelated
  • Crohn's disease regional enteritis
  • irritable bowel syndrome (K58.-) (from K50-K52)
  • megacolon (K59.3-) (from K50-K52)
Includesfrom K50-K52What K50-K52 covers
  • noninfective inflammatory bowel disease

Where it sits Source: CMS/NCHS

Under:Chapter 11: Diseases of the Digestive SystemK50-K52 Noninfective enteritis and colitisK51 Ulcerative colitis

Codes under K51.9 (2)

  • K51.90Ulcerative colitis, unspecified, without complicationsBillable
  • K51.91Ulcerative colitis, unspecified, with complicationsNot billable

Most relevant related codes MedCoder-derived

Read off the official notes above and this code’s own position in the tabular list. Which to report is a documentation question; Compare shows the two side by side.

CompareCheck ClaimView Related 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: FY2027Effective: October 1, 2026

Trace:FY2027 changesChange historyRelease, file and checksum

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. Check the Excludes1 note: if the documentation supports a condition named there, do not simply proceed with the code beneath 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. Where the codes beneath it include an unspecified code, that code applies when the record goes no further; otherwise query for the missing detail.

    ReviewK51.90, K51.91

  2. 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

Report the code beneath K51.9 that the documentation supports, not K51.9 itself. Then work the Use Additional Code note, and confirm that code is valid for the date of service on its own page.

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 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 the code beneath 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.

Don’t confuse K51.9 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of K51.9 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

  • K58— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of irritable bowel syndrome moves the case to K58; the two are not reported together unless documented as unrelated.

    Full comparison: K51.9 vs K58 →

  • K59.3— Excludes1 conflict (Excludes1 — generally not reported together)

    Not coded here — the tabular list excludes this pair for the same encounter.

    Not reported together with this code, except where the two conditions are documented as unrelated.

    What moves you there: Documentation of megacolon moves the case to K59.3; the two are not reported together unless documented as unrelated.

    Full comparison: K51.9 vs K59.3 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Coding context

Guidelines, coding notes, decision aids, relationships (with MS-DRG and CCSR classification), hierarchy, HCC, coverage and the context map: what a coder reaches for after the core. Each section names whether it is official source data, a MedCoder-derived relationship or MedCoder editorial.

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-derived 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

Reference

Index terms and tables, published questions and FAQ, every source behind this page with its release and checksum, the date-of-service check and the complete change history.

Common coding questions

MedCoder editorial

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 FY2027 tabular list, index and tables, effective October 1, 2026 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v44.0 (October 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-derived 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 editorial 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.

Current data releases:ICD-10-CM FY2027 · ICD-10-PCS FY2027 · HCPCS October 2026 · MS-DRG v44 · Medicare Code Editor v44.0 · NCCI PTP Q4 2026 · MUE Q4 2026 · NCD code lists 2026-01 · LCD export September 28, 2026 · All releases and sources

Labels on this page: Official source data · MedCoder-derived relationship · MedCoder editorial explanation. How to read the labels · All data sources and release dates · CMS coding rules

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 FY2027. 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, 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