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K51.913 vs K59.3

K51.913 (Ulcerative colitis, unspecified with fistula) compared with K59.3 (Megacolon, not elsewhere classified), from the official CMS tabular data.

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

Summary

These codes should not be reported together because K51.913’s tabular entry lists K59.3 under Excludes1.

Official rule
What is different?

The conditions named and billing status.K51.913 is “Ulcerative colitis, unspecified with fistula”; K59.3 is “Megacolon, not elsewhere classified”. K59.3 is a non-billable header; K51.913 is billable.

Registry fact

Can these codes be reported together?

No.K51.913’s entry carries an Excludes1 note covering K59.3: “megacolon (K59.3-)”. Both may be reported only when the documentation shows the two conditions are unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes1 relationship?

Yes.K51.913’s tabular entry: “megacolon (K59.3-)”. The note covers K59.3.

Official ruleGuide: Excludes1 vs Excludes2

Is there an Excludes2 relationship?

None.Neither entry carries an Excludes2 note that names the other code. K59.3 carries 1 Excludes2 note covering other codes; the side-by-side table quotes them.

Official rule

Is one more specific?

Not comparable.The codes sit in different categories; specificity is only comparable within one category.

Is one a parent or header code?

One is a header.K59.3 is a non-billable header, but K51.913 is not one of its subdivisions.

Registry fact

Are there sequencing instructions?

None.Neither entry carries a Code First or Use Additional Code note that names the other.

Official rule

Are there other coding relationships?

None found.No laterality, encounter-phase, Table of Neoplasms, Table of Drugs and Chemicals, or history-versus-active-disease relationship links these codes.

MedCoder-derived

Official rule: a tabular instructional note or a section of the ICD-10-CM Official Guidelines, quoted as published. Registry fact: the codes’ own published attributes (titles, billable status, position in the hierarchy, code set). MedCoder-derived: a reading MedCoder computes from those facts; it is not itself a rule. How to read the labels

Can these codes be reported together?

Excludes1 — generally not reported together

Excludes1 conflict

K51.913
Ulcerative colitis, unspecified with fistula
↔
K59.3
Megacolon, not elsewhere classified

What we found

No — do not report together.K51.913 carries an Excludes1 note covering K59.3: “megacolon (K59.3-)”

Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

What to review

Report one of the two. Both may be reported only when the documentation shows the two conditions are unrelated to each other.

Guide: Excludes1 vs Excludes2Check these on a claim

Why it matters

An Excludes1 note means the two conditions are not ordinarily reported together for the same encounter, because the classification treats them as mutually exclusive forms of the same condition. The documented exception is when the two conditions are unrelated to each other.

Source / rule

CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a

Official guidance behind these answers

  • Section I.A.12.a — Excludes1 · applies to: Excludes1

    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. An exception to the Excludes1 definition is the circumstance when the two conditions are unrelated to each other. If it is not clear whether the two conditions involving an Excludes1 note are related or not, query the provider. For example, code F45.8, Other somatoform disorders, has an Excludes1 note for "sleep related teeth grinding (G47.63)," because "teeth grinding" is an inclusion term under F45.8. Only one of these two codes should be assigned for teeth grinding. However psychogenic dysmenorrhea is also an inclusion term under F45.8, and a patient could have both this condition and sleep related teeth grinding. In this case, the two conditions are clearly unrelated to each other, and so it would be appropriate to report F45.8 and G47.63 together.

    ICD-10-CM Official Guidelines FY2027

Quoted from the ICD-10-CM Official Guidelines for Coding and Reporting in effect for the release shown. The tabular notes above are the code-level instruction; these sections are the convention that says how such a note is applied. Source document (CMS PDF) · Release and checksum

Side by side

Similar descriptions do not make codes interchangeable. The documentation and the official instructions decide which code applies.

Official descriptionDiffers
K51.913

Ulcerative colitis, unspecified with fistula

K59.3

Megacolon, not elsewhere classified

StatusDiffers
K51.913
Billable
K59.3
Non-billable header

A header is not reported on a claim; a code beneath it is.

Report instead: K59.31, K59.39

Excludes1Differs
K51.913
  • Crohn's disease [regional enteritis] (K50.-)
  • irritable bowel syndrome (K58.-)
  • megacolon (K59.3-)
K59.3
  • congenital megacolon (aganglionic) (Q43.1)
  • megacolon (due to) (in) Chagas' disease (B57.32)
  • megacolon (due to) (in) Clostridium difficile (A04.7-)
  • megacolon (due to) (in) Hirschsprung's disease (Q43.1)
  • change in bowel habit NOS (R19.4)
  • intestinal malabsorption (K90.-)
  • psychogenic intestinal disorders (F45.8)
Excludes2Differs
K51.913

None at this code

K59.3
  • functional disorders of stomach (K31.-)
Code firstDiffers
K51.913

None at this code

K59.3
  • , if applicable (T51-T65) to identify toxic agent
Use additional codeDiffers
K51.913
  • code to identify any associated fistulas, if applicable:
  • anal fistula (K60.3-)
  • anorectal fistula (K60.5-)
K59.3

None at this code

CategoryDiffers
K51.913

K51 Ulcerative colitis

K59.3

K59 Other functional intestinal disorders

ChapterSame for both

K00-K95 — Diseases of the Digestive System (K00-K95)

IncludesDiffers
K51.913
  • noninfective inflammatory bowel disease
K59.3
  • Dilatation of colon

No Code also and 7th character note at either code.

Notes are the code’s own tabular entry, quoted as published. A note that names the other code is the one the verdict above rests on. In a row that differs, notes every code shares are dimmed.

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Derived from the official CMS ICD-10-CM tabular data (FY2027). A coding-rule comparison, not billing advice: payer-specific edits and medical-necessity policy are outside its scope. All data sources